Background: Both efficacy and toxicity impact a persons experience ith chemotherapy, as recognized in a recently published ASCO frameork. A number of approved chemotherapy agents require early dose reductions from approved dosesschedules. We sought to simplify the evaluation of toxicity to a single number  scalar , to more easily compare the cost vs. benefit of a given systemic treatment. Methods: We developed matrices employing  1  linear,  2  eak exponential, and  3  strong exponential scores for all 790 grade 1-4 National Cancer Institute Common Toxicity Criteria. We generated summary toxicity scores from the matrix products of clinical trial toxicity data and the three toxicity matrices. The trace of the matrix products yields an index for a given treatment on a given trial. We term this index the Weighted Toxicity Score WTS . Results: As a group of studies to examine systematically, e identified 51 randomized clinical trials of kinase-directed inhibitors approved for treatment of cancer beteen 112004 and 72015. We correlated the frequency of dose reductions in each trial ith each difference and ratio of WTS  experimental vs. control arms . Differences in dose reduction rates in the 18 placebo-controlled studies ith complete data correlated most strongly ith differences in WTS using a eak exponential scoring matrix. Conversely, there as not a statistically significant relationship beteen WTS and the hazard ratio for progression free survival  PFS  beteen trial arms, indicating that greater toxicity as not associated ith greater PFS benefit. Conclusions: The WTS distills the toxicity of a given treatment into a single value. As a result, the WTS allos toxicity and benefit to be compared simultaneously. Iterations on WTS matrices may allo more accurate dose finding and comparison of chemotherapy agents across phase I-III clinical trials, or as a ay to calculate a toxicity area-under-the-curve, ith a goal of greater patient safety before and after regulatory approval.,J Clin Oncol 34, 2016  suppl; abstr 6605 00:00.0,Health Services Research and Quality of Care