The phrase "median duration" refers to the middle value or length of time in a set of durations. It represents the point where half of the durations are shorter and half are longer. Full definition
A similar trend was seen for median duration of response. (cancernetwork.com)
The response rate for patients receiving nivolumab was 26.1 percent, with a 12.1 month median duration of response before disease progression. (sciencedaily.com)
Hazard ratios were rarely reported directly, so we had to use the ratio of the observed median duration of symptoms in each group as an approximation to the hazard ratio. (bmj.com)