Over the last decade, the development of new therapeutic options has made more patients benefit from antitumoral strategies including several lines of chemotherapy, the aim of which is a long-term control of the disease progression. In such a context of "chronic" management, the choice of tumor response as a single parameter appears restrictive to assess those new therapeutic options. For that reason, we have recently proposed a composite index of relative efficacy including response rate as well as parameters related to tumour stabilization and duration of the response. The objective of this index, published as the In-RATE is to allow the comparison of two treatments a and b as follows: In-RATE a/b = (response rate a/response rate b) x (time to progression a/time to progression b) x (progression rate b/progression rate a). Values significantly higher or less than 1 suggest the superiority, in terms of efficacy, of treatments a or b, respectively. When retrospectively applied to randomised studies, the In-RATE showed that some results and conclusions based on the response rate as a unique endpoint might be reconsidered, and that a significant difference between protocols could be detected in published reports having concluded to statistical equivalence. This paper reviews the rationale and principle of this work, and discusses the potential clinical applications of the In-RATE.