PURPOSE Patient, tumor, and treatment factors can help predict the chance that a woman with a history of breast cancer diagnosis will be diagnosed with a second breast cancer within a year of a negative mammogram. This qualitative study elucidates breast cancer survivor and multispecialty physician perspectives on barriers/facilitators to clinical implementation of a risk-prediction tool to support surveillance decisions. MATERIALS AND METHODS We enrolled women who completed primary breast cancer treatment and physicians from November 2023 to April 2024. Participants were recruited through Breast Cancer Surveillance Consortium's registries; patients participated in one of four focus groups and physicians participated in individual semistructured interviews. Participants were presented with information about an interval cancer risk prediction tool and were prompted to share perspectives on facilitators and barriers to using such a tool. To identify salient themes, thematic analysis was undertaken by three research team members. RESULTS Participants included 40 physicians and 23 patients. Three themes emerged: (1) evidence needed for tool acceptance, (2) tool features to facilitate usage, and (3) barriers to tool adoption. Both cancer survivor and physician groups were accepting of risk prediction tool use for surveillance imaging when tool development information was available; they perceived the tool would fit within workflows, and data integrity could be verified. Both groups anticipated structural (time) and technological barriers (magnetic resonance imaging availability) could impede adoption. CONCLUSION Qualitative findings from focus groups and interviews analyzed thematically suggest implementing a risk prediction tool for surveillance imaging requires evidence transparency, health record integration, data integrity protection, and system supports to promote ease of use in clinical settings while mitigating unintended consequences. All are important to consider during tool development and implementation planning.

BACKGROUND:Limited evidence is available from randomized trials to guide clinical decision-making for cardiovascular disease (CVD) prevention with statins among women with breast cancer. We leveraged real-world data to estimate the effect of statin therapy vs usual care on the 5-year risk of CVD among breast cancer survivors. METHODS:We sequentially emulated target trials using the National Cancer Institute-Kaiser Permanente Breast Cancer Survivors Cohort. Women aged 40 - 84 years, diagnosed with stage 0-III breast cancer from 1993 - 2022, without CVD, no statins in the past 6 months, and low-density lipoprotein cholesterol from 100 - 160 mg/dL were included. The outcome was CVD (ischemic heart disease, stroke, and cardiomyopathy/heart failure). We compared statin therapy to usual care (no statins unless indicated) in intention-to-treat and per-protocol analyses. RESULTS:Statin initiators were more likely to be older with a higher prevalence of cardiovascular comorbidities. In the intention-to-treat analysis, the 5-year risk difference was 0.3% (95%CI: -0.9,1.5), and risk ratio was 1.04 (95%CI: 0.86,1.25) for statin vs usual care. At 5 years, the proportion adherent to their initial strategy was 48% for statin and 24% for usual care. In the per-protocol analysis, the risk difference was -0.9% (95%CI: -2.9,2.2) and the risk ratio was 0.85 (95%CI: 0.51,1.36) for statin vs usual care. CONCLUSIONS:Our findings suggest that statin therapy may reduce the risk of CVD for breast cancer survivors, but the estimates are too imprecise for specific recommendations. Future research is needed to understand reasons for statin discontinuation, and opportunities to encourage adherence in this high-risk population.

