Endocrine-based Therapy Research Articles

Palbociclib: Randomized Studies and Real-world Evidence as the Basis for Therapeutic Planning in Metastatic Breast Cancer.

Endocrine-based combination therapy with an inhibitor of the cyclin-dependent kinases 4 and 6 (CDK4/6 inhibitors) is currently the first-line therapy of choice for patients with hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-), locally advanced or metastatic breast cancer (mBC). The efficacy and safety of the treatment with palbociclib, the first CDK4/6 inhibitor approved for this indication, have been confirmed in large randomized controlled clinical trials (RCTs) with strictly defined patient cohorts. Since then, many relevant questions about CDK4/6 inhibition with palbociclib for mBC have been investigated in RCTs and real-world studies. Based on this evidence, palbociclib is widely used in clinical practice since many years because of its efficacy and good tolerability. The aim of this review is to summarize findings from RCTs and RWE considering clinically relevant aspects such as safety, tolerability, quality of life and efficacy with a focus on specific questions and patient characteristics. A critical discussion and review of the overall evidence for endocrine-based therapy with the CDK4/6 inhibitor palbociclib can contribute to support therapy decisions in daily clinical practice.

The role of everolimus in metastatic breast cancer and possibilities of moving forward-a narrative review.

In hormone-receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer endocrine-based therapies are preferred over chemotherapy. One of the treatment options is the combination of everolimus with exemestane or other endocrine drug in later lines mainly based on progression-free survival (PFS) results of the phase 3 BOLERO-2 trial. Altogether, clinical trials did not prove an overall survival (OS) benefit and considerable side effects hampered its application in the day-by-day practice. In recent years CDK4/6-inhibitors became a first-choice combination partner to the endocrine treatment, everolimus still has a place within the treatment armamentarium. Although everolimus is a targeted drug, there is no accepted predictive biomarker and further patient selection is not possible. However, several directions can be defined how to optimally use everolimus. For update information on everolimus treatment in breast cancer I have performed a literature search. I used the keywords "breast cancer" and "everolimus" and extended the search in PubMed from 01/01/2014 to 10/02/2023. I considered all phase 3 trials, the phase 1-2 trials with not repetitive information, studies with biomarker results and I also checked review articles to identify potential relevant other clinical trial reports. I also have made a search in clinicaltrials.gov for recently completed and ongoing trials. I summarized the search results in this concise and brief report focusing on main trial results and ongoing research with everolimus. The most promising research directions seem to be further investigations for useable predictive biomarkers, for combinations with other targeted drugs (even in a triple combination) and for the feasibility of pharmacologically guided dosing method.

CO172 Indirect Treatment Comparison of Efficacy and Safety of Capivasertib-Fulvestrant Versus Alpelisib-Fulvestrant for PIK3CA-Altered, HR-Positive, Advanced Breast Cancer after Disease Progression Following Endocrine-Based Therapy

CO172 Indirect Treatment Comparison of Efficacy and Safety of Capivasertib-Fulvestrant Versus Alpelisib-Fulvestrant for PIK3CA-Altered, HR-Positive, Advanced Breast Cancer after Disease Progression Following Endocrine-Based Therapy

Trastuzumab deruxtecan (T-DXd) vs physician’s choice of chemotherapy (TPC) in patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2 (HER2)-low or HER2-ultralow metastatic breast cancer (mBC) with prior endocrine therapy (ET): Primary results from DESTINY-Breast06 (DB-06).

LBA1000 Background: T-DXd is approved for HER2-low (IHC 1+ or 2+/ISH-negative) mBC after ≥1 line of chemotherapy (CT). DB-06 (NCT04494425) evaluated T-DXd in pts with HER2-low or -ultralow (IHC 0 with membrane staining), HR+ mBC after disease progression (PD) on endocrine-based therapy and no prior CT for mBC. Methods: Pts with HER2-low or -ultralow, HR+ mBC were randomized 1:1 to T-DXd 5.4 mg/kg or TPC. Pts had no prior CT for mBC, with ≥2 lines of ET for mBC, or 1 line of ET for mBC if PD occurred ≤24 months (mo) of adjuvant ET or ≤6 mo of ET+CDK4/6i for mBC. Primary endpoint was progression-free survival (PFS) by blinded independent central review (BICR) in HER2-low. Key secondary endpoints were PFS in intent-to-treat (ITT = HER2-low and -ultralow) and overall survival (OS). Other endpoints included objective response rate (ORR) and safety. Results: As of Mar 18, 2024, 866 pts (HER2-low, n=713; HER2-ultralow, n=153) were randomized; 90.4% had prior CDK4/6i. TPC group pts were selected for capecitabine (59.8%), nab-paclitaxel (24.4%) or paclitaxel (15.8%). T-DXd significantly improved PFS vs TPC in HER2-low (HR, 0.62 [95% CI 0.51, 0.74], P<0.0001; median, 13.2 vs 8.1 mo). ITT and HER2-ultralow results were consistent with HER2-low (Table). Median treatment duration was 11.0 mo (T-DXd) vs 5.6 mo (TPC). OS was immature at first interim analysis (HER2-low HR, 0.83 [95% CI 0.66, 1.05], P=0.1181; median follow up, 18.6 mo). Grade (Gr) ≥3 drug-related adverse events occurred in 40.6% (T-DXd) vs 31.4% (TPC). Adjudicated interstitial lung disease / pneumonitis occurred in 49 (11.3%; 0.7% Gr 3/4, 0.7% Gr 5) vs 1 (0.2% Gr 2) pts receiving T-DXd vs TPC. Conclusions: T-DXd showed a statistically significant and clinically meaningful PFS benefit vs TPC (CT) in HER2-low mBC. HER2-ultralow results were consistent with HER2-low. Safety was in line with known profiles. DB-06 establishes T-DXd as a standard of care following ≥1 endocrine-based therapy for pts with HER2-low and -ultralow, HR+ mBC. Clinical trial information: NCT04494425 .[Table: see text]

Tailoring advanced breast cancer treatment after cyclin-dependent kinase 4/6 inhibitors progression - real-world data analysis.

