Trastuzumab-based Retreatment after Lapatinib in Heavily Pretreated HER2 Positive Metastatic Breast Cancer: an Anatolian Society of Medical Oncology Study

Background: For HER2 positive metastatic breast cancer (MBC), continuing anti-HER2 therapy beyondprogression is associated with improved outcome. However retreatment with trastuzumab after lapatinibprogression is controversial. We retrospectively analyzed the efficacy of trastuzumab-based chemotherapy inHER2+ metastatic breast cancer patients whose disease progressed after lapatinib. Materials and
Methods:Between October 2010 and May 2013, 54 patients whose disease progressed after lapatinib were retreated withtrastuzumab-based chemotherapy. Efficacy and toxicity results were evaluated retrospectively.
Results: Themedian age of patients was 46 (range 27-67). Fourteen patients (26%) had metastases at the time of diagnosis.All of the patients had received trastuzumab in an adjuvant or metastatic setting, while 16 (30%) had receivedtwo lines of trastuzumab. All patients had received lapatinib plus capecitabine. The median chemotherapyline for the metastatic setting was 2 (range 1-7). Cranial metastases were identified in 27 (50%) patients. 53patients received trastuzumab-based chemotherapy following lapatinib progression while one patient receivedtrastuzumab monotherapy. Combination chemotherapy consisted of navelbin (n=33), taxane (n=10), gemcitabine(n=2), platinum (n=2) and platinum with taxane (n=6). The median treatment cycle was 5 (range 1-44). Among 49patients assessed for response 2 (4%) showed CR, 12 (25%) PR, 11 (22%) SD and 24 (49%) disease progression.Asymptomatic cardiotoxicity was reported in 2 (4%) of the patients. At a median follow-up of 9 months (1-39),median progression-free survival was 5 months (95% CI 4.1-5.9) and median overall survival was 10 months(95% CI 6.9-13.0). PFS and OS were not affected by the absence/presence of cranial metastases.
Conclusions:Retreatment with trastuzumab-based therapy after lapatinib progression showed efficacy in heavily treatedMBC patients.