Detection of Early-Stage Oral Cancer Lesions: A Survey of California Dental Hygienists

Discussion

Detection of early-stage oral cancer is dependent upon the clinician's knowledge of the visual appearance and tactile characteristics of the oral lesions and the features that differentiate malignant lesions from benign. Dental hygienists play a key role in the detection of precancerous and cancerous lesions.⁹ Do dental hygienists possess sufficient knowledge to detect early-stage oral cancer lesions? In our study we assessed this knowledge by asking survey respondents to view images of oral lesions and specify whether the lesions were suspicious or not. The respondents' correct identification of the six images ranged from 40-97%. However, nearly 10% of the respondents did not respond to at least 3 of the 6 knowledge questions, and it is unclear if this was due to a lack of oral cancer knowledge.

Image two was challenging for the respondents, with only 40% of the respondents correctly identifying the depicted lesion as erythroplakia, which has a high likelihood of malignant transformation. The other lesions may have been more obviously suspicious or benign. These data suggest that dental hygienists have the knowledge to detect obvious, or more advanced, lesions. However, due to the variety of benign lesions, such as bite trauma, or hyperkeratinization, less-obvious lesions may be difficult to distinguish as suspicious for oral cancer. Also, the difficulty in correctly identifying Image 2 may have been due to the photographic image itself. It may have been ambiguous in its clinical presentation to some respondents.

Using images to test knowledge addresses the potential limitation present when knowledge is measured by self-report. Previous studies assessed other health care professionals' oral cancer knowledge using various methods, usually multiple choice survey questions and self-report. For example, the survey reported by Applebaum et al. included risks of oral cancer, signs symptoms, and characteristics of lesions.¹⁰ Questions on the impact of early detection on patient survival and the characteristics of lesions associated with smokeless tobacco were included in the knowledge score by LeHew et al.¹¹ Because the surveys asked different questions, it is difficult to compare the results of the level of knowledge across the studies. Generally, survey respondents performed in the average range. In addition to assessing general oral cancer knowledge, investigators used a diagnostic ability scale to measure the correct identification of suspicious oral lesions.¹¹ At least two previously published surveys addressed dental hygienists' knowledge. Forrest et al. found that 67% of the respondents correctly answered oral cancer questions relating to risk factors.⁶ Similarly, another study reported that the majority of respondents performed poorly on the knowledge portion of the survey (53% correct).⁹ The findings of these studies underline that there is no standardized, obvious visual sign of oral cancer, and that the variety in appearance of oral lesions makes early detection challenging.

Oral cancer lesions are usually detected in the Oral Cancer Examination (OCE); Cotter et al. found a significant positive correlation between the identification of a suspicious lesion and the performance of oral cancer screening.¹² Visual examination and lymph node palpation are reported to be valued components of the OCE, yet are not always performed. The majority of our respondents reported conducting some type of palpation, with the lymph nodes and tongue reported to be the least commonly examined by palpation. According to Kujan et al., many dental hygienists are seriously misinformed of what constitutes a thorough examination.²

In the study by LeHew and colleagues, dentists were surveyed for their thoroughness conducting the OCE, an assessment of both skill and frequency of procedures.¹¹ These factors were also incorporated into the early detection practice scale, reported by Hassona.¹³ Based on this scale, participating medical and dental professionals reported average early detection practice, and only 18% reported that they routinely performed OCE in their practices.¹⁰ On the other hand, in a study of dental hygienists, Cotter et al. reported that 46% of their respondents “always” performed OCE, 24% performed OCE at the initial appointment, and 47% at the recall appointment.¹⁰ These percentages are lower than the values that our respondents reported: 80% conducting OCE at every treatment appointment and 82% performing palpation. The current results are also higher than the Forrest et al. study in which 25% of the respondents reported routinely palpating lymph nodes of their patients 100% of the time, while 51% reported not doing it at all.⁶ The inconsistency in the data may be explained by the lack of one standardized, explicit method for comprehensive OCE. Without a consistent method, integral steps of the OCE are being skipped. There is a striking need to establish a global consortium on oral cancer screening that will oversee research and provide recommendations for health professionals at regular intervals.²

Previous experience in detecting an oral cancer lesion or knowing a patient having a history of oral cancer were reported as facilitators, experiences that encouraged dental hygienists to bring a suspicious lesion to the attention of a dentist. Both of these factors may motivate a dental hygienist to continue to conduct thorough, comprehensive OCE. In fact, the current findings demonstrated that the respondents who conducted palpations were more likely to have known a person with a history of oral cancer and had previously detected a cancerous lesion. Making a personal connection enhances one's understanding of the value of OCE in early-stage lesion detection.

