Extensive-stage small-cell lung cancer in patients receiving atezolizumab plus carboplatin-etoposide: stratification of outcome based on a composite score that combines gene expression profiling and immune characterization of microenvironment.

PURPOSE: Small-cell lung cancer (SCLC) is an aggressive disease with a dismal prognosis. The addition of immune checkpoints inhibitors to standard platinum-based chemotherapy in first-line setting achieves a durable benefit only in a patient subgroup. Thus, the identification of predictive biomarkers is an urgent unmet medical need. EXPERIMENTAL DESIGN: Tumor samples from naive extensive-stage (ES) SCLC patients receiving atezolizumab plus carboplatin-etoposide were analyzed by gene expression profiling and two 9-color multiplex immunofluorescence panels, to characterize the immune infiltrate and SCLC subtypes. Associations of tissue biomarkers with time-to-treatment failure (TTF), progression-free survival (PFS) and overall survival (OS), were assessed. RESULTS: 42 patients were included. Higher expression of exhausted CD8-related genes was independently associated with a longer TTF and PFS while increased density of B lymphocytes correlated with longer TTF and OS. Higher percentage of M2-like macrophages close to tumor cells and of CD8+T cells close to CD4+T lymphocytes correlated with increased risk of TF and longer survival, respectively. A lower risk of TF, disease progression and death was associated with a higher density of ASCL1+tumor cells while the expression of POU2F3 correlated with a shorter survival. A composite score combining the expression of exhausted CD8-related genes, B lymphocyte density, ASCL1 tumor expression and quantification of CD163+macrophages close to tumor cells, was able to stratify patients into high-risk and low-risk groups. CONCLUSIONS: In conclusion, we identified tissue biomarkers and a combined score that can predict a higher benefit from chemoimmunotherapy in ES-SCLC patients.

Efficacy and Safety of Immune Checkpoint Blockade in Patients With Li-Fraumeni Syndrome.

A case series evaluating efficacy and safety of immune checkpoint blockade in Li-Fraumeni syndrome.

Managing sexual health challenges in breast cancer survivors: A comprehensive review.

The significant advancements in breast cancer management have led to an increase in the prevalence of breast cancer survivors. Despite their efficacy, these treatments can cause a variable range of side effects, significantly deteriorating the patients' quality of life. Sexual dysfunction, and in particular the genitourinary syndrome of menopause, represent one of the major causes of quality-of-life impairment among breast cancer patients, potentially affecting treatment adherence and compliance. If in the general population, hypoestrogenism-related symptoms are typically managed through systemic or topical estrogen administration, this approach is contraindicated in breast cancer patients for the potential increased risk of disease recurrence, urging the investigation of alternative measures. The aim of this review is to summarize the most up-to-date pharmacological and non-pharmacological interventions, as well as supportive measures, available for the management of sexual dysfunctions in breast cancer patients and survivors.

The emerging role of Schlafen-11 (SLFN11) in predicting response to anticancer treatments: Focus on small cell lung cancer.

Small cell lung cancer (SCLC) is characterized by a dismal prognosis. Many efforts have been made so far for identifying novel biomarkers for a personalized treatment for SCLC patients. Schlafen 11 (SLFN11) is a protein differently expressed in many cancers and recently emerged as a new potential biomarker. Lower expression of SLFN11 correlates with a worse prognosis in SCLC and other tumors. SLFN11 has a role in tumorigenesis, inducing replication arrest in the presence of DNA damage through the block of the replication fork. SLFN11 interacts also with chromatin accessibility, proteotoxic stress and mammalian target of rapamycin signalling pathway. The expression of SLFN11 is regulated by epigenetic mechanisms, including promoter methylation, histone deacetylation, and the histone methylation. The downregulation of SLFN11 correlates with a worse response to topoisomerase I and II inhibitors, alkylating agents, and poly ADP-ribose polymerase inhibitors in different cancer types. Some studies exploring strategies for overcoming drug resistance in tumors with low levels of SLFN11 showed promising results. One of these strategies includes the interaction with the Ataxia Telangiectasia and Rad3-related pathway, constitutively activated and leading to cell survival and tumor growth in the presence of low levels of SLFN11. Furthermore, the expression of SLFN11 is dynamic through time and different anticancer therapy and liquid biopsy seems to be an attractive tool for catching SLFN11 different expressions. Despite this, further investigations exploring SLFN11 as a predictive biomarker, its longitudinal changes, and new strategies to overcome drug resistances are needed.

