Unlocking the potential of Molecular Tumor Boards: from cutting-edge data interpretation to innovative clinical pathways.

The emerging era of precision medicine is characterized by an increasing availability of targeted anticancer therapies and by the parallel development of techniques to obtain more refined molecular data, whose interpretation may not always be straightforward. Molecular tumor boards gather various professional figures, in order to leverage the analysis of molecular data and provide prognostic and predictive insights for clinicians. In addition to healthcare development, they could also become a tool to promote knowledge and research spreading. A growing body of evidence on the application of molecular tumor boards to clinical practice is forming and positive signals are emerging, although a certain degree of heterogeneity exists. This work analyzes molecular tumor boards' potential workflows, figures involved, data sources, sample matrices and eligible patients, as well as available evidence and learning examples. The emerging concept of multi-institutional, disease-specific molecular tumor boards is also considered by presenting two ongoing nationwide experiences.

Tumor-Infiltrating Lymphocytes in Triple-Negative Breast Cancer.

Importance: The association of tumor-infiltrating lymphocyte (TIL) abundance in breast cancer tissue with cancer recurrence and death in patients with early-stage triple-negative breast cancer (TNBC) who are not treated with adjuvant or neoadjuvant chemotherapy is unclear. Objective: To study the association of TIL abundance in breast cancer tissue with survival among patients with early-stage TNBC who were treated with locoregional therapy but no chemotherapy. Design, Setting, and Participants: Retrospective pooled analysis of individual patient-level data from 13 participating centers in North America (Rochester, Minnesota; Vancouver, British Columbia, Canada), Europe (Paris, Lyon, and Villejuif, France; Amsterdam and Rotterdam, the Netherlands; Milan, Padova, and Genova, Italy; Gothenburg, Sweden), and Asia (Tokyo, Japan; Seoul, Korea), including 1966 participants diagnosed with TNBC between 1979 and 2017 (with follow-up until September 27, 2021) who received treatment with surgery with or without radiotherapy but no adjuvant or neoadjuvant chemotherapy. Exposure: TIL abundance in breast tissue from resected primary tumors. Main Outcomes and Measures: The primary outcome was invasive disease-free survival [iDFS]. Secondary outcomes were recurrence-free survival [RFS], survival free of distant recurrence [distant RFS, DRFS], and overall survival. Associations were assessed using a multivariable Cox model stratified by participating center. Results: This study included 1966 patients with TNBC (median age, 56 years [IQR, 39-71]; 55% had stage I TNBC). The median TIL level was 15% (IQR, 5%-40%). Four-hundred seventeen (21%) had a TIL level of 50% or more (median age, 41 years [IQR, 36-63]), and 1300 (66%) had a TIL level of less than 30% (median age, 59 years [IQR, 41-72]). Five-year DRFS for stage I TNBC was 94% (95% CI, 91%-96%) for patients with a TIL level of 50% or more, compared with 78% (95% CI, 75%-80%) for those with a TIL level of less than 30%; 5-year overall survival was 95% (95% CI, 92%-97%) for patients with a TIL level of 50% or more, compared with 82% (95% CI, 79%-84%) for those with a TIL level of less than 30%. At a median follow-up of 18 years, and after adjusting for age, tumor size, nodal status, histological grade, and receipt of radiotherapy, each 10% higher TIL increment was associated independently with improved iDFS (hazard ratio [HR], 0.92 [0.89-0.94]), RFS (HR, 0.90 [0.87-0.92]), DRFS (HR, 0.87 [0.84-0.90]), and overall survival (0.88 [0.85-0.91]) (likelihood ratio test, P < 10e-6). Conclusions and Relevance: In patients with early-stage TNBC who did not undergo adjuvant or neoadjuvant chemotherapy, breast cancer tissue with a higher abundance of TIL levels was associated with significantly better survival. These results suggest that breast tissue TIL abundance is a prognostic factor for patients with early-stage TNBC.

