Background: HER2 expression is an important prognostic and predictive factor of treatment efficacy in breast cancer. Trastuzumab, in particular, is a key drug in the treatment of HER2-positive recurrent breast cancer. However, the difference in treatment efficacy between trastuzumab monotherapy and combination therapy with chemotherapy is unclear. In order to elucidate this point, both treatments were compared in terms of efficacy by metastatic site, time to progression (TTP), and survival.
Patients and methods: The subjects were 1,471 breast cancer patients who had been evaluated for HER2 expression between 1998 and March 2006; 74 of these had recurrent breast cancer that had been treated with trastuzumab. Of these 74 patients, 39 received trastuzumab alone and 45 trastuzumab in combination with chemotherapy. The items of investigation were clinical effect, TTP, survival, biological markers such as ER/PgR, proliferation (Ki67) or p53 overexpression, nuclear grade, performance status (PS), lymph node metastasis, and tumor size.
Results: The HER2-positive rate was 23.3%, and the degree of malignancy in these HER2-positive patients was high; postoperative disease-free survival (DFS) was low. However, this tendency was clear in patients with hormone-responsive breast cancer. In patients with hormone-non-responsive breast cancer, HER2 negativity had a significantly higher Ki67 value, and there was no difference in DFS between patients with HER2-positive and -negative tumors. Among the 74 patients with recurrent breast cancer, the response rate to trastuzumab was 64.9%; however, among patients who received the combination treatment, the response rate was 86%. In patients with liver metastasis, the effect of trastuzumab alone was low, but that of the combination treatment was significantly high. TTP was 5.7 months and 15.9 months with trastuzumab alone and the combination therapy, respectively. Furthermore, a significant difference was seen in post-treatment survival; however, there was no significant difference in survival after a recurrence. In the multivariate analysis on factors for TTP, PS, clinical effect, and combination treatment were significant. However, good PS and early treatment were the significant factors in post-treatment survival.
Conclusions: The effect of trastuzumab in patients with recurrent breast cancer who received the combination treatment was significantly high and TTP was long. However, this was not a significant factor in terms of overall survival. In particular, a good PS and early treatment were important in post-treatment survival.