Abstract P1-13-01: Risk of recurrence following 5 years of adjuvant hormone therapy for hormone receptor positive early breast cancer.

Abstract

Abstract Background Introduction The MA.17 study and combined analysis of the ATLAS and aTTom studies provide evidence of DFS and modest OS benefit from 10 years of hormone therapy (HT) for hormone receptor positive early breast cancer. The benefit may be less for women diagnosed today, due to advances in chemotherapy, initial HT, and radiation therapy since the era when these trials were conducted. Side effects accrue to all users of longer HT while benefit is experienced only by those who avoid recurrence, which is related to the baseline prognostic factors such as stage, grade, and disease biology. Methods To enhance informed patient-physician discussions, starting with a cohort of 10815 stage I-III hormone receptor breast cancer diagnoses between 1989 and 2004, we examined event-free survival (EFS) in years 5 to 10 among 1,061 premenopausal (<45 years at diagnosis) and 6,615 menopausal (≥50 years at diagnosis) women without documented relapse, CLBC, or death within the first 5 years. All patients were referred to the BC Cancer Agency (BCCA) with newly diagnosed disease, and all patients had adjuvant HT. EFS was defined as freedom from recurrence, from CLBC, or from breast cancer death without prior documented recurrence. Results Median follow up for the 7676 patients is 11 years. Event rates (including CLBC) in the second 5 years from diagnosis for stage I, II and III cancers were 6%, 12%, 23% for the pre-menopausal cohort, and 5%, 14%, 26% for the post-menopausal cohort. EFS in years 5-10 varied significantly by grade as shown below: EFS years 5-10 after ER+ early Breast CancerStage, gradeAge 45 and younger at diagnosisAge 50 and older at diagnosis NEvents% EFS years 5-10 (95% CI)NEvents% EFS years 5-10 (95% CI)I, grade 1110698.2 (92.9,99.5)10375795.4 (93.7,96.6)I, grade 21741692.1 (86.7,95.3)133811194.6 (93.1,95.7)I, grade 368593.4 (83.2,97.5)3642994.8 (91.8,96.8)II, grade 174889.6 (78.0,95.3)6056193.0 (90.5,94.9)II, grade 22905186.3 (81.6,89.9)177330786.6 (84.8,88.2)II, grade 32103090.4 (85.4,93.8)82318781.9 (78.9,84.5)III, grade 160100531175.6 (59.6,86.0)III, grade 2591574.3 (60.6,84.1)2526774.3 (67.8,79.8)III, grade 3521178.0 (62.1, 87.9)1504072.0 (62.8,79.3)CI, confidence Intervals Recurrences (excluding CLBC) after 10 years was 2% for the 10815 cases (representing 12% of all recurrences). Conclusion These data suggest that pre and postmenopausal women with stage I cancers of any grade, and postmenopausal women with stage II grade 1 cancers who have not experienced a relapse in the first five years can expect a less than 10% risk of recurrence, breast cancer death, or CLBC without further HT over the next 5 years. Prolonged HT in the identified groups may result in higher probability of harm than benefit and may best be avoided, although long term data will be needed to fully inform this risk benefit analysis. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-13-01.