BackgroundOvarian carcinosarcoma (OCS), also known as malignant mixed Müllerian tumor, is a rare and highly aggressive subtype of epithelial ovarian cancer, accounting for less than 4% of all cases. It typically presents at advanced stages and is associated with dismal outcomes, with a five-year survival rate below 30%. Despite improvements in cytoreductive surgery and systemic therapies, long-term survival in stage IV disease remains exceedingly uncommon.Case presentationWe report two exceptional cases of stage IVB Müllerian carcinosarcoma occurring in BRCA wild-type postmenopausal women who achieved prolonged complete remission exceeding five years after multimodal management. The first patient, aged 61, presented with bilateral adnexal masses and a solitary pulmonary metastasis. She underwent primary cytoreductive surgery including hysterectomy, bilateral adnexectomy, lymphadenectomy, appendicectomy, and omentectomy, followed by six cycles of platinum-taxane chemotherapy. Residual pulmonary disease was later removed via video-assisted thoracoscopic lobectomy, confirming metastatic OCS. Post-recurrence, she received off-label maintenance with tamoxifen 20 mg daily for five years and remains disease-free at 70 months. The second patient, aged 70, presented with a pelvic mass invading the recto-sigmoid wall and a synchronous hepatic metastasis. She underwent extensive cytoreductive surgery including hysterectomy, en-bloc rectal resection, lymphadenectomy, cholecystectomy, and liver wedge resection, achieving complete macroscopic cytoreduction. Histology confirmed a Müllerian carcinosarcoma with a predominant endometrioid component. Postoperative chemotherapy with carboplatin-paclitaxel was followed by maintenance niraparib 100 mg twice daily for three years. She remains in complete remission at 60 months.DiscussionBoth patients demonstrate durable disease control in the absence of germline or somatic BRCA mutations, suggesting that long-term remission may be achievable even in BRCA-wild-type OCS through optimal surgery and individualized maintenance approaches. Tamoxifen, rarely employed in this setting, may have provided estrogen-receptor-mediated tumor suppression in the first case, while the second case highlights potential activity of PARP inhibition beyond BRCA mutation carriers.ConclusionThese two reports challenge the long-held perception of uniformly poor outcomes in metastatic ovarian carcinosarcoma. Complete cytoreductive surgery combined with tailored systemic and maintenance therapies can achieve sustained remission even in advanced-stage BRCA-wild-type patients. Broader molecular profiling and international collaboration are essential to refine management strategies for this rare and aggressive malignancy.

Triple negative breast cancer (TNBC) is historically defined as oestrogen receptor (ER) < 1% and HER2-negative. Increasing evidence supports that ER-low breast cancer (BC) (ER 1-10%) shares similar clinical behaviour and biology with classic TNBC. However, how ER cut-off definitions have been applied as eligibility criteria in clinical trials for TNBC over time remains unclear. In August 2024, the Clinicaltrials.gov database was systematically queried using the following string: "breast cancer" AND "interventional studies" AND "phase II-III-not applicable". We included trials started from January, 1, 2010 to August, 7, 2024 restricted to TNBC, using either ER<1% or any other ER cut-off up to 10%. Differences across study descriptors were assessed using Mann-Whitney U and χ2 tests. A total of 6747 studies were retrieved. Of 620 eligible trials, 474 (76.5%) restricted the inclusion to TNBC and 146 (23.5%) included ER-low tumours. The percentage of trials allowing ER-low was lower for phase III versus phase I and phase II (16.8%, 17.5%, and 27.2%, respectively; p = 0.018); in industry versus investigator-driven studies (11.6% vs 29.1%, p < 0.001), and in metastatic versus early-stage settings (18.0% vs 33.5%, p < 0.001). ER-low inclusion increased over time, particularly in investigator-driven trials (since 2015), while remaining limited in industry-sponsored studies. We evaluated the ER cut-off adopted in trials testing therapies for TNBC. Although more inclusive criteria have been applied in recent years, patients with ER-low disease remain largely excluded from registrational trials, particularly in the metastatic setting, potentially limiting access to effective therapies. Broadening inclusion criteria could improve treatment opportunities for this high-risk population.

