Introduction
There were 18.1 million new cancer cases in the United States in 2018, and it is estimated that by 2040 new cancer cases per year will increase to 29.5 million [
1]. Improvements in care and advances in treatment have helped to improve the survival rates, and it is expected that by 2030 there will be 22.2 million cancer survivors in the US [
1]. While cancer treatment is prescribed to be lifesaving, individuals can experience unpleasant and long-lasting side effects. These side effects vary in frequency, duration, and severity and can negatively impact the quality of life.
One prevalent side effect is changes in taste function. According to self-reported data, up to 93% of cancer patients report experiencing changes in taste perception [
2‐
6]. The sense of taste refers to the perception of five qualities (sweet, salt, sour, bitter, and umami) derived from the chemical stimulation of taste receptors in the tongue, pharynx, larynx, and soft palate [
7]. While taste and flavor are terms used interchangeably, they are distinct terms, with flavor referring to the combination of sensations from the gustatory, olfactory, chemesthesis, and somatosensory systems. These systems are separate sensory pathways with distinct peripheral and central neural mechanisms [
8]. While gustation and olfaction have distinct mechanisms, patients and consumers alike do not segment these sensations but rather describe their experience. For example, patients may describe their experience or symptoms as a “change in food flavor.” Similarly, smell loss can present itself as a reduction in food flavor; and it is only through clinical assessments do clinicians uncover the root cause for their complaints related to food flavor. Uncovering the specific sensory symptom is important for directing clinical support and treatment strategies. While both taste and smell symptoms are both prevalent among cancer patients, the present investigation is focused on taste as Nolden and colleagues (2018) identified that taste, rather than smell function, was associated with changes in food intake.
Loss or changes to taste perception can profoundly impact dietary intake, treatment outcome, and daily life. Among cancer patients, complaints of changes in taste function are associated with gastrointestinal problems (e.g., loss of appetite, constipation, diarrhea, abdominal cramp, nausea, and vomiting) [
3,
9], oral issues (e.g., oral pain, dry mouth, and oral mucositis) [
3,
10,
11], food-related problems (e.g., secondary anorexia, food aversions, weight loss, and malnutrition), compromised immunity, and reduced treatment outcomes [
12‐
14]. Together, these data and others demonstrate that altered taste perception is associated with lower quality of life due to its impact on physical and psychosocial dimensions [
2‐
5,
9,
15‐
18]. While more research is needed, these data support the theoretical framework that taste function may be necessary for identifying patients at greater risk for nutritional impact symptoms, gastrointestinal problems, quality of life, and treatment outcome.
There are different types of taste disorders, all falling under the classification of dysgeusia, the change in gustatory function. According to published literature, individuals experiencing taste disorders can be further classified as having reduced taste sensitivity (hypogeusia), enhanced taste sensitivity (hypergusia), complete loss of taste (ageusia), a persistent presence of an unpleasant sensation like bitter or metallic (palinageusia), or perception of a taste in the absence of a stimulus (phantageusia) [
15,
19‐
21]. To clinically diagnose these taste disorders, an objective test is considered the gold standard; however, most cancer-related taste assessments are evaluated using self-report. Among cancer patients, dysgeusia, generally described in the literature as changes in taste, is estimated to be between 17.6 and 93% [
2‐
6,
15,
22]. Several reviews have highlighted the variability in the reported prevalence of dysgeusia in cancer patients, mainly attributing it to the different methodologies used to evaluate taste function (e.g., self-reported vs. clinical assessment) and variability in clinical characteristics (e.g., cancer type and treatment) [
23,
24]. Another challenge is deciphering patient complaints (e.g., tastes bad) and translating these descriptions that use terminology we use in everyday life, which can be challenging to untangle. For example, the interchangeable nature of the use of terms taste and flavor makes it challenging for patients and clinicians to communicate and assess problems with taste perception [
7,
25,
26]. This challenge was also evident during the COVID-19 pandemic as noted by Parma and colleagues, as patients and consumers experience foods and beverages wholistically, rather than perceiving taste and smell in isolation.
