Taking vitamin supplements before or after a diagnosis of colorectal cancer (CRC) does not appear to impact the risk of CRC-specific death or all-cause mortality, according to an analysis published in JNCI Cancer Spectrum.
Researchers found no significant associations between mortality endpoints and the use of multivitamins, vitamin C, or vitamin E. There was a slightly increased risk of death among vitamin E users, but it did not reach statistical significance.
“Colorectal cancer survivors often use multivitamins and other over-the-counter dietary supplements, but evidence is limited regarding their potential associations with mortality,” the researchers wrote. “This study was conducted to better inform clinicians and colorectal cancer survivors about the potential benefits and/or harms of vitamins and supplements.”
The researchers analyzed data on patients from the Cancer Prevention Study-II Nutrition Cohort who were cancer-free at baseline in 1992 or 1993 but were diagnosed with CRC through June 2015. The study included pre-diagnosis data for 3176 CRC patients and post-diagnosis data for 1256 CRC patients.
Multivitamins were the most common supplements taken, with 49.7% of patients taking multivitamins before their CRC diagnosis and 58.5% of patients taking multivitamins after diagnosis. The pre- and post-diagnosis percentage of patients taking vitamin C was 27.8% and 28.1%, respectively. For vitamin E, the percentages were 27.5% and 29.4%, respectively.
In a multivariable analysis, there was no association between daily multivitamin use before diagnosis and all-cause mortality (hazard ratio [HR], 1.06; 95% CI, 0.96-1.17), CRC-specific mortality (HR, 0.98; 95% CI, 0.81-1.18), or non-CRC-specific mortality (HR, 1.10; 95% CI, 0.98-1.24).
Likewise, daily multivitamin use after CRC diagnosis was not associated with all-cause mortality (HR, 0.97; 95% CI, 0.85-1.11), CRC-specific mortality (HR, 1.00; 95% CI, 0.74-1.35), or non-CRC-specific mortality (HR, 0.96; 95% CI, 0.83-1.12).
Vitamin C use, before or after diagnosis, was not associated with any mortality outcome.
However, the researchers noted that pre-diagnosis vitamin E use was associated with a non-significant increase in the risk of all-cause mortality (HR, 1.08; 95% CI, 0.96-1.23) and non-CRC-specific mortality (HR, 1.13; 95% CI, 0.97-1.31).
Post-diagnosis vitamin E use was also associated with a non-significant increase in all-cause mortality (HR, 1.07; 95% CI, 0.92-1.25), CRC-specific mortality (HR, 1.06; 95% CI, 0.73-1.54), and non-CRC-specific mortality (HR, 1.09; 95% CI, 0.92-1.30).
“These results suggest that multivitamin use before or after diagnosis is not associated with mortality in colorectal cancer survivors,” the researchers wrote. “However, vitamin E use may be associated with increased risk of mortality and merits further investigation.”
Figueiredo JC, Guinter MA, Newton CC, et al. The associations of multivitamin- and antioxidant-use with mortality among women and men diagnosed with colorectal cancer. JNCI Cancer Spectr. Published online June 8, 2022. doi:10.1093/jncics/pkac041