Proposal of a Useful Surrogate Endpoint of the Overall Survival in Patients Undergoing Pulmonary Metastasectomy: The Time to Local Therapy Failure.

Background: A recent study demonstrated remarkable discrepancy between the relapse-free survival (RFS) and overall survival (OS) after pulmonary metastasectomy (PM) in the current era. As the RFS may not be a suitable parameter after PM, a more suitable parameter is needed for PM as a surrogate marker for OS.
Methods: A total of 134 consecutive patients who underwent PM were retrospectively analyzed. In the present study, we introduced a new endpoint, time to local treatment failure (TLTF). This endpoint was defined as the time interval between the first PM and the first untreatable recurrence by local treatment with curative intent or death due to any cause. We analyzed the correlation between the RFS and OS and between the TLTF and OS to validate whether or not the TLTF is a better parameter than the RFS after PM.
Results: Thus far, 78 patients have experienced relapse. Of these, 37 patients (47%) underwent local therapy with curative intent, 29 of whom are alive without local treatment failure. The 5-year OS, RFS and TLTF were 70.9%, 36.5%, and 57.6%, respectively. The concordance proportions for the RFS and OS and for the TLTF and OS were 0.634 and 0.851 for all patients, respectively. The Spearman's rank correlation coefficient for the RFS and OS was 0.639, while that for the TLTF and OS was 0.875.
Conclusions: The TLTF may be a good surrogate parameter for the OS after PM in the current era.