Study design for DESTINY-Breast Respond HER2-low Europe: T-DXd in patients with HER2-low advanced breast cancer.

Trastuzumab deruxtecan (T-DXd) is approved for the treatment of human epidermal growth factor receptor 2 (HER2)-low metastatic breast cancer (mBC). Results on T-DXd treatment in HER2-low mBC have so far been limited to clinical trials. DESTINY-Breast Respond HER2-low Europe (NCT05945732) is a multi-center, multi-country, observational, prospective, non-interventional study planning to enroll 1350 patients from 216 sites receiving T-DXd or conventional chemotherapy as their routine clinical care for advanced stage breast cancer in 12 European countries. This non-interventional study will provide real-world insight into T-DXd treatment for HER2-low mBC with data on effectiveness, safety and tolerability, patient-reported outcomes, treatment patterns, geriatric health status and HER2 testing. This will be beneficial for improving guidance to maximize patient treatment benefit.

Trastuzumab deruxtecan (T-DXd; Enhertu^®) is a medicine approved to treat cancers that produce a protein called HER2 on the surface of cancer cells. T-DXd works by targeting the HER2 protein to deliver chemotherapy directly to cancer cells. Until recently, breast cancers were classified as HER2-positive (high level of HER2 protein on cancer cells) or HER2-negative (very low level/no HER2 protein on cancer cells). T-DXd was approved for treating patients with HER2-positive advanced breast cancer in Europe in 2022. In 2023 the DESTINY-Breast04 clinical trial showed that T-DXd was more effective than current standard chemotherapies, when treating advanced breast cancer patients with low levels of the HER2 protein (historically classified as HER2-negative cancer). This trial led to the approval of T-DXd for treating advanced HER2-low breast cancer, providing a new treatment option for 50­60% of breast cancer patients. More information is needed about T-DXd treatment in the real world (for patients treated in the hospital, rather than in a clinical trial). This article describes the purpose and design of the DESTINY-Breast Respond HER2-low Europe study, which will collect and report more information about how effective T-DXd treatment is in the real world. This is a large study aiming to include 1350 eligible patients from 12 countries across Europe. Patients will report their experience of side effects (such as nausea and vomiting) to improve management of T-DXd treatment and maximize patient benefit. The study will also examine how elderly patients respond to T-DXd treatment, and how HER2 levels are being tested.Clinical Trial Registration: ICH CGP: NCT05945732, registered on 6 July 2023 (ClinicalTrials.gov).

Gene-expression assays to tailor adjuvant endocrine therapy for HR+/HER2- breast cancer.

Adjuvant endocrine therapy represents the standard of care for almost all HR+/HER2- breast cancers and different agents and durations are currently available. In this context, the tailoring and optimization of adjuvant endocrine treatment by reducing unnecessary toxic treatment while taking into account the biological heterogeneity of HR+/HER2- breast cancer represents a clinical priority. There is therefore a significant need for the integration of biological biomarkers in the choice of adjuvant endocrine therapy beyond currently used clinicopathological characteristics. Several gene-expression assays have been developed to identify patients with HR+/HER2- breast cancer who will not derive benefit from the addition of adjuvant chemotherapy. By enhancing risk stratification and predicting therapeutic response, genomic assays have also shown to be a promising tool for optimizing endocrine treatment decision. We here review evidence supporting the use of most common commercially available gene-expression assays (Oncotype DX, MammaPrint, Breast Cancer Index, Prosigna and EndoPredict) in tailoring adjuvant endocrine therapy. Available data on the use of genomic tests to inform extended adjuvant treatment choice based on the risk of late relapse and on the estimated benefit of a prolonged endocrine therapy are discussed. Moreover, preliminary evidence regarding the use of genomic assays to inform de-escalation of endocrine treatment, such as shorter durations or omission, for low risk patients are reviewed. Overall, gene expression assays are emerging as potential tools to further personalize adjuvant treatment for patients with HR+/HER2- breast cancers.

