Clinical outcomes of delayed start of trastuzumab treatment in patients with early breast cancer: ml25232 study

Abstract

Background: Breast cancer patients in low and middle income countries have limited access to targeted therapies such as trastuzumab. The discontinuous availability of trastuzumab created waiting lists and subsequent very delayed treatment. Since few studies have systematically analyzed possible deleterious effect of delayed trastuzumab treatment, we designed a study to investigate its consequences on overall survival and disease-free survival. Methods: This was a multicenter cohort study of HER2-positive early breast cancer patients (n=223) diagnosed between 01/05/2005 and 01/05/2010 in the Federation of Bosnia and Herzegovina. The study began in 01/01/2010, and enrollment was completed in 30/06/2012. Last follow up and cut off date for analysis was 31/03/2015. Results: A total of 223 women (median 55 years; IQR: 49-61 years) were recruited. Since 131 (59%) patients waited for > 6 months after surgery to receive trastuzumab, we categorized our patient cohort into three groups: non-waiting group (n=92; wait time <6 months), and waiting group 1 (n=85; wait time between 7 to 12 months) and waiting group 2 (n=46; > 13 month wait). OS at 5 years in non-waiting group was 84%, compared to 72% in wait group 1 and 75% in wait group 2 (p>0.05). DFS at 5 years in the non-wait group was 79%, compared to 65% in wait group 1, and 68% in wait group 2 (p>0.05). Conclusions: Unfortunate and unique circumstances in developing countries have created waiting lists for trastuzumab treatment-our systematic analysis of 223 women has shown that delayed start of trastuzumab treatment does not have a statistically significant effect on clinical outcomes, but shows a trend towards worse OS and DFS for women with delayed treatment. Thus, trastuzumab treatment has a persistent benefit even when administered with delayed start.