Importance:The magnitude of thyroid cancer overdiagnosis in the US, accounting for the true increase in underlying disease, has not been quantified. The implications of reducing thyroid ultrasonography use for these rates has not been calculated. Objective:To estimate US population-level rates of papillary thyroid cancer (PTC) overdiagnosis, and to identify the implications of reducing thyroid ultrasonography use for thyroid cancer incidence and overall mortality. Design, Setting, and Participants:This study used a validated simulation model (Papillary Thyroid Carcinoma Microsimulation Model) of contemporary PTC incidence in the adult US population between 1991 and 2019. Data analysis was conducted from June 2024 to August 2025. Exposures:Thyroid cancer incidence and referrals for ultrasonography of nonpalpable thyroid nodules. Main Outcomes and Measures:Model-estimated relative and absolute rates of PTC overdiagnosis, stratified by sex. The model estimated changes in the rates of thyroid cancer incidence and overall mortality if ultrasonography rates were reduced. Results:The simulation included all adults, aged 18 years or older, in the US. Between 1991 and 2019, the model estimated that 72% to 94% of PTC cases were overdiagnosed. While the proportion of overdiagnosis was slightly higher for women compared with men (75%-95% vs 63%-90%), the absolute rate of overdiagnosis was higher among women compared with men (13-17 per 100 000 individuals vs 3-5 per 100 000 individuals). This rate translated into 443 212 to 573 705 women and 107 804 to 154 504 men who were overdiagnosed with PTC over 28 years. Reducing use of thyroid ultrasonography for nonpalpable nodules by 33% and 67% would have decreased PTC incidence by 17% (18 to 15 per 100 000 individuals) and 41% (18 to 11 per 100 000 individuals) in 2019, respectively, a less than 0.1% change in overall mortality. Conclusions and Relevance:This study found that thyroid cancer overdiagnosis in the US remains substantial, even after accounting for possible increases in true incidence. This finding suggests an opportunity to reduce unnecessary thyroid ultrasonography referrals, particularly for nonpalpable nodules, and to reduce unnecessary diagnoses and treatment-related harms without increasing mortality.

INTRODUCTION:The Coronavirus 2019 (COVID-19) pandemic disrupted healthcare delivery across the United States, leading to a sharp decline in outpatient visits. Given that thyroid nodule evaluation and diagnosis typically occur in outpatient settings, we hypothesized that these disruptions would reduce thyroid cancer incidence. This study evaluates trends in thyroid cancer diagnosis, treatment, and outcomes at a U.S. comprehensive cancer center from 2017 to 2023. METHODS:We included adults with pathologically confirmed thyroid cancer diagnosis between January 1, 2017, and December 31, 2023. Primary analyses assessed (1) annual percent change (APC) in thyroid cancer incidence from 2017-2023 and (2) incidence trends across three periods: pre-pandemic (Jan 2017-Mar 2020), pandemic (Apr 2020-Mar 2021), and COVID-years (Apr 2021-Dec 2023). Annual incidence rates were calculated using the total number of individuals cared for within our health system each year as the denominator. Secondary outcomes included tumor size, extent and timing of surgery, and 1-year all-cause mortality across time periods. RESULTS:Among 1,031 patients (68% women, 92% White, mean age 52 ± 15.5), age- and sex-adjusted thyroid cancer incidence declined from 34 to 15.6 per 100,000 persons between 2017 and 2022, with an average APC of -14.4%. Diagnoses rose slightly in 2023 (21 per 100,000) compared to 2022 but remained 38% below 2017 levels. No significant differences were observed in tumor size, surgical treatment, gender ratio, or 1-year all-cause mortality across timeframes. CONCLUSION:Age- and sex-adjusted annual incidence of thyroid cancer declined steadily from 2017 to 2022. The annual decrease in thyroid cancer continued through the pandemic years. Tumor size and mortality remained stable across all years evaluated. The increase in diagnoses noted in 2023 may be a correction due to missed cases during the years of the pandemic or could represent a new steady state incidence after years of decline.