Impact of dose reductions on adjuvant abemaciclib efficacy for patients with high-risk early breast cancer: analyses from the monarchE study.

In monarchE, adjuvant abemaciclib significantly improved invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS), with sustained benefit beyond the 2-year treatment period. Abemaciclib dose reductions were allowed to proactively manage adverse events. Exploratory analyses to investigate the impact of dose reductions on efficacy were conducted. Across the three patient subgroups as defined by relative dose intensity (≤66%, 66-93%, ≥93%), the estimated 4-year IDFS rates were generally consistent (87.1%, 86.4%, and 83.7%, respectively). In the time-dependent Cox proportional hazard model, the effect of abemaciclib was consistent at the full dose compared to being reduced to a lower dose (IDFS hazard ratio: 0.905; 95% confidence interval: 0.727, 1.125; DRFS hazard ratio: 0.942; 95% confidence interval: 0.742, 1.195). These analyses showed that the efficacy of adjuvant abemaciclib was not compromised by protocol mandated dose reductions for patients with node positive, hormone receptor positive, human epidermal growth factor 2-negative, high-risk early breast cancer.

Gender minorities in breast cancer - Clinical trials enrollment disparities: Focus on male, transgender and gender diverse patients.

BACKGROUND: The last years have seen unprecedented improvement in breast cancer (BC) survival rates. However, this entirely apply to female BC patients, since gender minorities (male, transgender/gender-diverse) are neglected in BC phase III registration clinical trials. METHODS: We conducted a scoping review of phase III clinical trials of agents with a current positioning within the therapeutic algorithms of BC. RESULTS: We selected 51 phase III trials. Men enrollment was allowed in 35.3% of trials. In none of the trial inclusion/exclusion criteria referred to transgender/gender-diverse people. A numerical higher rate of enrolled men was observed in the contemporary as compared to historical group. We found a statistically significant association between the drug class and the possibility of including men: 100%, 80%, 50%, 33.3%, 25%, 10% and 9.1% of trials testing ICI/PARP-i, ADCs, PI3K/AKT/mTOR-i, anti-HER2 therapy, CDK4/6-i, ET alone, and CT alone. Overall, 77409 patients were enrolled, including 112 men (0.2%). None of the trial reported transgender/gender-diverse people proportion. Studies investigating PARP-i were significantly associated with the highest rate of enrolled men (1.42%), while the lowest rates were observed for trials of CT (0.13%), ET alone (0.10%), and CDK 4/6-I (0.08%), p < 0.001. CONCLUSIONS: We confirmed that gender minorities are severely underrepresented among BC registration trials. We observed a lower rate of men in trials envisaging endocrine manipulation or in less contemporary trials. This work sought to urge the scientific community to increase the awareness level towards the issue of gender minorities and to endorse more inclusive criteria in clinical trials.

Sex-related differences in serum biomarker levels predict the activity and efficacy of immune checkpoint inhibitors in advanced melanoma and non-small cell lung cancer patients.