Intermediate clinical endpoints in early-stage breast cancer: an analysis of individual patient data from the Gruppo Italiano Mammella and Mammella Intergruppo trials.

Background: Intermediate clinical endpoints (ICEs) are frequently used as primary endpoint in randomised trials (RCTs). We aim to assess whether changes in different ICEs can be used to predict changes in overall survival (OS) in adjuvant breast cancer trials. Methods: Individual patient level data from adjuvant phase III RCTs conducted by the Gruppo Italiano Mammella (GIM) and Mammella Intergruppo (MIG) study groups were used. ICEs were computed according to STEEP criteria. Using a two-stage meta-analytic model, we assessed the surrogacy of each ICE at both the outcome (i.e., OS and ICE are correlated irrespective of treatment) and trial (i.e., treatment effects on ICE and treatment effect on OS are correlated) levels. The following ICEs were considered as potential surrogate endpoints of OS: disease-free survival (DFS), distant disease-free survival (DDFS), distant relapse-free survival (DRFS), recurrence-free survival (RFS), recurrence-free interval (RFI), distant recurrence-free interval (DRFI), breast cancer-free interval (BCFI), and invasive breast cancer-free survival (IBCFS). The estimates of the degree of correlation were obtained by copula models and weighted linear regression. Kendall's τ and R2 ≥ 0.70 were considered as indicators of a clinically relevant surrogacy. Findings: Among the 12,397 patients enrolled from November 1992 to July 2012 in six RCTs, median age at enrolment was 57 years (interquartile range (IQR) 49-65). After a median follow-up of 10.3 years (IQR 6.4-14.5), 2131 (17.2%) OS events were observed, with 1390 (65.2%) attributed to breast cancer. At the outcome-level, Kendall's τ ranged from 0.69 for BCFI to 0.84 for DRFS. For DFS, DDFS, DRFS, RFS, RFI, DRFI, BCFI, and IBCFS endpoints, over 95% of the 8-year OS variability was attributable to the variation of the 5-year ICE. At the trial-level, treatment effects for the different ICEs and OS were strongly correlated, with the highest correlation for RFS and DRFS and the lowest for BCFI. Interpretation: Our results provide evidence supporting the use of DFS, DDFS, DRFS, RFS, RFI, DRFI, and IBCFS as primary endpoint in breast cancer adjuvant trials. Funding: This analysis was supported by the Italian Association for Cancer Research ("Associazione Italiana per la Ricerca sul Cancro", AIRC; IG 2017/20760) and by Italian Ministry of Health-5 × 1000 funds (years 2021-2022).

A Pilot Analysis of Whole Transcriptome of Human Cryopreserved Sperm.

Sperm cryopreservation is a procedure widely used to store gametes for later use, to preserve fertility in patients prior to gonadotoxic treatments or surgery, and for sperm donation programs. The purpose of the study was to assess the impact of cryopreservation on human sperm transcriptome. Semen samples were collected from 13 normospermic men. Each sample was divided into two aliquots. The total RNA was immediately extracted from one aliquot. The second aliquot was frozen and total RNA was extracted after a week of storage in liquid nitrogen. The RNA samples were randomized in four pools, each of six donors, and analyzed by microarrays. The paired Significance Analysis of Microarray was performed. We found 219 lower abundant transcripts and 28 higher abundant transcripts in cryopreserved sperm than fresh sperm. The gene ontology analysis disclosed that cryopreservation alters transcripts of pathways important for fertility (i.e., spermatogenesis, sperm motility, mitochondria function, fertilization, calcium homeostasis, cell differentiation, and early embryo development), although the increase of some transcripts involved in immune response can compensate for the harmful effects of freezing.

The Impact of Initial Tumor Response on Survival Outcomes of Patients With HER2-Positive Advanced Breast Cancer Treated With Docetaxel, Trastuzumab, and Pertuzumab: An Exploratory Analysis of the CLEOPATRA Trial.

