The Dentist’s Role in the Pre-Radiation Assessment and Management of a Patient Undergoing Head and Neck Radiation Therapy

Shyam A. Shah, D.M.D.; Vincent B. Ziccardi, D.D.S., M.D.

ABSTRACT

An understanding of a patient’s head and neck cancer (HNC) diagnosis and planned cancer therapy is required to effectively develop a dental treatment plan. Dentists are often asked to evaluate patients who are about begin or are already undergoing radiation therapy for HNC. With adequate assessment and management of the HNC patient, radiation-related complications, such as osteoradionecrosis and radiation caries, can be minimized. This manuscript is intended to help all dentists become comfortable with current protocols in managing patients undergoing radiation therapy.

A patient about to embark on treatment for head and neck cancer (HNC) has begun a journey that involves a multidisciplinary team of healthcare providers, as well as family and friends. HNC and its treatment are often accompanied by both short-term and long-term changes to a patient’s physical, mental and oral health. 1

Squamous cell carcinoma is the most common malignancy of HNC cases, at a rate of 90% of all oral and oropharyngeal malignancies. 2 An estimated 51,540 new cases of oral cavity and pharynx cancer and 53,990 new cases of thyroid cancer were projected in the United States in 2018, with incidence rates more than twice as high in men than in women. The estimated numbers of deaths in 2018 from these two cancers are 10,030 and 2,060, respectively. 3 Whether or not these cancers physically manifest themselves within the oral cavity, the dental provider often plays a crucial long-term role in their identification and management.

HNC can be treated by any or a combination of surgical resection, chemotherapy and radiation therapy (RT). For early stage disease, single-modality treatment, with either surgery or RT, is preferred. For more advanced disease, combined therapy is recommended. In such cases, surgical resection is encouraged first, followed by adjuvant RT, which generally allows for a lower dose. 4 We are all aware of the oral manifestations and complications of HNC RT. These well-documented complications include xerostomia, mucositis, trismus, caries and, potentially, radiation osteonecrosis, with greater predilection for the mandible.

Dentists play an active role in the management of patients undergoing HNC RT and should be consulted by the oncology team prior to initiation of radiation therapy to prevent and minimize post-radiation complications. Consequently, dentists are often asked by the oncology team to provide some form of “dental clearance” or assessment prior to the patient beginning radiation therapy. An understanding of the HNC diagnosis and planned cancer therapy is required to effectively develop a dental treatment plan.

This manuscript will review the dental management of a patient undergoing RT for HNC, as well as the anticipated dental needs during and after therapy.

Effects of Radiation Therapy in Head and Neck Cancer

Radiation therapy, while acting to damage cancer cells, can also have detrimental effects on adjacent healthy cells. Radiation does not destroy cancer cells right away but, rather, repeated doses of radiation damage DNA to the point where these cells are no longer able to replicate. Doses of ionizing radiation are measured in Grays (Gy) and vary widely based on the type of therapy and staging. To put these units into perspective, the average dose of radiation exposed to a human at sea level is about 0.27 mGy per year, primarily attributable to cosmic radiation (1000 mGy = 1 Gy). The average emergency room plain film radiograph exposes a patient to about 0.15 to 15 mGy, and the average CT scan exposes a patient to about 20 to 70 mGy. A single 1 to 2 Gy dose to the entire body results in acute radiation sickness, and 8 Gy is a lethal dose to the human body. 5 To eradicate a cancerous growth, a lethal dose must be targeted only to the involved cancer cells. To minimize damage to adjacent healthy tissues, modern radiation therapy is split into smaller doses over time. These fractionated doses are usually 1-2 Gy/fraction, with 1 to 2 fractions/day. 6

It is crucial for the dentist managing an HNC patient to reach out to the patient’s radiation oncologist to learn the total dose and field of radiation. The radiation modality should also be clarified. This radiation modality is usually intensity modulated RT (IMRT) or 3D conformal RT (3DCRT). IMRT distributes the radiation dosage gradient to adjust for high-risk ORN areas, thereby decreasing risk. 7 In general, patients undergoing IMRT receive less total radiation doses than if they were receiving 3DCRT. Full-mouth extractions were once considered normal pre-radiation treatment for patients about to undergo 3DCRT. With improvements in RT, such as IMRT, patients are fortunately no longer subjected to this treatment and are now able to receive comprehensive dental care, removing any pathology.

With high-radiation doses, irradiated tissues see a decrease in blood supply and healing ability. Invasive dental procedures such as extractions create open wounds, which may form chronic wounds, exposing bone and, eventually, leading to osteoradionecrosis (ORN). 8 Consequently, there is a higher risk of ORN with extractions performed after RT than before RT. Over the years, multiple studies have shown the risk of ORN significantly increasing as the cumulative mandibular dose exceeds 50 Gy. 1,8 Compared to the maxilla, the mandible is more susceptible to developing ORN and its complications due to its reduced blood supply (Figures 1, 2). Even with smaller doses, other complications of radiation therapy occur in a majority of patients, including dental caries, xerostomia, mucositis, and trismus due to muscle fibrosis. 9

Figure 1. CT slices showing osteonecrosis of anterior mandible resulting in pathologic fracture.