BACKGROUND: Immune Checkpoint Inhibitors (ICIs) lead to durable response and a significant increase in long-term survival in patients with advanced malignant melanoma (MM) and Non-Small Cell Lung Cancer (NSCLC). The identification of serum cytokines that can predict their activity and efficacy, and their sex interaction, could improve treatment personalization. METHODS: In this prospective study, we enrolled immunotherapy-naïve patients affected by advanced MM and NSCLC treated with ICIs. The primary endpoint was to dissect the potential sex correlations between serum cytokines (IL-1ß, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, GM-CSF, MCP-1, TNF-ɑ, IP-10, VEGF, sPD-L1) and the objective response rate (ORR). Secondly, we analyzed biomarker changes during treatment related to ORR, disease control rate (DCR), progression free survival (PFS) and overall survival (OS). Blood samples, collected at baseline and during treatment until disease progression (PD) or up to 2 years, were analyzed using Luminex xMAP or ELLA technologies. RESULTS: Serum samples from 161 patients (98 males/63 females; 92 MM/69 NSCLC) were analyzed for treatment response. At baseline, IL-6 was significantly lower in females (F) versus males (M); lower levels of IL-4 in F and of IL-6 in both sexes significantly correlated with a better ORR, while higher IL-4 and TNF-ɑ values were predictive of a lower ORR in F versus M. One hundred and sixty-five patients were evaluable for survival analysis: at multiple Cox regression, an increased risk of PD was observed in F with higher baseline values of IL-4, sPD-L1 and IL-10, while higher IL-6 was a negative predictor in males. In males, higher levels of GM-CSF predict a longer survival, whereas higher IL-1ß predicts a shorter survival. Regardless of sex, high baseline IL-8 values were associated with an increased risk of both PD and death, and high IL-6 levels only with shorter OS. CONCLUSIONS: Serum IL-1ß, IL-4, IL-6, IL-10, GM-CSF, TNF-ɑ, and sPD-L1 had a significant sex-related predictive impact on ORR, PFS and OS in melanoma and NSCLC patients treated with ICIs. These results will potentially pave the way for new ICI combinations, designed according to baseline and early changes of these cytokines and stratified by sex.

Efficacy of osimertinib and the role of sequential liquid biopsy in patients diagnosed with NSCLC harboring EGFR and BRAF mutations at baseline: insights from two case reports.

Epidermal Growth Factor Receptor (EGFR) and B-Raf (BRAF) mutations are two of the most important drivers identified in non-small-cell lung cancer (NSCLC). This report highlights two cases of patients diagnosed with metastatic NSCLC bearing concurrent EGFR and BRAF mutations at baseline and treated with osimertinib as first-line treatment. Molecular profiling was conducted in the tissue and plasma at the time of initial diagnosis, and subsequent repeated liquid biopsy examinations were planned after 10 days, 28 days, and at the time of radiological progression in the frame of the prospective translational study REM. These cases suggest that osimertinib may maintain its therapeutic effectiveness even in patients presenting with a baseline BRAF co-mutation. Notably, radiological responses align with liquid biopsy observations: in both instances, follow-up liquid biopsies indicate the clearance of EGFR-mutated circulating tumor DNA (ctDNA).

Osimertinib in Patients With Treatment-Naive EGFR-Mutant Non-small Cell Lung Cancer: Overall Survival, Post-progression Management and Budget Impact Analysis in Real-World.

