Subjective and objective taste and smell changes in cancer

Malnutrition is highly prevalent in cancer patients and an important predictor of morbidity, mortality, treatment response, and toxicity. Taste and smell changes (TSCs) are common and may contribute to malnutrition. Research has previously focused on patients receiving chemotherapy (CT) or head and neck radiotherapy (RT). However, TSCs may occur pre-treatment, with other treatment modalities, and in cancer survivors. This review evaluates objective and subjective assessment of taste and smell, discusses the prevalence of TSCs in cancer, and reviews the clinical sequelae of TSCs in cancer patients.

To critically evaluate objective and subjective assessment of TSCs, and the prevalence and clinical sequelae of TSCs in cancer.

A literature search was conducted using PubMed, CINAHL and Embase for English-language articles published January 2009-June 2016. Search terms included combinations of the following: chemosensory, taste, smell, cancer, chemotherapy, radiotherapy, hormone therapy, immunotherapy, survivors. Reference lists of articles retrieved were also reviewed.

Variation in objective and subjective assessment methodologies has resulted in difficulties interpreting the literature. TSC prevalence varies depending on stage of disease and treatment regimens, from 16% to 70% and 50% to 70% during CT and RT, respectively. TSCs in patients who are treatment-naïve, receiving hormone or immunotherapy treatment, post-treatment and cancer survivors have not been adequately studied. TSCs are associated with impaired nutritional status. The relationship between cancer-associated symptoms and nutritional status is not clearly defined.

There is no gold standard assessment tool for TSCs. Heterogeneity in study methods hinders conclusive identification of the most appropriate way to measure TSCs. Subjective measures may reflect the patient experience and more reliably predict changes in dietary behaviour. Evaluation of TSCs should form part of all nutritional assessments in cancer patients. The true prevalence and severity of TSCs at all stages of cancer could then be established.