INTRODUCTION: The CLEOPATRA trial (NCT00567190) established a dual anti-HER2 blockade in combination with docetaxel as the first-line standard of care for patients with metastatic HER2-positive breast cancer. While this treatment is overall associated with significant improvement in progression-free survival (PFS) and overall survival (OS), not all patients respond equally. We hypothesized that a radiological complete response (CR) at week 9 (i.e., first disease re-evaluation) is associated with prolonged OS and PFS compared to radiological partial response (PR) or stable disease (SD). METHODS: We performed an exploratory analysis of the CLEOPATRA study to address this question. RESULTS: Out of 362 patients treated with docetaxel, trastuzumab, and pertuzumab eligible for our analysis, 46 (12.7%) had radiological CR at week 9, 243 (67.1%) PR, and 73 (20.2%) SD per central RECIST v1.0. Radiological CR at first tumor re-evaluation was associated with a 60% risk reduction for death compared to SD (adjusted HR = 0.40 95% confidence interval (CI) 0.23-0.70), whereas no significant impact on survival was observed for PR (adjusted HR = 0.85 95% CI 0.60-1.20). The same was observed for PFS with adjusted HR = 0.30 (95% CI 0.18-0.48) for the CR subgroup and adjusted HR = 0.81 (95% CI 0.60-1.09) for the PR subgroup. In multivariate analysis, no variables were associated with radiological CR. CONCLUSIONS: Our findings suggest that radiological CR at first disease re-evaluation is associated with more prolonged survival; this might result from stronger dependence on HER2 pathway addiction, supporting the need for further translational research.

Ovarian Suppression: Early Menopause and Late Effects.

OPINION STATEMENT: Around 90% of breast tumours are diagnosed in the early stage, with approximately 70% being hormone receptor-positive. The cornerstone of adjuvant therapy for early-stage hormone receptor-positive breast cancer is endocrine therapy, tailored according to disease stage, biological characteristics of the tumour, patient's comorbidities, preferences and age. In premenopausal patients with hormone receptor-positive breast cancer, ovarian function suppression is a key component of the adjuvant endocrine treatment in combination with an aromatase inhibitor or tamoxifen. Moreover, it can be used during chemotherapy as a standard strategy for ovarian function preservation in all breast cancer subtypes. In the metastatic setting, ovarian function suppression should be used in all premenopausal patients with hormone receptor-positive breast cancer to achieve a post-menopausal status. Despite its efficacy, ovarian function suppression may lead to several side effects that can have a major negative impact on patients' quality of life if not properly managed (e.g. hot flashes, depression, cognitive impairment, osteoporosis, sexual dysfunction, weight gain). A deep knowledge of the side effects of ovarian function suppression is necessary for clinicians. A correct counselling in this regard and proactive management should be considered a fundamental part of survivorship care to improve treatment adherence and patients' quality of life.

Tumor Intrinsic Subtypes and Gene Expression Signatures in Early-Stage ERBB2/HER2-Positive Breast Cancer: A Pooled Analysis of CALGB 40601, NeoALTTO, and NSABP B-41 Trials.

