ABSTRACT
OBJECTIVES: Several studies have reported that patients operated on for non-small cell lung cancer (NSCLC) are at high risk of second primary lung cancer (SPLC). However, widely varying estimates of this risk have been reported, with very few studies taking into account that these patients are at particularly high competing risk of death, due to recurrence of the initial disease and to comorbidities. Risk factor evaluation over time has significant repercussions on the post-surgery surveillance strategy offered for NSCLC. This study primarily sought to measure the risk of SPLC in a long-term follow-up series, using statistical methods considering competing risks of death. MATERIALS AND METHODS: The cumulative SPLC risk was estimated using the cumulative incidence of patients with completely resected Stage I-III NSCLC diagnosed between 2002 and 2015 based on the Doubs and Belfort cancer registry (France). A proportional sub-distribution hazard model (sdRH) was used to investigate factors associated with SPLC risk in the presence of competing risks. RESULTS: Among the 522 patients, adenocarcinoma and Stage I or II disease accounted for 52.3% and 75.7% of patients, respectively. Overall, 84 patients developed SPLC (16.1%). The cumulative risk of SPLC was 20.2% at 10 years post-surgery (95% confidence interval [CI]: 15.3-23.2), and 25.2% (CI: 19.4-31.3) at 14 years post-surgery. On multivariate analysis, the SPLC risk was significantly higher in patients with postoperative thoracic radiotherapy (sdRH 2.79; 95% CI: 1.41-5.52; p = 0.003). CONCLUSION: This study using appropriate statistical methods to consider competing risks showed that after complete NSCLC resection, the cumulative incidence function of SPLC was high, with patients receiving postoperative thoracic radiotherapy at higher risk. These data support the need for life-long follow-up of patients who undergo NSCLC surgery, with the objective of screening for SPLC.
