Importance:Optimizing treatment decisions in metastatic breast cancer (MBC) can alleviate patients' burden and improve quality of life. Whether 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) can be used to better estimate outcomes is unknown. Objective:To evaluate clinical utility of early metabolic change on FDG-PET for improving outcome estimation compared with standard diagnostic evaluation in patients with newly diagnosed MBC. Design, Setting, and Participants:The multicenter IMPACT-MBC clinical cohort trial enrolled patients with nonrapidly progressive, newly diagnosed MBC from August 2013 to May 2018, before initiation of first-line systemic therapy. Baseline assessment included metastasis biopsy procedure and FDG-PET and CT imaging. Early FDG-PET was performed after 2 weeks of treatment, and CT response evaluation after 8 weeks. Clinical utility was defined as the ability of early FDG-PET to estimate progressive disease (PD) on CT, progression-free survival (PFS), and overall survival (OS). Data were analyzed from October 19, 2025, to February 13, 2026. Intervention:Early FDG-PET or standard-of-care (SOC) biopsy-based treatment. Main Outcomes and Measures:Clinical utility of molecular imaging to improve outcome estimation of standard diagnostics defined as the capacity to identify poor patient outcomes. Measures were PD at 8 weeks, PFS, and OS. Results:The analysis included 200 patients (median [range] age, 61 [32-84] years; 198 females [99%] and 2 males [1%]). Non-PD on early FDG-PET had a negative predictive value (NPV) of 94.7% (95% CI, 89.5%-97.4%) for non-PD on 8-week CT. This was similar in all MBC subtypes and bone-only disease. Patients with SOC treatment and non-PD on early FDG-PET (n = 133) had a median PFS of 19.4 (95% CI, 15.2-22.8) months and OS of 39.4 (95% CI, 33.7-48.3) months compared to 4.1 (95% CI, 3.3-15.5) months and 18.5 (95% 3 CI, 7.0-33.0) months, respectively (P < .001 for both). Patients with non-PD on 8-week CT but with PD on early FDG-PET had a median (IQR) PFS and OS of 9.5 (4.1-18.1) and 19.4 (8.7-33.0) months compared to 22.3 (15.3-96.1) months and 40.1 (23.4-72.7) months without PD. Conclusions and Relevance:In this clinical cohort trial of patients with nonrapidly progressive, newly diagnosed MBC before initiation of first-line systemic therapy, early FDG-PET after only 2 weeks of treatment identified patients with MBC with distinct long-term outcomes. Incorporating early FDG-PET can improve outcome estimation of standard CT assessment. Trial Registration:ClinicalTrials.gov Identifier: NCT01957332.

Background/Objectives: Outcome prediction in patients with estrogen (ER)-positive metastatic breast cancer (MBC) remains challenging. We investigated whether circulating tumor cell (CTC) count adds prognostic value in ER-positive MBC using immunohistochemical (IHC) or 16α-[18F]-fluoro-17β-estradiol (FES)-PET imaging. Methods: Patients with newly diagnosed non-rapidly progressive MBC receiving first-line endocrine monotherapy, with ER-positive IHC (biopsy) or FES-PET and available CTC count, were included. Associations of CTC count and CTC-ER status based on ESR1 mRNA expression with progression-free survival (PFS) and overall survival (OS) were analyzed, and the added prognostic value of CTC count (<5 vs. ≥5/7.5 mL) beyond a positive ER result was assessed. Results: In patients with ER-positive IHC (n = 98) or FES-PET (n = 99) out of 106 endocrine-treated patients, ≥5 CTCs were associated with shorter PFS (HR 1.86; p = 0.0047 and 1.75; p = 0.011) and OS (HR 3.19 and 3.22; both p < 0.01), respectively, compared with <5 CTCs. Adding CTC count to ER-positive IHC or FES-PET improved prognostic accuracy for PFS (p = 0.006 and 0.012) and OS (both p < 0.001). CTC-ER status (ESR1 RNA) was not associated with outcomes. Conclusions: CTC count adds prognostic value to PET- or biopsy-based ER analysis in endocrine-treated MBC.

