Clinical characterization, prognostic, and predictive values of HER2-low in patients with early breast cancer in the PALLAS trial (ABCSG-42/AFT-05/BIG-14-13/PrE0109).

BACKGROUND: Bidirectional crosstalk between HER2 and estrogen receptor (ER) pathways may influence outcomes and the efficacy of endocrine therapy (ET). Low HER2 expression levels (HER2-low) have emerged as a predictive biomarker in patients with breast cancer (BC). METHODS: PALLAS is an open, international, phase 3 study evaluating the addition of palbociclib for 2 years to adjuvant ET in patients with stage II-III ER-positive/HER2-negative BC. To assess the impact of HER2 expression on patient outcomes in the phase III PALLAS trial, we analyzed (1) the association between rate of HER2-low with demographic and clinicopathological parameters, (2) the prognostic value of HER2-low status on invasive disease-free survival (iDFS), distant relapse-free survival (DRFS), and overall survival (OS) and (3) HER2 expression's value as a predictive biomarker of response to palbociclib. HER2-low was defined as HER2 immunohistochemistry (IHC) 1 + or IHC 2 + with negative in situ hybridization (ISH). All pathologic evaluation was performed locally. Prognostic and predictive power of HER2 were assessed with Cox models. RESULTS: From the original PALLAS intention-to-treat population (N = 5753), 5304 patients (92.2%) were included in this analysis. Among these, 2254 patients (42.5%) were classified as having HER2 IHC 0 (HER2-0), and 3050 (57.5%) as having HER2-low disease (1838 with IHC 1 + and 1212 with IHC 2 +). Median follow-up was 59.8 months. HER2-low prevalence varied significantly across 21 participating countries (range 16.7% to 75.6%; p < 0.001) and was more frequent in patients enrolled in North America (63.1%) than in Europe (53.4%) or other regions (53.4%) (p < 0.001). HER2 status was not significantly associated with iDFS in a multivariable Cox model (hazard ratio 0.93, 95% confidence interval 0.81 - 1.06). No significant interaction was observed between treatment arm and HER2 status for iDFS (p = 0.43). Similar results were obtained for DRFS and OS. CONCLUSIONS: In this large, prospective, global patient cohort, no differences were observed in clinical parameters, prognosis, or differential benefit from palbociclib between HER2-0 and HER2-low tumors. Significant geographic variability was observed in the prevalence of HER2-low status, suggesting a high degree of variation in pathologic assessment of HER2 expression without impact on outcomes.

The Journey of Antibody-Drug Conjugates: Lessons Learned from 40 Years of Development.

Antibody-drug conjugates (ADC) represent one of the most rapidly expanding treatment modalities in oncology, with 11 ADCs approved by the FDA and more than 210 currently being tested in clinical trials. Spanning over 40 years, ADC clinical development has enhanced our understanding of the multifaceted mechanisms of action for this class of therapeutics. In this article, we discuss key insights into the toxicity, efficacy, stability, distribution, and fate of ADCs. Furthermore, we highlight ongoing challenges related to their clinical optimization, the development of rational sequencing strategies, and the identification of predictive biomarkers. Significance: The development and utilization of ADCs have allowed for relevant improvements in the prognosis of multiple cancer types. Concomitantly, the rise of ADCs in oncology has produced several challenges, including the prediction of their activity, their utilization in sequence, and minimization of their side effects, that still too often resemble those of the cytotoxic molecule that they carry. In this review, we retrace 40 years of development in the field of ADCs and delve deep into the mechanisms of action of these complex therapeutics and reasons behind the many achievements and failures observed in the field to date.

Heterogeneity of Residual Disease After Neoadjuvant Systemic Therapy in Breast Cancer: A Review.

