Purpose: In many primaries other than non-seminoma testis cancer, the risk of death due to cancer decreases with increasing disease-free interval duration after initial diagnosis and treatment. This effect is known as conditional survival and is relatively unexplored in stage III non-seminoma patients, where it may matter most in clinical decision-making. We examined the effect of disease-free interval duration on overall survival in stage III non-seminoma patients.
Materials and methods: Within the Surveillance, Epidemiology, and End Results Database (2004-2018), stage III non-seminoma patients were identified. Multivariable Cox regression analyses and conditional survival models were applied.
Results: Of 2,092 surgically treated stage III non-seminoma patients, 385 (18%) exhibited good vs. 558 (27%) intermediate vs. 1,149 (55%) poor prognosis. In multivariable Cox regression models, poor prognosis group independently predicted overall mortality (HR 3.3, P < 0.001). In conditional survival analyses based on 36 months' disease-free interval duration, 5-year overall survival estimates were as follows: good prognosis patients 96 vs. 89% at initial diagnosis without accounting for disease-free interval duration (Δ=+7); intermediate prognosis patients 94 vs. 85% at initial diagnosis without accounting for disease-free interval duration (Δ=+9); poor prognosis patients 94 vs. 65% at initial diagnosis without accounting for disease-free interval duration (Δ=+29).
Conclusions: Conditional survival estimates based on 36 months' disease-free interval duration provide a more accurate and more optimistic outlook for stage III non-seminoma patients than predictions defined at initial diagnosis, without accounting for disease-free interval duration.
Keywords: Cancer mortality, SEER program; Disease-Free survival; Prognoses; Testicular cancer; Testis cancer.
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