Importance Optimizing treatment decisions in metastatic breast cancer (MBC) can alleviate patients’ burden and improve quality of life. Whether 18 F-fluorodeoxyglucose positron emission tomography (FDG-PET) can be used to better estimate outcomes is unknown. Objective To evaluate clinical utility of early metabolic change on FDG-PET for improving outcome estimation compared with standard diagnostic evaluation in patients with newly diagnosed MBC. Design, Setting, and Participants The multicenter IMPACT-MBC clinical cohort trial enrolled patients with nonrapidly progressive, newly diagnosed MBC from August 2013 to May 2018, before initiation of first-line systemic therapy. Baseline assessment included metastasis biopsy procedure and FDG-PET and CT imaging. Early FDG-PET was performed after 2 weeks of treatment, and CT response evaluation after 8 weeks. Clinical utility was defined as the ability of early FDG-PET to estimate progressive disease (PD) on CT, progression-free survival (PFS), and overall survival (OS). Data were analyzed from October 19, 2025, to February 13, 2026. Intervention Early FDG-PET or standard-of-care (SOC) biopsy-based treatment. Main Outcomes and Measures Clinical utility of molecular imaging to improve outcome estimation of standard diagnostics defined as the capacity to identify poor patient outcomes. Measures were PD at 8 weeks, PFS, and OS. Results The analysis included 200 patients (median [range] age, 61 [32-84] years; 198 females [99%] and 2 males [1%]). Non-PD on early FDG-PET had a negative predictive value (NPV) of 94.7% (95% CI, 89.5%-97.4%) for non-PD on 8-week CT. This was similar in all MBC subtypes and bone-only disease. Patients with SOC treatment and non-PD on early FDG-PET (n = 133) had a median PFS of 19.4 (95% CI, 15.2-22.8) months and OS of 39.4 (95% CI, 33.7-48.3) months compared to 4.1 (95% CI, 3.3-15.5) months and 18.5 (95% 3 CI, 7.0-33.0) months, respectively ( P < .001 for both). Patients with non-PD on 8-week CT but with PD on early FDG-PET had a median (IQR) PFS and OS of 9.5 (4.1-18.1) and 19.4 (8.7-33.0) months compared to 22.3 (15.3-96.1) months and 40.1 (23.4-72.7) months without PD. Conclusions and Relevance In this clinical cohort trial of patients with nonrapidly progressive, newly diagnosed MBC before initiation of first-line systemic therapy, early FDG-PET after only 2 weeks of treatment identified patients with MBC with distinct long-term outcomes. Incorporating early FDG-PET can improve outcome estimation of standard CT assessment. Trial Registration ClinicalTrials.gov Identifier: NCT01957332

Score chart with predicted probability (%) to remain on WW at 12 months This model was based on the number of IMDC Risk factors (0, 1, 2), the number or involved organ sites (0 - 4) and the geometric mean [¹⁸F]FDG SUVmax as a continuous variable. The underlying formula is 100*(exp(-0.531)^exp(0.198*[IMDC score] + 0.039*[No of affected organ sites] + 0.170*[geometric mean [¹⁸F]FDG SUVmax] - 1.09))

Flow-chart patients according to RECIST-defined PD. *All patients had clinical disease progression; no CT-imaging was performed before initiation of systemic treatment ** In total 7 patients choose best supportive care. Three other patients underwent radiotherapy or surgery of all target lesions.

Flow diagram of patient enrolment. * Four patients were unfit for systemic treatment due to clinical deterioration resulting from rapid disease progression (n=3) or comorbidity and age (n=1). Three other patients did not wat systemic treatment.

