How to perform metastasis-free survival?

Question

[Ashleyca]

Hi all, I wonder how to perform metastasis-free survival. I consider that if a patients was found to have tumor metastasis, this event was assigned as "1"; if a paitent was not found to have tumor metastasis,this event was assigned as "0". But if a patient was found to have tumor recurrence, but was not found to have tumor metastasis, how to define this event? Thank for any help.

Sincerely, Ashley Tam

[Jean-Karim Heriche]

I am not an expert but it seems to me a matter of logic. If you're interested in metastasis, then a patient either has metastasis or he/she doesn't hence the 1/0 coding scheme. Accordingly a tumor recurrence without metastasis means a metastasis-free patient so code 0. Nowhere in the presence/absence scheme is there mention of tumor recurrence. Now if you're interested in the combination of tumor recurrence and metastasis then you need another coding scheme, maybe something that encodes all relevant categories, e.g. 0 for no recurrence, no metastasis, 1 for recurrence, no metastasis and so on or another binary variable with 1 for recurrence and 0 for no recurrence which you combine with the 0/1 for metastasis.