BRCA1/2 pathogenic variants (PVs) may influence metastatic dissemination in breast cancer (BC), but existing data are often confounded by differences in subtype distribution among carriers. We assessed associations between germline BRCA1/2 status and metastatic sites in HER2-negative BC. Patients treated for HER2-negative metastatic BC (2007–2025) with known BRCA1/2 mutation status were identified. Metastatic sites at diagnosis and throughout the disease history were collected. CNS involvement included brain metastases and/or leptomeningeal involvement. Among 184 patients (33 BRCA1, 28 BRCA2, 123 noncarriers), 131 presented a HR + BC and 53 a triple negative BC (TNBC). In HR + BC, BRCA1/2 carriers presented less frequently bone metastases at first metastatic diagnosis (31.4

BACKGROUND:Tumors with ≥1% estrogen receptor (ER) expression by immunohistochemistry (IHC) are classified as hormone receptor-positive. While this definition includes ER-low tumors (ER 1-9%), the clinical benefit of endocrine therapy (ET) in ER-low early-stage breast cancer (BC) remains uncertain. METHODS:This is a systematic review and meta-analysis of studies in early-stage ER-positive, HER2-negative BC reporting (i) ET efficacy within ER-low tumors and/or (ii) outcomes comparing ER-low versus ER-rich disease. Ovid MEDLINE, Embase, and conference abstracts were searched through January 2025. Endpoints were disease-free survival (DFS) and overall survival (OS). Random-effects meta-analyses were performed to derive pooled hazard ratios (HRs) with 95% confidence intervals (95% CI). Heterogeneity was assessed with the I² statistic. RESULTS:Of 8,982 records screened, 17 studies were included, comprising 10,232 patients with ER-low tumors and 58,662 with ER-rich disease. Among the ER-low group, receipt of ET was associated with a reduction of 33% in the risk of relapse or death (HR 0.67, 95% CI 0.54-0.85, I²=0%) and of 22% in the risk of death (HR 0.78, 95% CI 0.68-0.90; I²=19.2%). Compared with ER-rich disease, ER-low tumors had inferior outcomes for both DFS (HR 2.18, 95% CI 1.58-3.00; I²=78%) and OS (HR 2.08, 95% CI 1.30-3.31; I²=95.8%). CONCLUSIONS:In patients with ER-low tumors, ET use was associated with improved outcomes. These findings support consideration of ET in early-stage ER-low disease and the inclusion of these patients in trials evaluating novel ET-based therapies, alongside therapeutic approaches appropriate to their higher baseline risk of relapse.

1010 Background: Circadian rhythms regulate immune functions, and morning (AM) administration of immunotherapy (IO) is associated with survival in several solid tumors. However, whether time-of-day (ToDa) of IO delivery influences outcomes in early-stage triple-negative breast cancer (TNBC), and whether this effect depends on immune biomarkers, remains unknown. Methods: A-BRAVE randomized patients with high-risk early-stage TNBC to 1 year of adjuvant avelumab or observation. Infusion time of avelumab was retrieved from eCRF. AM-rate was calculated for each patient as the proportion of the first 4 infusions occurring before 12:30 PM (cohort median ToDa) and patients categorized as AM-dominant (AM-rate ≥50%) or PM-dominant. Tumor-infiltrating lymphocytes (TILs) and PD-L1 (Dako 73-10) were centrally assessed on treatment-naive tumor samples. We analyzed distant disease-free survival (DDFS) and overall survival (OS) by adjusted Cox models. Results: ToDa data were available for 221 avelumab-treated patients (94.0%); TILs and PD-L1 were evaluable in 188 (85%) and 195 (88%) of these, respectively. AM-rate was not associated with outcomes. However, ToDa effects were strongly immune-dependent. Increasing AM-rate was associated with improved DDFS and OS in immune-hot tumors (TILs [≥20%] or PD-L1 [≥21] high), but with worse outcomes in immune-cold tumors (TILs or PD-L1 low) (AM-rate*TILs interaction: DDFS p=0.008, OS p=0.001; AM-rate*PD-L1 interaction: DDFS p=0.030, OS p=0.039). These findings were concordant using AM-dominant vs. PM-dominant categorization (Table). Patients receiving immune-aligned treatment (immune-hot/AM-dominant OR immune-cold/PM-dominant) had superior survival compared with immune-misaligned (immune-hot/PM-dominant OR immune-cold/AM-dominant) and the observational arm (TILs-based: 3-year OS 95.7% vs 75.2% vs 78.0%; p<0.001; PD-L1-based: 3-year OS 93.4% vs 79.4% vs 76.1; p=0.035). Conclusions: In early-stage TNBC, time of IO administration may be a driver of efficacy, with opposing effects according to baseline immune milieu. Immune-informed circadian alignment may represent a previously unrecognized determinant of IO efficacy in TNBC. Clinical trial information: NCT02926196 . Outcome AM-dominant3-yr Rate % (95% CI) PM-dominant3-yr Rate % (95% CI) Log-rank p AM vs PM dominant HR (95% CI) TILs High DDFS 90.1 (81.3–99.8) 72.0 (56.4–91.9) 0.064 0.39 (0.13–1.21) OS 97.5 (92.8–100) 76.0 (61.0–94.7) 0.019 0.35 (0.10–1.20) TILs Low DDFS 63.1 (52.6–75.7) 84.7 (75.5–95.1) 0.003 2.61 (1.23–5.55) OS 74.9 (65.2–86.0) 94.3 (88.3–100) 0.003 3.84 (1.30–11.29) PD-L1 high DDFS 100 (100–100) 61.5 (40.0–94.6) 0.015 0.11 (0.01–0.94) OS 100 (100–100) 76.9 (57.1–100) 0.008 0.11 (0.01–1.03) PD-L1 low DDFS 66.4 (57.3–77.0) 83.0 (74.7–92.2) 0.026 1.82 (1.00–3.31) OS 79.8 (71.9–88.6) 91.5 (85.3–98.2) 0.025 2.05 (0.95–4.43)

