Surgery for thymic malignancy and nonthymic malignancy incidence: A national longitudinal study

Previous clinical series and registry analyses have identified a link between thymic malignancies and nonthymic malignancies observed concurrently or subsequent to a thymic malignancy diagnosis. The impact of surgery for thymic malignancies on the risk of subsequent nonthymic malignancies is controversial. We aimed to evaluate this impact in a nationwide setting.

Using the French National Discharge Database (2014-2023), we conducted a retrospective cohort study of adults diagnosed with a first thymic malignancy (International Classification of Diseases, 10th Revision code C37) recorded as the primary discharge diagnosis. Patients with nonthymic malignancies diagnosed before 2015 or within 6 months of thymic malignancy diagnosis were excluded. The primary outcome was nonthymic malignancies, with surgery for thymic malignancies as the main exposure. We measured nonthymic malignancies incidences across treatment groups in complete and propensity score-matched samples. Associations were estimated using time-dependent adjusted hazard ratios and odds ratios.

Among 3611 patients with thymic malignancy, 2616 (72.4%) underwent surgery for thymic malignancies, either alone (n = 2114) or within a multimodality approach (n = 502). The incidence of nonthymic malignancies was 30.08 (95% CI, 26.21-33.96) and 53.50 (95% CI, 44.26-62.73) per 1000 person-years in patients with and without surgery for thymic malignancies, respectively (log P < .001). In the complete sample, the adjusted hazard ratio of nonthymic malignancies after surgery for thymic malignancies was 0.85 (95% CI, 0.80-0.90; P < .001). In matched samples, the adjusted odds ratio was 0.66 (95% CI, 0.52-0.83; P < .001). Lung cancer showed the largest incidence reduction (adjusted hazard ratio, 0.79, 95% CI, 0.72-0.86; P < .001).

Surgery for thymic malignancies was associated with a reduced incidence of nonthymic malignancies in patients with thymoma.