Figure 2. Clinical appearance of same patient, with exposed bone present at extraction site.

The majority of radiation caries occur on the cervical and incisal edges of teeth due to the increased susceptibility of dentin to demineralization by a combination of decreased salivary flow, decreased pH, changes in the composition of saliva, changes in the microscopic tooth structure, and a shift in the oral flora towards cariogenic microorganisms. 10-12

Xerostomia manifests as changes in the oral flora, decreased remineralization of teeth, reduced breakdown and clearance of food and microbes, reduction in antibody and enzyme effects in the oral cavity and reduction in prosthesis retention. 13 This situation may make it uncomfortable for patients to tolerate removable prostheses. In turn, other conditions can be exacerbated, such as dental caries, candidiasis, mucosal atrophy and mucositis, compromised speech and altered tastes. RT doses greater than 30 Gy can cause permanent salivary gland dysfunction. Gland destruction is dose-dependent and reversible depending on the dose. It is important for the dental provider to be aware of late-effect xerostomia that can result months later from irreversible damage. 4

Oral mucositis (OM) initially manifests as erythema within the first four to five days of therapy. 14 As cumulative radiation doses approach 30 Gy, usually by two to three weeks after initiation of therapy, painful ulcers develop, predominantly affecting non-keratinized tissue. This is followed by ulceration and frank erythema by the fifth week. Patients will report difficulty with mastication and swallowing, resulting in odynophagia and dysphagia. After the completion of RT, healing begins and ulcerations are improved within four to six weeks. However, patients may soon develop chronic mucosal pain and sensitivity. 4,9,14

Pre-Radiation Dental Assessment

A recently diagnosed cancer patient, having seen multiple specialists and having undergone multiple tests, may or may not understand the complexity of the cancer and the anticipated treatment. The dentist will be just one of the many professionals the patient will see from the time of diagnosis. It is important for the dentist to understand and anticipate the patient’s psychological state from when he or she first presents asking for the dental clearance. Adequate time should be allotted to the first appointment to establish a positive doctor-patient relationship.

The pre-radiation dental assessment begins with a comprehensive oral evaluation, with increased attention given to the teeth within the field of radiation, which should have been identified by consultation with the radiation oncologist. While the general facets of this exam are similar to those in patients without cancer, consideration should be given to developing an efficient treatment plan that will enable the patient to begin RT in a timely manner. 15

A complete set of records should be taken, including a fullmouth series and panoramic radiograph if no recent studies are available. Full-arch impressions should also be taken, especially in anticipation of fabricating fluoride trays. The oral and perioral hard and soft tissues should be examined. A head and neck examination should be completed with evaluation of facial asymmetries, lesions, enlargements, lymph nodes and temporomandibular areas. Soft tissues should be evaluated, including the tongue, floor of mouth, palate and oropharynx. For all teeth, the following should be evaluated: periodontal condition (including mobility, pocketing, furcation involvement), extent of caries, erosion, abrasion and sharp cusps/restorations. 16

For patients with removable prostheses, the fit, retention and stability of the appliances should be evaluated. 17 Patients should be advised to avoid wearing ill-fitting or newly fabricated prostheses during RT, which can induce soft-tissue trauma, especially in the presence of xerostomia. 18

After the exam, a treatment plan should be developed that incorporates the oncologist’s desired cancer treatment timeline. If there is not enough time before the HNC medical team desires to proceed with radiotherapy, any restorable teeth with carious lesions should be provisionalized with a glass ionomer restoration. 19 If there is more time, the prognosis of the teeth should be weighed heavily in the plan and all carious restorations should be restored prior to the initiation of RT. When advanced procedures, such as endodontic or periodontal treatments, are indicated, but there is insufficient time to complete them, the involved teeth should be considered for extraction.

In deciding whether teeth should be extracted, prognoses of “questionable” and “poor” should be correlated with other risk factors, including the patient’s oral hygiene, age, cancer stage, total anticipated radiation dose, medical history, salivary flow, overall socioeconomic status and diet, as well as the patient’s approach to dental care. If it is likely that a tooth within the field of radiation will be extracted within the next few years, it should be considered for extraction prior to the initiation of radiation therapy. Such teeth often have deep or subgingival caries, large compromised restorations, pocketing greater than 5 mm, severe abrasion, mobility, furcation involvement, severe pulpal or periodontal infection, or a failing endodontic treatment. In general, a tooth with “severe dental decay with questionable restorable treatment success” should be extracted. 8 Also, unopposed teeth that may irritate opposing gingiva should also be considered for removal.

