Many TCGA samples have three rows in their clinical data that may be of interest for survival analysis: days to death, days to last follow-up, and days to sample procurement. My questions are, in this data, what does day 0 refer to, and what is sample procurement?
For instance, consider SKCM patient "tcga-fs-a1zc". His days to death value is "10870", his days to last follow up value is "NA", and his days to sample procurement value is "10158". If I were plotting his information on a Kaplan Meier plot, would his survival time be 10870, or 712? (10870-10158)