ISG15 and cancer: In a proportional hazards, multivariate analysis with cytoreduction status and age adopted as covariates, low ISG15 expression by cancer cells was associated with a poorer overall survival (HR 2.265, 95% CI:1.5–3.43, p < 0.001), and progression-free survival (HR 1.909, 95% CI:1.28–2.84, p = 0.001) (Supplementary Table S1).