The respondents of the current study reported these barriers or factors that influenced their decision not to bring a suspicious lesion to the attention of the dentist: personal experience in detecting a lesion that came back with a negative biopsy, the dentist not referring the dental hygienist's recommendations, as well as the supervising dentists conducting OCE themselves. Twenty-nine percent of our respondents reported that their supervising dentists wanted to conduct the OCE themselves. Similarly, Bigelow et al. reported that the patient does not perceive urgency without the support from a dentist.⁹ While not asked in the current study as a survey question, lack of public and dentists' awareness of dental hygienists' competence with OCE appears to be a barrier to early diagnosis. Postponement of oral cancer diagnosis is often caused by delays from both patients and health professionals, partially due to poor awareness regarding oral cancer among the public and health care professionals alike.

The delay in detection and diagnosis of lesions is often attributed to the asymptomatic nature and the difficulty in differentiating premalignant and malignant lesions from benign conditions.⁶ For example, the majority of respondents incorrectly identified image 2 as not suspicious for oral cancer, indicating the difficulty in differentiation and suggesting the need for more extensive education of visually ambiguous malignant lesions. Education in identifying the visual appearance of early lesions may improve the early detection ability of professionals and increase the awareness needed to reduce delays in treatment.¹⁰ Also, the lack of a standardized method for OCE examination may contribute to the low detection rate. Professionals may be using their experience and clinical judgment to decide which structures to examine and palpate rather than an examination based on evidence. Steps in one standardized method are illustrated in the sequential photographs in the dental hygiene textbook, Darby and Walsh.¹⁴ Having knowledge of the necessary steps in performing a thorough exam⁶ and implementing one consistent method with clear and realistic steps may be a positive step toward increasing the detection of oral cancer lesions at an early stage.

The focus of this article was OCEs for all patients. Factors encouraging OCEs were based on the dental hygienists' experiences with lesions and relationships, not on patients being high or low risk. It is unknown whether dental hygienists may not routinely do an OCE, but do at least conduct one when the patient is at high risk. In Table II, 9% of the respondents selected “other” as frequency of OCE. Perhaps it can be speculated that the “other” was selected based on the respondents conducting OCEs only on high-risk patients. An ongoing study is assessing whether dental hygienists are more diligent in performing OCE when potentially treating high-risk patients. The danger of that philosophy is that early-stage lesions may be missed on patients without any risk factors, so OCE for all patients is recommended.

This study and many other studies of OCE conclude that there is a need for continued or mandatory continuing education on oral cancer knowledge and practices to make a difference in prevention and early detection of oral cancer in our patient population.^{4,6,9-13,15,16,17,18} Specifically, continuing education courses that include hands-on technique workshops were found to positively change attitudes and behaviors of OCE.⁴ These workshops should focus on palpation technique for specific areas to comprise a comprehensive OCE.⁹ The results from the current study suggest that continuing education courses, as well as entry-level education, should focus on the visual appearance of early-stage oral cancer lesions and one standardized method of OCE to ensure all valuable steps are performed thoroughly.

Limitations of this study include selection bias: respondents who completed the survey may have greater interest in the topic due to personal experience with oral cancer or oral cancer detection. Also, the low response rate (12%) yielded a response bias, which would affect the ability to generalize the results to all dental hygienists in California. The study population was limited to California dental hygienists whose email addresses were in the CDHA database. Although this database included both members and nonmembers, it is presumed that more members than nonmembers were in their database, as our data (Table I) indicates that 79% of the respondents were CDHA members. That value would not be representative of the California dental hygienists. However, the remainder of the demographic characteristics does appear similar to the California dental hygiene population. Another limitation was that OCE practices were based on self-report, which often results in a social desirability bias.