Objective: An important question in determining long-term prognosis for women with ovarian cancer is whether risk of death changes the longer a woman lives. Large real-world datasets permit assessment of conditional survival (CS) given both prior overall survival (OS) and real-world progression-free survival (rwPFS).
Methods: Using a longitudinal dataset from US oncology centers, this study included 6778 women with ovarian cancer. We calculated CS rates as the Kaplan-Meier probability of surviving an additional 1 or 5 years, given no mortality (OS) or disease progression (rwPFS) event in the previous 0.5-5 years since first-line chemotherapy initiation, adjusted for factors associated with OS based on multivariable Cox regression.
Results: Median study follow-up was 9 years (range, 1-44) from first-line initiation to data cutoff (17-Feb-2021). Median OS was 58.0 months (95% CI, 54.9-60.8); median rwPFS was 18.4 months (17.4-19.4). The adjusted 1-year CS rate (ie, rate of 1 year additional survival) did not vary based on time alive, whereas the adjusted 5-year CS rate increased from 48.5% (47.0%-50.1%) for women who had already survived 6 months to 66.4% (63.3%-69.6%) for those already surviving 5 years (thus surviving 10 years total). The adjusted 1-year CS rate increased from 90.4% (89.5%-91.4%) with no rwPFS event at 6 months to 97.6% (96.4%-98.8%) with no rwPFS event at 5 years; adjusted 5-year CS rate increased from 53.7% (52.0%-55.5%) to 85.0% (81.2%-88.9%), respectively.
Conclusions: This analysis extends the concept of CS by also conditioning on time progression-free. Patients with longer rwPFS experience longer survival than patients with shorter rwPFS.
Keywords: Conditional survival; Observational study; Ovarian cancer; Progression-free survival; Real world.
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