Abstract P6-18-34: Treat ER+ight Canadian prospective observational study in HR+ advanced breast cancer: 3rd interim analysis

Abstract

Treat ER+ight is the 1st prospective observational study in Canadian HR+ HER2– advanced breast cancer patients currently receiving endocrine therapy (ET) alone or in combination with targeted therapy (TT) in the first, second or third line setting (NCT02753686). Methods: This pre-planned interim analysis describes baseline characteristics, treatment patterns and safety/toxicity of patients enrolled in ET and ET+TT cohorts. At data cut-off (November 2017), 200 patients were enrolled from 24 sites since March 2016. The median follow-up time at data cut-off was 8.1 months and 182 patients were evaluable for this analysis. Results: ET (n=73)ET + TT (n=109)Baseline Patient and Disease Characteristics Median age, years (range)71 (37-92)65 (39-87), p=0.017ECOG 0-1 (%)6274Median time since primary BC diagnosis, years (range)5 (0-37)6 (0-31)Median time with advanced BC diagnosis, years (range)1 (0-16)1 (0-8)Sites of Metastases (%) Bone only4027Visceral6073Location of Metastases (%) Lungs5747Liver2348, p=0.006Bone4846Lymph Nodes2735Enrollment Therapy (%) Everolimus+exemestane-29Fulvestrant17-Palbociclib+letrozole-16Palbociclib+fulvestrant-12Tamoxifen11-Exemestane6-Letrozole3-Anastrozole2-Palbociclib+exemestane-1Everolimus+tamoxifen-0.5Unknown11Start Dose of Targeted Therapy Everolimus (n=53); 10, 7.5, 5mg (%)-72, 4, 24Palbociclib (n=54); 125, 100mg, unknown (%)-89, 9, 2On-Study Adverse Events ≥15% (all-grade, %) Fatigue2332Nausea1224Diarrhea1120Cough815Alopecia316Neutropenia017 Conclusions: The majority of patients enrolled (64%) were receiving endocrine-based targeted therapy (CDK4/6 inhibitor or mTOR inhibitor) combinations. ET+TT patients were younger with more visceral disease and liver metastases compared to patients receiving endocrine therapy alone. Real-world starting dose of targeted therapies appears to be lower than the approved full dose for 11% of patients receiving palbociclib and 28% of patients receiving everolimus. Incidence of reported all-grade adverse events appears to be lower than previously reported in randomized trials and may be a consequence of real-world under-reporting of adverse events as well as the heterogeneous nature of the treatment cohorts. There does however appear to be a trend toward increased incidence of adverse events in the ET+TT cohort compared to the ET cohort. Citation Format: Doyle C, Califaretti N, Dent S, Iqbal N, Mates M, Kulkarni S, Bains P, Glenns V, Perri SR, Chia S. Treat ER+ight Canadian prospective observational study in HR+ advanced breast cancer: 3rd interim analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-34.