Retrospective observational study of patients with luminal breast cancer in early stages: 10-year follow-up—Which luminal breast cancer relapse?

e12586 Background: Luminal BC is a heterogeneous group of breast cancer (1), with molecular signatures of better prognoses and others of worse prognoses being found. Prosigna test provide the molecular BC subtype, an individualized prognostic score called “ROR score”. Our main objective is to analyze in 10 years which Luminal early BC patients have local and distant relapses. See if there is a correlation between ROR and relapse. As second objective is select this group of patients who relapse and analyze the presence of CAF S1 for a future study. Methods: We performed a retrospective observational study from the two main hospitals in Málaga (Spain) We included 415 women 43-79 years with EBC defined as T1 or T2 primary breast cancer <30 mm in the largest dimension) node negative. Molecular BC subtype analyzed by IHC and genomic platform Prosigna) The patients were treated with breast-conserving surgery with clear excision margins hypofractionated radiotherapy and adjuvant endocrine therapy. We followed them from 2014 to the present. Results: 415 patients. We made genetic platform Prosigna to all of them luminal A 55%, Luminal B 37%, Basal like 4.8% and Her2 3.6%. The median follow-up was 9.1 years. The cumulative incidence of recurrence in Luminal BC was 2.29% (44.4% locoregional 55.55% distant recurrence). In 55.55% of the patients that relapsed had a Prosigna test with high ROR score, in 11.11% of the patients that relapsed had a Prosigna test with an intermediate ROR score and in 33.33 of the patients that relapsed had a Prosigna test with a low ROR score. Conclusions: In our study the cumulative incidence of recurrence in Luminal BC was 2.29 % and the ROR score provided a good estimate of the risk of relapse. Currently we use genomic platforms as Prosigna to estimate the ROR and adapt treatments to the risk. However, until now there is no biological or translational study focusing on T1N0 luminal BC. Subsequently, there exists a real need for new strategies to determine the long-term prognosis of these patients. We selected a group of patients to analyze the presence of CAF S1 fibroblast for a future study. Distant recurrence in T1N0 Luminal BC is strongly associated with the presence of CAF-S1 fibroblast The determination of CAF-S1 could more accurately predict recurrence in this subgroup of patients and could be a target for future treatments.