INTRODUCTION: The observational multicenter prospective FLOWER study (NCT04965701) confirmed effectiveness and safety of osimertinib in the real-world (RW) management of untreated EGFR-mutant advanced non-small cell lung cancer (aNSCLC) patients. METHODS: Herein, we report updated survival data, post-progression management, cost/effectiveness and budget impact (BI) of osimertinib compared with a RW population receiving gefitinib or erlotinib. RESULTS: Overall, 189 Caucasian patients receiving first-line osimertinib were included. After a follow-up of 20.7 months, 74(39.2%) patients discontinued osimertinib, median time-to-treatment discontinuation (mTTD) was 27.9 months, overall survival 36.8 months. At progression, tissue biopsy was performed in 29 (56.9%), liquid biopsy in 15 (29.4%) and both in 7 (13.7%) cases. The most frequent resistant mechanism was MET amplification (N = 14, 29.8%). At data cutoff, 13 (6.9%) patients were continuing osimertinib beyond progression; 52 (67.5%) received second-line treatment; no further treatments were administered in 25 (32.5%) cases. Thirty-three (63.4%) patients received chemotherapy, 12(23.1%) TKIs combination. Cost-effectiveness analysis showed a total cost per patient based on RW mTTD of 98,957.34€, 21,726.28€ and 19,637.83€ for osimertinib, erlotinib and gefitinib, respectively. The incremental cost-effectiveness ratio (ICER)/month for osimertinib was 359,806.0€/life-year-gained (LYG) and 197,789.77€/LYG compared to erlotinib and gefitinib. For osimertinib, the BI-gap between RW-TTD and theoretical-TTD was 16,501.0€ per patient. CONCLUSIONS: This updated analysis confirms the effectiveness of osimertinib in RW. Although the ICER of osimertinib seems not cost-effective, additional costs for the management of disease progression to old generation TKIs were not considered in this study. The BI-gap suggests RW mTTD as a more reliable measure for expense estimation.

Real-world impact of the introduction of chemo-immunotherapy in extended small cell lung cancer: a multicentric analysis.

Background: Recent clinical trials demonstrated longer survival in extended small cell lung cancer (SCLC) patients treated with immunotherapy in addition to chemotherapy. However, the magnitude of benefit is modest and the impact in real-world setting has to be fully established. Methods: We collected clinical data and radiological imaging of patients affected by extended or relapsing SCLC and consecutively treated according to clinical practice between 2016 and 2023. As primary end-point, we compared pre-defined outcome indicators before and after the introduction of chemo-immunotherapy (May 2020): 6-month and 12-month progression free survival (PFS) rate, 12-month and 18-month overall survival (OS). Among those who were treated after May 2020, patients who did not receive immunotherapy according to treating physician's choice were included in the analysis to minimize clinical selection bias. Results: The analysis included 214 patients: 132 (61.7%) were treated in an Academic cancer center and 82 (38.3%) in two community hospitals; 104 were treated before May 2020. Median PFS of the overall study population was 4.8 months (95% confidence interval [95% CI]: 4.4-5.4), median OS was 7.1 months (95% CI: 6.3-7.7). Estimated PFS and OS were significantly longer in patients treated after May 2020 with hazard ratio (HR) for PFS and OS of 0.61 (95% CI: 0.46-0.81, p < 0.001) and 0.70 (95% CI: 0.52-0.93, p = 0.015), respectively. 6-month PFS rate increased from 27% to 40% (p = 0.04) while 12-months PFS raised from 1% to 11% (p = 0.003). 12-month and 18-month OS rate increased from 15% to 28% (p = 0.03) and from 2.1% to 12% (p = 0.009), respectively. After May 2020 the median number of hospitalization days per patient decreased significantly and the incidence of severe AEs was similar. Among patients treated with chemo-immunotherapy, the onset of immune-related AEs was associated with improved PFS and OS (HR 0.55, 95% CI: 0.35-0.89, p = 0.012 and HR 0.47, 95%CI 0.28-0.77, p = 0.002, respectively). Conclusions: The real-world analysis shows a meaningful improvement of outcome indicators after the introduction of chemo-immunotherapy, with reduction of the duration of hospitalization, thus supporting the use of chemo-immunotherapy and the need for further biomarker research.

The study of primary and acquired resistance to first-line osimertinib to improve the outcome of EGFR-mutated advanced Non-small cell lung cancer patients: the challenge is open for new therapeutic strategies.