Background The National Health Interview Survey (NHIS), a nationwide in-person and telephone survey of the civilian non-institutionalized population, is used to measure progress towards Healthy People objectives on cancer screening. Survey reports have been compared to medical record data to assess validity of these questions; however, few studies have assessed reliability, or response consistency over time. We assessed the test-retest reliability of questions on cervical, colorectal, breast and lung cancer screening from the 2021 and 2022 NHIS. Methods We surveyed 1,770 adults ages 18 + years with and without prior screening for breast, cervical, colorectal, and lung cancer from four U.S. health systems (three in Washington state and one in Michigan) to examine validity of the NHIS questions. Among people who completed the validity survey, we randomized individuals to receive an additional survey one month later (N = 944) and three months later (N = 822). We calculated Cohen’s Kappa, Gwet’s AC1, and simple concordance to assess reliability. Results Among our study sample, 535 (56.7% of those assigned) to one month follow-up and 537 (65.0%) assigned to three month follow-up completed the reliability survey. Among these, 36 (6.6%) and 94 (17.6%) of those assigned to one and three month follow-up respectively were excluded from reliability analyses because they had additional screening tests after completing the validity survey. Cohen’s Kappa showed strong-to-moderate reliability for being up to date with mammography screening: 0.83 at one month and 0.78 at three months; reliability for other screening tests was considerably lower: 0.61 and 0.60 for cervical, 0.57 and 0.62 for colorectal, and 0.72 and 0.58 for lung and one and three months, respectively. Conclusions We found strong-to-moderate reliability of responses recalling breast cancer screening at one and three months following an initial survey. Reliability may not be a major threat to self-reported cancer screening behavior.

The National Health Interview Survey (NHIS) is used to measure progress on cancer screening. We assessed the validity of questions on cervical, colorectal, breast, and lung cancer screening from the 2020, 2021, and 2022 NHIS, using electronic medical records (EMRs) as our standard for accuracy. We surveyed 1770 adults aged 21+ years for breast, cervical, colorectal, and lung cancer from 4 US health systems. We made slight changes in question order and wording to improve the understanding of questions. We compared survey responses for screening adherence with EMR data as a gold standard, calculating sensitivity, specificity, positive predictive value, negative predictive value, Cohen's Kappa, and reports-to-records ratio. Self-reported screening adherence had high sensitivity for most cancer types (range 0.79-0.96). We found good agreement for breast cancer screening using Cohen's Kappa (0.81) and more modest agreement for the other 3 cancer sites (0.59-0.65). The reports-to-records ratio showed overreporting of cancer screening, ranging from 12% to ⁓50% more screening reported for the United States Preventive Services Task Force (USPSTF)-recommended screening periodicity compared to medical record data. NHIS questions that assess cancer screening provide reasonably accurate estimates. However, some misclassification with expected bias toward overreporting of screening suggests that improvements in measuring screening adherence are needed.

BACKGROUND:Chemotherapy dose reductions are associated with poorer survival. To better understand the role of clinician- and facility-level factors in chemotherapy dosing, we conducted an analysis within a large, real-world cohort of women with stages I-IIIA breast cancer. METHODS:Our cohort included 8540 breast cancer patients receiving chemotherapy at Kaiser Permanente Northern California between 2006 and 2019. Patients were treated across 22 facilities by 198 clinicians. We evaluated associations between clinician- and facility-level factors related to dose reductions at the start of chemotherapy (first cycle dose proportion, FCDP, <90%) and throughout treatment (average relative dose intensity, ARDI, <90%). Prevalence ratios (PR) and corresponding 95% confidence intervals (CI) were estimated for the clinician and facility factors in relation to chemotherapy dose reductions. RESULTS:Factors associated with an increased likelihood of dose reduction were increased clinician years since medical school (FCDP < 90%: PR≥30 vs. <10 years = 1.78, P-trend = .03; ARDI < 90%: PR≥30 vs <10 years = 1.29, P-trend = .03) and treatment at less urban facilities (ARDI < 90%: PR<100% vs 100% urban = 1.38, P-trend = .002). Factors associated with a decreased likelihood of dose reduction were higher annual clinician volume of stage I-IIIA breast cancer patients (FCDP < 90%: PR≥30 vs ≤15 patients =  0.64, P-trend = .03; ARDI < 90%: PR≥30 vs ≤15 patients =  0.76, P-trend = .01), higher treatment facility annual volume of stage I-IIIA breast cancer patients (ARDI < 90%: PR≥200 vs <75 patients = 0.85, P-trend = .03), and a larger practice size (FCDP < 90%: PR≥10 vs ≤5 oncologists = 0.53, P-trend = .02). CONCLUSIONS:Clinician- and facility-level factors were associated with chemotherapy dose reductions. Practice-level changes, such as increasing breast cancer patient volumes and practice size, may support optimal dosing practices.

