Relationship between long-term outcomes and optimal time interval in patients with bilateral synchronous multiple primary lung cancers: a multi-institutional cohort study.

[BACKGROUND] With the advancement of diagnostic technology and changes in living environment, the incidence of synchronous multiple primary lung cancer (sMPLC) is increasing. This study aims to investigate the impact of surgical timing on clinical outcomes.

[METHODS] This multi-institutional cohort study retrospectively enrolled 901 patients with bilateral sMPLC who underwent two surgeries from January 2017 to December 2022. Three different subgroups were determined based on the time interval between the 1 surgery and the 2 surgery: Group-I (time interval ≤ 90 days), Group-II (90 days < time interval ≤ 180 days) and Group-III (time interval > 180 days).

[RESULTS] For the entire cohort, the median follow-up time from the second surgery was 49.2 months. The clinical outcomes of patients in Group-II were more favourable than those in Group-I and Group-III (log-rank, OS,  = 0.0037; DFS,  < 0.0001). According to multivariable Cox regression analyses, patients in Group-I (HR, 1.704; 95% CI, 0.828-3.51;  = 0.148) and Group-III (HR, 5.369; 95% CI, 2.664-10.819;  < 0.001) may be associated with poor prognosis compared with those in Group-II. In addition, patients in Group-III had a high incidence of postoperative complications, and significantly reduced lung function was identified among patients in Group-I.

[CONCLUSIONS] For patients with bilateral sMPLC, our research identified a potential correlation between the interval of subsequent surgeries and patient prognosis. We suggest that an interval of 90 to 180 days between surgeries may be the most beneficial.