ASCO GU 2018: Multivitamin Use and Risk of Prostate Cancer Recurrence: Data from the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE)

San Francisco, CA (UroToday.com) As clinicians, we often get asked about dietary modifications or lifestyle modifications that may help prevent and improve prostate cancer. However, there has been very little data to support any dietary supplement / vitamins in reducing the risk of prostate cancer or improving outcomes.

Daily multivitamins (MV), those that provide the daily recommended dose of vitamins, are often taken by patients. While common among men, especially men with cancer, data on MV use and risk of PCa recurrence is limited.

In this study, the authors conducted a prospective study of 1,375 men with non-metastatic PCa. Specifically, they assessed whether MV use after diagnosis was associated with risk of recurrence. Participants completed a comprehensive lifestyle survey a median of 2 y after diagnosis and were followed through 2016. Recurrence was defined as: PCa death, bone metastasis from PCa, biochemical recurrence, or initiation of secondary treatment.

Over a median follow-up of 10 years, 142 recurrence events of PCa were identified. Of the cohort, 858 (62%) men were current MV users, 216 (16%) were past users, and 299 (22%) were never users. Exposure time was captured.

Current MV users tended be younger and have received RP as primary treatment. MV use was not associated with BMI, smoking, cT-stage, Gleason grade or PSA at diagnosis.

Overall, on multivariable analysis, MV use was not associated with risk of PCa recurrence (current vs. never HR: 0.69; 95% CI: 0.45, 1.07; p-trend: 0.09). However, long-term MV users (≥10 y; n = 396) had a 56% lower risk of PCa recurrence compared to never users (HR: 0.44; 95% CI: 0.25, 0.78; p-trend: 0.006); it should be noted that men with <5 years or 5-9 years MV use were no different than non-users.

Interestingly, among the 845 men who had a radical prostatectomy (RP), current MV users had a 44% lower risk of PCa recurrence compared to past/never users (HR: 0.56; 95% CI: 0.34, 0.91; p-value: 0.02). MV use was not associated with risk of PCa recurrence among the 441 men who did not have a RP – unfortunately, no treatment details were provided regarding non-RP treatments.

Based on these results, the authors conclude that long-term MV use may be associated with (but not necessarily directly causal to) reduced recurrence in men with PCa. In particular, men who underwent RP were noted to have better outcomes when taking MVs.

Limitations / Discussion Points:

  1. It is important to note that MV use, especially long-term MV use, may be a surrogate for better healthcare and more patient participation in their own healthcare. Patients not taking vitamins may just represent a patient population in poorer health or less likely to follow-up on their prostate cancer.
  2. Competing risks analysis were not completed. Patients on MV long-term, if healthier overall, may just be surviving longer and developing PCa recurrence; or are less likely to die of other causes before PCa recurrence.
  3. Patients undergoing RP are generally healthier than patients choosing other definitive therapies – again introducing selection bias in the results.

While an interesting study, it is not randomized and important confounding variables have not been addressed.
they consider to be thorough.

Presented by: Erin Van Blarigan, ScD

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Twitter: @tchandra_uromd at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA
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