Most survivors of squamous cell head and neck cancers report that their sense of taste is dulled, changed or lost during radiation treatment, causing them to lose interest in eating and diminishing their quality of life.
In a study of taste and smell dysfunction with 40 cancer survivors, scientists at the University of Illinois Urbana-Champaign found that the tips of these individuals’ tongues were significantly less sensitive to bitter, salty or sweet tastes than peers in the control group who had never been diagnosed with cancer.
In a paper published in the journal Chemical Senses, the U. of I. team said this diminished taste sensitivity suggested that the taste buds on the front two-thirds of the cancer survivors’ tongues or a branch of the chorda tympani facial nerve, which carries signals from the tip of the tongue to the brain, may have been damaged during radiation therapy.
“While most studies suggest that patients’ ability to taste recovers within a few months of treatment, patients report that they continue to experience taste dysfunction for years after treatment ends,” said M. Yanina Pepino, a professor of food science and human nutrition at the U. of I.
“Our primary goal in this study was to test the hypothesis that radiation therapy is associated with long-term alterations in patients’ senses of smell and taste.”
While undergoing radiation and/or chemotherapy, head and neck cancer patients may lose taste buds, triggering a transient reduction in their ability to taste – a condition called hypogeusia – or their perception of tastes may be altered, a condition called dysgeusia that can also occur when nerves are damaged during cancer surgery, she said.
“Taste buds’ average lifespan of about 10 days enables rapid recovery from injury if the stem cells are preserved, yet it also makes the short-lived and long-lived cells within taste buds particularly vulnerable to the direct cytotoxic and anti-proliferative effects of chemotherapy and radiotherapy,” Pepino said.
Prior studies that explored taste loss and perception in these patients showed mixed results. Many of these studies involved “whole mouth” experiments that may not have detected regional damage to the taste buds at the front of the tongue or to the chorda tympani section of the facial nerve, said graduate student Raul Alfaro, the lead author of the study.
The U. of I. team assessed participants’ smell and taste functions separately and explored whether sensory interactions between taste and retronasal odors – aromas from food and beverages that are perceived in the oral cavity while eating or drinking – differed for the cancer survivors and the people in the control group.
The team assessed participants’ ability to taste regionally by applying cotton swabs soaked in flavored solutions to the tips of their tongues.
They also evaluated participants’ whole-mouth taste function by having them swish solutions around in their mouths for five seconds and spit them out. For this test, the participants were presented with nine cups of liquids that contained both taste and smell sensory components.
The cups contained two concentrations of strawberry extract in a sucrose solution, lemon extract in citric acid, salt in a vegetable broth and caffeinated instant coffee. They also received one cup of deionized water.
After sipping each sample, participants were asked to identify its taste quality – sweet, salty, bitter, umami (savory) or no sensation – and to rate the smell and taste intensity of the sample on a scale that ranged from “no sensation” to “strongest of any kind.”
Participants tasted the samples twice – once wearing a nose clip and once without – to determine whether their taste perception differed when the nose clip blocked their retronasal olfactory cues.
When participants’ sense of taste was assessed using the whole-mouth test with or without the nose clip, they similarly rated the taste and smell of nearly all of the samples.
However, when participants’ sense of taste was assessed regionally at the tip of the tongue, the cancer survivors were more likely to respond they did not perceive a taste or to misidentify the taste quality – such as bitter, salty or sweet – of multiple samples.
“Although the results from the whole-mouth taste test suggested that head and neck cancer survivors’ taste function was normal and well preserved, results from the regional tests indicated that they had some deficits,” Pepino said. “Subtle taste dysfunction in the tip of the tongue persisted for several months after they completed their oncology treatments.
“Taste dysfunction at the tip of the tongue might sound unimportant; however, there is an elegant cross-talk between the nerves that conveys signals from the tip and the back of the tongue, such that taste signals in the tip of the tongue inhibit signaling from the back.
This system allows taste intensity to remain constant in the whole mouth, even when taste signaling coming from the tip of the tongue is reduced. However, reduced signal input can also lead to phantom tastes, metallic taste and other oral symptoms.”
