Incidence of second malignancies in patients with thymic carcinoma and thymic neuroendocrine tumor.

Objectives: Thymic carcinoma and thymic neuroendocrine tumor (NET) are rare and are more likely to develop second malignancies. The purpose of this study was to explore the incidence and lifetime risk of second malignancies in thymic carcinoma and thymic NET.

Methods: The standardized incidence ratio (SIR) and the age-adjusted cancer incidence of the thymic carcinoma and thymic NET patients with second malignancies were retrospectively calculated by using the Surveillance, Epidemiology, and End Results (SEER) database. Prognosis results were also determined by Kaplan-Meier analysis and Cox regression.

Results: 1130 patients with thymic carcinoma (73 patients had second malignancies) and 263 patients with thymic NET (19 patients had second malignancies) from 2000 to 2018 are included. Patients with thymic carcinoma (SIR: 1.36, 95% CI 1.08-1.69) and with thymic NET (SIR: 1.73, 95% CI 1.13-2.54) demonstrate an increased overall risk of developing second malignancies in various organ systems. The age-adjusted cancer incidence of second malignancies in patients with thymic carcinoma is 3058.48 per 100,000 persons (4178.46 per 100,000 persons in patients with thymic NET). Age at diagnosis is a significant risk factor for the development of second malignancies.

Conclusion: The incidence of second malignancies in patients with thymic carcinoma and thymic NET is significantly higher than the patients in the normal population. The occurrence of second malignancies is not related to the use of different treatments. It is important to extend the follow-up period and add other screening methods.