Dietary Supplement Use During Chemotherapy and Survival Outcomes of Patients With Breast Cancer Enrolled in a Cooperative Group Clinical Trial (SWOG S0221)
- Study type
- Observational study
- Study name
- SWOG S0221
- Design
- Prospective observational (cohort) study ancillary to a treatment trial; Cox proportional hazards regression with a landmark approach at 6 months after enrolment
- Sample size
- 1,134 patients
- Source
- JCO · 2020
In plain words
Many patients take vitamin supplements during chemotherapy, but little is known about their safety. In this study of more than a thousand women with breast cancer, taking vitamin B12 and iron during chemotherapy was linked with worse treatment results, and antioxidant supplements also showed signs of a higher risk of the cancer coming back. Multivitamins showed no link with worse results. Always talk to your doctor before taking any supplement during chemotherapy.
Key results
Treatment arms and regimens
Patients had been randomised in an intergroup metronomic trial of cyclophosphamide, doxorubicin and paclitaxel. Supplement use before and during treatment was recorded. Dose details in the full text.
Source of the regimen details: Abstract of the paper; dose details in the full text
Doses are given for the information of specialists, as in this study’s protocol, and are not a prescription. Every drug must be prescribed by the treating physician for the individual patient.
Study population
Patients with breast cancer randomised in an intergroup "metronomic" trial of cyclophosphamide, doxorubicin and paclitaxel, who were asked about supplement use at enrolment and during treatment.
Endpoints
Association of dietary supplement use (antioxidants, vitamin B12, iron, multivitamins) with disease recurrence, disease-free survival and overall survival. Recurrence and survival were indexed with a landmark approach at 6 months after enrolment.
Safety and side effects
This study did not report treatment adverse events; its focus was the association of supplement use with recurrence and survival. Iron and vitamin B12 were associated with more recurrence and lower survival, and antioxidants also showed signs of an increased risk of recurrence (and to a lesser extent death).
Clinical significance and place in guidelines
These findings support advising caution with dietary supplements (other than multivitamins) during chemotherapy. Because this study is observational, it shows an association, not proof of cause and effect; the status of formal guideline recommendations should be checked separately.
Limitations
The design is observational and the associations are not necessarily causal. Some associations (such as antioxidants) were not statistically significant, and associations with individual antioxidants were probably weaker because of small numbers. Other limitations should be checked in the full text.
This summary was prepared by the editorial team from the published paper; the original paper is the final reference. Read the original abstract on PubMed.