Coming to your senses: detecting taste and smell alterations in chemotherapy patients. A systematic review

Context: Taste alterations (TAs) and smell alterations (SAs) are frequently observed, yet understudied side effects in chemotherapy patients, considerably affecting patients' quality of life.

Objectives: This review provides a systematic evaluation of the literature on TAs and SAs in cancer chemotherapy patients and discloses understudied research questions.

Methods: A systematic methodology based on the PRISMA guidelines was applied to identify original research articles with TAs and SAs as primary outcomes in chemotherapy patients. MEDLINE and Embase were searched using Medical Subject Heading and free-text terms. Study extraction and evaluation were done by three reviewers using predefined criteria.

Results: The search revealed 22 eligible studies, including three randomized controlled trials. Different measurement approaches were identified, with a clear trend toward self-report measures during the past decade. The methodological quality of the included studies varied, especially reports on SAs, which were inconsistent and hard to interpret. Regarding TAs, there is evidence that taste thresholds increase during chemotherapy. Qualitative changes, for example, metallic taste, are frequent but cannot be attributed to specific chemotherapy regimens. There are large research gaps regarding TAs and SAs in different patient populations and the impact of different chemotherapy regimens. Adequate management strategies are rare.

Conclusion: Current research results do not allow firm conclusions concerning the occurrence, severity, and quality of TAs and SAs under different chemotherapy regimens. Patient information on TAs and SAs, therefore, largely is based on the clinician's experience. In the palliative care setting, TAs and SAs need further investigation in the light of their importance in preventing food-related problems and maintaining a reasonable quality of life.