The development of targeted therapy in epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC) patients has radically changed their clinical perspectives. Current first-line standard treatment for advanced disease is commonly considered third-generation tyrosine kinase inhibitors (TKI), osimertinib. The study of primary and acquired resistance to front-line osimertinib is one of the main burning issues to further improve patients' outcome. Great heterogeneity has been depicted in terms of duration of clinical benefit and pattern of progression and this might be related to molecular factors including subtypes of EGFR mutations and concomitant genetic alterations. Acquired resistance can be categorized into two main classes: EGFR-dependent and EGFR-independent mechanisms and specific pattern of progression to first-line osimertinib have been demonstrated. The purpose of the manuscript is to provide a comprehensive overview of literature about molecular resistance mechanisms to first-line osimertinib, from a clinical perspective and therefore in relationship to emerging therapeutic approaches.

Tissue and circulating biomarkers of benefit to immunotherapy in extensive-stage small cell lung cancer patients.

Extensive stage-Small-Cell Lung Cancer (ES-SCLC) is an aggressive cancer with dismal prognosis. The addition of immune-checkpoint inhibitors (ICIs) to platinum-based chemotherapy have been consistently demonstrated to improve outcomes and survival, becoming the new standard in first - line treatment of ES-SCLC patients. However, despite positive results reported in the pivotal trials, longer benefit appears evident only for a selected group of patients. Several predictive biomarkers have been studied so far but the prospective identification of patients more likely to experience better outcome seems to be challenging in SCLC. Indeed, classical immune predictive biomarkers as PD-L1 and tumor mutational burden (TMB) seem not to correlate with outcomes. Recently, a new molecular classification of SCLC based on differential expression of genes associated with specific clinical behaviors and therapeutic vulnerability have been presented suggesting a new field to be investigated. Despite the achievements, these studies focused mainly on inter-tumoral heterogeneity, limiting the exploration of intra-tumoral heterogeneity and cell to cell interactions. New analysis methods are ongoing in order to explore subtypes plasticity. Analysis on single biopsies cannot catch the whole genomic profile and dynamic change of disease over time and during treatment. Moreover, the availability of tissue for translational research is limited due to the low proportion of patients undergoing surgery. In this context, liquid biopsy is a promising tool to detect reliable predictive biomarkers. Here, we reviewed the current available data on predictive role of tissue and liquid biomarkers in ES-SCLC patients receiving ICIs. We assessed latest results in terms of predictive and prognostic value of gene expression profiling in SCLC. Finally, we explored the role of liquid biopsy as a tool to monitor SCLC patients over time.

Long-term patient-reported outcomes from monarchE: Abemaciclib plus endocrine therapy as adjuvant therapy for HR+, HER2-, node-positive, high-risk, early breast cancer.

BACKGROUND: In monarchE, abemaciclib demonstrated a sustained benefit in invasive disease-free survival and a tolerable safety profile at 42-months median follow-up. With no expected disease-related symptoms, therapies in the adjuvant setting should preserve quality of life (QoL). With all patients off abemaciclib, we report updated patient-reported outcomes (PROs) for the full 2-year treatment period and follow-up. METHODS: Patients completed PROs including FACT-B, FACT-ES, and FACIT-Fatigue at baseline, 3, 6, 12, 18, and 24 months during treatment, and 1, 6, and 12 months after treatment discontinuation. Mixed effects repeated measures model estimated changes from baseline within and between arms for QoL scales and individual items. Meaningful changes were prespecified and no statistical testing was performed. Frequencies of responses to items associated with relevant adverse events and treatment bother were summarized. RESULTS: At baseline, completion rates for PRO instruments were >96 %. Mean changes from baseline for all QoL scales were numerically similar within and between arms (ie, less than prespecified thresholds). The same was observed for all individual items, except diarrhea. Within abemaciclib arm, meaningful differences for diarrhea were observed at 3 and 6 months (mean increases of 1.19 and 1.03 points on 5-point scale, respectively). During treatment, most patients in both arms (69-78 %) reported being bothered "a little bit" or "not at all" by side effects. Overall, patterns for fatigue were similar between arms. During post-treatment follow-up, PROs in both arms were similar to baseline. CONCLUSION: PRO findings confirm a tolerable and reversible toxicity profile for abemaciclib. QoL was preserved with the addition of adjuvant abemaciclib to endocrine therapy, supporting its use in patients with HR+, HER2-, high-risk early breast cancer.

