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Understanding affected anatomy, physiology essential to management of taste disorders
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Editor’s note: HemOnc Today’s regular columns for advanced practice providers (APPs) tackle common issues APPs face, discuss day-to-day practice and regulatory concerns, and share research advances. To contribute to this column, contact Alexandra Todak at stodak@healio.com.
Ranging from acute toxicity to late complications, adverse events associated with head and neck cancer treatment rank among the most significant perhaps in the entire field of oncology.
Some patients must undergo surgery, radiation and chemotherapy to cure their disease, and each treatment modality carries its own unique consequences.
Pancytopenia, nausea/vomiting, altered taste and appetite, tinnitus, sensorineural hearing loss, immunosuppression, renal impairment, mucositis, difficult/painful swallowing and constipation are all quite common among patients receiving treatment for head and neck cancer. Treatment also increases the risk for dental caries, periodontitis, osteoradionecrosis and lymphedema.
Following surgical resection (if possible), standard-of-care treatment involves 6 weeks of stereotactic body radiotherapy with concurrent chemotherapy (commonly platinum agents or taxanes) or targeted therapy. Because of the physical location of the disease, treatment impacts the patient’s ability to ingest adequate fluid and nutritional intake. More than 75% of patients receiving chemoradiation will experience taste disorders, further increasing the risk for malnutrition.
Anatomy and etiology
Each containing 50 to 150 epithelial cells, taste buds are located throughout the tongue, oropharynx, pharynx, larynx, epiglottis and esophagus, and saliva is necessary to transmit taste stimuli to taste buds.
Taste sensation is comprised of five qualities — sweet, bitter, salty, sour and umami/savory — all of which are affected by SBRT. Umami taste is especially important because its loss can decrease overall interest in eating and lead to further weight loss. Umami taste recovery might be delayed or permanent.
Taste receptor cells have an average life span of 10 days and are innervated by afferent neurons, which allow stimulus ions to enter the cell through protein channels in the cell membrane. The facial nerve (VII), the glossopharyngeal nerve (IX) and the vagus nerve (X) work together to transmit taste sensation to the brain, specifically the medulla, where it is then sent to the thalamus and primary gustatory cortex. The trigeminal nerve (V) also plays a role because its branches extend throughout the oropharynx, nasopharynx and sinuses, and it is responsible for irritating and burning sensations from foods such as hot peppers.
Any alteration in this sequence can drastically change the taste of food and beverage, especially structural changes in receptor and transport proteins, cation channels and changes in the composition of saliva and taste pore mucus. Although temporary in most cases, saliva production can be inhibited as early as 1 week after SBRT initiation. As little as 10 Gy of radiation to the parotid gland can cause permanent impairment.
Dysgeusia is defined as any alteration in sense of taste, usually through a persistently sweet, sour, salty, bitter or metallic taste. Hypogeusia is decreased taste function to stimuli, whereas ageusia is absent taste function.
Management
Taste impairment presents during treatment and may extend indefinitely.
Galloway and Amdur suggest that “the simplest and most important way to minimize acute toxicity is to avoid overtreatment,” highlighting the importance of current radiotherapy planning to minimize damage to salivary glands and other structures. To alleviate painful mucositis and thick oral secretions, patients should gargle with a salt and baking soda mixture several times a day and increase fluid intake as much as possible; this should occur during treatment, but also may be helpful long after its conclusion.
The involvement of nutritionist colleagues is of paramount importance for those undergoing head and neck cancer treatment. Dietary counseling should include help with food choices and preparation, as increased flavoring through spices and umami foods can greatly help. Tart and sweet flavors may be particularly helpful for those with hypogeusia, as well as strongly flavored marinades and sauces. Use of plastic utensils may minimize metallic taste that silverware lends. Alternate sources of protein such as beans, tofu and Greek yogurt should be incorporated if meat sources are unpalatable. Patients may suck on sugar-free hard candies, mints, frozen fruit, popsicles and ice chips. Supplementation with zinc has been extensively studied, and its efficacy is variable. Medications including amifostine, clonazepam, gabapentin, cannabinoids and megestrol are being studied for their use in taste dysfunction. Researchers are hopeful that complementary therapies such as hyperbaric oxygen and acupuncture will show benefit on a large scale in future studies.
‘Widespread’ complications
Taste dysfunction and altered nutrition are widespread among patients receiving and recovering from head and neck cancer treatment.
Although total prevention of these complications is usually not feasible, a review of the affected anatomy and physiology can illuminate treatment strategies so APPs can minimize negative effects and maximize quality of life for their patients both during treatment and beyond.
References:
Galloway T and Amdur TG. Management and prevention of complications during initial treatment of head and neck cancer. UpToDate. Available at: www.uptodate.com/contents/management-and-prevention-of-complications-during-initial-treatment-of-head-and-neck-cancer. Accessed on June 10, 2019.
Iannotta J and Wisotsky C. Oncology Times. 2017;doi:10.1097/01.COT.0000515945.17571.4f.
Mann NM and Lafrenier D. Anatomy and etiology of taste and smell disorders. UpToDate. Available at: https://www.uptodate.com/contents/anatomy-and-etiology-of-taste-and-smell-disorders. Accessed on June 11, 2019.
Sroussi HY, et al. Cancer Med. 2017;doi:10.1002/cam4.1221.
For more information:
David L. Jennings II, MSN, RN, AGPCNP-BC, is a nurse practitioner at Levine Cancer Institute at Atrium Health. He also is a HemOnc Today Editorial Board Member. He can be reached at david.jennings@atriumhealth.org.
Disclosure: Jennings reports no relevant financial disclosures.