A population-based study of trastuzumab-mediated cardiotoxicity among early stage breast cancer patients treated with adjuvant trastuzumab

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10640 Background: Given the risk of cardiotoxicity demonstrated with trastuzumab (T) in the MBC literature, adjuvant T trials incorporated stringent cardiac monitoring. In 2005, several of these trials were reported with impressive DFS improvements. As a result of these trials, women in the province of British Columbia with HER-2 positive early stage breast cancer were offered T either concurrently or sequentially with their primary chemotherapy regimen. Given the paucity of data surrounding adjuvant T-mediated cardiotoxicity among the general population, we performed a retrospective review of cardiac toxicity among all patients receiving adjuvant T at the BCCA. Methods: Patients receiving adjuvant T between July 1, 2005 and December 31, 2005 either sequentially or concurrently with their primary chemotherapy regimen were identified by screening the BCCA pharmacy database. A chart review was conducted and the T start date; LVEF values at 0, 3 and 6 months; and patients with symptoms suggestive of congestive heart failure were identified. The mean LVEF values at 0, 3 and 6 months were calculated. Results: 133 patients received adjuvant T alone after completing their primary chemotherapy. The mean baseline LVEF was 60.5%. Of the 101 and 11 patients available for analysis at 3 and 6 months, the mean LVEF was 58.5% and 58.4%, respectively. 5 patients (3.8%) developed symptoms of CHF. 58 patients received adjuvant T concurrently with their primary chemotherapy (four cycles of AC followed by four cycles of concurrent paclitaxel and T). Of these, only 18 patients had an LVEF measured at 0 and 3 months, with a mean LVEF of 64.6% and 63.6%, respectively. Of the 7 patients who also had an LVEF measured at 6 months, the mean was 60.5% for an absolute decrease of 4.1% from baseline. One patient (1.7%) had symptomatic CHF. Conclusions: A clinically meaningful rate of cardiotoxicity is seen with both sequential and concurrent adjuvant T. In particular, we have demonstrated a higher rate of cardiotoxicity with adjuvant T alone than was observed in the HERA trial. These findings support ongoing stringent cardiac monitoring among the general population treated with adjuvant T. [Table: see text]