Despite the high prevalence and adverse effects of altered taste function, clinicians often overlook taste-related symptoms as they are non-life threatening [
22]. Due to the lack or limited support from clinicians, with few to no options for treatments or management strategies, cancer patients describe adjusting their lives to cope with taste alterations on their own. In some cases, cancer patients describe taste loss as an unavoidable side effect of having cancer or cancer treatment [
5,
16,
27]. The combination of losing their sense of taste and lack of clinical support is detrimental to their quality of life, causing many negative emotions, including disappointment, frustration, and sadness, and interferes with their daily rituals, especially around dining events and roles with their family members [
2,
16,
23,
28].
There is a need to improve clinical support for cancer patients suffering from taste loss. Currently, there is a limited understanding of clinicians’ familiarity and knowledge of taste alterations. Therefore, this study aims to evaluate clinicians’ familiarity and knowledge of terminologies and methods for assessing and diagnosing gustatory function. This information can be used to inform and develop targeted training and educational material for clinicians to better support cancer patients suffering from changes in taste function.
Discussion
The present study examines clinicians’ current knowledge and understanding of taste alterations and taste-related terminologies, including taste disorder classifications and methods used in assessing taste function. The present study provides evidence that many clinicians remain unfamiliar with differences between taste and flavor, with less than a quarter of the participants selecting the correct definitions for both taste and flavor. These findings support prior work, in which dietitians and other oncology professionals describe the use of taste and flavor as being interchangeable [
24,
25]. We expected that most participants would be unable to define different classifications of taste disorders; yet, in the present study, most participants correctly defined almost all the types of classifications of taste disorders. It is possible that participants were able to guess the definitions through the process of elimination, as the question format was a matching task. Taken together, this study, along with others [
7,
24,
25,
29], suggests that for clinicians providing care for cancer patients, there is a knowledge gap regarding taste, flavor, and classifications of different taste disorders. Terminology that is confusing and misleading, and in this case differs from the common usage of the words, is thought to be one barrier to providing adequate care [
7,
24,
25,
29], resulting in frustration for both clinicians and patients. This can make it challenging and difficult to communicate, diagnose, and treat patients, including whether their symptoms are only taste-related or include other systems involved with smell, flavor, and food hedonics [
18,
25].
There are a variety of methods to evaluate taste function in clinics [
30,
31] and in research settings [
16,
18,
31‐
34]. Here, we reported that roughly half of the participants believe that taste assessment tools are somewhat challenging. Within the cancer population, self-assessment through questionnaires is the most common [
25]. This trend is reflected in the present study with most participants reporting using self-reported questionnaires followed by informal interviewing, with only a quarter of the participants indicated to be using psychophysical methods in diagnosing dysgeusia. Even though self-assessment is convenient and easily accessible, most questionnaires do not differentiate between taste and flavor, raising concerns as to whether these questions accurately capture patient experiences [
34,
35]. As an example, changes in retronasal olfaction are often diagnosed as “taste loss” or dysgeusia in instances that do not utilize a psychophysical method for diagnosing patients.
Moreover, differing methods of assessing taste loss results has made it challenging to summarize and compare findings within the published literature, resulting in wide variations in incidence and severity of taste loss among cancer patients [
2,
36,
37]. Development of a validated and standardized assessment tool that is easy to administer will help to reduce the disparity in the use of different taste assessment tools among clinicians and may lead to better estimates of taste function and recovery in research and clinical studies. In the recent event of COVID-19, significant efforts have been made in developing questionnaires to assess both the quantity and quality of self-reported perception of chemosensory modalities in smell, taste, and chemesthesis (oral irritation). One such questionnaire is the GCCR questionnaire (Global Consortium for Chemosensory Research), which measures the self-reported smell, taste, and chemesthesis functions in addition to assessing the presence of nasal blockage and COVID-19. This questionnaire was developed by a group of chemosensory experts using a crowdsourced approach that would be a fast and easy-to-administer tool to measure the self-reported taste disorders of cancer patients in a clinical setting. It is anticipated that the high prevalence of loss of taste and smell among those suffering from a COVID-19 infection will increase the awareness of the importance of taste and smell and allow for more funds available to support research on the chemosenses.