Breast cancer responds heterogeneously to treatment. This study evaluated the efficacy of image registration-based lesion tracking for assessing lesion-wise response in metastatic breast cancer (MBC). [18F]FDG PET/CT images from 15 patients with MBC from the multi-center IMPACT-MBC study were analyzed. Manual segmentation identified 644 lesions in baseline scans and 804 lesions in 2-week post-treatment scans. A deformable image registration method, validated for whole-body PET/CT scans of patients with cancer, was applied. Lesion tracking was performed using spatial overlap resulting from within-subject image registration, yielding a precision of 0.93 ± 0.07, a sensitivity of 0.87 ± 0.17, and an F1 score of 0.89 ± 0.10. Performance was consistent across lesion sites and lesion count-based disease burden. Sensitivity decreased for lesions under 1 mL. Image registration direction did not affect results. Between-subject registration enabled quantitative visualization and analysis of metabolic response patterns in bone lesions across the cohort. Results demonstrate the potential for automated, accurate lesion-wise response assessment, which may improve treatment monitoring in MBC.

1019 Background: Optimizing patient outcome prediction in metastatic breast cancer (MBC) can potentially reduce patients’ and healthcare burden. Molecular imaging to visualize early metabolic change, baseline whole-body human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER) expression might achieve this. In the prospective multicenter IMPACT study, we evaluated the clinical utility of molecular imaging to improve standard diagnostics in patients with newly diagnosed MBC of all subtypes. Methods: Patients underwent extensive workup, including baseline metastasis biopsy, [18F]FDG-PET, [89Zr]trastuzumab-PET (HER2-PET), [18F]FES-PET, and early [18F]FDG-PET after 2 weeks. Treatment was based on HER2 or ER subtype determined in biopsy (immunohistochemistry, IHC; standard-of-care) or PET findings (HER2- and [18F]FES-PET; investigational) in case of negative biopsy but positive HER2 and/or [18F]FES-PET scan. Clinical utility of molecular imaging was defined as the capacity to identify poor patient outcome, measured as progressive disease (PD) on CT at 8 weeks, progression-free survival (PFS), and overall survival (OS). Results: Two hundred patients were included. Progression on early [18F]FDG-PET was related to poor outcome in all subtypes (median PFS 4.1 versus 19.4 months, OS 19.4 versus 45.0 months). Early [18F]FDG-PET correctly predicted non-PD on 8 week CT (specificity 90.5%, negative predictive value 94.1%), but sensitivity and positive predictive value for PD was low (50 and 37.5%, respectively). However, early [18F]FDG-PET related better to long-term outcome than CT: patients with non-PD on 8 week CT, but with progression on early [18F]FDG-PET, had a median PFS and OS of 9.5 and 22.3 months respectively, compared to 19.4 and 50.1 months without [18F]FDG-PET progression (PFS HR 1.76 (95%CI 1.0 – 2.9), OS HR 1.93 (1.0 – 3.5)). HER2 or ER subtype was discrepant between biopsy and PET in 52 out of 200 (26%) patients, yielding investigational PET-based treatment options in 41 (21%) patients. In patients with HER2-positive biopsy IHC disease who received standard HER2-targeting treatment, median PFS with positive- versus negative HER2-PET was 23.2 and 4.5 months, respectively. In patients with biopsy IHC HER2-negative disease but positive HER2-PET, median PFS was with investigational HER2-targeted treatment 11.4 months, without 7.4 months. The pattern was similar in ER-positive disease, although less pronounced for biopsy- and PET-based subtypes. Conclusions: This study supports the clinical utility of molecular imaging with [18F]FDG-PET, HER2-PET, and [18F]FES-PET, to improve standard diagnostics for outcome and subtype assessment in patients with newly diagnosed MBC. Clinical trial information: NCT01957332 .