Pathologic complete response after neoadjuvant treatment is considered a surrogate of cure in triple-negative breast cancer, yet around 10% of patients still relapse. Whether baseline stromal tumor-infiltrating lymphocytes can stratify this residual risk is unknown. Here, we report on GAMBIT, a multicentric real-world retrospective study of 2457 patients with triple-negative breast cancer or estrogen receptor-low disease, HER2-negative, of whom 1192 obtained a pathological complete response and 690 have evaluable tumor infiltrating lymphocytes. Among patients with pathological complete response, clinical nodal status and tumor infiltrating lymphocytes are independently prognostic and patients with clinical node-positive/low-tumor infiltrating lymphocytes tumors experience substantially worse outcomes, with five-year distant relapse-free survival of 83.4% and overall survival of 85.8%. In this high-risk subgroup, five-year cumulative incidence of central nervous system reaches 7.5%, including 6.9% presenting as isolated central nervous system relapse. In this work, we identify a high-risk subgroup despite pathologic complete response and provide a framework supporting risk-adapted trial design incorporating central nervous system-directed strategies.

Background Outcomes and characteristics of endocrine-resistant, PIK3CA-mutated HR+/HER2- advanced breast cancer patients in real-world are poorly investigated.Here, we explored the role of circulating PIK3CA mutations in endocrine-resistant patients in the ongoing prospective, multicentric CHAMBER study. Methods PIK3CA was analyzed by NGS panel covering the full exonic region of PIK3CA gene.Endocrine resistance was defined as: i) primary: relapse during the first 2 years of adjuvant ET, or ii) secondary: relapse after 2 years of starting or within 1 year of completing ET.Overall survival (OS) was calculated from the start of first-line to death from any cause. Progression free survival 1 (PFS1) was calculated from the start of first-line to progression or death. Results Among the overall CHAMBER population, 22% patients met the criteria for endocrine-resistance (74/337).The study population consisted in 95% women and 5% men; median age at diagnosis was 50 years (IQR 44-63); 75% of the women was postmenopausal;86% of the total population presented with a secondary endocrine-resistance, 64% had visceral relapse, 74% had less than 3 metastatic sites, 79% had received first-line CDK4/6 inhibitor.PIK3CA status was available for 63/74 pts, with a 29% prevalence of mutation.PIK3CAmut was a negative prognostic factor for OS (median 65 [wt] vs 36 months [mut], log-rank p 0.024 HR 2.61 [95% CI 1.10-6.22]) and PFS1 (median 22 [wt] vs 10 months [mut], log-rank p 0.012, HR 2.24 [95% CI 1.18-4.26]). Conclusion The co-occurrence of endocrine-resistance and PIK3CAmut identifies a population with unfavorable prognosis, reinforcing the rationale of escalated therapies.

