Risk of Second Primary Cancer Among Patients with Cardio-Esophageal Cancer in Finland: A Nationwide Population-Based Study

Purpose: The occurrence of a second primary cancer (SPC) after primary esophageal carcinoma (EC) or gastric cardia carcinoma (GCC) is well acknowledged. However, previous research on the risk of SPC among these patients has been predominantly conducted in Asian countries. Yet, notable population-dependent variation in histological types and risk profiles exists. This register-based study assesses the histology-specific risk of SPC among individuals initially diagnosed with a first primary EC or GCC. Patients and Methods: We obtained data on 7197 patients diagnosed with EC/GCC in Finland between 1980 and 2022 from the Finnish Cancer Registry. Standardized incidence ratios (SIR) of SPC were subsequently calculated relatively to the cancer risk of the general population. Results: The average and median follow-up times were 2.8 years and 10.5 months. Adenocarcinomas and squamous cell carcinomas comprised 57.8% (n = 4165) and 36.6% (n = 2631) of all cases, respectively. An increased SIR was noted among EC/GCC patients after 15–20 years of follow-up (SIR 1.49, 95% CI: 1.01–2.11). Among adenocarcinoma patients, an increased SIR for SPCs of the digestive organs was seen in the 40–54-year-old group (SIR 9.86, 95% CI: 3.62–21.45). Squamous cell carcinoma patients displayed increased SIRs for cancer of the mouth/pharynx (SIR 3.20, 95% CI: 1.17–6.95) and respiratory organs (1.77, 1.07–2.76). Conclusion: Healthcare professionals should be aware of the increased risk of SPCs occurring in the mouth/pharynx, respiratory and digestive organs in survivors of EC/GCC. Patients should be advised about this risk and remain alert for symptoms, even beyond the standard 5-year follow-up period.