Importance: Biologic features may affect pathologic complete response (pCR) and event-free survival (EFS) after neoadjuvant chemotherapy plus ERBB2/HER2 blockade in ERBB2/HER2-positive early breast cancer (EBC). Objective: To define the quantitative association between pCR and EFS by intrinsic subtype and by other gene expression signatures in a pooled analysis of 3 phase 3 trials: CALGB 40601, NeoALTTO, and NSABP B-41. Design, Setting, and Participants: In this retrospective pooled analysis, 1289 patients with EBC received chemotherapy plus either trastuzumab, lapatinib, or the combination, with a combined median follow-up of 5.5 years. Gene expression profiling by RNA sequencing was obtained from 758 samples, and intrinsic subtypes and 618 gene expression signatures were calculated. Data analyses were performed from June 1, 2020, to January 1, 2023. Main Outcomes and Measures: The association of clinical variables and gene expression biomarkers with pCR and EFS were studied by logistic regression and Cox analyses. Results: In the pooled analysis, of 758 women, median age was 49 years, 12% were Asian, 6% Black, and 75% were White. Overall, pCR results were associated with EFS in the ERBB2-enriched (hazard ratio [HR], 0.45; 95% CI, 0.29-0.70; P < .001) and basal-like (HR, 0.19; 95% CI, 0.04-0.86; P = .03) subtypes but not in luminal A or B tumors. Dual trastuzumab plus lapatinib blockade over trastuzumab alone had a trend toward EFS benefit in the intention-to-treat population; however, in the ERBB2-enriched subtype there was a significant and independent EFS benefit of trastuzumab plus lapatinib vs trastuzumab alone (HR, 0.47; 95% CI, 0.27-0.83; P = .009). Overall, 275 of 618 gene expression signatures (44.5%) were significantly associated with pCR and 9 of 618 (1.5%) with EFS. The ERBB2/HER2 amplicon and multiple immune signatures were significantly associated with pCR. Luminal-related signatures were associated with lower pCR rates but better EFS, especially among patients with residual disease and independent of hormone receptor status. There was significant adjusted HR for pCR ranging from 0.45 to 0.81 (higher pCR) and 1.21-1.94 (lower pCR rate); significant adjusted HR for EFS ranged from 0.71 to 0.94. Conclusions and relevance: In patients with ERBB2/HER2-positive EBC, the association between pCR and EFS differed by tumor intrinsic subtype, and the benefit of dual ERBB2/HER2 blockade was limited to ERBB2-enriched tumors. Immune-activated signatures were concordantly associated with higher pCR rates and better EFS, whereas luminal signatures were associated with lower pCR rates.

International multidisciplinary consensus on the integration of radiotherapy with new systemic treatments for breast cancer: European Society for Radiotherapy and Oncology (ESTRO)-endorsed recommendations.

Novel systemic therapies for breast cancer are being rapidly implemented into clinical practice. These drugs often have different mechanisms of action and side-effect profiles compared with traditional chemotherapy. Underpinning practice-changing clinical trials focused on the systemic therapies under investigation, thus there are sparse data available on radiotherapy. Integration of these new systemic therapies with radiotherapy is therefore challenging. Given this rapid, transformative change in breast cancer multimodal management, the multidisciplinary community must unite to ensure optimal, safe, and equitable treatment for all patients. The aim of this collaborative group of radiation, clinical, and medical oncologists, basic and translational scientists, and patient advocates was to: scope, synthesise, and summarise the literature on integrating novel drugs with radiotherapy for breast cancer; produce consensus statements on drug-radiotherapy integration, where specific evidence is lacking; and make best-practice recommendations for recording of radiotherapy data and quality assurance for subsequent studies testing novel drugs.

Real-World Outcomes of Trastuzumab Deruxtecan in Patients With HER2+ Metastatic Breast Cancer: The DE-REAL Study.