We further identified that clinicians report not having adequate access to training or educational materials to learn about taste alterations and taste management strategies. Over half of the participants reported not having access to adequate information about taste alterations. This could be demonstrated by the observed confusion between the classification of taste and flavor, leading to confusion between patients and clinicians, and can become challenging when assessing dysgeusia. These findings support previous studies that emphasize the need for standardized terminology and validated taste assessment methods that are appropriate for clinical settings, along with accessible educational materials [
24,
25]. For example, Boltong and colleagues (2011) noted that of the 89 medical entries examined, only 6 oncology clinicians referred to the terms of taste to clearly mean the sense of taste (i.e., sweet, sour, bitter, salty, and umami), whereas most referred elements of flavor and hedonics such as smell or touch, liking, appetite, or cognitive processing [
25].
From the present study and prior work, clinicians report inadequate training and access to educational material. Belqaid and colleagues (2018) report that healthcare professionals’ involvement in supporting cancer patients to manage taste and smell alterations is limited but emphasize that the better involvement of clinicians has the potential to influence the patients for the adjustment to taste and smell alterations [
16]. Based on the current study results, participants suggested a specific website for clinicians to provide information on taste, flavor, taste disorders, symptoms, and strategies that may help patients to manage their taste problems [
25]. Increased education may facilitate improved communication between clinician and patient and could facilitate a feeling of support. Providing support for taste loss could improve patients’ quality of life since otherwise they may adjust their lives not to trust their senses [
16]. The improvement in diagnosing and supporting cancer patients experiencing taste loss may help to address other co-occurring nutrition impact symptoms such as loss of appetite, impaired food enjoyment, altered food intake, early satiety, depression, and anxiety [
10,
12,
18,
37‐
39]. Therefore, taste-related support could help patients’ nutritional status by improving their food intake and appetite. Overall, improving clinician training and knowledge regarding taste loss and reducing the communication barrier regarding taste will help patients feel supported and may lead to an improvement in their nutritional status and quality of life [
40,
41].
For this study, the aim was to estimate clinicians’ knowledge of dysgeusia, which relied on an online survey. One limitation of this study is the use of multiple-choice and matching questions, which inherently lends itself to the risk of guessing and through the process of elimination. This limitation results in the possibility of overestimating the education and familiarity in this study. This study revealed the gaps in the availability and accessibility of educational materials to learn about taste alterations and brought up potential ways for such educational materials could be developed. This information could directly be used in developing educational materials specifically about taste alterations and may help to bring awareness of the lack of support that clinicians have about treating patients with taste alterations.
Conclusion
There is growing evidence supporting the consequence of taste loss and its negative impact on health. The present study highlights clinicians’ knowledge and experience in supporting and managing cancer patients’ taste problems. Based on our findings and others, there is confusion regarding the vocabulary for taste and related terminology and unfamiliarity with taste assessment. Here, we conclude that clinicians lack adequate access to educational material, which differs from previous viewpoints suggesting this was due to taste symptoms not being life-threatening. The development of educational material and assessment tools that are easy to use, validated, and standardized will help to reduce barriers for clinicians and help to improve patient care. Supporting cancer patients for their taste symptoms may have profound clinical outcomes, such as improving food involvement, nutritional intake, and overall quality of life. This work demonstrates the need to improve training for clinicians, with a need to develop clinical assessment tools for clinical settings, and empirically evaluate treatments and management strategies for addressing cancer patients’ taste symptoms. While the current study focuses on taste symptoms, in order to provide comprehensive clinical support to patients, it is critical to consider olfactory function in addition to other sensory inputs (e.g., chemesthesis). Addressing these limitations will help to increase the resources for clinicians to support their patients, helping to improve patient outcomes and quality of life.
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.