Original Title: Avis: Injections de vitamine C à haute dose chez les patients atteints d’un cancer au Québec

Authors' objectives: Observational studies in the late 1970s reported increased overall survival and quality of life in patients with various types of terminal cancer treated with high-dose vitamin C injections. Other publications reported that plasma levels of vitamin C in cancer patients were decreased compared to those of non-cancer patients, and that these levels would vary depending on the severity and stage of the disease. These results led to the hypothesis that high-dose intravenous administration of vitamin C could restore or elevate plasma levels of vitamin C in cancer patients and have a beneficial effect on their survival and quality of life. Since then, many clinical and preclinical laboratory studies (cellular and animal models) evaluated whether vitamin C at very high concentrations could, through the action of different cellular mechanisms, exert anticancer activity or increase the effectiveness of antineoplastic treatments.

Authors' results and conclusions: RESULTS: (1. Health needs and sociocultural aspects): • Cancer patients have requested access to vitamin C injections in order to better manage the side effects associated with oncology treatments and, to a lesser extent, to treat the disease. According to these requests, improving their quality of life and daily routine is a need that must be looked at. (2. Practice profile): • Injectable vitamin C is indicated in Quebec and elsewhere in Canada for the prevention and treatment of scurvy and as a parenteral food supplement. There is no recognized indication for injectable ascorbic acid products to reduce the side effects of oncological treatments or to treat cancer. (3. Level of scientific evidence assessment): • All of the studies included in this assessment are subject to numerous methodological limitations and have a very high risk of bias. The very low methodological quality of the studies jeopardizes the credibility and reliability of many outcomes of interest, as well as the confidence that can be placed in their statistical significance. These limitations create real uncertainty about the interpretation of the available results. (4. Efficacy): • The available data, from studies of low methodological quality, are insufficient and do not allow to conclude whether high-dose vitamin C injections in patients with cancer are effective in: - reducing symptoms associated with the disease; - reducing adverse events associated with antineoplastic treatments; - improve performance status; - improve quality of life; - improve overall survival, progression-free survival and tumor response to treatment. • The available data are insufficient and do not allow to conclude about the effect that vitamin C could have on the efficacy of antineoplastic treatments in cancer patients. In the absence of good quality data in humans, there remains a major concern about the possible interaction between vitamin C and the antineoplastic treatments received and the effect that vitamin C may have on patients’ health and disease progression. (5. Safety): Safety • The available data are limited and make it difficult to conclude on the tolerability and safety of high-dose vitamin C injections in cancer patients. However, in the few studies included, these effects seem to be infrequent and of low intensity. • Certain medical conditions -- renal insufficiency, glucose-6-phosphate dehydrogenase (G6PD) enzyme deficiency, or medical conditions sensitive to increased fluids -- can lead to severe complications, including severe hemolytic anemia and kidney failure when high-dose intravenous vitamin C is administered to patients.

Authors' recommendations: In light of all the information available and in the absence of a demonstration of clinical efficacy, INESSS is of the opinion that high-dose vitamin C should not be offered to people with cancer, regardless of the therapeutic goal sought. This treatment modality should only be offered in the context of a clinical trial. In support of this position, INESSS considers that: • Information regarding the high degree of uncertainty associated with the available scientific data on high-dose vitamin C injections, as well as the reasons why the accessibility of this treatment varies from province to province in Canada, should be communicated to patients and clinicians who have an interest in this treatment; • Information about treatments with proven clinical efficacy and clinical trials in which patients can participate should be clearly communicated. The appropriateness of updating this recommendation will be determined based on new data in support of any of the dimensions evaluated here, notably the publication of results of clinical trials currently underway.

Authors' methods: A systematic review of data from the literature was conducted to document the efficacy and safety of high-dose intravenous vitamin C injections. A rigorous methodological approach supported by validated processes used at the Institute was adopted for this evaluation. Stakeholder consultations, including clinical experts as well as representatives of patient and caregiver associations, were conducted. The literature reviewed included cancer patients of all types and stages treated with high-dose intravenous vitamin C. Scientific, experiential and contextual data were integrated and submitted to a deliberative process that resulted in findings and the recommendation.

Project Status: Completed

URL for project: https://www.inesss.qc.ca/publications/repertoire-des-publications/publication/injections-de-vitamine-c-a-haute-dose-chez-les-patients-atteints-dun-cancer-au-quebec.html

Year Published: 2022

URL for published report: https://www.inesss.qc.ca/publications/repertoire-des-publications/publication/injections-de-vitamine-c-a-haute-dose-chez-les-patients-atteints-dun-cancer-au-quebec.html

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: Canada

Province: Quebec

Organisation Name: Institut national d'excellence en sante et en services sociaux

Contact Address: L'Institut national d'excellence en sante et en services sociaux (INESSS) , 2021, avenue Union, bureau 10.083, Montreal, Quebec, Canada, H3A 2S9;Tel: 1+514-873-2563, Fax: 1+514-873-1369

Contact Name: demande@inesss.qc.ca

Contact Email: demande@inesss.qc.ca

Copyright: Gouvernement du Québec