finds a new study from JAMA Otolaryngology–Head & Neck Surgery.
Taste dysfunction can affect up to 90% of patients undergoing radiotherapy for head and neck cancer. While the ability to taste usually returns after the treatment concludes, some patients can still feel the lingering effects of radiotherapy on taste function long after the treatment concludes. It can lead to weight loss and dry mouth which can, in turn, negatively affect quality of life.
“Taste dysfunction has profound effects on quality of life in patients with head and neck cancer, and the oral cavity dose could be significantly lower with modern radiotherapy techniques,” wrote the researchers, who were led by Miao-Fen Chen, MD, PhD, of Chang Gung University, Taoyuan City, Taiwan. “This study provides useful dose constraints of the oral cavity that may be associated with reduced taste dysfunction.”
Degradation of taste is an important quality of life factor for head and neck cancer patients. A 2021 systematic review published in the journal Radiotherapy and Oncology found that acute taste dysfunction affected 96% of patients as measured objectively, and 79% as measured subjectively. While most patients recover an estimated 23-53% of patients experience long-term dysfunction.
In 2019, a study published in the journal Chemical Senses found that 31% of head and neck cancer patients had long-term changes to taste at 27 months after intensity-modulated radiotherapy (IMRT), with dysfunction associated with glossectomy and oral cavity radiation doses greater than 50 Gy, but the study only used one quality of life subjective measure to evaluate taste function.
In the new JAMA study, researchers reported the results of a longitudinal using the whole-mouth solution method for basic tastes, including salt, sweet, sour, and bitter.
Study methodology
The study included 87 patients (mean age, 58 years; 90% men) who were enrolled between 2017 and 2020 from a single hospital. 45 patients received primary intensity-modulated radiotherapy and 42 received postoperative radiotherapy. 78 patients received volumetric arc therapy, and 9 received intensity-modulated radiotherapy. The radiotherapy was directed to minimize the effect on the parotid glands and oral cavity.
Researchers measured taste dysfunction according to detection thresholds based on solutions with different concentrations. After moving the solution around the mouth and spitting it out, patients were asked to identify taste components. Following a water rinse, they tested a solution with another concentration of taste components. A number was assigned based on the concentration level they were able to detect, with nigher numbers indicating greater sensitivity.
Two to four weeks after initiation of radiotherapy, there were drops in taste scores for salt (4.7 to 1.4), sweet (4.2 to 1.8), sour (4.5 to 2.3), and bitter (4.7 to 1.2). 1 week after radiotherapy, those mean scores increased to 2.6, 2.6, 2.9, and 2.3 respectively. Over the following 3 months, mean scores reflected general recovery to near preradiotherapy levels (4.2, 3.9, 4.1, and 4.0, respectively). At 6 months and 1 year, the scores were equivalent to preradiotherapy levels.
Objective taste tests were performed on 81 participants. 33.3% had taste dysfunction 6 months after radiotherapy. 6 months after, 8.9% had taste dysfunction. At 3 months following radiotherapy, taste dysfunction was associated with an oral cavity mean dose of 4,000 cGy or higher (relative risk, 2.87; 95% confidence interval, 1.21-6.81) or 5,000 cGy or higher (RR, 2.04; 95% CI, 1.12-3.72). At 6 months, taste dysfunction was predicted by glossectomy (RR, 5.63; 95% CI, 1.12-28.15) and oral cavity mean dose 5,000 cGy or greater (RR, 7.79; 95% CI, 0.93-64.92).
The researchers quantified the relationship between mean oral cavity dose and probability of developing taste dysfunction at 3 and 6 months. 3 months after radiotherapy, 25 Gy predicted a 15% chance, 38 Gy predicted a 25% chance, and 60 Gy predicted a 50% chance. At 6 months, the numbers were 57, 60, and 64 Gy.
The study was limited by being conducted at a single center and its small sample size, and it recruited patients varied significantly in treatment modality and disease subtype.