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) represent the gold standard of the hormone receptor positive human epidermal growth factor receptor 2 (HER-2) negative advanced breast cancer. However, optimal treatment after disease progression is a matter of debate. We aimed to assess predictive and prognostic factors associated with the treatment outcome following CDK4/6i progression. We retrospectively analyzed patients who progressed on CDK4/6i treatment between 2018 and 2024. Treatment based on molecular findings (PIK3CA mutation), genetic findings (BRCA1/2 germline mutation), or adapted to the change in the tumor phenotype in rebiopsy (anti-HER2 therapy in the transformation to HER-2-positive disease) was grouped into tailored treatment and compared to the endocrine-based therapy and chemotherapy alone. Five hundred twelve patients were treated with CDK4/6i. Two hundred patients with disease progression were enrolled in the study. Duration of response to CDK4/6i was not predictive of the response to subsequent treatment, whereas the progression in the central nervous system was the worst prognostic factor. Thirty patients were ineligible for subsequent treatment. Survival after CDK4/6i progression was significantly longer in patients eligible for tailored treatment. The median PFS in patients with tailored treatment (n=19) was 13.5 months vs. 4.9 months in patients with non-tailored therapy (n=151; p=0.045). 12-month PFS was 54.1% with tailored treatment [95% CI 24.1-76.7%] compared to 18.5% with non-tailored therapy [95% CI 11.6-26.6%]. The median OS for patients treated with a tailored approach was not reached compared to 11.5 months with non-tailored treatment (p=0.016). The 24-month OS for patients treated with a tailored approach was 80.2% [95% CI 40.3-94.8%] compared to 21.1% [95% CI 12.2-31.7%] for patients with non-tailored treatment. Tailoring of subsequent treatment strategy seems to be essential for achieving long-term benefit. Further studies are required, as the prognosis after CDK4/6i progression remains dismal, especially in cases affecting the central nervous system.

Health-related quality of life with sacituzumab govitecan in HR+/HER2- metastatic breast cancer in the phase III TROPiCS-02 trial.

The TROPiCS-02 study (NCT03901339) demonstrated that sacituzumab govitecan (SG) has superior clinical outcomes over treatment of physician's choice (TPC) chemotherapy in patients with hormone receptor-positive, human epidermal growth factor 2 receptor-negative (HR+/HER2-) metastatic breast cancer (mBC). Here, we present health-related quality of life (HRQoL) patient-reported outcome (PRO) findings from this study. Eligible adults with HR+/HER2- mBC who previously received a taxane, endocrine-based therapy, a CDK4/6 inhibitor, and 2-4 lines of chemotherapy were randomized 1:1 to receive SG or TPC until progression or unacceptable toxicity. PROs were assessed at baseline and on day 1 of each cycle, using the European Organization for Research and Treatment of Cancer Quality-of-Life Core 30 (EORTC QLQ-C30), EQ-5D-5L, and PRO Common Terminology Criteria for Adverse Events (PRO-CTCAE). Compared to TPC, overall least square mean change from baseline was significantly better for SG for physical functioning and dyspnea, but worse for diarrhea. Time to first clinically meaningful worsening or death was significantly longer for SG in global health status/quality of life, physical functioning, fatigue, emotional functioning, dyspnea, insomnia, and financial difficulties of the EORTC QLQ-C30 and the EQ-VAS, but longer for TPC in diarrhea. Few patients in both arms reported experiencing any worsening to level 3 or 4 treatment-related symptomatic events during treatment, as assessed by 16 PRO-CTCAE items, except for diarrhea frequency and amount of hair loss, which favored TPC. SG was associated with an HRQoL benefit in most symptoms and functioning, compared with TPC. This supports the favorable profile of SG as a treatment option for patients with pretreated HR+/HER2- mBC.

Abstract PO2-05-03: Costs associated with adverse events in patients receiving treatment for hormone receptor positive/human epidermal growth factor receptor-2 negative metastatic breast cancer

Abstract Background:Adverse event (AE)-related health care resource utilization (HCRU) and costs are an important component in understanding the economic burden associated with managing patients (pts) with cancer and can inform treatment decision-making and access for pts, providers, and payers. At present, there are little data on AE-related HCRU and costs among pts receiving late-line treatment for hormone receptor positive (HR+)/human epidermal growth factor receptor-2 negative (HER2–) metastatic breast cancer (mBC). As such, the objective of this analysis was to describe the AE-related HCRU and costs among pts with HR+/HER2– mBC receiving chemotherapy (CT) who have received prior CT and endocrine-based therapies (ET). Methods: This retrospective study included pts who had at least 1 prior ET, had completed at least 2 CTs, had initiated their third (or greater) CT (post-ET) in the metastatic setting between Jan 2016 and Mar 2022, and were included in the Optum Research Database. The start date for the current line of CT was the index date. Pts were followed until disenrollment from health plan, study end date (Jun 2022), or death. AEs included in this study were based on clinical impact; these AEs were then organized into categories. AE-related HCRU and costs were reported as per pt per month (PPPM) and included outpatient visits, office visits, emergency room visits, inpatient stays, other medical costs (eg, laboratory/ancillary costs), and pharmacy costs. Costs were adjusted to 2021 US dollars using the Consumer Price Index. Results: A total of 769 pts were included with a mean age of 64 y (standard deviation: 13 y) and baseline National Cancer Institute comorbidity score of 0 (44%) or 1–2 (39%). 51% were commercially insured. A total of 715 (93%) pts had ≥1 AE during the follow-up period; the mean total PPPM cost associated with AEs was $7421 (Table 1) and the majority of costs were driven by ambulatory visits (office and outpatient visits: $3846 PPPM; Table 1) and inpatient stays ($3042 PPPM; Table 1). Among pts who experienced AEs, AEs that were associated with the highest mean total PPPM costs included infections, hepatoxicity, gastrointestinal toxicity and renal failure events. The costs associated with infections and renal failures were predominantly driven by inpatient stay costs ($5540 and $3298 PPPM, respectively; Table 1). Conclusions: This real-world analysis suggests that there is high prevalence of AEs associated with CTs in late-line (≥3 CTs) HR+/HER2– mBC, which may lead to a substantial economic burden and suboptimal treatment outcomes. Newer, effective therapies with manageable AE profiles may offer a better benefit-to-risk profile and improve outcomes compared with chemotherapies. Citation Format: Anju Shah, Amy Sainski-Nguyen, Kristin Moore, MK Rehnquist, Rita Nanda. Costs associated with adverse events in patients receiving treatment for hormone receptor positive/human epidermal growth factor receptor-2 negative metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-05-03.

