Crossover in Adjuvant Trastuzumab Trials: Sparing Toxicity in Patient Care

Design and reporting of randomized control trials for drug therapies in the adjuvant setting require a nuanced consideration of patient crossover. Adjuvant trials can be susceptible to the misuse of crossover and may distort the interpretation of findings. We sought to investigate and describe crossover and/or postprogression access to trastuzumab within adjuvant trastuzumab randomized control trials for human epidermal growth factor receptor 2-positive breast cancer patients.

Seven clinical trials for adjuvant trastuzumab in human epidermal growth factor receptor 2-positive breast cancer were identified through a meta-analysis published in the Lancet . Primary study publications were located through MEDLINE, Google Scholar, and trials were identified, when possible, using Clincialtrials.gov.

Sixteen publications, describing 7 studies, were reviewed. Four (57%) trials reported offering patients within the control arm the opportunity to crossover and receive trastuzumab in the adjuvant setting. Two (29%) trials did not report nor discuss crossover within the publication. Five (71%) trials reported the total number of patients who crossed over among the control arms. No trials specified the proportion of control patients who received trastuzumab at recurrence.

Trials for adjuvant trastuzumab did not disambiguate between crossover (1) in the adjuvant setting or (2) at recurrence. Due to the low reported rate of crossover, it is questionable if participants received the standard of care.