Understanding which patients with human epidermal growth factor receptor 2 (HER2)-negative or -low metastatic breast cancer (MBC) benefit from HER2-targeted strategies is urgently needed. We assessed the whole-body heterogeneity of HER2 expression on 89Zr-trastuzumab PET (HER2 PET) and the diagnostic performance of HER2 PET in a large series of patients, including HER2-negative and -low MBC. Methods: In the IMPACT-MBC study, patients with newly diagnosed and nonrapidly progressive MBC of all subtypes were included. Metastasis HER2 status was determined by immunohistochemistry and in situ hybridization.89Zr-trastuzumab uptake was quantified as SUVmax and SUVmean HER2 immunohistochemistry was related to the quantitative 89Zr-trastuzumab uptake of all metastases and corresponding biopsied metastasis, uptake heterogeneity, and qualitative scan evaluation. A prediction algorithm for HER2 immunohistochemistry positivity based on uptake was developed. Results: In 200 patients, 89Zr-trastuzumab uptake was quantified in 5,163 metastases, including 186 biopsied metastases. With increasing HER2 immunohistochemistry status, uptake was higher (geometric mean SUVmax of 7.0, 7.6, 7.3, and 17.4 for a HER2 immunohistochemistry score of 0, 1, 2, or 3+, respectively; P < 0.001). High uptake exceeding 14.6 (90th percentile) was observed in one third of patients with a HER2-negative or -low metastasis biopsy. The algorithm performed best when lesion site and size were incorporated (area under the curve, 0.86; 95% CI, 0.79-0.93). Conclusion: HER2 PET had good diagnostic performance in MBC, showing considerable whole-body HER2 heterogeneity and uptake above background in HER2-negative and -low MBC. This provides novel insights into HER2-negative and -low MBC compared with standard HER2 immunohistochemistry on a single biopsy.

Background: In metastatic breast cancer (MBC), [18F]fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG-PET/CT) can be used for staging. We evaluated the correlation between BC histopathological characteristics and [18F]FDG uptake in corresponding metastases. Patients and Methods: Patients with non-rapidly progressive MBC of all subtypes prospectively underwent a baseline histological metastasis biopsy and [18F]FDG-PET. Biopsies were assessed for estrogen, progesterone, and human epidermal growth factor receptor 2 (ER, PR, HER2); Ki-67; and histological subtype. [18F]FDG uptake was expressed as maximum standardized uptake value (SUVmax) and results were expressed as geometric means. Results: Of 200 patients, 188 had evaluable metastasis biopsies, and 182 of these contained tumor. HER2 positivity and Ki-67 ≥ 20% were correlated with higher [18F]FDG uptake (estimated geometric mean SUVmax 10.0 and 8.8, respectively; p = 0.0064 and p = 0.014). [18F]FDG uptake was lowest in ER-positive/HER2-negative BC and highest in HER2-positive BC (geometric mean SUVmax 6.8 and 10.0, respectively; p = 0.0058). Although [18F]FDG uptake was lower in invasive lobular carcinoma (n = 31) than invasive carcinoma NST (n = 146) (estimated geometric mean SUVmax 5.8 versus 7.8; p = 0.014), the metastasis detection rate was similar. Conclusions: [18F]FDG-PET is a powerful tool to detect metastases, including invasive lobular carcinoma. Although BC histopathological characteristics are related to [18F]FDG uptake, [18F]FDG-PET and biopsy remain complementary in MBC staging (NCT01957332).

