Differences between taxanes in time on therapy and associated discontinuation events in metastatic breast cancer: Results from a U.S. claims analysis.

Abstract

158 Background: Taxanes in metastatic breast cancer (mBC) have demonstrated clinical benefits but have different toxicity profiles. This study evaluated differences in time to discontinuation (D/C) between taxanes overall and by specific events associated with D/C (i.e., death, adverse events (AE), subsequent therapy). Methods: Women receiving >1 dose of either paclitaxel (P), docetaxel (D), or nab-paclitaxel (nab-P) between 2006-2009 were identified by ICD-9 codes indicative of mBC from a commercial payer claims database. Logistic regression and Cox-proportional hazards models were used to compare rates of D/C and time to D/C, respectively. Control variables were age, use of prior or concurrent chemo, and comorbidity score. Drug D/C was defined as no taxane administration for 35 days. AE within 35-days after D/C were considered taxane-associated. Death or disenrollment from the insurance plan within 90 days and initiation of subsequent therapy within 60 days after D/C were considered temporally associated with D/C. Results: 4,503 pts with mBC were included (2,599 received D; 1,643 received P, and 261 received nab-P). The most common reason for D/C in all pts was AEs (37.8%), initiation of subsequent therapy (34.4%), and death or disenrollment (8.4%). A higher proportion of pts on D (29.4%) and P (17.5%) had D/C due to neutropenia vs nab-P (6.9%, p<0.001 for both comparisons). A higher proportion of pts on nab-P (12.3%) continued on therapy until death/disenrollment vs D (8.9%, p 0.046) or P (7.1%, p 0.023). Similarly, a higher proportion of pts on nab-P (51.2%) initiated subsequent therapy at D/C of taxane vs D (31%) or P (37.3%; p<0.01 for both comparisons). Median time to D/C was 85 days for each of D and P, and 127 days for nab-P (p<0.05). Median time to D/C associated with AEs, neutropenia, death/disenrollment or subsequent therapy were significantly longer for nab-P compared with D or P (p<0.05). Conclusions: Women treated for mBC stayed on nab-P therapy 50% longer than with other taxanes. This time on therapy advantage also indicated that pts on nab-P were less likely to D/C due to AEs, more likely to stay on therapy, and more likely to be candidates for subsequent therapies.