Activity of trastuzumab (t) beyond disease progression in HER2 over-expressing metastatic breast cancer (MBC)

1066 Background: In HER-2 over-expressing MBC patients (pts), preclinical evidence suggests that T therapy should be continued until disease progression. On the other hand, the activity of T beyond disease progression is unknown. Methods: We retrospectively evaluated HER-2 over-expressing (score 3+ by IHC or 2+ and FISH amplified) unselected MBC pts treated at our institution with successive T-based cytotoxic therapies. Results: From 06/2001 to 06/2006 59 patients (57 female and 2 male) receiving at least 1 T-based regimen for advanced breast carcinoma were identified. Characteristics of patients at initiation of T were as follows: median age 51 years (32–73), pre-menopausal 28/57 (49%), HER-2 IHC 3+ 49/59 (83%), negative hormonal receptor status 34/59 (58%), visceral disease 45/59 (76%), adjuvant chemotherapy 47/59 (80%), chemo-naïve for MBC 30/59 (51%), median number of previous chemotherapy lines for MBC prior to T 1 (0–2). A total of 37, 16 and 9 patients received respectively a 2 nd , 3 rd and 4 th T-based regimen. In the 1 st T-based line there was an overall response rate (ORr) of 60% (clinical benefit-CB- 83%) while 2 nd T-based line yielded an ORr of 29% (CB 62%). None of the 16 and 9 patients who received respectively a 3 rd and 4 th T-based line responded to treatment. At a median follow up of 26 months (range 7–78), median time to progression was 9.5 months (95%c.i. 8.2–10.9), 6.7 months (95%c.i. 3.9–9.4), 4.0 months (95%c.i. 2.4–6-0) and 4.5 months (95%c.i. 3.7–8.3) from 1 st to 4 th T-based line respectively. Overall survival (OS) was 37 months (95%c.i. 22.4–53.4). No significant difference was observed in OS between the 22 patients receiving only 1 T-based line and the 37 patients who underwent at least 2 T-containing regimens (28 months vs 38 months, p=0.85). Conclusions: In HER-2 positive MBC patients T beyond disease progression maintains activity in terms of CB, TTP and OS. Prospective randomized trials are warranted to draw definitive results. No significant financial relationships to disclose.