Trastuzumab use and survival in HER2 (+) nonmetastatic breast cancer among Turkish women.

Abstract

56 Background: HER2 overexpression observed in 10-25% of breast cancers is associated with rapid proliferation. HER2-targeted trastuzumab has been used in metastatic breast cancer, and since 2004 in early breast cancer. However, trastuzumab therapy is expensive and long lasting resulting sometimes in cardiac side effects. In this study we tried to find out whether there was a subgroup of early breast cancer patients trastuzumab could be omitted. Methods: Records of patients treated for HER2-positive breast cancer in Istanbul Medical School between Jan 2000 and Sept 2009 were retrospectively evaluated. Disease-free survival (DFS) and overall survival (OS) were calculated either from follow-ups, or by calling. Kaplan meier and LogRank tests have been used for comparison (P<0.05, 95% CI). Results: Follow up period was 32.2±14.9mo for trastuzumab group (TG, n:87) compared to 47.4±20.8mo for non-trastuzumab group (NTG, n:63) (P=0.0001). Groups were similar for age, menopausal status, size (T), histological grade and type, location, hormone responsiveness, presence of lymphovascular invasion, surgery, and use of local/systemic/hormonal therapy. NTG had more N0 cases (44.4% vs. 12.6%, P=0.0001), breast related deaths (15.9% vs. 5.7%, P=.042) and systemic metastases (27% vs. 13.8%, P=.043). Number of local recurrences was similar. Mean DFS and OS were significantly less in TG (P<0.0001). However differences between DFS and OS of groups were not significant despite a considerable increase for both in TG at fifth year (P=0.147, P=0.450). No difference in DFS and OS between TG and NTG was observed when patients who had chemotherapy and/or radiotherapy and/or hormonotherapy were compared to those who did not. OS was not different between TG and NTG for T1, T2, and T3 tumors and for patients ≤35y. But in N2 and N3 tumors, use of trastuzumab increased OS significantly (P=0.007). Conclusions: Both number of events and systemic relapses were less in TG but we could not find a significant difference in DFS and OS between TG and NTG in Turkish nonmetastatic cancers. Prolonged follow up might be necessary to search for the subgroup who would not benefit, if any, as an incremental benefit in both DFS and OS was observed with trastuzumab use at fifth year.