Changing odds of survival over time among patients undergoing surgical resection of extremity soft tissue sarcoma

Abstract

Background While survival after surgical treatment of extremity soft tissue sarcoma (STS) is traditionally reported as actuarial survival, conditional survival (CS) may be more clinically relevant as it accounts for time already survived. We compared actuarial survival and CS of STS patients. Materials and Methods We analyzed 567 patients who underwent surgery for localized extremity STS. Actuarial survival was estimated using the Kaplan‐Meier method. Cox proportional hazards model was used to evaluate factors associated with disease‐specific survival. Five‐year CS (CS5) estimates at “χ” year(s) after surgery were calculated as CS5 = S(χ + 5)/S(χ). Results Whereas actuarial survival decreased over time, CS5 increased. The postsurgical 1‐, 3‐, and 5‐year CS5 values were 84.5%, 90.0%, and 93.8%, respectively, whereas the 6‐, 8‐, and 10‐year actuarial survival rates were 82.0%, 79.4%, and 78.5%, respectively. The calculated CS5 exceeded actuarial survival especially in patients with risk factors such as large tumor size and Federation Nationale des Centers de Lutte Contre le Cancer (FNCLCC) grades 2 and 3 tumors. Patients with tumor size ≥5 cm had an actuarial survival of 73.9% at 10 years compared to a CS5 of 95.4% in patients alive at 5 years. Likewise, patients with FNCLCC grade 3 tumors had an actuarial survival of 71.1% at 10 years compared to a CS5 of 96.0% in patients alive at 5 years. Conclusions Survival estimation by determination of CS can be dynamic and accurate especially in high‐risk patients. CS can be useful for survival prediction and clinical decision making in extremity STS patients.