BACKGROUND:For most cytotoxic drugs, guidelines recommend body-surface-area-based dosing, yet some patients start with reduced doses, potentially reflecting tolerability concerns. The relationship between first-cycle dose reductions and subsequent delivery is unclear. METHODS:The authors analyzed data from women with stage I-IIIA breast cancer treated with adjuvant chemotherapy. Sankey diagrams illustrated trajectories from first-cycle dose proportion (FCDP) to average relative dose intensity (ARDI, ratio of received to expected dose intensity across the regimen), and cumulative dose proportion (CDP, ratio of total received to expected dose). Poisson regression estimated adjusted prevalence ratios for reduced FCDP (<95% vs. ≥95%) and three outcomes: ARDI reduction beyond initial FCDP, receiving fewer cycles, and CDP reduction beyond initial FCDP. Analyses assessed effect modification by age, body mass index (BMI), and comorbidities. Dosing was analyzed for cytotoxic and HER2-targeted therapy. RESULTS:A total of 8772 (90.8%) patients started with FCDP ≥95%; most maintained ARDI ≥95% (65.1%) and CDP ≥95% (79.9%). In multi-variable models, FCDP <95% was not significantly associated with further ARDI or CDP reductions or receipt of fewer cycles. BMI modified these associations (p-interaction = .004 for fewer cycles; p-interaction = .03 for CDP), with positive associations among overweight but not obese or normal-weight patients. FCDP <95% was linked to a lower likelihood of further ARDI reductions for both therapy types and lower likelihood of cumulative dose reduction in HER2-targeted therapy. CONCLUSIONS:Early dosing decisions shaped subsequent chemotherapy delivery. Most patients who began at full dose maintained consistent dosing, whereas early reductions did not stave off subsequent changes, underscoring the need to balance safety with adequate dose intensity.

BACKGROUND:Older women (>65 years) diagnosed with breast cancer may be at risk for chemotherapy dose reductions. We evaluated associations of age at diagnosis with 2 measures of chemotherapy dose reductions: first cycle dose proportion (FCDP) < 90% and average relative dose intensity (ARDI) < 90%. METHODS:From the Optimal Breast Cancer Chemotherapy Dosing study, we included 10 166 women aged 18+ years treated with adjuvant chemotherapy for stage I-IIIA breast cancer at Kaiser Permanente Northern California (KPNC) and Washington (KPWA) between 2004 and 2019. We examined associations between age at diagnosis with FCDP < 90% (reflecting clinician intent at chemotherapy initiation) and ARDI < 90% (reflecting average dose across the chemotherapy course). We used generalized linear models of the Poisson family with a log-link function and robust standard errors to calculate prevalence ratios (PR) for FCDP < 90% and ARDI < 90% with 95% confidence intervals (CI) adjusted for patient and tumor characteristics, with and without adjusting for pre-existing comorbidities. All tests for statistical significance were 2-sided. RESULTS:The proportion of women with FCDP < 90% ranged from 2.9% among women aged 18-39 years to 18.6% among women aged 75+ years. Before adjusting for comorbidities, women aged 75+ years were more likely to have FCDP < 90% (PR = 4.88; 95% CI = 3.58 to 6.66) and ARDI < 90% (PR = 1.91; 95% CI = 1.58 to 2.32) versus women aged 40-49 years. Results were similar after adjusting for comorbidities as a composite comorbidity score or individual comorbidities. CONCLUSION:Older age at diagnosis was strongly associated with chemotherapy dose reductions in this population-based cohort, particularly at chemotherapy initiation but also across the course of treatment.