Abstract Background: Anti-HER2 antibody drug conjugates (ADCs) can assert an effect in part of patients with HER2-low breast cancer. In light of patient burden and financial sustainability, biomarkers to select responding patients are urgently needed, but so far, none have been identified. In the IMPACT trial (NCT01957332), patients with newly diagnosed and non-rapidly progressive metastatic breast cancer (MBC) of all subtypes (including HER2-negative, -low, and –positive disease) were included. We assessed the performance of Zirconium-89 (89Zr)-trastuzumab positron emission tomography (HER2-PET) in HER2-low and negative MBC. Methods: All patients received extensive workup, including a metastasis biopsy and HER2-PET at baseline. HER2 status was determined by immunohistochemistry (IHC) and in situ hybridization. ⁸⁹Zr-trastuzumab uptake was quantified as maximum and mean standardized uptake values (SUVmax, SUVmean) in metastases and healthy background tissue. Quantitative ⁸⁹Zr-trastuzumab uptake of all metastases and corresponding biopsied metastasis, was related to HER2 IHC status. Results: In 200 patients, ⁸⁹Zr-trastuzumab uptake was quantified in 5,163 metastases. With increasing HER2 IHC status, uptake was higher (geometric mean SUVmax 7.0, 7.6, 7.3, and 17.4 with HER2 IHC 0, 1, 2, or 3+, in respectively 71, 71, 20, and 24 biopsied metastases (P  0.001 between IHC 0 and 3+). SUVmax in lesions was heterogeneous within and between patients for all HER2 IHC groups. All HER2 IHC groups, also HER2-negative and -low, had uptake exceeding that of the healthy background (geometric mean tumor-to-background ratio SUVmax >1 in all groups, increasing with higher HER2 IHC). Of patients with a HER2 IHC 0 biopsy, 27.8% had at least one metastasis elsewhere in the body, with uptake exceeding the overall 90th SUVmax percentile of 14.6; in HER2 low IHC1+ and 2+, this was 31.9% and 30%. Conclusions: In this largest series with HER2-PET in patients with MBC, we show that ±30% of patients with HER2-low or -negative IHC in the biopsy, in fact, have metastases with high HER2 uptake elsewhere in the body. This spatial heterogeneity provides novel insights into HER2-negative and -low disease compared to standard HER2 IHC of a single biopsy. As HER2-PET uptake is related to ADC response in HER2 positive MBC1, HER2-PET is a potential biomarker for anti-HER2 ADC effect in HER2-low and -negative MBC as well. Reference: 1. Gebhart G, et al. Ann Oncol 2016;27(4): 619-624. Supported by the Dutch Cancer Society grant 2012-5565 Citation Format: Carolien Schroder, Jasper van Geel, Bertha Eisses, Adrienne Brouwers, Sjoerd Elias, Frederike Bensch, Evelien Kuip, Agnes Jager, Andor Glaudemans, Bert van der Vegt, Willemien Menke-van der Houven van Oordt, Elisabeth de Vries. Spatial HER2 heterogeneity on HER2-PET in HER2-low and negative disease: potential biomarker for antibody-drug conjugate effect [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-13-03.

Abstract Purpose: Watchful waiting (WW) can be considered for patients with metastatic clear-cell renal cell carcinoma (mccRCC) with good or intermediate prognosis, especially those with <2 International Metastatic RCC Database Consortium criteria and ≤2 metastatic sites [referred to as watch and wait (“W&W”) criteria]. The IMaging PAtients for Cancer drug SelecTion-Renal Cell Carcinoma study objective was to assess the predictive value of [18F]FDG PET/CT and [89Zr]Zr-DFO-girentuximab PET/CT for WW duration in patients with mccRCC. Experimental Design: Between February 2015 and March 2018, 48 patients were enrolled, including 40 evaluable patients with good (n = 14) and intermediate (n = 26) prognosis. Baseline contrast-enhanced CT, [18F]FDG and [89Zr]Zr-DFO-girentuximab PET/CT were performed. Primary endpoint was the time to disease progression warranting systemic treatment. Maximum standardized uptake values (SUVmax) were measured using lesions on CT images coregistered to PET/CT. High and low uptake groups were defined on the basis of median geometric mean SUVmax of RECIST-measurable lesions across patients. Results: The median WW time was 16.1 months [95% confidence interval (CI): 9.0–31.7]. The median WW period was shorter in patients with high [18F]FDG tumor uptake than those with low uptake (9.0 vs. 36.2 months; HR, 5.6; 95% CI: 2.4–14.7; P < 0.001). Patients with high [89Zr]Zr-DFO-girentuximab tumor uptake had a median WW period of 9.3 versus 21.3 months with low uptake (HR, 1.7; 95% CI: 0.9–3.3; P = 0.13). Patients with “W&W criteria” had a longer median WW period of 21.3 compared with patients without: 9.3 months (HR, 1.9; 95% CI: 0.9–3.9; Pone-sided = 0.034). Adding [18F]FDG uptake to the “W&W criteria” improved the prediction of WW duration (P < 0.001); whereas [89Zr]Zr-DFO-girentuximab did not (P = 0.53). Conclusions: In patients with good- or intermediate-risk mccRCC, low [18F]FDG uptake is associated with prolonged WW. This study shows the predictive value of the “W&W criteria” for WW duration and shows the potential of [18F]FDG-PET/CT to further improve this.

