Background: Consumption of herbs, food used as medicine and dietary supplements (HFDSs) is common in cancer patients. Herbs and food-drug interactions (HFDIs) can lead to serious adverse effects and can be prevented. We previously reviewed cytochrome P-450 (CYP)-mediated HFDI for 261 HFDSs and we classified the risk of CYP inhibition and induction on a level of evidence scale from 1 (high evidence, supported by several clinical studies) to 5 (low evidence, only limited preclinical data)., Patients and Methods: We conducted a prospective, non-interventional study (NCT04128865) to assess whether self-assessment of patients could detect HFDI classified as 'probable' (i.e. level 1, 2 or 3 of the scale) in a population of cancer patients. Patients were invited through a tablet application to report their consumption of herbs, regular CYP-interacting food consumption and dietary supplements, as well as some clinical data and cancer treatments. The patient's completion of the survey could be supervised by a health care professional or not. A prespecified threshold of 5% of HFDIs classified as 'probable' detected with the application was deemed relevant., Results: Between 29 March 2018 and 22 June 2018, 143 patients completed the survey. Ninety-five patients (66%) reported at least one current systemic cancer treatment and were included in the analyses. Seventy-four patients reported an intake of at least one HFDS (77.9%), while 21 patients reported no HFDS (22.1%). Twenty-two HFDIs classified as 'probable' were found in 16 patients (16.8%) with the application, which was significantly superior to the prespecified threshold (P = 0.02). The interactions were reported with food (n = 19, 86%) more frequently than with herbs (n = 3, 14%) or with dietary supplements (no interaction reported)., Conclusions: Self-assessment of HFDS interaction with cancer treatment with an application is feasible and should be considered in daily routine. Prospective interventional studies should be conducted to better assess the clinical benefits of this approach., Competing Interests: Disclosure OM is an employee and shareholder of Amgen since 1 February 2022. OM has consulting activities for Amgen, Astra-Zeneca, Bayer, Blueprint Medicines, Bristol Myers-Squibb, Eli-Lilly, Incyte, Ipsen, Lundbeck, MSD, Novartis, Pfizer, Roche, Servier, Vifor Pharma; board membership for Amgen, Astra-Zeneca, Bayer, Blueprint Medicines, Bristol Myers-Squibb, Eli-Lilly, Lundbeck, MSD, Novartis, Pfizer, Roche, Servier, Vifor Pharma; speaker bureau of Eli-Lilly, Roche, Servier; stock ownership of Amplitude surgical, Transgene and employee of Gustave Roussy and ESMO (Annals of Oncology). AG, as part of the Drug Development Department (DITEP), is a Principal/sub-Investigator of Clinical Trials for Abbvie, Adaptimmune, Aduro Biotech, Agios Pharmaceuticals, Amgen, Argen-X Bvba, Arno Therapeutics, Astex Pharmaceuticals, Astra Zeneca, Astra Zeneca Ab, Aveo, Bayer Healthcare Ag, Bbb Technologies Bv, Beigene, Bioalliance Pharma, Biontech Ag, Blueprint Medicines, Boehringer Ingelheim, Boston Pharmaceuticals, Bristol Myers Squibb, Bristol-Myers Squibb International Corporation, Ca, Celgene Corporation, Cephalon, Chugai Pharmaceutical Co., Clovis Oncology, Cullinan-Apollo, Daiichi Sankyo, Debiopharm S.A., Eisai, Eisai Limited, Eli Lilly, Exelixis, Forma Tharapeutics, Gamamabs, Genentech, Gilead Sciences, Glaxosmithkline, Glenmark Pharmaceuticals, H3 Biomedicine, Hoffmann La Roche Ag, Incyte Corporation, Innate Pharma, Institut De Recherche Pierre Fabre, Iris Servier, Janssen Cilag, Janssen Research Foundation, Kura Oncology, Kyowa Kirin Pharm. Dev., Lilly France, Loxo Oncology, Lytix Biopharma As, Medimmune, Menarini Ricerche, Merck Kgaa, Merck Sharp & Dohme Chibret, Merrimack Pharmaceuticals, Merus, Millennium Pharmaceuticals, Molecular Partners Ag, Nanobiotix, Nektar Therapeutics, Nerviano Medical Sciences, Novartis Pharma, Octimet Oncology Nv, Oncoethix, Oncomed, Oncopeptides, Onyx Therapeutics, Orion Pharma, Oryzon Genomics, Ose Pharma, Pfizer, Pharma Mar, Philogen S.P.A., Pierre Fabre Medicament, Plexxikon, Rigontec Gmbh, Roche, Sanofi Aventis, Sierra Oncology, Sotio A.S, Syros Pharmaceuticals, Taiho Pharma, Tesaro, Tioma Therapeutics, Wyeth Pharmaceuticals France, Xencor, Y’s Therapeutics; research grants from Astrazeneca, BMS, Boehringer Ingelheim, Janssen Cilag, Merck, Novartis, Pfizer, Roche, Sanofi; and non-financial support (drug supplied) from Astrazeneca, Bayer, BMS, Boringher Ingelheim, Johnson & Johnson, Lilly, Medimmune, Merck, NH TherAGuiX, Pfizer, Roche. SC has consulting activities for Novartis, Gilead, Atara, Pierre Fabre, Janssen, Takeda, Abbvie, Astra Zeneca. All other authors have declared no conflicts of interest., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)