Abstract PO4-12-12: An Updated analysis of risk factor identification and Hyperglycemia prevention with alpelisib + fulvestrant in PIKC3A-mutated, hormone-receptor positive, human epidermal growth factor-2 negative advanced breast cancer

Abstract Background: SOLAR-1 investigated use of alpelisib (ALP) + fulvestrant (FLV) in patients (pts) with hormone-receptor positive (HR+)/human epidermal growth factor-2 negative (HER2-), PIK3CA-mutated advanced breast cancer (ABC) after progression on endocrine-based therapy and demonstrated a clinically significant increase in all-grade (G) and G3-4 hyperglycemia (HG) compared to placebo + FLV. Current guidance recommends an insulin sensitizer (metformin, thiazolidinedione, SGLT2i) at HG onset. Given high rates of HG, a preventative protocol and identification (ID) of associated risk factors (RFs) was implemented to minimize HG, dose reductions and discontinuation. Although METALLICA investigated the implementation of metformin for hyperglycemia prophylaxis, there is limited data for alpelisib use and hyperglycemia prevention in high risk or controlled type 2 diabetic patients. Duke Breast Oncology Clinic (DBOC) implemented a preventive strategy to minimize HG and treatment disruptions in patients receiving alpelisib, including pre-diabetic and controlled-diabetic patients. Methods: This single-center, retrospective study included pts receiving at least one 28-day cycle of ALP+FLV between June 2019 and April 2023. One week prior to ALP initiation, pts initiated an insulin-sensitizer. Pts had fasting plasma glucose (FPG) levels drawn on day 8, 15, 28, and monthly while on ALP. The primary outcome was incidence of G2-4 HG. Descriptive statistics were used to summarize results. Number of RFs for HG (age ≥ 65 years, BMI ≥ 25 kg/m2, baseline FPG ≥ 100 mg/dL, and A1c ≥ 5.7%) were compared between pts with and without HG using Wilcoxon rank-sum test. Results A total of 30 pts (29 females; 1 male) were included with a median age of 60 years. The cohort was 70% White, 23% Black, while 67% were overweight/obese, and 50% had a history of type 2 diabetes mellitus (T2DM), gestational diabetes, or pre-diabetes. 29 pts received a CDK4/6 inhibitor prior to starting ALP. By day 28, 13 pts (43%) had G2-4 HG, with only 4 (13%) having G3 HG and zero having grade 4. Pts with G2-4 HG had a median of 2 RFs compared to only 1 RF if no HG. 8 pts (27%) required a temporary hold of ALP and 5 pts (17%) required a dose reduction in ALP due to HG. 25 pts permanently discontinued ALP; 14 due to disease progression and 8 due to an adverse event with only 3 due to HG. Median duration of ALP was 86 days (range 24-442), with 5 pts continuing to receive ALP at time of analysis. Patients with grade 2-4 HG by day 28 after ALP initiation had an older median age (66 years), higher BMI (median 28.1 kg/m2), higher baseline FPG (median 100 mg/dL), and higher baseline HbA1c (median 5.6%) compared to those without grade 2-4 HG (Table). Conclusions: Implementation of a HG prevention protocol with ALP in the real-world setting demonstrated fewer G3-4 HG events compared to that seen in SOLAR-1 (13% vs 36.6%) but slightly higher than METALLICA (6%) although we included a higher risk patient population. An increase in HG-associated RFs correlated with a higher incidence of G2-4 HG. Early risk identification and optimization of prophylactic antihyperglycemics can reduce ALP dose reductions and discontinuations secondary to HG. ALP use in higher-risk patients can be considered with a HG prevention protocol. Table 1. Hyperglycemia outcomes Citation Format: Heather Moore, Sarah Burnette, Emily Poehlein, Hui-Jie Lee, Kelly Westbrook, Thomas Bagwell, Kervin Novido, Susan Dent. An Updated analysis of risk factor identification and Hyperglycemia prevention with alpelisib + fulvestrant in PIKC3A-mutated, hormone-receptor positive, human epidermal growth factor-2 negative advanced breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-12-12.

Abstract PS15-01: A first-in-human phase 1 study of SIM0270, a brain-penetrant oral selective estrogen receptor degrader (SERD), in patients with ER+/HER2- locally advanced or metastatic breast cancer

