Changing Odds of Survival Over Time among Patients Undergoing Surgical Resection of Gallbladder Carcinoma

Background: While survival after malignancies is traditionally reported as actuarial survival, conditional survival (CS) may be more clinically relevant by accounting for “accrued” survival time as time progresses. We sought to compare actuarial and CS among patients with gallbladder carcinoma (GBC). Methods: A total of 312 patients who underwent curative intent surgery for GBC between 2000 and 2014 were identified using a multi-institutional database. Overall survival (OS) was estimated using the Kaplan–Meier method. CS was calculated as the probability of surviving an additional 3 years at year “x” after surgery using the formula CS₃ = S_(x+3)/S_x. Results: Among all patients, the median actuarial OS was 24.8 months (IQR 13.3–88.9). While actuarial survival decreased over time, 3-year CS (CS₃) increased, with CS₃ at 2 years after surgery noted to be 61.8 % compared with the 5-year actuarial OS of 31.6 %. Factors associated with reduced actuarial OS were positive margin status (HR 3.61, 95 % CI 2.47–5.26), increasing tumor size (HR = 1.02, 95 % CI 1.01–1.02), higher tumor grade (HR 2.98, 95 % CI 1.47–6.04), residual disease at repeat resection (HR = 2.78, 95 % CI 1.49–3.49, p < 0.001), and lymph node metastasis (HR = 1.95, 95 % CI 1.39–2.75, all p < 0.001). The calculated CS₃ exceeded the actuarial survival within each high-risk patient subgroup. For example, patients with residual disease at repeat resection had an actuarial survival 23.1 % at 5 years versus a CS₃ of 56.3 % in patients alive at 2 years (Δ = 33.2 %). Conclusions: CS provides a more accurate, dynamic estimate for survival, especially among high-risk patients. CS estimates can be used to accurately predict survival and guide clinical decision making.