Vegetable and fruit consumption and cancer of unknown primary risk: results from the Netherlands cohort study on diet and cancer

BACKGROUND: Cancer of Unknown Primary (CUP) is a metastatic cancer for which the primary lesion remains unidentifiable during life and little is also known about the modifiable risk factors that contribute to its development. This study investigates whether vegetables and fruits are associated with CUP risk. METHODS: We used data from the prospective Netherlands Cohort Study on Diet and Cancer which includes 120,852 participants aged between 55 and 69 years in 1986. All participants completed a self-administered questionnaire on cancer risk factors at baseline. Cancer follow-up was established through record linkage to the Netherlands Cancer Registry and the Dutch Pathology Registry. As a result, 867 incident CUP cases and 4005 subcohort members were available for case-cohort analyses after 20.3 years of follow-up. Multivariable adjusted hazard ratios were calculated using proportional hazards models. RESULTS: We observed no associations between total vegetable and fruit consumption (combined or as separate groups) and CUP risk. However, there appeared to be an inverse association between the consumption of raw leafy vegetables and CUP. With respect to individual vegetable and fruit items, we found neither vegetable nor fruit items to be associated with CUP risk. CONCLUSIONS: Overall, vegetable and fruit intake were not associated with CUP incidence within this cohort. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12885-022-09502-7.