The Causes of Death and Conditional Survival for Long-Term Survivors of Thymoma

Abstract

Data on the morality cause for long-time survival of thymoma is limited. The previous study hinted that thymoma may be a chronic disease rather than a curable cancer. we performed a large-scale retrospective analysis to assess long-term cause of death in patients with thymoma. This study reviewed thymoma patients from the Surveillance, Epidemiology, and End Results (SEER) database between January1975 and December 2016.Conditional survival and annual hazard rates was calculated with Kaplan-Meier, and cause-specific mortality was performed using Fine-Gray competing risks analysis. Of 3105 patients were identified (median [range] age,58 (18-93), years), 1615 (52.0%) were male,1028(33.1%) were 65 years or older and 1360(43.8%)patients was at locally advanced (IIB-III) disease. The 10-year overall survival (OS) and cancer-specific survival (CSS) rates were 55.5% (95% CI, 53.4-57.6%) and 74.4% (95% CI, 72.4-76.3%) respectively. Smoothed hazard showed that the annual overall death hazard of death increased steadily, but the hazard of thymoma-related death began to decline at about 4 years and is exceeded by other causes at death. However, the annual risk of death by thymoma remain about 1-2% at 5-25 years. Similarly, the conditional OS increased slowly with increased survival time however the cancer-specific survival based decreased slowly. The cumulative incidence of the most common causes of death was 23.1% for thymoma, 5.4% for heart of disease, and 3.9% for the second cancer in 10 years, 28.5%,8.3 and 7.0% in 15 years, and 31.8%,11.8% and 10.8% in 25 years. After 5 years of survival, the death of heart was the main cause of non-thymoma death. The 10-years survivors' older patients (≥65 years) or with radiotherapy suffered more heart specific death (adjust P< 0.001, P = 0.015, respectively). The risk of cancer-specific death and other causes of death shift over time for patients with thymoma. The non-cancer cause, especially heart diseases which may be the vital competing cause of death, increased with prolongation of survival time.