Importance For patients with early ERBB2 (formerly HER2 )–positive breast cancer, there is a need to identify biomarkers to guide treatment de-escalation. Objective To evaluate the association of tumor-infiltrating lymphocytes (TILs) with distant disease-free (DDFS) and overall survival (OS) for patients with ERBB2 -positive early breast cancer. Design, Setting, and Participants The ShortHER randomized clinical trial was a multicentric trial in Italy that enrolled patients with ERBB2 -positive breast cancer from December 2007 to October 2013. Patients received 9 weeks or 1 year of adjuvant trastuzumab combined with chemotherapy. Tumor samples were evaluated for TILs. Herein, patients were evaluated at a median follow-up of 9 years, and data were analyzed from February 2023 to August 2024. Intervention Four cycles of anthracycline-based chemotherapy followed by 4 courses of taxanes combined with trastuzumab for 1 year (long arm) or 3 courses of taxanes combined with trastuzumab for 9 weeks followed by reduced-dose anthracycline-based chemotherapy for 3 courses (short arm). Main Outcomes and Measures The association of TILs with DDFS and OS was assessed with Cox models. Results Of 1253 patients enrolled in the ShortHER trial, 866 women (median [IQR] age, 56 [48-64] years) had evaluable TILs. In Cox models with relevant factors, each 5% TIL increment was associated with improved DDFS (hazard ratio [HR], 0.87; 95% CI, 0.80-0.95; P = .001) and OS (HR, 0.89; 95% CI, 0.81-0.98; P = .01). The 10-year OS rate was 91.3% for patients with TILs 20% or higher, 93.3% for patients with TILs 30% or higher, and 98.1% for patients with TILs 50% or higher, resulting higher vs lower TIL counterparts. Patients with TILs lower than 20% showed a better outcome with the long vs short treatment (10-year DDFS, 88.7% vs 81.0%), whereas patients with TILs 20% or higher showed the opposite (10-year DDFS, 87.1% vs 92.2%; P for interaction = .01). Similarly, patients with TILs 20% or higher had a 10-year OS rate of 89.3% in the long arm vs 93.1% in the short arm (HR, 0.36; 95% CI, 0.10-1.36); patients with TILs lower than 20% had a 10-year OS rate of 91.3% in the long arm vs 86.9% in the short arm (HR, 1.36; 95% CI, 0.82-2.23; P for interaction = .06). Conclusions and Relevance This follow-up analysis of the ShortHER randomized clinical trial is, to our knowledge, the first demonstration of an independent effect of TILs in terms of OS for patients with ERBB2 -positive early breast cancer treated with adjuvant chemotherapy and anti- ERBB2 therapy. Patients with TILs 20% or higher who de-escalated trastuzumab duration and chemotherapy dose were not exposed to an excess risk of distant relapse or death. Trial Registration EudraCT: 2007-004326-25

Evolution of PD-L1 status from primary BC to relapse according to phenotypic evolution from primary BC to metastases. Sankey plots showing the evolution of PD-L1 status from primary breast cancer to relapse, according to phenotypic evolution (stable triple-negative breast cancer, from ER+/HER2- to ER-low, and from ER+/HER2- to triple-negative breast cancer).

Supplementary Table 2 - Representativeness of Study Participants

Multivariate analysis for overall survival and post relapse survival in the retrospective cohort in patients with ER+/HER2- primary BC. Multivariable Cox proportional hazards analyses for overall survival and post-relapse survival in the retrospective cohort of patients with primary ER+/HER2- breast cancer; hazard ratios (HRs) with 95% confidence intervals and p-values are reported.

Workflow of the study. The flow diagram of the study shows an overview of the two cohorts and the analyses performed.

Supplementary Figure 2 – Association between baseline TILs and pCR in: 2a) the overall cohort and 2b) the cohort of patients receiving taxane-only neoadjuvant chemotherapy (plus anti-HER2 treatment).