Importance: Over the past 2 decades, systemic therapy for early-stage breast cancer has gradually moved from the adjuvant to the neoadjuvant setting. Administration of systemic therapy before surgery leads to potential improvements in surgical outcomes and allows for the assessment of the pathologic response to treatment. For patients with residual disease (RD), 3 adjuvant strategies have been shown to improve outcomes: (1) adjuvant trastuzumab emtansine for ERBB2-positive disease, (2) adjuvant capecitabine for triple-negative disease, and (3) adjuvant olaparib for patients with germline BRCA variants. Furthermore, studies are testing novel drugs in the postneoadjuvant setting. Given the potential to tailor adjuvant therapy based on the response to preoperative systemic therapy, recognizing the complexities of response to neoadjuvant therapy and moving beyond the binary paradigm of RD vs experiencing a pathologic complete response is becoming increasingly necessary. Observations: Novel antibody-drug conjugates, anti-ERBB2 tyrosine kinase inhibitors, and immune checkpoint inhibitors are being evaluated as additional rescue options in phase 3 trials for patients with RD after neoadjuvant treatment. Concomitantly, the prognostic role of RD has been refined by the introduction of the residual cancer burden. In addition, the genomic landscape of RD has been found to be associated with long-term prognosis, as has the immune background of the disease evaluated via the presence of tumor-infiltrating lymphocytes. Lastly, the dynamics of circulating tumor DNA may allow for further improvement in prognostication by understanding which patients harbor detectable minimal RD. Conclusions and Relevance: Escalating adjuvant treatment has led to meaningful survival improvements among patients with breast cancer and RD after neoadjuvant therapy. Uncovering the anatomic and biological intricacies of RD will allow for increased precision in postneoadjuvant treatments, moving beyond the binary paradigm of RD vs pathologic complete response, toward more tailored rescue strategies in the adjuvant setting.

Dual HER2 inhibition: mechanisms of synergy, patient selection, and resistance.

HER2-targeted therapies for patients with HER2+ breast cancer are rapidly evolving, offering a range of more complex and personalized treatment options. Currently, an array of anti-HER2 monoclonal antibodies, tyrosine kinase inhibitors and antibody-drug conjugates are administered, sometimes alongside chemotherapy or endocrine therapy, both in curative and palliative contexts. However, the heterogeneous nature of HER2+ breast cancer demands a deeper understanding of disease biology and its role in responsiveness to novel HER2-targeted agents, as well as non-HER2-targeted therapies, in order to optimize patient outcomes. In this Review, we revisit the mechanisms of action of HER2-targeted agents, examine the evidence supporting the use of dual HER2 blockade in patients with HER2-amplified tumours, and explore the role of biomarkers in guiding future treatment strategies. We also discuss potential implications for the future treatment of patients with HER2+ breast cancer.

Is cancer back?-psychological issues faced by survivors of breast cancer.

Breast cancer survival rates have shown notable improvements over the years thanks to advancements in detection, treatment modalities, and supportive care. However, survivors often encounter challenges when reintegrating into daily life and managing persistent physical and psychological concerns. This review article aims to delve into the multifaceted emotional complexities faced by survivors, encompassing a spectrum of issues from fear of recurrence to body image insecurities, thus emphasizing the imperative for comprehensive support. Articles were reviewed through searches of PubMed and through searches of the author's own file. We will examine not only the risk factors contributing to heightened psychological distress but also the periods of vulnerability and the most common unmet needs encountered by these individuals. Additionally, we will discuss various psychological interventions and strategies designed to promote resilience and enhance the quality of life post-diagnosis. Furthermore, we will underscore the pressing need for ongoing, specific research endeavors aimed at addressing the long-term psychological impacts of cancer recurrence on survivorship. By shedding light on these critical aspects, we aim not only to provide insight into the challenges faced by survivors but also to advocate for the importance of integrating comprehensive psychological support into survivorship care. Through this thorough exploration, we seek to empower both survivors and healthcare professionals alike, facilitating a deeper understanding of the complexities inherent in the breast cancer survivorship journey. Ultimately, our aim is to highlight the crucial aspects that must be considered by healthcare professionals in providing holistic care to breast cancer survivors.

The radiologist's role in detecting systemic anticancer therapy-related interstitial lung disease: an educational review.