Background In the delivery of cancer care, patients may experience modifications to their intended chemotherapy regimen for reasons such as toxicity, tolerability, and scheduling challenges. Understanding modifications from the intended chemotherapy in the real-world setting of cancer care may affect treatment planning and inferences of real-world treatment effectiveness. Methods By leveraging data from the Optimal Breast Cancer Chemotherapy Dosing Study, this research studied 12,558 women receiving chemotherapy for primary stage I-IIIA breast cancer at Kaiser Permanente Northern California (2006-2019) and Kaiser Permanente Washington (2004-2015). Modifications in chemotherapy administered from intended, both overall and by regimen, are described. Prevalence ratios (PRs) were calculated for associations between regimen attributes and treatment modifications via generalized linear models of the Poisson family with a log-link function and robust standard errors. Results Intent to receive a guideline-concordant regimen was associated with a lower likelihood of modifications from the intended chemotherapy (vs. non-guideline concordant) (PR, 0.74; 95% CI, 0.69-0.79), as was receiving a dose-dense regimen (vs. non-dose dense) (PR, 0.84; 95% CI, 0.78-0.91). Those receiving any neoadjuvant chemotherapy (vs. adjuvant only) were more likely to have modifications from the intended chemotherapy (PR, 1.29; 95% CI, 1.19-1.41). Increasing numbers of cycles and drugs administered were associated with a higher likelihood of modifications (p(trend) < .001). Conclusions Breast cancer chemotherapy regimens used in the real-world setting were examined. Chemotherapy modifications varied markedly by regimen and by characteristics of the regimen administered. Given that more than one in three women in this cohort did not receive chemotherapy as intended, these novel findings may be informative in treatment planning and for future research assessing real-world treatment effectiveness.

Radiotherapy increases contralateral breast cancer risk, while hormone therapy reduces it; their combined effects are unclear. Data from two US retrospective cohort studies of 5-year breast cancer survivors (stage I-III, ages 20–84), Kaiser Permanente (KP, 1990–2012) and SEER (1990–2013), were analysed. Contralateral breast radiation doses were estimated for the KP cohort. Multivariable Poisson regression estimated relative risks (RRs) and excess relative risks per Gray (ERR/Gy), stratified by hormone therapy use. KP cohort (n = 9053) included 353 contralateral breast cancer cases (73% ER+); SEER cohort (n = 244,834) included 10,470 cases (72% ER+). Among women with ER+ first breast cancer, radiotherapy increased the risk of ER+ contralateral breast cancer in non-users of hormone therapy (KP RR = 2.2, 95%CI:1.20–4.14; SEER RR = 1.12, 1.04–1.21), but not in users (KP RR = 0.88, 0.61–1.26; SEER RR = 1.03, 0.94–1.12). In KP, higher radiation dose increased risk of ER+ contralateral breast cancer among non-users (ERR/Gy=1.39, 95%CI:0.33,3.66), but not among users (ERR/Gy= –0.13, –0.36,0.23). Radiotherapy also increased risk of ER– contralateral breast cancer (KP RR = 1.85, 95%CI: 0.95–3.59; SEER RR = 1.12, 1.01–1.23), especially in younger exposed women (SEER RR = 1.31, 1.02-1.69 for age <40 vs 40+ years). Additionally, the risk increased linearly with radiation dose to the contralateral breast (ERR/Gy=0.87, 0.04,2.72). Radiotherapy increased contralateral breast cancer risk, but hormone therapy appeared to mitigate this risk for ER+ cases. These findings have important implications for individuals exposed to chest radiation.

Contralateral breast (CB) cancer is the most common subsequent cancer among breast cancer survivors, and radiotherapy has been linked to CB cancer risk. The purpose of this work was to evaluate doses to subregions of the contralateral breast from historical breast cancer treatments carried out in the United States between 1990 and 2012. We extracted treatment data from radiation therapy summaries for 2,442 radiotherapy patients during that period. We estimated CB doses for five breast regions: the upper inner quadrant (UIQ), lower inner quadrant, upper outer quadrant, lower outer quadrant (LOQ), and nipple, using extracted data and out-of-beam CB dose measurements. The mean treatment dose was approximately 5,000 cGy for tangential fields, which comprised 84% of the photon fields, and this remained constant throughout our study period. Most of the dose to the contralateral breast was from the tangential fields, and it varied by contralateral breast region. The UIQ of the contralateral breast received the highest median dose which decreased by 23% from 185 cGy in 1990-1994 to 143 cGy in 2005 and later (P < 0.0001). The LOQ dose received the lowest dose, which also decreased by 24% from 74 to 56 cGy (P < 0.0001). This decrease was due to the reduction in the utilization of physical wedges and an increase in the field-in-field technique, particularly after 2005. We observed a significant reduction in CB doses from breast radiotherapy in the United States between 1990 and 2010, which can be attributed to the impact of advanced radiotherapy techniques.

