Assessment of a dietary questionnaire in cancer patients receiving cytotoxic chemotherapy.

PURPOSE: Few studies have examined the influence of diet on survival and chemotherapy-associated toxicities in patients with cancer. Although several comprehensive dietary questionnaires have been validated and calibrated in healthy populations, similar studies have not been performed among cancer patients.
METHODS: Two hundred patients with colorectal, breast, or neuroendocrine cancer undergoing treatment with cytotoxic chemotherapy completed a self-administered, 131-item, semiquantitative food frequency questionnaire. Using the questionnaire, we calculated dietary intakes of carotenoids, tocopherols, and fatty acids, and correlated these values with relevant biomarkers measured in simultaneously collected plasma specimens.
RESULTS: The Pearson correlation coefficients for various carotenoids as measured by the questionnaire, with the corresponding measurements in plasma specimens, ranged from 0.33 to 0.44 (all P < .001), adjusted for total energy intake, body mass index, age, sex, smoking status, and total plasma cholesterol. Similarly, the adjusted correlation between self-reported total vitamin E intake and plasma alpha-tocopherol was 0.34 (P < .001). Correlations between questionnaire and plasma measurements of trans-fat, eicosapentaenoic acid, and docosahexaenoic acid were 0.55, 0.29, and 0.42 (all P < .001), respectively. These levels of correlation are consistent with those reported in similar studies of self-reported diet in otherwise healthy populations.
CONCLUSION: Among patients with cancer receiving cytotoxic chemotherapy, questionnaire-based measurements of various micronutrients and dietary factors appeared to predict meaningful differences in the corresponding measurements in plasma specimens. This dietary questionnaire could offer an informative and practical means for assessing the influence of diet in cancer patients receiving chemotherapy.