Immune-Related Diarrhea and Colitis in Non-small Cell Lung Cancers: Impact of Multidisciplinary Management in a Real-World Setting.

INTRODUCTION: Immune-related adverse events (irAEs) constitute a challenge in the clinical management of solid tumors. This study aims to collect real-world data on the occurrence of immune-mediated diarrhea and colitis (IMDC) in advanced non-small cell lung cancer (aNSCLC) treated with immune checkpoint inhibitors (ICIs) and to assess the clinical impact of a multidisciplinary approach (MDA) on IMDC management. METHODS: We retrospectively collected data on patients with aNSCLC consecutively treated with ICIs, either as single agent or in combination with chemotherapy, between September 2013 and July 2022. Among patients developing IMDC, we conducted blinded revision of colonic biopsies and evaluated the clinical impact of the introduction of MDA through predefined indicators. RESULTS: Among the 607 patients included, 84 (13.8%) experienced IMDC. Pathological review highlighted a high prevalence of microscopic colitis (28%), with a collagenous pattern linked to longer symptoms duration (P = .01). IMDC occurred more frequently in females (P = .05) and PD-L1 expressors (P = .014) and was correlated with longer progression-free survival (17.0 vs 5.8, P < .001) and overall survival (28.3 vs 9.5, P < .001). The introduction of MDA was associated with increased employment of diagnostical tools such as fecal calprotectin test (P < .001), colonoscopy (P < .001), and gastroenterological evaluation (P = .017) and a significant decrease in both grade 3 conversion rate (P = .046) and recurrence after rechallenge (P = .016). Hospitalization rate dropped from 17.2% to 3.8% (P: ns). CONCLUSION: These findings highlight the clinical relevance of IMDC and support the incorporation of a MDA to optimize the clinical management of this irAE to improve patient care. Prospective validation has been planned.

Metastatic site patterns by intrinsic subtype and HER2DX in early HER2-positive breast cancer.

BACKGROUND: Even with contemporary treatment strategies, more than 10% of HER2-positive early stage breast cancer patients may experience distant metastasis as first event during follow-up. Tools for predicting unique patterns of metastatic spread are needed to plan personalized surveillance. We evaluated how molecular heterogeneity affects the pattern of distant relapse in HER2-positive breast cancer. METHODS: A total of 677 HER2-positive stage I-III breast cancer patients from ShortHER trial, Cher-LOB trial, and 2 institutional cohorts were included. PAM50 molecular subtypes and research-based HER2DX scores were evaluated. The cumulative incidence of distant relapse as the first event (any site and site specific) was evaluated using competing risk analysis. Median follow-up was 8.4 years. Tests of statistical significance are 2-sided. RESULTS: Stage III and high HER2DX risk score identified patients at the highest risk of distant relapse as first event (10-year incidence 24.5% and 19.7%, respectively). Intrinsic molecular subtypes were associated with specific patterns of metastatic spread: compared with other subtypes, HER2-enriched tumors were more prone to develop brain metastases (10-year incidence 3.8% vs 0.6%, P = .005), basal-like tumors were associated with an increased risk of lung metastases (10-year incidence 11.1% vs 2.6%, P = .001), and luminal tumors developed more frequently bone-only metastases (10-year incidence 5.1% vs 2.0%, P = .042). When added to stage or HER2DX risk score in competing risk regression models, intrinsic subtype maintained an independent association with site-specific metastases. CONCLUSIONS: The integration of intrinsic molecular subtypes with stage or HER2DX risk score predicts site-specific metastatic risk in HER2-positive breast cancer, with potential implications for personalized surveillance and clinical trials aimed at preventing site-specific recurrence.