An increasing number of people worldwide are being diagnosed with oral and oropharyngeal cancer. The contribution of the dental team from the start of the patient’s therapy helps to reduce the serious side effects of treatment; dental care is an important part of patient rehabilitation.

By Dr Mary Burke

Cancer of the oral cavity and oropharynx is a serious problem globally; together, these conditions are the sixth most common cancers worldwide. There are wide differences in incidence between countries; in Europe oral cancer is more common in Eastern Europe than other parts and it is the most common cancer in men in Sri Lanka, India, Pakistan and Bangladesh. Even in countries where it is still relatively uncommon the incidence is rising. The effects of treatment for oral cancer can be very devastating in terms of quality of life for patients and their carers; five year survival is about 50% in most countries, but worse for late stage tumours and low socio-economic groups. However, since, increasingly more people are survivors at five years, efforts to improve the quality of life are very important. The complexities of treatment and managing its sequelae require dedicated multi-disciplinary team involvement and dental team contribution before, during and after cancer treatment.

Primary prevention
The dental team should promote a healthy lifestyle and assist in effecting lifestyle changes to prevent oral cancer. In addition, for people who have had oral cancer, stopping high risk habits such as smoking improves survival and reduces recurrence. The aetiology of oral cancer is multi-factorial but the main risk factors are tobacco, alcohol and betel quid chewing; ultra-violet light is a risk factor for lip cancer. Genetic variations affect the degree of risk on exposure to carcinogens, but it is estimated that 80% of oral cancers can be attributed to tobacco and alcohol use, and lifestyle changes could prevent these.

Tobacco use by men and women is widespread across the world; all forms of tobacco are carcinogenic. Alcohol is consumed in most communities, Islamic populations and some small groups being exceptions. It is estimated that 20% of the world’s population chew betel quid, especially in Asian communities. These risk factors act separately and when together act synergistically.

There is increasing evidence that the human papilloma virus (HPV) subtypes 6 and 16 are involved in tonsillar and oropharyngeal cancer in young people. The role of HPV in cervical cancer has led to vaccination programmes; whether this will have an impact on the incidence of oral cancer has still to assessed.

There is a correlation between low intake of fruit and vegetables and increased risk of cancers, including oral cancers. Daily consumption of at least five portions of fruit and vegetables is recommended.

Secondary prevention
Early detection of oral cancer gives better outcomes and reduces the economic cost of cancer. Dentists should be diligent in history taking, undertake examination for oral cancerous lesions and be conversant with urgent referral protocols. There are no national screening programmes; to be effective it is necessary to reach high risk groups and it is difficult to predict malignant transformation in precancerous lesions. All healthcare professionals should therefore note the urgent referral guidance [Table 1].

Multidisciplinary approach to care
The impact of cancer and its treatment requires input from many disciplines. Ideally a dentist and dental hygienist are part of the team to ensure seamless and timely contribution to patient care. In the longer term visits to specialist centres are less frequent and the primary care setting becomes very important for lifelong care.

Treatment
Surgery is the main treatment for oral cancer; if the tumour is small surgery may be used as single modality treatment, and the defect closed. In the case of larger interventions, such as a maxillectomy, advances in micro-vascular surgery have led to more reconstruction rather than leaving defects, which improves quality of life.

Radiotherapy is very effective for head and neck cancer and may be given alone if surgery is not practicable, or after surgery for larger tumours where it is likely that the tumour has spread. The acute toxic effects of radiotherapy (mucositis, dysphagia, xerostomia) and late effects (xerostomia, taste disturbance, osteoradionecrosis, trismus) have a significant impact on quality of life and dental health.

Intensity modulated radiotherapy (IMRT) is a development that is becoming increasingly available. Radiation can be shaped to the tumour allowing greater sparing of surrounding tissues such as the salivary glands and pharyngeal muscles. This results in less xerostomia and dysphagia. It is likely it will have a less adverse effect on the dentition, with a reduction in the high caries rate which is seen after radiotherapy.

Systemic chemotherapy may be included in management of oral cancer. Concomitant chemotherapy (during radiotherapy) is usually given in three cycles. This reduces recurrence with improved survival time but patient tolerance can be problematic. Induction chemotherapy (before radiotherapy) reduces tumour size prior to radiotherapy and reduces metastases.

Role of the Dental Team
Early involvement of the dental team is important and there is usually only a short window of time to arrange assessment and treatment, as well as the need to work around other planning patients require. Major concerns for the dental team are caries, trismus and osteoradionecrosis.
Caries is a major risk after radiotherapy. Contributing factors are the reduction in salivary flow and pH, changes in oral flora and high sugar dietary supplements used to restore nutrition [Figure 1]. In addition trismus may develop as a result of surgery or radiotherapy, making access for oral hygiene or dental treatment very difficult in the future. Osteoradionecrosis (ORN) of the jaw is non-healing exposed bone in an irradiated jaw. This may happen spontaneously after radiotherapy, but extraction of a tooth after radiotherapy is the most common cause. It is most likely in areas of highest radiation and especially the posterior part of the mandible, but any bone directly in the beam is likely to receive a dose that could result in ORN. It is a lifetime risk [Figure 2].