BACKGROUND: Trastuzumab deruxtecan (T-DXd) demonstrated unprecedented efficacy in patients with pretreated HER2+ metastatic breast cancer (mBC). However, few data are available about its efficacy in routine clinical practice. In this multicenter retrospective study, we examined effectiveness and safety of T-DXd in a real-world population. METHODS: Clinico-pathological information about patients with HER2+ mBC who received T-DXd were collected from 12 Italian hospitals. HER2 status was determined locally. Patients who received at least one administration of T-DXd, as any therapy line for advanced disease were included in the analysis. The primary endpoint was real-word PFS (rwPFS). RESULTS: One hundred and forty-three patients were included. Median age was 66 (range: 37-90), and 4 men were included. Hormone receptor (HR) status was positive in 108 (75%) patients and negative in 35(25%). T-DXd was administered as first, second, third, or subsequent lines in 4 (3%), 16 (11%), 42 (29%), and 81 (57%) patients, respectively. Among 123 patients with measurable disease, the ORR was 68%, and the DCR was 93% (9 CRs, 74 PRs, and 30 SD). Nine (7%) patients had a primary resistance to T-DXd. With a median follow-up of 12 months, the median rwPFS was 16 months. RwPFS was 84%, 59%, and 39% at 6, 12, and 18 months, respectively. A favorable trend in rwPFS was reported in patients receiving T-DXd as I/II line versus further lines (17 vs. 15 months; P = .098). Any-grade toxicity was registered in 84 patients (59%). Most common adverse events (AEs) reported were nausea (33%), neutropenia (21%), and asthenia (21%). Liver toxicity and diarrhea were uncommon (5% and 1%). Severe toxicities was registered in 18% of patients, and the most frequent were neutropenia, nausea/vomiting, and ILD observed in 15, 2, and 3 patients. AEs led to dose reduction in 37 patients (26%). Dose reduction and AEs do not affect patients' response and survival outcomes. CONCLUSIONS: Efficacy and safety of T-DXd were confirmed in an unselected real-world population of HER2+ mBC. These results are consistent with the results of known findings, and no new safety concerns were reported.

Omission of radiation therapy after breast-conserving surgery for biologically favourable tumours in younger patients: The wrong answer to the right question.

In this perspective paper, the findings of the recently published LUMINA study are critically evaluated, with an emphasis on the need for careful interpretation and a thoughtful approach in clinical practice. The LUMINA trial, which investigates the role of adjuvant endocrine therapy in low-risk breast cancer patients, is assessed for its limitations, including a highly selective patient cohort and an insufficient follow-up period. The importance of long-term data and further trials to inform clinical decisions effectively is emphasized. While the LUMINA study does not support an immediate change in practice, it is seen as a foundation for generating hypotheses to guide ongoing clinical trials. This important study has served as inspiration to develop this perspective paper, which takes into account ongoing studies and the toxicity profile of postoperative treatments in low-risk recurrence breast cancer. The need for a patient-cantered approach is stressed, considering individual wishes and desires in decision-making, despite the complexity of articulating these aspects in guidelines. A wise interpretation of available findings is essential to ensure sound clinical decision-making before broadly applying omission of radiation therapy.

Taxanes for the treatment of breast cancer during pregnancy: an international cohort study.

INTRODUCTION: The addition of taxanes to anthracycline-based chemotherapy is considered standard of care in the treatment of breast cancer. However, there are insufficient data regarding the safety of taxanes during pregnancy. The aim of this study was to describe the incidence of obstetric and neonatal adverse events associated with the use of taxane-containing chemotherapy regimens for the treatment of breast cancer during pregnancy. METHODS: This is a multicenter, international cohort study of breast cancer patients treated with taxanes during pregnancy. A descriptive analysis was undertaken to synthetize available data. RESULTS: A total of 103 patients were included, most of whom were treated with paclitaxel and anthracyclines given in sequence during gestation (90.1%). The median gestational age at taxane initiation was 28 weeks (range = 12-37 weeks). Grade 3-4 adverse events were reported in 7 of 103 (6.8%) patients. The most common reported obstetric complications were intrauterine growth restriction (n = 8 of 94, 8.5%) and preterm premature rupture of membranes (n = 5 of 94, 5.3%). The live birth rate was 92 of 94 (97.9%), and the median gestational age at delivery was 37 weeks (range = 32-40 weeks). Admission to an intensive care unit was reported in 14 of 88 (15.9%) neonates, and 17 of 70 (24.3%) live births resulted in small for gestational age neonates. Congenital malformations were reported in 2 of 93 (2.2%). CONCLUSION: Obstetric and neonatal outcomes after taxane exposure during pregnancy were generally favorable and did not seem to differ from those reported in the literature with standard anthracycline-based regimens. This study supports the use of taxanes during gestation when clinically indicated.