PURPOSE:Our objective was to assess the transition from digital mammography (DM) to digital breast tomosynthesis (DBT) screening, the authors compared diagnostic workup type and frequency, workup pathways, and time to resolution of abnormal screening between DBT and DM. METHODS:This cohort study included screening examinations with an abnormal results from 2011 to 2020 at 107 facilities across six Breast Cancer Surveillance Consortium registries. Diagnostic workup included diagnostic DM, diagnostic DBT, ultrasound, MRI, and biopsy within 90 days of the abnormal result on screening mammography. Workup modalities and number of workup procedures were compared using differences in proportion and 95% confidence intervals (CIs). Time to diagnostic resolution between DBT and DM was compared using a log-rank test. RESULTS:Among 77,123 DBT and 197,589 abnormal DM screening examinations with abnormal results, the number of imaging modalities in the diagnostic pathway was similar. The first workup procedure was more often ultrasound after abnormal results on DBT compared with DM (21.1% versus 4.7%). Biopsy rates were higher for DBT versus DM (16.2% versus 14.0%; difference in proportions = 2.27; 95% CI, 1.97-2.58) with biopsies after DM versus DBT more likely surgical versus fine-needle aspiration or core (5.8% versus 3.2%; difference in proportions = 2.6; 95% CI, 2.19-3.01), resulting in a rate of excision biopsy per 1,000 screens with abnormal findings of 5.1 for DBT and 8.0 for DM. Time to diagnostic resolution was similar (median, 10 days). CONCLUSIONS:This study revealed differences in the type of diagnostic workup pathways after abnormal results on screening DBT versus DM. Although the biopsy rate was higher after abnormal results on DBT, the biopsy type may be more invasive (surgical excision) after abnormal results on DM.

547 Background: ASCO guidelines state that most cytotoxic drugs should be dosed according to full body surface area (BSA) without limiting the dose on the basis of obesity. This approach is supported by a lack of evidence to suggest that patients with obesity, when fully-dosed, experience higher risk of toxicity. Indeed, historical evidence suggests that obese, fully-dosed patients may experience lower risk of neutropenia than normal weight patients. However, questions remain regarding the representativeness of historical trial data on which this evidence is based. We examined this issue in the Optimal Breast Cancer Chemotherapy Dosing (OBCD) Study. Methods: The OBCD Study is a real-world cohort of 34,109 women diagnosed with stage I-IIIA breast cancer at Kaiser Permanente Northern California and Kaiser Permanente Washington between 2004-2019. Among women receiving the full dose of chemotherapy at treatment initiation (≥90% of intended dose, n = 7,644), we examined risk of toxicities in women with obesity (BMI ≥30 kg/m 2 ) compared to non-obese women (BMI 18.5- < 30 kg/m 2 ). We examined hematologic (neutropenia, anemia, thrombocytopenia) and non-hematologic (nephrotoxicity, hepatotoxicity, neuropathy, and cardiotoxicity) toxicities. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated using Cox proportional hazards regression, adjusted for covariates including prevalent comorbid conditions. Secondary analyses examined associations pertaining to specific BMI groups and also stratified by administration schedule (standard vs dose-dense). Results: Fully-dosed patients with obesity experienced lower risk of neutropenia (HR: 0.80; 95% CI: 0.73-0.88) and any hematologic toxicity (HR: 0.83; 95% CI: 0.75-0.91) but increased risk of neuropathy (HR: 1.34; 95% CI: 1.18-1.52), cardiotoxicity (HR: 2.30; 95% CI: 1.13-4.67), and non-hematologic toxicities overall (HR: 1.31; 95% CI: 1.15-1.48). The strength of these associations increased with increasing BMI category. The inverse association between obesity and hematologic toxicity was evident for standard administration schedules (HR: 0.54; 95% CI: 0.45-0.66) but not dose-dense schedules. However, the positive association between obesity and non-hematologic toxicities persisted regardless of administration schedule. Conclusions: Women with obesity given the full BSA-determined chemotherapy dose are less likely to experience neutropenia than fully-dosed non-obese women. Importantly, this holds among patients with more severe obesity, but not when restricted to newer dose-dense administration schedules. Findings also suggest that fully-dosed patients with obesity may experience higher risks for neuropathy and cardiotoxicity. These findings highlight the importance of better understanding the risks and benefits of dosing strategies as treatments and patient populations continue to evolve.