Systemic anticancer therapies (SACTs) are the leading cause of drug-induced interstitial lung disease (ILD). As more novel SACTs become approved, the incidence of this potentially life-threatening adverse event (AE) may increase. Early detection of SACT-related ILD allows for prompt implementation of drug-specific management recommendations, improving the likelihood of AE resolution and, in some instances, widening the patient's eligibility for future cancer treatment options. ILD requires a diagnosis of exclusion through collaboration with the patient's multidisciplinary team to rule out other possible etiologies of new or worsening respiratory signs and symptoms. At Grade 1, ILD is asymptomatic, and thus the radiologist is key to detecting the AE prior to the disease severity worsening. Planned computed tomography scans should be reviewed for the presence of ILD in addition to being assessed for tumor response to treatment, and when ILD is suspected, a high-resolution computed tomography (HRCT) scan should be requested immediately. An HRCT scan, with < 2-mm slice thickness, is the most appropriate method for detecting ILD. Multiple patterns of ILD exist, which can impact patient prognosis. The four main patterns include acute interstitial pneumonia / acute respiratory distress syndrome, organizing pneumonia, hypersensitivity pneumonitis, and non-specific interstitial pneumonia; their distinct radiological features, along with rarer patterns, are discussed here. Furthermore, HRCT is essential for following the course of ILD and might help to determine the intensity of AE management and the appropriateness of re-challenging with SACT, where indicated by drug-specific prescribing information. ILD events should be monitored closely until complete resolution. CRITICAL RELEVANCE STATEMENT: The incidence of potentially treatment-limiting and life-threatening systemic anticancer therapy-related interstitial lung disease (SACT-related ILD) events is likely increasing as more novel regimens become approved. This review provides best-practice recommendations for the early detection of SACT-related ILD by radiologists. KEY POINTS: Radiologists are crucial in detecting asymptomatic (Grade 1) ILD before severity/prognosis worsens. High-resolution computed tomography is the most appropriate method for detecting ILD. Drug-induced ILD is a diagnosis of exclusion, involving a multidisciplinary team. Familiarity with common HRCT patterns, described here, is key for prompt detection. Physicians should highlight systemic anticancer therapies (SACTs) with a known risk for interstitial lung diseases (ILD) on scan requisitions.

Exploring a Novel Approach to Spare Classic Chemotherapy in HER2-Low, ER-Positive Breast Cancer Based on Trastuzumab Deruxtecan Combined with Endocrine Therapy.

BACKGROUND: Breast cancer presents diverse molecular subtypes affecting treatment strategies. Human epidermal growth factor receptor 2 (HER2)-low, hormone receptor-positive (HR+) breast cancer poses a challenge due to limited targeted therapies. Current neoadjuvant treatment primarily utilizes chemotherapy, with conflicting results regarding efficacy in patients with HER2-low breast cancer. Trastuzumab deruxtecan (T-DXd) shows promise in HER2-low metastatic disease, and preliminary evidence suggests synergy with endocrine therapy. OBJECTIVE: This editorial explores the hypothesis that neoadjuvant T-DXd with or without endocrine therapy offers efficacy in the clinical management of HR+/HER2-low breast cancer. METHODS: We propose a phase II study with two treatment arms: T-DXd + letrozole and T-DXd alone. The primary endpoint is the radiological complete response rate. Secondary endpoints include pathological complete response rate, safety, event-free survival, and overall survival. Exploratory analyses will compare the arms to identify potential for optimizing treatment efficacy and minimizing side effects. CONCLUSIONS: This study design allows for initial assessment of T-DXd with or without endocrine therapy in the treatment of HER2-low breast cancer. The findings may pave the way for personalized treatment strategies and inform future research, potentially leading to a chemotherapy-sparing approach.

Effect of age on safety and efficacy of novel cancer drugs investigated in early-phase clinical trials.

BACKGROUND: Elderly patients are underrepresented in clinical trials, particularly in early-phase studies. Our study assessed the safety and efficacy of novel anti-cancer treatments investigated in early-phase clinical trials, comparing outcomes between younger and elderly patients. METHODS: This retrospective study analyzed data from patients enrolled in phase I/II trials at our center between January 2014 and April 2021. We evaluated clinicopathologic characteristics, toxicity, and clinical efficacy, categorizing patients into younger (≤ 65 years) and elderly (> 65 years) groups. RESULTS: 419 patients were included with a median age of 56 years. Among these, 107 (26 %) were older than 65 years. Predominant cancers included breast (48 %), lung (10 %), and melanoma (5 %). Patients were treated in 64 trials, predominantly receiving immunotherapy-based (47 %) or targeted therapy-based (45 %) treatment. Elderly presented with poorer ECOG performance status (P = 0.001) and had fewer prior therapy lines (P = 0.01) than younger patients. Grade ≥ 3 adverse events (AEs) were similar across age groups (31 % younger vs 33 % elderly; P = 0.7), including in combination therapy scenarios. However, elderly patients experienced more AEs with antibody-drug conjugates compared to younger counterparts (56 % vs 14 %, P = 0.036) and were more likely to discontinue treatment due to toxicity (15 % vs 7 %; P = 0.011). No significant age-related differences in response rates and survival outcomes were observed across treatment modalities, except for immunotherapy-based regimens for which elderly patients exhibited higher response rates, disease control rates, and prolonged progression-free survival. CONCLUSIONS: Our findings suggest that elderly exhibit comparable safety and efficacy outcomes to younger patients in early-phase clinical trials for new cancer drugs. This underscores the importance of including elderly patients in phase I/II trials to ensure the generalizability of study results and mitigate age-related disparities in cancer treatment access.