Development of new oncology drugs has increased since the improved understanding of cancer's complex biology. The oncology field has become the top therapeutic research area for new drugs. However, only a limited number of drugs entering clinical trials will be approved for use as the standard of care for cancer patients. Molecular imaging is increasingly perceived as a tool to support go/no-go decisions early during drug development. It encompasses a wide range of techniques that include radiolabeling a compound of interest followed by visualization with SPECT or PET. Radiolabeling can be performed using a variety of radionuclides, which are preferably matched to the compound on the basis of size and half-life. Imaging can provide information on drug behavior in vivo, whole-body drug target visualization, and heterogeneity in drug target expression. This review focuses on current applications of molecular imaging in the development of small molecules, antibodies, and antihormonal anticancer drugs.

Medical students at the UMCG are introduced to the basicprinciples of medical research during the 3-year bachelor’speriod. These experiences increase awareness of the impor-tanceofresearchandgivethemthecompetencytoexploretheliterature and to find the gaps and limits of health science. Inthe3-yearmaster’speriod,studentspracticetheseskillsduringa research clerkship of 26 weeks. Many opportunities are of-fered locally, but students can also choose to go abroad.Personally, I wanted to go to a famous oncology researchcenter in the world, because I want to pursue a career in on-cology. I was lucky to find a supervisor who knew about TheUniversity of Texas MD Anderson Cancer Center, and I wasimmediately enthusiastic. A great advantage to Texas washaving a family member living close to Houston. InMarch 2014, I had the first encounter with my supervisor atUMCGandsoonafterthatIcontactedmysupervisorinHous-ton. In June, I started writing my proposal and organizing therequireddocuments and could start my electivein November.Planning a research project abroad is not easy. You needsponsorship letters from your university and from yoursponsoring supervisor abroad for obtaining a visa fromthe consulate. I had to create an online profile on theMD Andersonwebsiteforuploadingtherequireddocuments.And besides that, you need letters to apply for funding.Every student has to select a research topic, review liter-ature, generate data, and interpret research findings. Howev-er, in doing a research project abroad, you have to deal witha lot more. For example, you need to find a place to stayshort-term, to learn about other cultures, and sometimes tospeak a foreign language, which is not always easy, espe-cially in presenting research. Also, you need to navigatepublic transport or buy a car. I decided to travel by bicycle,which was uncommon in Houston. Finally, if you haveproblems, your friends and family are not easily availableto you for support.Iexperiencedmanybenefitsfrommyinternationalresearchexperience at MD Anderson: attending lectures given by fac-ulty from a top international institution and invited scientificleaders from elsewhere, being exposed to research methodsfrom an international context, practicing how to work in aforeign language, improving my social skills, expanding mycultural awareness, growing my professional network, andlearning how to cope with unexpected situations (e.g., orga-nizing visa documents). I learned how cancer registries work,howtheirlimitationsandbenefitsinfluencetheresearchques-tions asked, how to analyze data, including how to manageoutliers and small numbers, and how to analyze and presentresearchoutcomes. Ofcourse, addingthis uniqueopportunityto my CV was a highlight.I was fortunate to have ideal supervisors. They were avail-ableanytime,includingafter5p.m.,whichhelpswhentimeisshort.Theyunderstoodandrespectedmypositionasastudentand knew the extent of their responsibilities to help me withmy clerkship research project. Having knowledgeable super-visors is critical to a successful traineeship, in that they have