Raw numbers for performance statistic calculations

Modifications to intended chemotherapy regimens may be due to various reasons and may impact patient outcomes. Understanding which factors are associated with chemotherapy modifications can help inform treatment planning and improve cancer care. We examined the association between patient/tumor factors and modifications to intended chemotherapy in women with Stages I–IIIA breast cancer who were treated at Kaiser Permanente Northern California and Kaiser Permanente Washington from 2005 to 2019. Modifications were defined as any dose reductions in the first cycle or throughout chemotherapy, regimen change, treatment delay (single delay >14 days) or receiving fewer cycles of any drugs than expected. We used generalized linear models of the Poisson family with a log‐link function to calculate prevalence ratios (PRatios). Of 9700 women receiving adjuvant chemotherapy, 34.6% had chemotherapy modifications. Selected results are shown: positive associations were observed with age (PRatio 80+ vs. 18–39 : 1.93; 95% confidence interval [CI]: 1.50–2.50; p ‐trend <.001), body mass index (BMI) (PRatio ≥35 vs. 18.5 to <25 : 1.53; 95% CI: 1.41–1.65; p ‐trend <.001), and Charlson comorbidity index (PRatio 3+ vs. 0 : 1.33; 95% CI: 1.19–1.48; p ‐trend <.001), while more recent years of diagnosis were associated with decreased prevalence of treatment modifications (PRatio 2015‐2019 vs. 2005–2009 : 0.65; 95% CI: 0.61–0.69; p ‐trend <.001). Stage was also positively associated (PRatio Stage IIIA vs. I : 1.24; 95% CI: 1.13–1.35; p ‐trend <.001), as was human epidermal growth factor‐2 positive status (PRatio: 1.99; 95% CI: 1.89–2.10). In conclusion, patients with the highest likelihood of chemotherapy modifications represent those who may have more complex prescribing needs, including those of older age, higher BMI, and more comorbidity. Further understanding of how modifications could impact outcomes within these groups can inform and improve cancer care.