Pregnancy After Breast Cancer in Young BRCA Carriers: An International Hospital-Based Cohort Study.

Importance: Young women with breast cancer who have germline pathogenic variants in BRCA1 or BRCA2 face unique challenges regarding fertility. Previous studies demonstrating the feasibility and safety of pregnancy in breast cancer survivors included limited data regarding BRCA carriers. Objective: To investigate cumulative incidence of pregnancy and disease-free survival in young women who are BRCA carriers. Design, Setting, and Participants: International, multicenter, hospital-based, retrospective cohort study conducted at 78 participating centers worldwide. The study included female participants diagnosed with invasive breast cancer at age 40 years or younger between January 2000 and December 2020 carrying germline pathogenic variants in BRCA1 and/or BRCA2. Last delivery was October 7, 2022; last follow-up was February 20, 2023. Exposure: Pregnancy after breast cancer. Main Outcomes and Measures: Primary end points were cumulative incidence of pregnancy after breast cancer and disease-free survival. Secondary end points were breast cancer-specific survival, overall survival, pregnancy, and fetal and obstetric outcomes. Results: Of 4732 BRCA carriers included, 659 had at least 1 pregnancy after breast cancer and 4073 did not. Median age at diagnosis in the overall cohort was 35 years (IQR, 31-38 years). Cumulative incidence of pregnancy at 10 years was 22% (95% CI, 21%-24%), with a median time from breast cancer diagnosis to conception of 3.5 years (IQR, 2.2-5.3 years). Among the 659 patients who had a pregnancy, 45 (6.9%) and 63 (9.7%) had an induced abortion or a miscarriage, respectively. Of the 517 patients (79.7%) with a completed pregnancy, 406 (91.0%) delivered at term (≥37 weeks) and 54 (10.4%) had twins. Among the 470 infants born with known information on pregnancy complications, 4 (0.9%) had documented congenital anomalies. Median follow-up was 7.8 years (IQR, 4.5-12.6 years). No significant difference in disease-free survival was observed between patients with or without a pregnancy after breast cancer (adjusted hazard ratio, 0.99; 95% CI, 0.81-1.20). Patients who had a pregnancy had significantly better breast cancer-specific survival and overall survival. Conclusions and Relevance: In this global study, 1 in 5 young BRCA carriers conceived within 10 years after breast cancer diagnosis. Pregnancy following breast cancer in BRCA carriers was not associated with decreased disease-free survival. Trial Registration: ClinicalTrials.gov Identifier: NCT03673306.

CDK4/6 inhibition in hormone receptor-positive/HER2-negative breast cancer: Biological and clinical aspects.

A dysregulated cell division, one of the key hallmarks of cancer, results in uncontrolled cellular proliferation. This aberrant process, mediated by a dysregulated cell-cycle machinery and overactivation of cyclin-dependent kinase (CDK) 4 and 6, can potentially promote tumorigenesis. The clinical application of CDK 4/6 inhibitors, developed to inhibit cell-cycle progression, in the treatment regimens of breast cancer (BC) patients is expanding. Currently, three agents, ribociclib, palbociclib, and abemaciclib, are approved for treating patients with hormone receptor-positive and human epidermal growth factor receptor 2 (HER2)-negative metastatic BC. In addition, abemaciclib is FDA and EMA-approved for patients with hormone receptor-positive HER2-negative, node-positive, early BC at high risk of recurrence. Emerging data suggest potential anti-tumor effects beyond cell cycle arrest, providing novel insights into the agent's mechanisms of action. As a result, a broader application of the CDK4/6 inhibitors in patients with cancer is achieved, contributing to enhanced optimized treatment in the adjuvant and neoadjuvant settings. Herein, the immunomodulatory activities of CDK4/6 inhibitors, their impact on the cell's metabolic state, and the effect on the decision of the cell to undergo quiescence or senescence are discussed. Moreover, this review provides an update on clinical trial outcomes and the differences in the underlying mechanisms between the distinct CDK4/6 inhibitors.