Adjuvant Trastuzumab Emtansine Versus Paclitaxel Plus Trastuzumab for Stage I Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer: 5-Year Results and Correlative Analyses From ATEMPT.

PURPOSE: Long-term outcomes of patients with stage I human epidermal growth factor receptor 2 (HER2)-positive breast cancer receiving adjuvant trastuzumab emtansine (T-DM1) remain undefined, and prognostic predictors represent an unmet need. METHODS: In the ATEMPT phase II trial, patients with stage I centrally confirmed HER2-positive breast cancer were randomly assigned 3:1 to adjuvant T-DM1 for 1 year or paclitaxel plus trastuzumab (TH). Coprimary objectives were to compare the incidence of clinically relevant toxicities between arms and to evaluate invasive disease-free survival (iDFS) with T-DM1. Correlative analyses included the HER2DX genomic tool, multiomic evaluations of HER2 heterogeneity, and predictors of thrombocytopenia. RESULTS: After a median follow-up of 5.8 years, 11 iDFS events were observed in the T-DM1 arm, consistent with a 5-year iDFS of 97.0% (95% CI, 95.2 to 98.7). At 5 years, the recurrence-free interval (RFI) was 98.3% (95% CI, 97.0 to 99.7), the overall survival was 97.8% (95% CI, 96.3 to 99.3), and the breast cancer-specific survival was 99.4% (95% CI, 98.6 to 100). Comparable iDFS was observed with T-DM1 irrespective of tumor size, hormone receptor status, centrally determined HER2 immunohistochemical score, and receipt of T-DM1 for more or less than 6 months. Although ATEMPT was not powered for this end point, the 5-year iDFS in the TH arm was 91.1%. Among patients with sufficient tissue for HER2DX testing (n = 187), 5-year outcomes significantly differed according to HER2DX risk score, with better RFI (98.1% v 81.8%, hazard ratio [HR], 0.10, P = .01) and iDFS (96.3% v 81.8%, HR, 0.20, P = .047) among patients with HER2DX low-risk versus high-risk tumors, respectively. CONCLUSION: Adjuvant T-DM1 for 1 year leads to outstanding long-term outcomes for patients with stage I HER2-positive breast cancer. A high HER2DX risk score predicted a higher risk of recurrence in ATEMPT.

Invasive lobular breast cancer: Focus on prevention, genetics, diagnosis, and treatment.

Invasive lobular cancer (ILC) is the most common of the breast cancer special types, accounting for up to 15% of all breast malignancies. The distinctive biological features of ILC include the loss of the cell adhesion molecule E-cadherin, which drives the tumor's peculiar discohesive growth pattern, with cells arranged in single file and dispersed throughout the stroma. Typically, such tumors originate in the lobules, are more commonly bilateral compared to invasive ductal cancer (IDC) and require a more accurate diagnostic examination through imaging. They are luminal in molecular subtype, and exhibit estrogen and progesterone receptor positivity and HER2 negativity, thus presenting a more unpredictable response to neoadjuvant therapies. There has been a significant increase in research focused on this distinctive breast cancer subtype, including studies on its pathology, its clinical and surgical management, and the high-resolution definition of its genomic profile, as well as the development of new therapeutic perspectives. This review will summarize the heterogeneous pattern of this unique disease, focusing on challenges in its comprehensive clinical management and on future insights and research objectives.

Prognosis and treatment outcomes for patients with stage IA triple-negative breast cancer.

To evaluate the role of chemotherapy in stage IA triple-negative breast cancer, we conducted a retrospective population-based study including 8601 patients. The use of chemotherapy significantly increased from 2010 to 2019 in patients with T1b and T1c tumors (p = 0.001 and p < 0.001, respectively). Receipt of chemotherapy was associated with improved breast cancer-specific survival (BCSS, adjusted hazard ratio = 0.70; p = 0.006), particularly in patients with T1c tumors (5-year BCSS 94.5% vs. 91.2%).

Adjuvant nivolumab, capecitabine or the combination in patients with residual triple-negative breast cancer: the OXEL randomized phase II study.