Diagnostic imaging is a critical step in obtaining a timely breast cancer diagnosis. The American College of Radiology (ACR) recommends initial diagnostic evaluation with breast ultrasound for women 18-29 with focal breast symptoms and initial diagnostic evaluation with mammography and/or ultrasound for women 30-39 with symptoms. These guidelines are evidence-based and deviation from them has the potential to lead to performance of unnecessary exams and/or delayed diagnosis. We evaluated the prevalence of appropriate diagnostic imaging among breast cancer patients <40 years. Data were from the Carolina Mammography Registry (CMR), a community-based registry of breast imaging in North Carolina that links to cancer diagnoses from the North Carolina Central Cancer Registry. The analysis included CMR women aged 18-39 years who were diagnosed with breast cancer between 2005-2021 and had at least one breast imaging exam (any type or indication) in the year before diagnosis (n=311). Women with a self-reported first-degree family history of breast cancer or imaging facility-reported increased risk were excluded due to differing guidelines for high-risk women. Presence of self-reported symptoms (lump, nipple discharge, pain or other) were obtained from pre-diagnosis exams. Use of appropriate imaging was based on the ACR Appropriateness Criteria for women with symptoms (described above). Between-group differences were assessed using the Fisher exact text. The majority of patients were 35-39 years old (63%), with fewer in 30-34 year (27%) and 18-29 year (10%) age groups. Symptom data was available for 98% of women, with symptoms present for 59% (18-29: 60%; 30-34: 70%; 35-39: 54%). The most common diagnostic approach in the year prior to diagnosis was ultrasound alone (50%) followed by mammography alone (28%). Use of multiple diagnostic modalities was uncommon (ultrasound plus mammogram: 10%; ultrasound plus MRI: 1%). 97% of patients with diagnostic imaging received an exam consistent with ACR guidelines, though appropriate imaging was lower among women 18-29 (76%) compared with women 30-34 (100%) or 35-39 (99%) (P<0.0001). This pattern was consistent for women with symptoms (18-29: 65%; 30-34: 100%; 35-39: 100%; P<0.0001), but there was no difference by age among women without symptoms (18-29: 100%; 30-34: 100%; 35-39: 97%; P>0.99). Limitations of our analysis include that some women may have obtained exams at facilities outside the CMR, which may lead to under-ascertainment of appropriate imaging or of symptoms if ongoing symptoms were not documented on subsequent exams. In sum, 35% of women 18-29 with self-reported symptoms received diagnostic imaging that was not consistent with ACR recommendations. Departures from ACR guidelines may be due to unique clinical situations, non-receipt of a recommended exam, or other factors. Future research will investigate provider, patient, and health system factors that influence breast imaging patterns among women 18-39 and the impact of different imaging approaches on prognosis among young breast cancer patients. Sarah J. Nyante, Thad Benefield, Anisha P. Ganguly, Caroline A. Thompson, Sasha Anderson, Erin J. Aiello Bowles, Genevieve A. Woodard. Use of recommended diagnostic breast imaging among women under 40 in a community-based registry [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: The Rise in Early-Onset Cancers—Knowledge Gaps and Research Opportunities; 2025 Dec 10-13; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(23_Suppl):Abstract nr A026.

Ultrasound/MRI use by age and racial/ethnic group

PURPOSE:We examined clinician- and facility-level factors associated with selection of nonguideline chemotherapy at treatment initiation in women with stage I-IIIA breast cancer (BC). METHODS:The Optimal Breast Cancer Chemotherapy Dosing Study collected information on chemotherapy delivery in an integrated health care delivery system. This analysis included 9,758 women treated with chemotherapy for stage I-IIIA BC between 2006 and 2019 at Kaiser Permanente Northern California (KPNC). Prevalence ratios (PRs) and corresponding 95% CIs were estimated for the clinician and facility factors in relation to nonguideline regimen (NGR) use. Analyses were stratified by time (pre- and post-2015) to reflect the period before and after KPNC's transition to a subspecialized care model. Secondary outcomes focused on nonguideline drug combinations (NGDCs) and nonguideline administration schedules (NGASs). RESULTS:Women treated by clinicians with substantially greater time since medical school (30+ years v <10 years since medical school) were more likely to receive NGR (PR, 1.38; 95% CI, 1.01 to 1.88; P trend = .01) with significant associations observed for both NGDC and NGAS. While not associated in the primary analysis, larger practice size (10+ oncologists) was associated with a lower likelihood of NGDC use compared with smaller practices (<5 oncologists; PR, 0.43; 95% CI, 0.26 to 0.70; P trend = .01). Time stratification revealed that, in the study's early years, clinician sex and years since medical school were associated with NGR use, but neither association remained post-2015. CONCLUSION:Clinician and facility characteristics significantly influenced the use of NGR in stage I-IIIA BC treatment. Notably, associations diminished over time, suggesting that health system changes in care delivery may enhance guideline adherence and reduce the impact of nonclinical factors on treatment decisions.