Evaluating the Utility of a 'N-of-1' Precision Cancer Medicine Strategy: The Case for 'Time-to-Subsequent-Disease Progression'.

It is increasingly recognized that cancer is a highly heterogeneous group of illnesses even within a particular organ site (e.g., breast, lung, colon, etc.). This observation presents a serious challenge to the traditional concept of phase 3 randomized trials designed to define therapeutic efficacy of a novel treatment strategy. For while 10% of the patients with a common malignancy (e.g., non-small-cell lung cancer) may be sufficient to consider such an effort, enrolling a sufficient number of patients into a clinical trial in a timely manner to define clinical utility would be extremely difficult if the population in question represented only 1% of this population, and essentially impossible if one wished to explore the benefits of treatment in a rarer neoplasm (e.g. ovarian cancer). Therefore, in the new era of precision cancer medicine, alternative research designs are imperative. One option would be to compare the time-to-disease progression of an individual cancer patient following treatment with a novel therapeutic to the time-to-disease progression for that specific patient on her/his immediately preceding treatment. The rationale for this strategy and early experience with this innovative approach to evaluating the efficacy of anticancer therapy is highlighted in this report.