Chemotherapy and immune checkpoint inhibitors have a role in the post-neoadjuvant setting in patients with triple-negative breast cancer (TNBC). However, the effects of nivolumab, a checkpoint inhibitor, capecitabine, or the combination in changing peripheral immunoscore (PIS) remains unclear. This open-label randomized phase II OXEL study (NCT03487666) aimed to assess the immunologic effects of nivolumab, capecitabine, or the combination in terms of the change in PIS (primary endpoint). Secondary endpoints included the presence of ctDNA, toxicity, clinical outcomes at 2-years and association of ctDNA and PIS with clinical outcomes. Forty-five women with TNBC and residual invasive disease after standard neoadjuvant chemotherapy were randomized to nivolumab, capecitabine, or the combination. Here we show that a combination of nivolumab plus capecitabine leads to a greater increase in PIS from baseline to week 6 (91%) compared with nivolumab (47%) or capecitabine (53%) alone (log-rank p = 0.08), meeting the pre-specified primary endpoint. In addition, the presence of circulating tumor DNA (ctDNA) is associated with disease recurrence, with no new safety signals in the combination arm. Our results provide efficacy and safety data on this combination in TNBC and support further development of PIS and ctDNA analyses to identify patients at high risk of recurrence.

Evolution of HER2 expression between pre-treatment biopsy and residual disease after neoadjuvant therapy for breast cancer.

INTRODUCTION: We have previously found that HER2 expression is dynamic, and can change from the primary breast tumor to matched recurrences. With this work, we aimed to assess the dynamics of HER2 during neoadjuvant treatment.(NAT). METHODS: We reviewed HER2 expression in pre- and post-treatment samples from consecutive patients with early-stage breast cancer that received NAT and underwent surgery at Dana-Farber Brigham Cancer Center between 01/2016-08/2022. The primary outcome was evolution of HER2 expression from pre- to post-NAT specimens in patients with residual disease. RESULTS: Among 1613 patients receiving NAT, 1080 had residual disease at surgery. A total of 319 patients (29.5%) experienced a change in HER2 expression (HER2 0 vs. HER2-low vs. HER2-positive) from the pre-treatment sample to residual disease, with roughly equal distribution between decreased (50.5%) and increased HER2 expression (49.5%). Similar rates of change in HER2 expression were observed with anthracycline-based (31.8%) or taxane/platinum-based regimens (32.4%). Patients with HER2-0 or HER2-low tumors at diagnosis were likelier to experience a change in HER2 expression post-NAT compared to HER2-positive (32.3% vs. 21.3%, p < 0.001). Changes in HER2 expression post-NAT were prognostic among patients with HER2-positive tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 71.6% vs. 89.6%, p = 0.006) but not among those with HER2-negative tumors at diagnosis (3-year recurrence-free survival for change vs. no change: 79.3% vs. 81.1%, p = 0.31). CONCLUSIONS: Nearly 30% of patients with early-stage breast cancer showed a change in HER2 expression after NAT. Changes in HER2 expression post-NAT were only prognostic in the setting of HER2-positive tumors becoming HER2-negative at surgery.

Prevalence and spectrum of germline BRCA1 and BRCA2 in a cohort of ovarian cancer patients from the Salento peninsula (Southern Italy): a matter of preventive health.

OBJECTIVES: The aim of this exploratory, descriptive study was to characterize the deleterious BRCA1 and BRCA2 variants evaluated by genetic testing in a group of Ovarian cancer patients living in the Salento peninsula (Southern Italy). METHODS: From June 2014 to July 2023, patients with histologically confirmed high-grade serous carcinoma, fallopian tube, or primary peritoneal cancer who were referred to Lecce Familial Cancer Clinic were considered. BRCA-mutation genetic testing was performed on these patients. Socio-demographic data and cancer epidemiology were assessed, and Next Generation Sequencing and Sanger DNA sequencing were performed. RESULTS: The median age at the diagnosis of 332 ovarian cancer patients collected was 57 years. The pedigree analyses showed that 28.6% had familial cases and 39.7% had sporadic cases. Of the 319 patients submitted to genetic testing, 29.8% were carriers of BRCA1/2 mutation, 75.8% at BRCA1 and 24.2% at BRCA2 gene. Of the 21 BRCA1 mutations, the variant c.5266dupC was the most frequent alteration (28.4%). With respect to BRCA2, 13 mutations were found and the variant c.9676delT was the most frequently recorded (6.3%). CONCLUSIONS: This study reveals that the prevalence of germline mutations in the BRCA1 and BRCA2 genes was higher than reported by other studies. A broader understanding of the prevalence and role of BRCA mutations in development, response to treatment, and prognosis represents an exciting and developing area of ovarian cancer treatment and prevention.

Immunotherapy for Early-Stage Triple Negative Breast Cancer: Is Earlier Better?

