Starting and stopping cancer drugs: The need for randomized trials.

Precision oncology has gained widespread popularity over the past decade, and increasingly oncologists strive to provide the right treatment to the right patient. To date, precision efforts have focused on the specific mutational target(s), food/ drug interactions, functional oncology, or dose of drug given. Moreover, the tumor and blood samples of hundreds of thousands of patients with cancer have been sequenced in the United States alone with the goal of identifying and prescribing the most precise treatment. Despite this broad consideration of precision oncology, one neglected aspect of precision oncology is identifying the optimal start time and stopping point for cancer therapies. Is it possible to improve overall survival (OS) or quality of life for patients with more precise initiation and discontinuation of therapy? In this commentary, we review the historical basis to initiate, discontinue or switch therapies. We emphasize that largely these time points were selected arbitrarily, and subsequently constrained by historical accident. We highlight randomized efforts to better elucidate the time points in starting or stopping therapy. Finally, we provide suggestions for a research agenda on precision timing of anti-cancer drugs.