Vitamin C as an Adjunctive Therapy in Cancer: A Systematic Review and Meta-Analysis of Outcomes in Solid and Hematologic Malignancies.

Vitamin C has gained interest as an adjunctive treatment in oncology due to its antioxidant effects, potential to enhance cancer therapy, and ability to improve quality of life. This systematic review and meta-analysis aimed to assess the therapeutic impact of vitamin C in patients with solid and hematologic malignancies. A comprehensive search was conducted in PubMed, Cochrane, Embase, ClinicalTrials.gov, and Google Scholar from inception to August 2025, in accordance with PRISMA guidelines. A total of 43 studies were included, with 19 focusing on hematologic malignancies (695 patients) and 24 on solid tumors (827 patients). Data were extracted and analyzed using Kaplan-Meier survival plots via the MetaSurvival package (R version 4.2.1; R Foundation for Statistical Computing, Vienna, Austria). Selected studies were also described narratively. In hematologic malignancies, the median age was 60.92 years, and 49.07% were male. The pooled median overall survival (mOS) was 34.42 months, and median progression-free survival (mPFS) was 14.09 months (95% CI: 9.54-20.50). The estimated mean OS and PFS were 27.80 months (95% CI: 22.78-31.58) and 19.63 months (95% CI: 15.97-22.53), respectively. Among solid tumors, pancreatic cancer showed a mOS of 15.2 months and lung cancer 13.4 months. Vitamin C was also associated with reduced inflammation, oxidative stress, and radiotherapy-related side effects, as well as improved quality of life. Vitamin C may enhance tolerability and patient-reported outcomes in cancer therapy. While survival benefits were observed in hematologic malignancies, evidence remains inconsistent in solid tumors, underscoring the need for larger, well-designed trials.