Overall survival: still the gold standard: why overall survival remains the definitive end point in cancer clinical trials.

Overall survival (OS) is the gold standard primary end point to evaluate the outcome of any drug, biologic, intervention, or procedure that is assessed in oncologic clinical trials. OS is universally recognized as being unambiguous, unbiased, with a defined end point of paramount clinical relevance, and positive results provide confirmatory evidence that a given treatment extends the life of a patient. Clinical trialists relentlessly attempt to devise more easily measured, cost-effective, and readily available event-driven end points as predictive surrogates of a definitive outcome, such as OS, and reduce the time with which clinical trials deliver definitive results. For some treatment modalities used in a limited number of cancer types, certain event-driven surrogates, eg, progression-free survival or time-to-progression may predict OS benefit. Biologic, cell-based, and vaccine-generated treatments are rapidly expanding the oncologist's armamentarium to combat cancers and pose a dilemma in that response may not be reflected by progression-free survival, time-to-progression, or other surrogates? As targeted therapies march forward, will each new therapy require a unique biomarker validated for every disease indication? Moreover, adjuvant treatments have demonstrated efficacy and given the current limited possibility of cure in the metastatic setting, should other end points, eg, quality-of-life, emerge as valid outcomes to demonstrate benefit. Clinical trials must continue to assess OS until biologically plausible measures are developed and emerge as valid early end point surrogates to replace the gold standard.