Clinical characteristics of second primary malignancies among first primary malignancy survivors: A single-center study, 2005–2020

The cancer survivor population is growing due to advances in detection and treatment. For improved long-term patient management, it is critical to examine the clinical characteristics and outcomes of second primary malignancies (SPMs). An SPM is defined as a second distinct pathological diagnosis, with the same or different origin as the first primary malignancy (FPM). In the present retrospective study, categorical clinical variables were compared between subgroups and the impact on overall survival was evaluated. A total of 1,188 patients with an FPM were included, of which 102 experienced an SPM (8.59%). When compared with the patients who did not develop an SPM, patients with an SPM were significantly older at first diagnosis, had a higher pathological stage and higher rates of biliary tract disease and thyroid disease. In addition, patients with an SPM were more likely to have received postoperative chemotherapy (28.43 vs. 12.16%, P<0.0001) and to be long-term consumers of cigarettes and alcohol (25.00 vs. 8.95%, P<0.05). In addition, an increase in the number of regimens received but not in the number of courses of chemotherapy was associated with a reduction in the time interval to SPM development. Non-small cell lung cancer (NSCLC) was the most common type of FPM (18.27%). In patients with NSCLC the occurrence of SPMs was relatively low (5.07%) and the SPM-associated mortality rate was 2.30%. Breast cancer was the second common type of FPM (12.09%). Patients with breast cancer had a relatively high likelihood of developing an SPM (9.30%), for which family history of malignancy and postoperative chemotherapy were identified as potential risk factors. Patients with stomach cancer were the most vulnerable to SPM (17.95%) and patients with digestive tract cancer had the longest time interval between the FPM and SPM development. In addition, thyroid adenoma was identified as a potential risk factor for SCLC. The findings of the present study may provide valuable guidance for the short- and long-term monitoring of FPM survivors.