Abstract Background: ER+/HER2- breast cancer is the most prevalent subtype, and endocrine-based therapy is the standard treatment. SIM0270 is a brain-penetrant and highly potent oral SERD that has demonstrated ER degradation and robust antitumor activity across various preclinical models, including those with intracranial xenograft tumors. Methods: This Phase 1 study evaluates the safety, pharmacokinetics and preliminary anti-tumor activity of SIM0270 as monotherapy and/or in combination with palbociclib or everolimus in patients with HR+/HER2- advanced or metastatic breast cancer. The primary objective of the phase 1a study, which consisted of the dose escalation stage and the dose expansion stage, is to determine the maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) of SIM0270 as monotherapy. A Bayesian Optimal Interval design (BOIN) was adopted. SIM0270 was administered orally daily in 28-day cycles. Here we report preliminary monotherapy data. Results: As of May 22nd 2023, 45 female patients were enrolled, receiving SIM0270 at dose levels of 10 mg (n=4), 30 mg (n=4), 60 mg (n=9), 90 mg (n=6), 120 mg (n=11), 200 mg (n=5), or 300 mg (n=6). The median age was 56 years (range, 40-73) and ECOG performance status was 0 (18%) or 1 (82%). Most patients were heavily pretreated, with a median of 2 prior endocrine-based therapies (range, 0-5) and a median of 2 prior chemotherapies (range, 0-8). Thirty-one patients (69%) received prior fulvestrant, 42 (93%) received prior aromatase inhibitors, and 28 (62%) received prior CDK4/6 inhibitors. Visceral metastases were present in 33 patients (72%), and brain metastases in 7 patients (16%). The most common TEAEs were sinus bradycardia (51%), anemia (38%), hypalbuminaemia (31%), hypercholesterolaemia (24%), urinary tract infection (24%), asthenia (24%), electrocardiogram (ECG) QT prolonged (24%), and dizziness (22%). Most of the TEAEs were Grade 1-2. Grade 3 TRAEs were ECG QT prolonged, gamma-glutamyltransferase(γ-GT) increased and dizziness in 2 patients each. All AEs were manageable with dose interruption or reduction, except only 1 patient discontinued treatment of SIM0270 due to TRAE (Grade 3 γ-GT increased). Four patients experienced dose-limiting toxicities (DLTs): 1 with Grade 3 ECG QT prolonged at 200mg dose level, 1 with Grade 3 ECG QT prolonged and 2 with Grade 3 dizziness at 300mg dose level. All DLTs were resolved with dose interruption then reduction. The MTD of single-agent SIM0270 was established as 200mg QD. Pharmacokinetic analysis revealed a T1/2 of approximately 70 hours, and the AUC and Cmax increased in an approximately linear manner with dose escalation. Concentration in cerebrospinal fluid was measured in 1 patient after 41 days treatment of SIM0270, which is consistent with preclinical data and suggested high concentration of SIM0270 in the brain of patients. Among 31 response evaluable patients (per RECIST 1.1 criteria), 4 PRs (3 unconfirmed) were observed, yielding an ORR of 12.9%. Brain lesions were all stable in 4 evaluable patients per RANO-BM criteria. In patients with ESR1 mutations at baseline and samples available for analysis, 4/6(67%) exhibited a reduction or loss of mutant ESR1 upon SIM0270 treatment. Conclusions: Single-agent SIM0270 was well tolerated and showed favorable antitumor activity in heavily pretreated advanced or metastatic ER+/HER2- breast cancer patients, including those previously treated with CDK4/6 inhibitors and fulvestrant. Phase 1a dose expansion with single-agent SIM0270 is ongoing, and the RP2D will be determined based on further accumulative data of tolerability and efficacy. (NCT05293964) Citation Format: Jiong Wu, Jian Zhang, Qingyuan Zhang, Yuping Sun, Hongtao Li, Yongmei Yin, Yehui Shi, Wenfeng Li, Yunjiang Liu, Min Yan, Chen Yang, Lili Zhu, Yang Yang, Liting Xue. A first-in-human phase 1 study of SIM0270, a brain-penetrant oral selective estrogen receptor degrader (SERD), in patients with ER+/HER2- locally advanced or metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS15-01.

Abstract PO2-20-03: VERITAC-3: A randomized phase 3 study, with a lead-in, of first-line vepdegestrant + palbociclib vs letrozole + palbociclib in estrogen receptor–positive/human epidermal growth factor receptor 2–negative advanced breast cancer

Abstract Background: Vepdegestrant (ARV-471) is a selective, orally administered PROteolysis TArgeting Chimera (PROTAC) estrogen receptor (ER) degrader. In the phase 2 portion (VERITAC) of a first-in-human phase 1/2 study (NCT04072952), vepdegestrant 200 mg once daily (QD) was well tolerated and had clinical activity in heavily pretreated patients with ER+/human epidermal growth factor receptor 2–negative (HER2-) advanced breast cancer and was selected as the recommended phase 3 dose (RP3D) for vepdegestrant monotherapy. A phase 1b cohort of the phase 1/2 study is evaluating the safety and clinical activity of vepdegestrant plus palbociclib in patients with ER+/HER2- breast cancer after prior endocrine-based therapy; prior cyclin-dependent kinase (CDK)4/6 inhibitor therapy was permitted. Preliminary results showed encouraging activity for the combination based on clinical benefit rate (CBR; rate of confirmed complete response, partial response, or stable disease ≥24 weeks); an increase in palbociclib exposure was observed relative to historical palbociclib pharmacokinetic data and was accompanied by a higher incidence of grade 3/4 neutropenia compared with prior palbociclib and endocrine therapy combination studies, which was managed by monitoring and standard palbociclib dose modifications. The global, randomized phase 3 VERITAC-3 study (NCT05909397) will compare the efficacy and safety of vepdegestrant plus palbociclib vs letrozole plus palbociclib as first-line treatment for patients with ER+/HER2- advanced breast cancer. An open-label study lead-in (SLI) will evaluate the safety and tolerability of vepdegestrant 200 mg QD plus 2 doses of palbociclib (100 mg QD and 75 mg QD) in patients with ER+/HER2- advanced breast cancer to select the RP3D of palbociclib for this combination. Trial Design: Approximately 50 and 1130 patients will be enrolled in the SLI and the phase 3 parts of the study, respectively. Eligible patients (aged ≥18 years) must have histologically or cytologically confirmed ER+/HER2- locoregionally recurrent or metastatic breast cancer, with no prior treatment in the advanced setting, and no prior treatment in any setting with CDK4/6 inhibitors, vepdegestrant, fulvestrant, elacestrant, or other investigational agents (including novel endocrine therapy, selective ER degraders, selective ER covalent antagonists, and complete ER antagonists). Patients with measurable disease per RECIST v1.1 or nonmeasurable bone-only disease are eligible. Patients with disease recurrence during or ≤12 months after completion of adjuvant endocrine therapy are excluded. For the SLI, patients are randomized 1:1 to receive vepdegestrant 200 mg QD in combination with palbociclib 100 mg QD or 75 mg QD and are treated in 28-day cycles with vepdegestrant given continuously and palbociclib given for 21 days followed by 7 days off treatment. The objective of the SLI is to identify the RP3D of palbociclib in combination with vepdegestrant, which will be determined through the primary outcome measures of incidence of grade 4 neutropenia, study drug dose reduction, and study drug discontinuation within the first 4 cycles of treatment. Secondary outcome measures include safety, antitumor activity (objective response rate, CBR, and duration of response), and plasma concentrations of study drugs. In the planned phase 3 portion of the trial, patients will be randomized to vepdegestrant plus palbociclib or letrozole plus palbociclib. The primary efficacy endpoint of the phase 3 portion is progression-free survival based on blinded independent central review. Enrollment began June 2023 and is ongoing. Citation Format: Seth Wander, Erika Hamilton, Mario Campone, Michael Danso, Sara Hurvitz, Hiroji Iwata, Colombe Chappey, Derek Yang, Julia Perkins Smith, Yuan Liu, Yuanyuan Zhang, Sibyl Anderson, Michelino de Laurentiis. VERITAC-3: A randomized phase 3 study, with a lead-in, of first-line vepdegestrant + palbociclib vs letrozole + palbociclib in estrogen receptor–positive/human epidermal growth factor receptor 2–negative advanced breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-20-03.