Clinicopathological features according to ER expression in the TONIC trial cohort Clinicopathological features of patients in the TONIC trial cohort, reported according to ER expression status (ER-low vs ER-0).

Representativeness of Study Participants. Representativeness of study participants in the context of advanced breast cancer, with information on sex, age, race/ethnicity, geography, and overall comparability to the general patient population.

Supplementary Table 3 – Multivariate Cox analysis for disease-free survival (DFS) in patients with residual disease (RD) after surgery

Genes up-regulated or down-regulated in estrogen-receptor (ER)-low (ER 1-9%) vs ER-positive (>10%) by quantitative Significance Analysis of Microarrays (SAM) analysis List of genes significantly up- or down-regulated in tumors that switched from ER+/HER2– to ER-low (1–9%) compared with tumors maintaining a stable ER-positive (≥10%) phenotype, as identified by quantitative Significance Analysis of Microarrays (SAM).

Supplementary Figure 3 – Matched evaluation of baseline TIL (b-TILs) and residual (RD-TILs) in the overall RD cohort (Fig. 3a), the high RD-TILs cohort (Fig. 3b) and in the low RD-TILs cohort (Fig. 3c).

Importance For patients with early ERBB2 (formerly HER2)-positive breast cancer, there is a need to identify biomarkers to guide treatment de-escalation. Objective To evaluate the association of tumor-infiltrating lymphocytes (TILs) with distant disease-free (DDFS) and overall survival (OS) for patients with ERBB2-positive early breast cancer. Design, Setting, and Participants The ShortHER randomized clinical trial was a multicentric trial in Italy that enrolled patients with ERBB2-positive breast cancer from December 2007 to October 2013. Patients received 9 weeks or 1 year of adjuvant trastuzumab combined with chemotherapy. Tumor samples were evaluated for TILs. Herein, patients were evaluated at a median follow-up of 9 years, and data were analyzed from February 2023 to August 2024. Intervention Four cycles of anthracycline-based chemotherapy followed by 4 courses of taxanes combined with trastuzumab for 1 year (long arm) or 3 courses of taxanes combined with trastuzumab for 9 weeks followed by reduced-dose anthracycline-based chemotherapy for 3 courses (short arm). Main Outcomes and Measures The association of TILs with DDFS and OS was assessed with Cox models. Results Of 1253 patients enrolled in the ShortHER trial, 866 women (median [IQR] age, 56 [48-64] years) had evaluable TILs. In Cox models with relevant factors, each 5% TIL increment was associated with improved DDFS (hazard ratio [HR], 0.87; 95% CI, 0.80-0.95; P = .001) and OS (HR, 0.89; 95% CI, 0.81-0.98; P = .01). The 10-year OS rate was 91.3% for patients with TILs 20% or higher, 93.3% for patients with TILs 30% or higher, and 98.1% for patients with TILs 50% or higher, resulting higher vs lower TIL counterparts. Patients with TILs lower than 20% showed a better outcome with the long vs short treatment (10-year DDFS, 88.7% vs 81.0%), whereas patients with TILs 20% or higher showed the opposite (10-year DDFS, 87.1% vs 92.2%; P for interaction = .01). Similarly, patients with TILs 20% or higher had a 10-year OS rate of 89.3% in the long arm vs 93.1% in the short arm (HR, 0.36; 95% CI, 0.10-1.36); patients with TILs lower than 20% had a 10-year OS rate of 91.3% in the long arm vs 86.9% in the short arm (HR, 1.36; 95% CI, 0.82-2.23; P for interaction = .06). Conclusions and Relevance This follow-up analysis of the ShortHER randomized clinical trial is, to our knowledge, the first demonstration of an independent effect of TILs in terms of OS for patients with ERBB2-positive early breast cancer treated with adjuvant chemotherapy and anti-ERBB2 therapy. Patients with TILs 20% or higher who de-escalated trastuzumab duration and chemotherapy dose were not exposed to an excess risk of distant relapse or death. Trial Registration EudraCT: 2007-004326-25

