High-Dose Intravenous Vitamin C and Mistletoe Therapy in Breast Cancer: A Prospective Cohort Study on Overall Survival in Palliative Care

Background: High-dose intravenous vitamin C (IVC) and mistletoe therapy are widely used in palliative care as complementary interventions to relieve symptoms and improve quality of life. However, prospective evidence regarding their impact on overall survival in breast cancer remains limited. We investigated the longitudinal association between individual complementary therapies and overall mortality in female breast cancer patients. Methods: This prospective cohort study analyzed 748 female breast cancer patients. To account for time-varying exposure and prevent immortal time bias, Cox proportional-hazards regression models incorporating time-dependent covariates with a counting-process structure were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality. Multivariable models were adjusted for baseline clinical, metabolic, and metastatic confounders. Survival curves were generated using the Simon–Makuch method. Results: During a median follow-up of 10.0 months (interquartile range: 2.9–30.2 months), 109 patients (14.6%) died. In multivariable time-dependent Cox regression analysis, high-dose IVC therapy (HR: 0.561, 95% CI: 0.319–0.986, p = 0.045) and mistletoe therapy (HR: 0.463, 95% CI: 0.231–0.927, p = 0.030) were independently associated with significantly reduced overall mortality risk. Hyperthermia therapy showed no significant association with mortality after multivariable adjustment (HR: 1.497, 95% CI: 0.794–2.820, p = 0.212). Conclusions: High-dose IVC and mistletoe therapies were independently associated with lower overall mortality in female breast cancer patients. These findings support further investigation of these modalities as potential integrative adjuncts to standard care.