Abstract PO3-05-02: Impact of hormone receptor expression level in HR+/HER2- metastatic breast cancer in the large French ESME cohort

Abstract Background: In patients (pts) with early breast cancer (BC), the level of expression of estrogen receptor (ER) evaluated by immunohistochemistry is prognostic and predictive while progesterone receptor (PR) expression has an additional prognostic value. Allred scoring combines the percentage of positive cells and the intensity of staining. It is widely used for treatment choice for early BC. In metastatic setting, its role is less defined. Methods: The ESME database is a French National cohort of all consecutive pts who initiated a first-line treatment for metastatic BC (MBC) between January 2008 and December 2020 in one of the 18 French Comprehensive Cancer Centers (NCT03275311). For this study, we selected pts with HER2- MBC, known ER expression and intensity percentages, known PR status and who received endocrine-based therapy as first-line metastatic treatment. Primary objective was to evaluate the overall survival (OS) and first line progression-free survival (PFS1) under endocrine therapy according to ER and PR expression level. ER expression was defined using Allred score on the last available tumor sample. PR status was defined using a positive (≥10%)vs negative ( < 10%) threshold. Secondary objective was to evaluate clinical PFS1 whether de novo or recurrent MBC and according to type of first line therapy (mono- vs combined endocrine therapy). Results: In the ER+ ± PR+/HER2- population, 8269 pts had information on ER percentage and staining intensity. Median follow-up was 53.4 months (95%CI [51.9; 54.7]). Allred score distribution, OS and PFS1 are described in table 1. Median OS was 43.1 months [41.1; 45.0] for the PR- group compared with 52.3 months [50.5; 54.4] for the PR+ group. After adjustments, patients with a PR- tumour had still a worse prognosis (HR=1.20, 95%CI [1.12-1.28], p<0.001). Median PFS1 was 10.2 months[9.6; 10.8]and 14.8 months[14.2; 15.4] for pts with PR- vs PR+ tumour (HR=1.36 (1.29-1.43), p<0.001) and PR status remained significant prognostic factor independently of de novo or recurrent status and association or not with a targeted therapy. Conclusion: ER expression evaluated using the Allred scoring, as well as PR positivity, retain prognostic value in first-line MBC patients. Table 1 : OS and PFS according to Allred status, de novo status and type of endocrine therapy. * Selected variables on multivariate model include PR status, age, SBR grade, histological subtype, number of metastatic site, type of metastasis (non visceral, visceral, brain visceral), HER 2 (0 vs 1-2), metastatic-free interval, mono- vs combined endocrine therapy. Citation Format: Marie Alexandre, Florence Castan, Thibault De La Motte Rouge, Audrey Mailliez, Etienne Brain, Thomas Bachelot, Monica Arnedos, Florence Dalenc, Jean-Marc Ferrero, Vincent Massard, Isabelle Desmoulins, Marie-Ange Mouret-Reynier, Christelle Levy, Anthony Gonçalves, Anca Berghian, Aude-marie Savoye, Jean-Sébastien frenel, Lise Bosquet, Suzette Delaloge, William Jacot. Impact of hormone receptor expression level in HR+/HER2- metastatic breast cancer in the large French ESME cohort [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-05-02.

Abstract PS17-07: Interim analysis of giredestrant + inavolisib in MORPHEUS Breast Cancer: a Phase Ib/II study of giredestrant treatment combinations in estrogen receptor-positive, HER2-negative, locally advanced/metastatic breast cancer

Abstract BACKGROUND Patients with estrogen receptor-positive metastatic breast cancer (ER+ mBC) almost always progress on first-line endocrine therapy (ET), which is usually combined with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i). Finding effective ET combinations after progression following CDK4/6is remains a challenge. Giredestrant (GIR) is a highly potent, nonsteroidal, oral, selective ER antagonist and degrader. Inavolisib (INAVO) is a highly potent PI3Kα-selective inhibitor that promotes degradation of mutated p110α. After first-line treatment (tx) with a CDK4/6i, PIK3CA mutations (mut), which are common, persist and remain a sensitive oncogenic target in these patients. We present a 16-week interim analysis of GIR vs GIR + INAVO in MORPHEUS BC (NCT04802759). METHODS Patients whose tumors harbored a PIK3CAmut and who had disease progression on up to two lines of endocrine-based therapy (including at least one prior line of CDK4/6i) for locally advanced (LA)/mBC were randomized 1:6 to receive GIR (30 mg orally daily [PO QD]) or GIR + INAVO (9 mg PO QD) tx until disease progression or unacceptable toxicity. Given the small numbers, the GIR arm is presented for overall safety. Primary endpoints are safety and objective response rate (ORR). Other endpoints include progression-free survival (PFS), disease control rate (DCR), and pharmacokinetics. Genetic alterations were identified centrally in baseline circulating tumor DNA using the FoundationOne Liquid CDx assay. In cases where PIK3CAmut could not be determined centrally, local blood or tissue results are used. RESULTS As of April 18, 2023, seven and 15 patients were enrolled in the GIR and GIR + INAVO arms, respectively; 71% (n = 5) and 67% (n = 10) received one prior line of therapy in the LA/mBC setting; 14% (n = 1) and 33% (n = 5) received two prior lines; and one GIR-arm patient received four prior lines. Prior fulvestrant (FUL) was received by 53% of patients in the GIR + INAVO arm (n = 8). For GIR + INAVO, the ORR was 47% (n = 7); the complete response rate was 7% (n = 1); and the partial response (PR) rate was 40% (n = 6). The DCR at 12 weeks was 80% (12/15 patients). The median PFS was 10.3 months (95% confidence interval = 6.5, not evaluable) with 47% of patients (n = 7) having events. In the GIR + INAVO arm, 5/6 patients with an ESR1mut had a PR (83%) and one (17%) had stable disease. No clinically relevant drug–drug interaction was observed. Safety data are presented in the table. Two patients experienced grade 3 hyperglycemia, one of whom had baseline elevated HbA1c and has been on insulin therapy since the event. The other patient received a single day of insulin treatment. In the GIR + INAVO arm, the incidence of rash and stomatitis (all grade 1) was 13% each. CONCLUSIONS An encouraging efficacy signal was observed with GIR + INAVO when compared cross-trial with BYLieve arm A (PMID: 33794206). ORRs were 47% in MORPHEUS BC vs 21% in BYLieve for patients with measurable disease (although no prior FUL was allowed in BYLieve). Safety of GIR + INAVO was aligned to the individual safety profiles of each of the drugs, with no new safety signals identified and a favorable tolerability profile for a PI3Kα inhibitor-based combination. Table. Safety summary Data are % of patients. AE, adverse event; GIR, giredestrant; INAVO, inavolisib; TRAE, treatment-related adverse event; tx, treatment. Citation Format: Hope Rugo, Maria Gion, Cristina Hernando, Kyung Hae Jung, Mafalda Oliveira, Melinda Telli, Gregory Vidal, Sina Vatandoust, Jing Zhu, Richard Schwab, Huy Ngo, Erika Ferreira, Ann Collier, Vanessa Breton, Einav Gal-Yam. Interim analysis of giredestrant + inavolisib in MORPHEUS Breast Cancer: a Phase Ib/II study of giredestrant treatment combinations in estrogen receptor-positive, HER2-negative, locally advanced/metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS17-07.

