Conditional Relative Survival Among Patients With Gastric Cancer Undergoing Surgery: A Hospital-Based Cohort Study.

Purpose: Conditional relative survival (CRS) estimates the probability of survival after surgery compared with the general population. We assessed 5-year CRS up to 5 years after gastric resection.

Materials and methods: We analyzed 15,601 gastric cancer patients who underwent gastric resection between 1996 and 2018. Relative survival (RS) was defined as the ratio of observed survival in cancer patients to the expected survival in the general population. The 5-year CRS was the 5-year RS among patients who had survived a given number of years after surgery.

Results: Five-year CRS increased from 87.2% at one year to 95.4% at 5 years post-surgery. The most substantial increase was observed in stage III cancer, from 53.2% at one year to 85.2% at 5 years. If patients survived 5 years after surgery, their 5-year CRS was 95.4% for those under 40, 96.4% for those aged between 40 and 64, 92.7% for those aged between 65 and 79, and 99.4% for those 80 or older. Recent surgeries showed higher 5-year CRS at the time of surgery and improved CRS during early follow-up. Although there could be concerns about death from postoperative complications, patients in their 80s did not show lower RS than younger patients. Across operation types, total gastrectomy yielded lower 5-year CRS than distal gastrectomy from baseline through 5 years after surgery.

Conclusions: CRS improved over time, indicating that with careful candidate selection, surgery is safe, even for elderly patients. Additionally, patients who have undergone total gastrectomy may require nutritional support and long-term care.