Prevalence of dietary modification and supplement use in patients with metastatic renal cell carcinoma (mRCC).
Authors: Ebrahimi Hedyeh , Battle Dena , Zengin Zeynep Busra , Dizman Nazli , Meza Luis A , Castro Daniela V. , Govindarajan Ameish , Mercier Benjamin D. , Chawla Neal Shiv , Chehrazi-Raffle Alex , Tripathi Abhishek , Liu Sandy , Vaishampayan Ulka N. , Staehler Michael D. , Pal Sumanta Monty 
Published: March 2023

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Background: Mounting data suggests that dietary modification and supplement use, including probiotics, may modulate outcomes with immunotherapy in cancer therapy (Spencer CN et al. Science 2021; Dizman N et al. Nature Medicine 2022). For the first time, we sought to quantify the use of these measures among patients with metastatic renal cell carcinoma (mRCC). Methods: An online survey was administered by Kidney Cancer Research Alliance (KCCure), a non-profit patient advocacy group, between July 22 and Sept 22 to a patient mailing list (N=1,532). Only patients diagnosed with mRCC and under active systemic therapy were included for analysis in the current study. Select questions were directed at dietary modification patterns and supplement usage. Patients were additionally surveyed regarding out-of-pocket spending patterns related to supplement purchases and to what extent they shared information about their supplement intake with their physicians. The student's t-test and Chi-square test were used to compare sociodemographic characteristics between participants who did and did not report supplement intake. Results: Out of 1,062 patients with renal cell carcinoma who participated in this survey, 289 met the inclusion criteria (M:F, 145:143). The median age was 61. The majority of patients identified themselves as white (91%), were from the US (86.8%), and had completed a bachelor's degree (52.9%). 21.1%, 46.1%, and 32.6% lived in urban, suburban, and rural locations, respectively. The most common reported first-line treatments were nivolumab/ipilimumab (32.4%) and axitinib/pembrolizumab (13.1%). 22.4% of respondents reported spending >$100/month on supplements, and 8.3% reported spending >$250/mo. Dietary modifications following a cancer diagnosis were reported by 34.9% of respondents, out of which 19.8% followed the Mediterranean diet and 18.8% adopted a ketogenic diet. 50.8% of respondents reported supplement intake. The most widely utilized supplements were cannabidiol (CBD) oil/marijuana, probiotics, and Vitamin C, reported by 28.0%, 24.2%, and 18.6% of respondents, respectively. 83.4% of respondents noted that they consistently report supplement usage to their physicians. There were no statistically significant associations between supplement use and age, sex, living area, or education. Conclusions: A substantial proportion of patients with mRCC use dietary modification and supplements as an adjunct to their antineoplastic treatment. Interventions such as probiotic use and ketogenic diets, which are the subject of a prospective study in mRCC (NCT05119010; NCT05122546), may already be used by many patients. More careful attention to nutrition and supplement use in clinical trial candidates may minimize the impact of these potential confounders.