The pre-radiation treatment should begin with a dental prophylaxis or, if necessary, nonsurgical periodontal therapy. As there is greater risk of ORN with extractions performed after RT than before RT, extractions should be completed as soon as possible, with as little trauma as possible. Protocols for extractions prior to HNC RT have been developed. 20,21 This should then be followed by restoration of carious lesions, endodontic therapy and recontouring of restorations. 10 Radiation therapy should begin no sooner than 14 days after extractions, but may be initiated sooner by the oncology team when the benefits outweigh the risks. 21,22 The dentist should reinforce that the patient complete the treatment plan prior to RT, including restorations. 23 However, it is important to note that in certain late-stage carcinomas, the oncology team may proceed with radiation therapy without dental clearance. In that case, the dentist should provide recommendations during treatment.

Management during Radiation Therapy

While this manuscript focuses on dental assessment and clearance prior to radiation therapy, it is important to reinforce that the patient should be followed throughout the course of radiation therapy with a more frequent follow-up schedule, with routine re-evaluation at least every three months. 11,15 During the process of assessing and treating the patient, it is also important to set expectations about what RT-related sequelae the patient may face. The patient should be motivated to improve his or her compliance throughout radiation therapy, with a goal of preventing the incidence of new caries.

Fluoride trays should have been fabricated and provided to the patient for use prior to the initiation of RT. A topical fluoride formulation should be prescribed to the patient for the custom trays for use at least once a day during RT. 24,25 At follow-ups, the provider should identify any new caries. Unlike typical caries, post-radiation carious lesions often present with total enamel delamination, followed by decay of the underlying dentin, usually at cervical and incisal/cuspal areas. 26

Xerostomia leads to the majority of oral RT complications, with changes in oral flora and colonization, decreased remineralization of teeth, reduced breakdo wn and clearances of food and microbes, reduction in antibody and enzyme effects in the oral cavity and reduction in pros thesis retention. 27 These all may, consequently, lead to dental caries, candidiasis, mucosal atrophy and mucositis, compromised speech and altered tastes, with a generalized decreased quality of life. Salivary flow can also be improved by physical means, such as sugar-free hard can dies, and sialogogues, such as pilocarpine. When saliva flow cannot be adeq uately stimulated, wetting agents and other commercial saliva substitutes, such as Biotene and Oral Balance, are also often used. 27

The patient should be monitored for the development of oral mucositis. Maintenance of oral hygiene and reduction of sources of mucosal irritation should be reinforced for prevention of OM. This includes minimizing use of oral prostheses, brushing softly with fluoride toothpaste, and maintaining a soft, non-cariogenic diet. Early signs of OM include erythema, edema, burning sensations and increased sensitivity to hot or spicy food. These can then progress into white desquamative patches, followed by painful ulcers that can be secondarily infected. 28 Mouthrinses with topical anesthetics and anti-inflammatory agents have been successful in managing patients who develop OM. Since smoking and alcohol use during and after RT increases the patient’s risk of developing ORN, it is important that the patient avoid these substances. 7

For patients who present with a dental emergency during or after RT, priority should be given to avoiding extractions, and other options, such as endodontic therapy, should be attempted first. If unsure how to proceed with dental emergencies and invasive treatment, the radiation oncologist should be consulted or the patient should be referred to a specialist with advanced experience in managing patients undergoing RT.

Conclusion

The risk of ORN can be reduced by appropriately managing a patient with HNC from the time of diagnosis. Frequent communication and follow-up with the patient and his or her medical team should enable the dentist to provide optimal care during radiation therapy. With proper assessment and planning, management of a patient undergoing radiation therapy for head and neck cancer need not be a daunting task for the dentist. p

Neither of the authors reported any conflicts of interest. Queries about this article can be sent to Dr. Shah at shah82@sdm.rutgers.edu.

REFERENCES

1. Kufta K, et al. Pre-radiation dental considerations and management for head and neck cancer patients. Oral Oncology 2018;76:42-51.

2. Chi AC, Day TA, Neville BW. Oral cavity and oropharyngeal squamous cell carcinoma—an update. CA: A Cancer Journal for Clinicians 2015;65(5):401-421.

3. Cancer Facts and Figures 2018. 2018, American Cancer Society: Atlanta.

4. Epstein JB, et al. Oral complications of cancer and cancer therapy. CA: A Cancer Journal for Clinicians 2012;62(6):400-422.

5. Miller V . Natural and medical radiation dosages. 2012 [cited 2019] Available from: http:// large.stanford.edu/courses/2012/ph241/miller2/.

6. Popovtzer A, Eisbruch A. Radiotherapy for Head and Neck Cancer: Radiation Physics, Radiobiology, and Clinical Principles. In Cummings Otolaryngology. 2015. p. 1109.e4.

