Background \ud \ud Glioblastoma multiforme (GBM) is an aggressive brain tumor. Patients commonly rely on family caregivers for physical and emotional support. We previously demonstrated that caregiver mastery measured shortly after diagnosis was predictive of GBM patient survival, corrected for known predictors of survival (n = 88).\ud \ud \ud \ud Objective \ud \ud The aims of this study were to verify the contribution of caregiver mastery and investigate the added value of mastery over other predictors to predict 15-month survival.\ud \ud \ud \ud Methods \ud \ud Data collected for a longitudinal study (NCT02058745) were used. Multivariable Cox regression analyses were performed for models with known clinical predictors (patient age, Karnofsky Performance Status, type of surgery, O6-methylguanine-DNA-methyltransferase promotor methylation status), with and without adding caregiver mastery to predict mortality. The added value of each model in discriminating between patients with the lowest and highest chances of survival at 15 months was investigated through Harrell's concordance index.\ud \ud \ud \ud Results \ud \ud In total, 41 caregiver-patient dyads were included. When evaluating solely clinical predictors, Karnofsky Performance Status and patient age were significant predictors of mortality (hazard ratio [HR], 0.974; 95% confidence interval [CI], 0.949–1.000; and HR, 1.045; 95% CI, 1.002–1.091, respectively). Adding caregiver mastery, these clinical predictors remained statistically significant, and mastery showed an HR of 0.843 (95% CI, 0.755–0.940). The discriminative value improved from C = 0.641 (model with known clinical predictors) to C = 0.778 (model with mastery), indicating the latter is superior.\ud \ud \ud \ud Conclusions \ud \ud We confirm that caregiver mastery is associated with GBM patient survival.\ud \ud \ud \ud Implications for Practice \ud \ud Incorporating support and guidance for caregivers into standard care could lead to benefits for caregiver well-being and patient outcomes.