Abstract PO1-05-05: Overall survival (OS) and subsequent therapy patterns in Japanese patients with HR+/HER2− advanced breast cancer (ABC) treated with palbociclib (PAL) plus letrozole (LET) in first-line setting (1L)

Abstract Background: PAL is a first-in-class cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) for the treatment of HR+/HER2− ABC. In PALOMA-2 study, PAL plus LET demonstrated a numerically, not statistically significant, prolonged OS versus placebo plus LET (53.9 vs 51.2 months; HR, 0.956; 95% CI, 0.777–1.177) in patients with HR+/HER2− ABC in 1L. Subgroup analyses showed a similar trend in Asia/Pacific region (73.4 vs 55.1 months; HR, 0.744), however, data specific to Japanese subgroup have not been reported. An open-label, single-arm, multicenter Japanese phase 2 study (J-Ph2) investigated the efficacy and safety of PAL plus LET in postmenopausal Japanese women with HR+/HER2− ABC in 1L and showed a median progression-free survival (PFS) of 35.7 months (95% CI, 21.7–46.7) in the final analysis of PFS. However, OS data were immature at the data cutoff. Here, we report the findings from a follow-up study of J-Ph2 (NCT04735367) evaluating OS and subsequent therapy in these Japanese patients. Methods: Patients (N=42) who participated in J-Ph2 were enrolled in this follow-up study. The primary endpoint was OS, defined as the time from the first dose of PAL plus LET in J-Ph2 to date of death due to any cause. Secondary endpoints included chemotherapy-free survival (CFS) and type and duration of subsequent therapy. Median OS, CFS, duration of subsequent therapy and associated 95% CIs were estimated using the Kaplan–Meier method. Outcomes were also assessed for baseline demographic and disease characteristic subgroups including visceral or nonvisceral metastatic disease, disease-free interval (DFI; ≤12 months, >12 months, de novo metastatic), and duration of 1L PAL use (≤24 months or >24 months). Results: Patients had a median age of 62.5 years; 48% had visceral metastases; 33% had de novo disease; 48% had a TFI >12 months; 93% had an ECOG performance status (PS) of 0. At a median follow up of 89.7 months, the median OS was 85.4 months (95% CI, 64.3–not estimable [NE]). Median OS was longer in patients with nonvisceral versus visceral metastases (not reached [NR] vs 67.3 months), with TFI >12 months versus ≤12 months (85.4 vs 45.4 months), or with duration of 1L PAL use >24 months versus ≤24 months (NR vs 47.5 months). Median CFS was 69.1 months (95% CI, 24.2–85.4), and that was longer in patients with nonvisceral versus visceral metastases (77.5 vs 37.5 months). At the data cutoff, 3 patients (7.1%) were still receiving PAL plus LET (90.9–93.2 months). Subsequent therapy after disease progression was administered to 34 of 42 patients (81%). Of these patients, 28 (82%) received endocrine-based therapy, while 3 (9%) patients each received chemotherapy and other therapy, respectively. The median duration of the first subsequent therapy was 8.3 months (95% CI, 3.9–12.2), and that was similar among patients with nonvisceral versus visceral metastases (7.8 vs 8.3 months). Conclusion: This interim analysis showed a median OS of >7 years with 1L PAL plus LET. Patient demographics (geographic, racial factors), disease characteristics (ECOG PS, visceral metastases), and subsequent therapy decisions may have contributed to the extended median OS observed in this study. Further, this report provides insight into real-world subsequent treatment patterns following PAL plus ET. Table Citation Format: Masato Takahashi, Tomofumi Osako, Hiroyuki Yasojima, Kenichi Inoue, Masahiro Kawashima, Hideki Maeda, Mitsuya Ito, Yasuaki Sagara, Kan Yonemori, Masaya Hattori, Naohito Yamamoto, Eriko Tokunaga, Shozo Ohsumi, Yutaka Yamamoto, Akemi Ichikawa, Yasuaki Muramatsu, Norikazu Masuda. Overall survival (OS) and subsequent therapy patterns in Japanese patients with HR+/HER2− advanced breast cancer (ABC) treated with palbociclib (PAL) plus letrozole (LET) in first-line setting (1L) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-05-05.