PURPOSE OF REVIEW: In this narrative review, we discuss the optimal timing of immune checkpoint inhibitors (ICI) in early triple negative breast cancer (TNBC), the landscape of predictive biomarkers for the use of immunotherapy, and the mounting literature suggesting a benefit for an early use of ICI. RECENT FINDINGS: TNBC is associated with a poor prognosis relative to other breast cancer subtypes, and until recently, the treatment of TNBC was limited to cytotoxic chemotherapy. In 2021, the immune-checkpoint inhibitor, pembrolizumab, was approved in combination with neoadjuvant chemotherapy for patients with high-risk early stage TNBC. This approval changed the treatment paradigm of early TNBC concomitantly raised several challenges in clinical practice, pertaining to patient selection, toxicity management, and post-neoadjuvant treatment, among others. The introduction of neoadjuvant chemoimmunotherapy has transformed the treatment landscape for early TNBC. However, several challenges, including patient selection, toxicity management, and the identification of predictive biomarkers, need to be addressed. Future research should focus on refining the timing and duration of immunotherapy, optimizing the chemotherapy partner, and exploring novel predictive biomarkers of response or toxicity.

Evaluation of the Geographical Accessibility of Genome-Matched Clinical Trials on a National Experience.

BACKGROUND: Molecular-driven oncology allows oncologists to identify treatments that match a cancer's genomic profile. Clinical trials are promoted as an effective modality to deliver a molecularly matched treatment. We explore the role of geographical accessibility in Italy, and its impact on patient access to clinical trials. MATERIAL AND METHODS: We retrospectively reviewed molecular data from a single-institutional case series of patients receiving next-generation sequencing testing between March 2019 and July 2020. Actionable alterations were defined as the ones with at least one matched treatment on Clinicaltrials.gov at the time of genomic report signature. We then calculated the hypothetical distance to travel to reach the nearest assigned clinical trial. RESULTS: We identified 159 patients eligible for analysis. One hundred and one could be potentially assigned to a clinical trial in Italy, and the median distance that patients needed to travel to reach the closest location with a suitable clinical trial was 76 km (interquartile range = 127.46 km). Geographical distribution of clinical trials in Italy found to be heterogeneous, with Milan and Naples being the areas with a higher concentration. We then found that the probability of having a clinical trial close to a patient's hometown increased over time, according to registered studies between 2015 and 2020. CONCLUSIONS: The median distance to be travelled to the nearest trial was generally acceptable for patients, and trials availability is increasing. Nevertheless, many areas are still lacking trials, so efforts are required to increase and homogenize the possibilities to be enrolled in clinical trials for Italian patients with cancer.

Baseline Tumor Size as Prognostic Index in Patients With Advanced Solid Tumors Receiving Experimental Targeted Agents.

BACKGROUND: Baseline tumor size (BTS) has been associated with outcomes in patients with cancer treated with immunotherapy. However, the prognostic impact of BTS on patients receiving targeted therapies (TTs) remains undetermined. METHODS: We reviewed data of patients with advanced solid tumors consecutively treated within early-phase clinical trials at our institution from 01/2014 to 04/2021. Treatments were categorized as immunotherapy-based or TT-based (biomarker-matched or not). BTS was calculated as the sum of RECIST1.1 baseline target lesions. RESULTS: A total of 444 patients were eligible; the median BTS was 69 mm (IQR 40-100). OS was significantly longer for patients with BTS lower versus higher than the median (16.6 vs. 8.2 months, P < .001), including among those receiving immunotherapy (12 vs. 7.5 months, P = .005). Among patients receiving TT, lower BTS was associated with longer PFS (4.7 vs. 3.1 months, P = .002) and OS (20.5 vs. 9.9 months, P < .001) as compared to high BTS. However, such association was only significant among patients receiving biomarker-matched TT, with longer PFS (6.2 vs. 3.3 months, P < .001) and OS (21.2 vs. 6.7 months, P < .001) in the low-BTS subgroup, despite a similar ORR (28% vs. 22%, P = .57). BTS was not prognostic among patients receiving unmatched TT, with similar PFS (3.7 vs. 4.4 months, P = .30), OS (19.3 vs. 11.8 months, P = .20), and ORR (33% vs. 28%, P = .78) in the 2 BTS groups. Multivariate analysis confirmed that BTS was independently associated with PFS (P = .03) and OS (P < .001) but not with ORR (P = .11). CONCLUSIONS: Higher BTS is associated with worse survival outcomes among patients receiving biomarker-matched, but not biomarker-unmatched TT.