Previous immune checkpoint inhibitor therapy is associated with decreased COVID-19-related hospitalizations and complications in patients with cancer: Results of a propensity-matched analysis of the OnCovid registry.

OBJECTIVES: To date, studies have not provided definitive answers regarding whether previous immune checkpoint inhibitor (ICI) treatment alters outcomes for cancer patients with COVID-19. METHODS: The OnCovid registry (NCT04393974) was searched from February 27, 2020, to January 31, 2022, for patients who received systemic anti-cancer therapy in the 4 weeks before laboratory-confirmed COVID-19 diagnosis. Propensity-score matching using country, vaccination status, primary tumor type, sex, age, comorbidity burden, tumor stage, and remission status investigated differences in predefined clinical outcomes comparing those who had or had not received ICIs. RESULTS: Of 3523 patients screened, 137 ICI-only and 1378 non-ICI met inclusion criteria. Before matching, ICI patients were older, male, enrolled at centers in Italy, and had histories of smoking, thoracic cancers, advanced cancer stages, and active malignancies (P ≤0.02). After matching, there were 120 ICI and 322 non-ICI patients. ICI patients had no differences (odds ratio: 95% CI) in presenting COVID-19 symptoms (0.69: 0.37-1.28), receipt of COVID-specific therapy (0.88: 0.54-1.41), 14-day (0.95: 0.56-1.61), or 28-day (0.79: 0.48-1.29) mortalities. However, ICI patients required less COVID-19-related hospitalization (0.37: 0.21-0.67) and oxygen therapy (0.51: 0.31-0.83) and developed fewer complications (0.57: 0.36-0.92). CONCLUSION: In this propensity-score matched analysis, previous ICI therapy did not worsen and potentially improved COVID-19 outcomes in patients with cancer.

Surgery of the primary tumor in patients with de novo metastatic breast cancer: a nationwide population-based retrospective cohort study in Belgium.

PURPOSE: We aimed to assess the impact of surgery of primary tumor in overall survival (OS) of women with de novo metastatic breast cancer. METHODS: Nationwide, population-based retrospective cohort study of women diagnosed with de novo metastatic breast cancer in Belgium, between Jan/2010-Dec/2014. Data was obtained from the Belgian Cancer Registry and administrative databases. "Surgery" group was defined by surgery of primary tumor up to nine months after diagnosis. We excluded women who did not receive systemic treatment or did not complete nine months follow-up after diagnosis. All the subsequent analyses reporting on overall survival and the stratified outcome analyses were performed based on this nine-month landmark cohort. OS was estimated using Kaplan-Meier method and compared using adjusted Cox proportional hazards models controlling for confounders with 95% confidence intervals (CI). We performed a stratified analysis according to surgery timing and a propensity score matching analysis. RESULTS: 1985 patients, 534 (26.9%) in the "Surgery" and 1451 (73.1%) in the "No Surgery" group. Patients undergoing surgery were younger (p < 0.001), had better performance status (PS) (p < 0.001), and higher proportion of HER2-positive and triple-negative breast cancer (p = 0.012). Median follow-up was 86.0 months (82.6-88.5). Median OS was 60.1 months (57.1-68.2) in the "Surgery" vs. 41.9 months (39.8-44.2) in the "No Surgery" group (adjusted HR 0.56; 0.49-0.64). OS was similar when surgery was performed upfront or after systemic treatment. Propensity score matching analysis confirmed the same findings. CONCLUSION: Among patients receiving systemic treatment for de novo metastatic breast cancer and surviving nine months or more, those who received surgery of the primary tumor within nine months of diagnosis have longer subsequent survival than those who did not.