Introduction: In patients with triple negative breast cancer (TNBC), achieving a pathological complete response (pCR) after neoadjuvant treatment (NAT) is associated with better survival. However, up to 10% of these patients relapse after surgery. Understanding the pattern and determinants of this failure is essential. This study aims to describe the pattern of relapse in patients with pCR after NAT and to compare it with the non-pCR counterpart. Methods: This retrospective, multicenter study included 898 patients with TNBC (estrogen-receptor <10%, HER2-negative) treated with NAT between 2001 and 2023 at nine European Institutions. We collected the type of first relapse-free survival (RFS) event (locoregional relapse, distant relapse, death without other event) and the site of metastasis for patients with distant relapse as the first event. The cumulative incidence of specific events was evaluated using competing risk analysis and compared between pCR (ypT0/is ypN0) and non-pCR cohorts. Results: The study population included 443 (49.3%) patients with pCR and 455 (50.7%) with non-pCR. Patients with pCR had less frequently stage III disease (22.1% vs 33.3%, p<0.001). Median TILs were higher in the pCR vs non-pCR group (median 15% [IQR 7-40] vs 10% [IQR 5-30], p<0.001). As part of NAT, most patients received anthracyclines (95.8%) and taxanes (89.2%), more patients in the pCR group received carboplatin (45.8% vs 38.0%, p=0.017) and immunotherapy (8.6% vs 5.1%, p=0.038). Adjuvant chemotherapy was more common in the non-pCR cohort (46.5% vs 6.3%, p<0.001). With a median follow up of 4.6 years (95%CI 4.3-4.9),171 events occurred: 30 in the pCR cohort and 141 in the non-pCR cohort. RFS was significantly longer for pCR vs non pCR (5-yr RFS 92.7% vs 67.2%, p<0.001). The cumulative incidence of distant metastasis in the overall population was 15.4% at 5 years, significantly lower in pCR vs non-pCR cohort: 4.1% vs 25.8%, p<0.001. The same was observed for distant metastasis involving visceral site as first event: 5-yr cumulative incidence was 10.6% in the overall population, 3.6% in pCR vs 17.1% in non-pCR cohorts, p<0.001. No difference in the cumulative incidence of CNS relapse without extracranial disease (CNS-only) as first event was observed between the two groups: 5-yr cumulative incidence was 2.6% in pCR vs 2.3% in non-pCR cohorts, p=0.693. Next, we analyzed the frequency of site-specific first metastasis among patients who experienced a distant metastasis as first event. Over the total of distant relapse events, visceral involvement was more frequent in pCR vs non-pCR cohorts (15/17 88.2% vs 74/110 67.3%, p=0.094). The predominant site of distant relapse in the pCR cohort was CNS-only: 10/17 (58.8%) vs (9/110) 8.2% in non-pCR, p<0.001. The second most frequent site of distant relapse in pCR-cohort was liver (n=5/17, 29.4%) without significant difference vs non-pCR (n= 29/110, 26.4%). Baseline characteristics of patients who developed CNS-only relapse as first event did not differ between pCR and non-pCR cohorts and were as follows: median age 51 years (range 34-72), stage III 52.6%, nodal involvement 73.7%, Grade 3 94.1%, median TILs 13% (IQR 2-25). Conclusions: In patients with TNBC achieving pCR after NAT, CNS relapse without extracranial disease is the predominant first relapse site. Identifying factors predicting this dismal event in an otherwise low-risk population is urgently needed, as these patients could participate in in targeted follow-up programs and clinical trials investigating more aggressive therapeutic approaches after NAT. Our data also challenge the appropriateness of systematic avoidance of CNS staging in early TNBC at diagnosis, especially in patients at increased risk. Citation Format: Davide Massa, Esther Lips, Sylvie Giacchetti, Claudio Vernieri, Federico Piacentini, Luisa Carbognin, Moira Ragazzi, Carmen Criscitiello, Andrea Botticelli, Giorgio Bonomi, Federica Miglietta, Gaia Griguolo, Francesca Zanghì, Davide Napetti, Marina La Commare, Giuseppe Fotia, Giacomo Mazzoli, Clementine Bouchez, Laetitia Someil, Giulio Martinelli, Elisa Gasparini, Emilio Bria, Marleen Kok, Valentina Guarneri, Maria Vittoria Dieci. Central Nervous System as the Primary Site of First Relapse in Patients with Triple-Negative Breast Cancer Achieving Pathological Complete Response After Neoadjuvant Treatment [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr PS14-09.