Abstract PO2-05-02: Real-world experience of patients receiving treatment for hormone receptor-positive/human epidermal growth factor receptor-2 negative metastatic breast cancer: A global analysis of symptoms and side effects

Abstract Background: Advances in treatment for patients (pts) with hormone receptor-positive (HR+)/human epidermal growth factor receptor-2 negative (HER2–) metastatic breast cancer (mBC) have improved overall survival, but treatment resistance is common and median survival remains only a few years. These pts usually need chronic therapy and often experience symptoms and side effects. There is limited knowledge on pts’ experiences outside the clinical trial setting, largely because this information is not routinely reported. This analysis leverages a unique database of physician- and pt-reported data to describe symptoms and side effects among a real-world, geographically diverse population of pts receiving treatment for HR+/HER2– mBC. Methods: This retrospective cohort study used Adelphi Disease Specific Programme Real World Data, comprising validated, linked pt and physician questionnaire data from the US, France, Germany, Italy, Spain, and UK. Eligible pts were ≥18 y, currently receiving treatment for advanced BC and not enrolled in a clinical trial. Data were collected between August 2022 and February 2023. Physician surveys provided data on individual pt demographics and disease characteristics, comorbidities, treatment history, and treatment (including adherence). Physicians also reported presence or absence of symptoms and side effects after treatment initiation for each pt they considered. A subset of pts completed one-time validated quality of life (QOL) instruments, including the European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire (EORTC QLQ-C30) and EORTC QLQ-breast (BR23). Results: Data from 1578 pts receiving treatment for HR+/HER2– mBC were analyzed. Mean age was 65-y, 91% were white, 71% had de novo mBC, and 82% had ECOG performance status 0-1 at the start of current treatment. Across all lines of therapy, 71% of pts were receiving endocrine-based therapy, 16% were receiving chemotherapy only, and 13% were receiving other therapies; 40% of all pts were receiving second or later lines of any systemic therapy (2L+). Among all pts, the most common physician-reported symptoms and side effects (in ≥10% of pts) were bone pain (30%), change in appetite (13%), weight loss (12%), neutropenia (11%), and joint/muscle pain (11%). Pts on 2L+ therapy experienced a greater frequency of symptoms and side effects than those on first-line therapy (Table). Of 220 pts who completed QOL questionnaires, the most commonly reported symptoms and side effects (in ≥70% of pts) were feeling tired (87%), worry about future health (80%), general worrying (79%), needing to rest during the day (74%), feeling weak (74%), having trouble doing strenuous activity (71%), and trouble taking a long walk (71%). These were common irrespective of pt age, disease state (recurrent vs de novo), current treatment regimen, and line of therapy. Conclusions: This real-world analysis shows that both physicians and pts identified substantial symptoms and side effects during treatment. These were pervasive across the population and more common in those receiving 2L+ therapy, although it remains unclear which were due to treatment or disease. Thus, it is important to continue to develop treatments and supportive care to improve both clinical outcomes and pt QOL. Citation Format: MK Rehnquist, Ann Partridge, Annabel Lambert, Allison Kurian, Natalia Sadetsky, Emily Freeman, Lisa Carey. Real-world experience of patients receiving treatment for hormone receptor-positive/human epidermal growth factor receptor-2 negative metastatic breast cancer: A global analysis of symptoms and side effects [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-05-02.

Sacituzumab Govitecan (Trodelvy)

CADTH reimbursement reviews are comprehensive assessments of the clinical effectiveness and cost-effectiveness, as well as patient and clinician perspectives, of a drug or drug class. The assessments inform non-binding recommendations that help guide the reimbursement decisions of Canada’s federal, provincial, and territorial governments, with the exception of Quebec. This review assesses sacituzumab govitecan (Trodelvy), 180 mg lyophilized powder for solution for injection, for IV use. Indication: For the treatment of adult patients with unresectable, locally advanced or metastatic, HR-positive, human epidermal growth factor receptor 2-negative (immunohistochemistry [IHC] 0, IHC 1+ or IHC 2+/in situ hybridization-negative) breast cancer who have received endocrine-based therapy and at least 2 additional systemic therapies in the metastatic setting.

Autophagy and senescence facilitate the development of antiestrogen resistance in ER positive breast cancer.

Estrogen receptor positive (ER+) breast cancer is the most common breast cancer diagnosed annually in the US with endocrine-based therapy as standard-of-care for this breast cancer subtype. Endocrine therapy includes treatment with antiestrogens, such as selective estrogen receptor modulators (SERMs), selective estrogen receptor downregulators (SERDs), and aromatase inhibitors (AIs). Despite the appreciable remission achievable with these treatments, a substantial cohort of women will experience primary tumor recurrence, subsequent metastasis, and eventual death due to their disease. In these cases, the breast cancer cells have become resistant to endocrine therapy, with endocrine resistance identified as the major obstacle to the medical oncologist and patient. To combat the development of endocrine resistance, the treatment options for ER+, HER2 negative breast cancer now include CDK4/6 inhibitors used as adjuvants to antiestrogen treatment. In addition to the dysregulated activity of CDK4/6, a plethora of genetic and biochemical mechanisms have been identified that contribute to endocrine resistance. These mechanisms, which have been identified by lab-based studies utilizing appropriate cell and animal models of breast cancer, and by clinical studies in which gene expression profiles identify candidate endocrine resistance genes, are the subject of this review. In addition, we will discuss molecular targeting strategies now utilized in conjunction with endocrine therapy to combat the development of resistance or target resistant breast cancer cells. Of approaches currently being explored to improve endocrine treatment efficacy and patient outcome, two adaptive cell survival mechanisms, autophagy, and "reversible" senescence, are considered molecular targets. Autophagy and/or senescence induction have been identified in response to most antiestrogen treatments currently being used for the treatment of ER+ breast cancer and are often induced in response to CDK4/6 inhibitors. Unfortunately, effective strategies to target these cell survival pathways have not yet been successfully developed. Thus, there is an urgent need for the continued interrogation of autophagy and "reversible" senescence in clinically relevant breast cancer models with the long-term goal of identifying new molecular targets for improved treatment of ER+ breast cancer.

Sacituzumab Govitecan: A Review in Unresectable or Metastatic HR+/HER2- Breast Cancer.