Additional co-authors of the study were food science and human nutrition professor Anna E. Arthur, who is also the Sylvia D. Stroup Scholar in Nutrition and Cancer, and an oncology dietitian with the Carle Cancer Center; Dr. Kalika P. Sarma, a radiation oncologist at Carle Foundation Hospital and a clinical assistant professor in the Carle Illinois College of Medicine; and then-research fellow Sylvia L. Crowder.
Funding: The work was supported by grants from the U.S. Department of Agriculture National Institute of Food and Agriculture, the Academy of Nutrition and Dietetics, and the Division of Nutritional Sciences at the U. of I.
Taste and smell alterations are often reported by patients with cancer receiving systemic antitumor therapy, with reported prevalences of 56–76% and 16–49%, respectively [1, 2]. The occurrence of taste and smell alterations varies between cancer types and treatment regimens, with many different antitumor agents including irinotecan, taxane-based and platinum-based chemotherapy, and tyrosine kinase inhibitors being associated with high TSA prevalence [2, 3]. In addition, concomitant treatments such as radiotherapy can be important contributing factors.
Taste and smell alterations associated with cancer and its treatment can be variable and have differential impact on patients’ chemosensory capabilities . In patients with cancer, sensory alterations can include hyposensitivity, describing a reduction in taste and/or smell sensitivity, hypersensitivity, evidenced by an increase in taste and/or smell sensitivity, a distortion of normal taste (dysgeusia), or a taste perception without an external stimulus (phantogeusia) [4, 5].
The exact mechanism underlying the diversity in chemosensory profiles observed in patients is not yet fully understood. Sensory alterations have been associated with decreased quality of life in patients with cancer and have a negative impact on social-emotional functioning [6,7,8].
Taste and smell alterations are considered important causes of malnutrition that is highly prevalent in patients with cancer undergoing systemic antitumor therapy [9,10,11]. Sensory alterations are associated with a decrease in appetite and a reduction in energy and nutrient intake, adversely affecting patients’ nutritional status and leading to subsequent weight loss [4, 12,13,14,15].
Malnutrition is associated with a high morbidity and mortality rate, more complications, and poorer tolerance to antitumor therapy [16, 17]. Therefore, timely assessment of the nutritional state and involvement of the dietitian should become standard practice in the integrated care for patients with cancer. If normal oral intake is not sufficient to meet energy and protein needs, oral nutritional supplements (ONS) are a well-established step to preserve an adequate intake .
The effectiveness of ONS for nutrition support depends on the acceptability of the product by the patient and on patient compliance . The presence of taste and smell alterations may impact sensory perception and palatability to ONS . Unfortunately, ensuring compliance to ONS is challenging in daily practice.
Therefore, more efforts on the sensory design of ONS are needed to personalize nutritional support, optimize palatability and acceptability of ONS, and to meet the likings of as many patients as possible to support compliance. To compensate for sensory alterations, some patients describe the need for more intense stimuli by deliberately adding more spices, salt, and ginger to their meals to stimulate a sensory response, while others describe a need for less intense flavors [12, 21].
The trigeminal nerve innervates the mucous membranes of the nasal and oral cavities, and plays a fundamental role in chemosensation and the overall “flavors” of food. The trigeminal nerve endings can be activated by an array of physical (mechanical force, temperature) and chemical agents, and can evoke a sensation such as the pungent or sharp feel of chili peppers, horseradish, wasabi roots, and Szechuan pepper, the coolness of peppermint, and the tingle of carbonated drinks . These preferences could be incorporated into the sensory development of ONS, to better address the sensory alterations of patients with cancer.
Usually, explorations of the appreciation of different ONS have been performed in healthy volunteers. Less is known about the likings of patients with sensory alterations who undergo systemic antitumor treatment. This study aimed to explore the occurrence of taste and smell alterations in patients receiving systemic antitumor therapy, and to investigate overall liking of new ONS prototype flavors specifically designed to better address sensory alterations in these patients.
reference link : https://link.springer.com/article/10.1007/s00520-021-06049-4
Original Research: Closed access.
“Taste and Smell Function in Head and Neck Cancer Survivors” by M. Yanina Pepino et al. Chemical Senses