7. Owosho AA, et al. The prevalence and risk factors associated with osteoradionecrosis of the jaw in oral and oropharyngeal cancer patients treated with intensity-modulated radiation therapy (IMRT): The Memorial Sloan Kettering Cancer Center experience. Oral Oncology 2016;64:44-51.

8. Hentz C, e t al. Establishing a targeted plan for prophylactic dental extractions in patients with laryngeal cancer receiving adjuvant radiotherapy. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology 2016;122(1):43-49.

9. Sroussi HY , et al. Common oral complications of head and neck cancer radiation therapy: mucositis, infections, saliva change, fibrosis, sensory dysfunctions, dental caries, periodontal disease, and osteoradionecrosis. Cancer Medicine 2017;6(12):2918-2931.

10. Gupta N, et al. Radiation-induced dental caries, prevention and treatment: a systematic review. National Journal Maxillofacial Surgery 2015;6(2):160-166.

11. Fattore L, Rosenstein HE, Fine L. Dental rehabilitation of the patient with severe caries after radiation therapy. Special Care in Dentistry: Official Publication American Association of Hospital Dentists, Academy of Dentistry for Handicapped and American Society for Geriatric Dentistry 1986;6(6):258-261.

12. Andrej MK, et al. Radiation-related damage to dentition. The Lancet. Oncology 2006;7(4):326-335.

13. Porter SR, Fedele S, Habbab KM. Xerostomia in head and neck malignancy. Oral Oncology 2010;46(6):460-463.

14. Murdoch-Kinch CA, Zwetchkenbaum S. Dental management of the head & neck cancer patient treated with radiation therapy. Today’s FDA:Official monthly journal of Florida Dental Association 2011:40.

15. Beech N, et al. Dental management of patients irradiated for head and neck cancer. Australian Dental Journal 2014;59(1):20-28.

16. Schuurhuis JM, et al. Evidence supporting pre-radiation elimination of oral foci of infection in head and neck cancer patients to prevent oral sequelae. A systematic review. Oral Oncology 2014;51(3):212-220.

17. Joshi VK. Dental treatment planning and management for the mouth cancer patient. Oral Oncology 2010;46(6):475-479.

18. Toljanic JA, Saunders VW. Radiation therapy and management of the irradiated patient. Journal Prosthetic Dentistry 1984;52(6):852-858.

19. De Moor R, et al. Two-year clinical performance of glass ionomer and resin composite restorations in xerostomic head- and neck-irradiated cancer patients. Clinical Oral Investigations 2011;15(1):31-38.

20. Sulaiman F, Huryn JM, Zlotolow IM. Dental extractions in the irradiated head and neck patient: a retrospective analysis of Memorial Sloan-Kettering Cancer Center protocols, criteria, and end results. Journal Oral and Maxillofacial Surgery 2003;61(10):1123-1131.

21. Ben-David MA, et al. Lack of osteoradionecrosis of the mandible after intensity-modulated radiotherapy for head and neck cancer: likely contributions of both dental care and improved dose distributions. International Journal Radiation Oncology, Biology, Physics 2007;68(2):396-402.

22. Wahl MJ. Osteoradionecrosis prevention myths. International Journal Radiation Oncology, Biology, Physics 2006;64(3):661-669.

23. Brennan MT, et al. Dental disease before radiotherapy in patients with head and neck cancer. Journal American Dental Association 2017;148(12):868-877.

24. Kanchan PD, et al. Effectiveness of fluoride varnish application as cariostatic and desensitizing agent in irradiated head and neck cancer patients. International Journal Dentistry 2013:824982-5.

25. Thariat J, et al. Compliance with fluoride custom trays in irradiated head and neck cancer patients. Supportive Care in Cancer 2012;20(8):1811-1814.

26. Walker MP, et al. Impact of radiotherapy dose on dentition breakdown in head and neck cancer patients. Practical Radiation Oncology 2011;1(3):142-148.

27. Epstein JB, et al. A double-blind crossover trial of Oral Balance gel and Biotene ® toothpaste versus placebo in patients with xerostomia following radiation therapy. Oral Oncology 1999;35(2):132-137.

28. Kostler WJ, et al. Oral mucositis complicating chemotherapy and/or radiotherapy: options for prevention and treatment. CA: A Cancer Journal for Clinicians 2001;51(5): 290-315.

Dr. Shah

Shyam A. Shah, D.M.D., is a general dentist and clinical instructor, Department of Oral and Maxillofacial Surgery, Rutgers School of Dental Medicine, Newark, NJ.

Dr. Ziccardi

Vincent B. Ziccardi, D.D.S., M.D., FACS, is professor and chair, Department of Oral and Maxillofacial Surgery, Rutgers School of Dental Medicine, Newark, NJ.