Sacituzumab govitecan (TRODELVY®) is a first-in-class trophoblast cell-surface antigen 2 (Trop-2)-directed antibody and topoisomerase I inhibitor conjugate that is approved globally as monotherapy for the treatment of adults with unresectable locally advanced or metastatic, hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-; defined as immunohistochemistry 0, 1+ or 2+ and in situ hybridization-negative) breast cancer who have received endocrine-based therapy and ≥2 additional systemic therapies in the advanced setting. In the phase III TROPiCS-02 trial, intravenous sacituzumab govitecan demonstrated statistically significant and clinically meaningful improvements in progression-free survival and overall survival compared with physician's choice of chemotherapy (capecitabine, eribulin, gemcitabine or vinorelbine) in adults with metastatic HR+/HER2- breast cancer. Sacituzumab govitecan had a generally manageable tolerability profile in these patients; the most common treatment-related grade ≥3 adverse events included neutropenia, diarrhoea, leukopenia, anaemia, fatigue and febrile neutropenia. Sacituzumab govitecan carries regulatory warnings for severe neutropenia and severe diarrhoea. Sacituzumab govitecan demonstrated an overall benefit in terms of health-related quality of life. Current evidence indicates that sacituzumab govitecan is an effective treatment option, with a generally manageable tolerability profile, for patients with pre-treated, unresectable locally advanced or metastatic HR+/HER2- breast cancer.

Sacituzumab Govitecan (Trodelvy)


 CADTH recommends that Trodelvy should be reimbursed by public drug plans for the treatment of adult patients with unresectable locally advanced or metastatic hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative (IHC 0, IHC 1+, or IHC 2+/ISH–) breast cancer who have received endocrine-based therapy and at least 2 additional systemic therapies in the metastatic setting, if certain conditions are met.
 Trodelvy should only be covered to treat adult patients with unresectable locally advanced or metastatic HR-positive, HER2-negative breast cancer who have been previously treated with at least 1 taxane, at least 1 prior anticancer hormonal treatment, and at least 1 cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor in any setting, have experienced treatment failure after 2 to 4 prior systemic chemotherapy regimens for metastatic disease, and have good performance status.
 Trodelvy should only be reimbursed if it is prescribed by clinicians with expertise and experience in treating breast cancer in approved centres, and if the price of Trodelvy is reduced.

What are the needs in oral antitumor therapy? An analysis of patients' and practitioners' preferences.

Since the European approval of CDK4/6 inhibitors in 2016, the treatment of patients with hormone-receptor-positive, HER2-negative metastatic breast cancer has changed significantly. Compared with chemotherapy, endocrine-based therapy has different treatment regimens and is associated with new side effects. Oral therapy aims for optimal drug efficacy and long treatment times while maintaining maximum independence and quality of life resulting in the conservation of medical staff resources. A monocentric analysis of therapy preferences of practitioners (25 nurses and physicians) and patients (11 on endocrine monotherapy, 17 on endocrine-based therapy, and 14 on intravenous chemotherapy) was performed using specific questionnaires. Preferences were assessed using a four-point Likert scale or bidirectional response options. All patients were highly supportive of oral therapy (mean agreement score on the Likert scale 1.3, p < 0.001 vs. all other options) and a consultation interval of 4 weeks (2.0, p = 0.015 vs. 3 weeks). Practitioners also preferred oral therapy (1.4) and visits every 4 weeks (1.6). In general, patients on oral therapies reported higher compatibility of their therapy with daily life than patients on chemotherapy (1.6 and 1.7 vs. 2.6, p = 0.006). Outpatient oncology is the main source of information for all patients, mainly in case of side effects (2.0) and open questions (1.8). Regarding oral antitumor therapy regimens, patients do not show a significant preference for a specific regimen, while practitioners prefer a continuous regimen (1.6) over a 21/7 regimen (21 days on and 7 days off therapy, 2.5). Patients are likely to accept mild side effects (e.g., neutropenia, diarrhea, polyneuropathy, fatigue) and would still adhere to their initial choice of regimen (continuous or 21/7). Only when side effects occur with a severity of CTCAE grade 3 do patients prefer the regimen in which the side effects occur for a shorter period of time. Patients and practitioners prefer oral antitumor therapy-both continuous and 21/7 regimens-over other application forms. Patient education and proper therapy management, supported by additional tools, contribute to the specific management of side effects and high adherence. This allows quality of life to be maintained during long-term therapy with CDK4/6 inhibitors in patients with metastatic breast cancer.

Overall survival in Japanese patients with ER+/HER2− advanced breast cancer treated with first-line palbociclib plus letrozole

BackgroundAn open-label, single-arm, Japanese phase 2 study (J-Ph2) investigated the efficacy and safety of first-line (1L) palbociclib (PAL) + letrozole (LET) in postmenopausal Japanese women with ER+/HER2− advanced breast cancer (ABC). In the final analysis, median progression-free survival was 35.7 months (95% CI 21.7–46.7); but overall survival (OS) data were immature. Here, we report the findings from a follow-up study of J-Ph2 (NCT04735367) evaluating OS and subsequent therapy in these Japanese women.MethodsPatients (N = 42) who participated in J-Ph2 were enrolled in the OS follow-up study. The primary endpoint was OS and secondary endpoints included type and duration of subsequent therapy.ResultsPatients were a median age of 62.5 years; 48% had visceral metastases. At a median follow-up of 89.7 months, the median OS was 85.4 months (95% CI 64.3–not estimable). Median OS was longer in patients with nonvisceral versus visceral metastases (not reached vs 67.3 months), or with treatment-free interval > 12 months versus ≤ 12 months (85.4 vs 45.4 months), or with treatment duration ≥ 24 months versus < 24 months (not reached vs 47.5 months). Of patients who received a first subsequent therapy (81%), most (67%) continued endocrine-based therapy, while 7% received chemotherapy. The median duration of the first subsequent therapy was 8.3 months (95% CI 3.9–12.2), and the median chemotherapy-free survival was 69.1 months (95% CI 24.2–85.4).ConclusionsIn this population of Japanese women with ER+/HER2− ABC, median OS was over 7 years with 1L PAL + LET, supporting the use of 1L PAL + endocrine therapy.Trial numberNCT04735367.