Before cancer treatment
Patients should have a dental assessment prior to radiotherapy.  Full mouth radiographs of teeth and adjacent structures are recommended. Treatment before radiotherapy may include:
1. Extractions: teeth of poor prognosis should be extracted at least two weeks before commencement of radiotherapy to allow healing. Criteria for tooth assessment are shown in Table 2. If the patient is having induction chemotherapy it is necessary to ensure adequate platelet and white blood cell levels at the time of extraction and liaise with the oncologist.
2. Preventive advice: information on the effects of radiotherapy and the need for excellent oral care should be provided. Written instruction leaflets are preferable.
3. Restorations and scaling should be provided as required to ensure the mouth is healthy.

During cancer treatment
Immediately after surgery, 0.2% chlorhexidine mouthwash is advised if maintaining oral hygiene is difficult. Is should only be used for a short time and patients are encouraged to brush their teeth as soon as possible. Mucositis is very sore inflammation of the mucosa, with erythema and ulceration [Figure 3]. It develops after about 10 days of radiotherapy and may be so severe that patients are hospitalised or a break in treatment is necessary. Chemotherapy can also cause severe mucositis. Patients may find a soft toothbrush and benzydamine rinse (Difflam, 3M) helpful during this time. Generally treatment is unsatisfactory, but the condition is time-limited and the mucosa heals a few weeks after completion of radiotherapy.

After treatment
As soon as possible after radiotherapy patients should be reviewed and the preventive regime reinforced. A high fluoride regime that is acceptable to the patient in terms of taste and ease of use is important. Individual protocols may therefore be developed, but a high fluoride toothpaste (for example Duraphat 5000, Colgate-Palmolive) and an alcohol free 0.05% sodium fluoride mouthwash at a different time of day are recommended. Fluoride varnish may be applied at three monthly dental visits. Use of xylitol or reminerilising substances such as calcium phosphate and casein phosphopeptide (GC Tooth Mousse) may be beneficial but have not been tested in this patient group.

Patients should be informed of the risks of high sugar diets, and,  in discussion with the dietician, sugary food supplements should be reduced as soon as a normal swallowing is achieved. This is not possible for all patients. Candidiasis is a common problem in head and neck cancer patients; the diagnosis can be confirmed by a microbiological swab. Antifungal agents should be prescribed, either nystatin topically (as pastilles or as a suspension if lack of saliva makes dissolving pastilles difficult) or fluconazole. Patients who develop trismus after radiotherapy should have jaw exercises to assist opening. A Therabite appliance can be used but a simple stack of wooden spatulas placed between the incisors in increasing numbers can be effective.

The most frequent and distressing symptom after radiotherapy is dry mouth. There are many products on the market for relief of xerostomia and patients should choose what suits them best, but products with low pH should only be used by edentulous patients. Most patients find sips of water the most satisfactory; otherwise Biotene OralBalance System (GSK) or BioXtra (Quench Pharma) are recommended. If there is some salivary function, stimulation by chewing sugar-free gum is ideal.

Taste disturbance is common with radiotherapy. This condition starts within a few days and persists for two years; it may never return to normal. Taste alteration cannot at present be resolved but dietary counselling to reduce unpleasant tastes and improve eating experience by introducing foods with pleasing appearance, textures and smell may be helpful. Taste disturbance does not correlate with xerostomia. It may result from a direct effect on the taste buds.

Longer term maintenance
Following radiotherapy, patients remain at high risk for dental disease and should be seen at frequent intervals (the recommendation is at least every three months in the first year). Symptoms can be addressed, preventive care reinforced and treatment given promptly. Delivery of dental care may be difficult. Trismus makes access difficult and jaw opening is tiring as well as patients needing frequent sips of water to overcome the unpleasant effects of dry mouth. Instruments do not glide easily over dry mucosa. Some patients who have had extensive pharyngeal surgery or radiotherapy do not have fully functional laryngeal reflexes and are at risk of aspiration. Patients are likely to know this and indicators are that they are not allowed oral nutrition. Great care should be taken, using excellent suction and a rubber dam.

After radiotherapy,  extractions should be avoided as far as possible. Even teeth that become broken down are often best managed by endodontics and decoronation rather than risking ORN from extraction. Periodontally involved teeth may be left to exfoliate. Essential extractions should be carried out with minimal trauma and primary closure of the socket. It is recommended to give antibiotic orally one hour before extraction and for 2 weeks afterwards, plus chlorhexidine rinse (0.2%) before and during healing. Sockets should be reviewed until there is healing. If the socket is not healing, twice daily flushing with chlorhexidine in a syringe by the patient is beneficial. Pentoxifylline 400mg twice daily with once daily vitamin E 1000 IU have been used to improve healing in cases of ORN, and may be beneficial prophylactically.

Rehabilitation
Dentures may be difficult to manage in patients with xerostomia, and even slight denture trauma can lead to ORN. Adhesive bridges to replace single teeth are very useful but it is often best to accept a shortened dental arch. Eating difficulties are mostly associated with xerostomia and swallowing difficulty rather than lack of teeth. Prosthetic rehabilitation for patients after major jaw resection and radiotherapy is complex. Specialist restorative services increasingly provide implant retained bridges and implant supported dentures.

Further reading
The author recommends Oral Healthcare for People Living with Oral Cancer. Editor Crispin Scully. Oral Oncology 46; June 2010.

The author
Mary Burke BDS, FDS RCS Eng
Consultant in Special Care Dentistry
Department of Sedation and Special Care Dentistry
Floor 26, Tower Wing
Guy’s Hospital
Great Maze Pond
London, SE1 9RT, UK