Introduction: Survival of patients after cytoreductive surgery (CRS) and heated intraperitoneal chemotherapy for appendiceal neoplasms is projected by conventional overall survival (OS) curves that do not address the survival time a patient has already accrued. We sought to study the conditional survival (CS) after CRS, contingent on patients surviving a fixed duration of time after surgery.
Methods: A retrospective analysis of 493 appendiceal cancer patients from a prospective database was performed. OS was calculated for patients who achieved a complete CRS. CS was estimated based on Kaplan-Meier curves to determine what the patient's long-term survival (3-, 5-, 7-, or 10-year) would be if they were alive at 1, 2, or 3 years from surgery.
Results: OS at 5 and 10 years for 137 low-grade patients with complete resections was 83.3 and 74.2 %, respectively. For low-grade patients still alive at 3 years, 5- and 10-year CS was 93.4 and 83.2 %, respectively. For the 35 high-grade patients with complete CRS who survived to 3 years, CS at 10 years was 41.7 %, while their 10-year conventional OS was 24.6 %.
Conclusions: Conventional analysis underestimates OS due to unpredictable variations in tumor biology. When adjusted for time already elapsed since surgery, improvements in survival estimates are more pronounced with high-grade tumors. CS outcomes can be used in determining the optimal frequency of long-term follow-up of these patients.