275P 15-year incidence of invasive local, regional or contralateral events as first subsequent breast cancer event among HR+ premenopausal patients in SOFT and TEXT

Background: After >15 years median follow-up of SOFT and TEXT, we observed a persistent reduction in breast cancer-free interval (BCFI) events with the addition of ovarian function suppression (OFS) to tamoxifen vs tamoxifen (T), and further reduction with exemestane (E)+OFS.We examined the 15y incidence of invasive local-regional or contralateral BC events as the first BC relapse among premenopausal pts in SOFT and TEXT.Methods: Between 2003-2011, 3047 SOFT pts were randomized to 5y of T, T+OFS or E+OFS, and 2660 TEXT pts were randomized to T+OFS or E+OFS.Chemotherapy was optional and a stratification factor.Approximately 60% of SOFT and TEXT pts had undergone breast-conserving surgery with radiotherapy mandatory.BCFI events included invasive local or regional recurrence, invasive contralateral BC (L/R/CB) or distant recurrence.We estimated the cumulative incidence (cum inc) of L/R/CB as first BCFI event(s), with distant recurrence or death as competing risks, reported with 95% confidence intervals (CI).Results: BCFI events were reported for 668 of 3047 SOFT pts and 533 of 2660 TEXT pts, of which 292 (44%) and 218 (41%) were L/R/CB as first events, respectively.Between 10y to 15y, the cum inc of first L/R/CB increased by approximately 5% for pts assigned to T, and by 3-3.5% for those assigned to OFS regimens (Table ).Among the 350 SOFT pts who were age <35y, 32 had L/R/CB as first events (29% of all 112 pts who had BCFI events) and 15y cum inc of first L/R/CB was 16.5% (9.8-24.7),7.2% (3.1-13.7)and 8.4% (3.6-15.8)after T, T+OFS and E+OFS, respectively.