The length of time from either the date of diagnosis or the start of treatment for a disease, such as cancer, that half of the patients in a group of patients diagnosed with the disease are still alive. In a clinical trial, measuring the median survival is one way to see how well a new treatment works. Also called [[median overall survival]]. 

Example:

Median survival of [[glioblastoma]], the most aggressive variant, is 16 months in patients treated with [[maximum safe resection]], radiotherapy, and concurrent and adjuvant temozolomide in clinical trial populations
((Stupp R, Mason WP, van den Bent MJ et al. Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med. 2005;352 (10):987–996.))
((Weller M, van den Bent M, Hopkins K et al. EANO guideline for the diagnosis and treatment of anaplastic gliomas and glioblastoma. Lancet Oncol. 2014;15 (9): e395–e403.)).