Measuring the multidimensional aspects of tolerability.

As new cancer therapies emerge and evolve, there is a need for a better understanding of their safety and tolerability. Safety and tolerability are distinct, albeit related, constructs; an unsafe treatment cannot be considered tolerable, whereas safe treatments may not be tolerable to some patients. Cancer treatment tolerability is a multidimensional construct, and is influenced both by the profile of adverse events and by whole-person factors. This commentary provides definitions of safety, tolerability, adverse events, and toxicity by relating these constructs to the adverse event reporting paradigm. Measures, including summary indicators, that reflect the tolerability of cancer treatments are also identified. The commentary concludes with a discussion of how evaluations of tolerability may be meaningfully incorporated into the design and interpretation of future cancer treatment trials.