Radiation therapy is a common and effective treatment for cancers in the head and neck regions. While it uses high-energy rays to destroy cancer cells, it can also damage adjacent healthy tissues. Long-term side effects persist or develop months to many years after treatment. Severity depends on the total radiation dose and the specific areas treated. These effects stem from progressive damage leading to chronic inflammation and fibrosis, which is the hardening and scarring of tissues. Understanding these changes requires life-long monitoring and management.
Chronic Oral and Dental Damage
Chronic dry mouth, or xerostomia, is a frequent long-term effect resulting from irreversible damage to the salivary glands. Glands like the parotid are sensitive to radiation, causing fibrous tissue development and a permanent reduction in saliva volume and quality. This alters the mouth’s environment, often making saliva thick. The lack of protective saliva significantly increases the risk of radiation-related dental decay, or caries, as the mouth’s natural pH balance is disrupted. This accelerated decay is often aggressive, affecting the area near the gum line. Meticulous oral hygiene is necessary to mitigate this risk.
A more serious complication is osteoradionecrosis (ORN) of the jaw, where bone tissue dies due to poor blood supply following high-dose radiation. The mandible is the most frequently affected bone. ORN can be triggered by trauma, such as a tooth extraction, and presents a lifelong risk, potentially leading to pain, infection, and fractures.
Impairments to Swallowing and Soft Tissue Integrity
Damage to the soft tissues and muscles of the throat can lead to dysphagia, or difficulty swallowing, which may develop or worsen long after treatment. This impairment is caused by fibrosis, the formation of hardened scar tissue in the pharyngeal and laryngeal muscles necessary for swallowing. Internal lymphedema, or swelling of the throat tissues, can also contribute.
Fibrosis affecting the chewing muscles can result in trismus, the restricted ability to open the mouth. Trismus increases with higher radiation doses and can significantly impair speech, nutrition, and dental care. Physical therapy and stretching exercises are often needed to improve jaw mobility.
Lymphedema, or chronic swelling in the face and neck, occurs when radiation damages the lymph vessels. This condition can be external or internal, affecting the throat and larynx, which can cause hoarseness and breathing difficulties. Skin within the treated field can also show chronic changes, including a woody texture, atrophy, pigmentation changes, and small, dilated blood vessels (telangiectasias).
Endocrine and Sensory System Dysfunctions
If the thyroid gland is included within the radiation field, a common long-term effect is hypothyroidism, or an underactive thyroid. Radiation damage impairs the gland’s ability to produce sufficient hormones, leading to symptoms like fatigue, weight gain, hoarseness, and cold intolerance. This condition requires lifelong hormone replacement therapy.
Sensory structures are susceptible to damage, manifesting as various neuropathies. Sensorineural hearing loss can occur due to direct radiation damage to the inner ear structures. This risk is heightened if the patient received ototoxic chemotherapy like cisplatin. Patients may also experience chronic ear pain or altered sense of taste or smell.
If the eyes or optic nerves are within the radiation volume, vision impairment can develop, including cataracts or optic neuropathy. Peripheral neuropathy can affect nerves extending into the shoulder and arm, such as the brachial plexus. This nerve damage can cause chronic pain, numbness, tingling, or muscle weakness, with symptoms sometimes appearing years after treatment.
Strategies for Long-Term Monitoring and Care
Survivors require specialized and continuous follow-up care focused on cancer surveillance and chronic side effect management. The follow-up schedule is intense initially, transitioning to annual visits with the oncology team. Monitoring includes regular physical exams and periodic imaging to check for recurrence. Management strategies are highly specific and involve a multidisciplinary team.
Oral and Dental Management
A comprehensive dental evaluation is recommended every six to twelve months, often including prescription-strength fluoride to combat caries. Patients with trismus benefit from physical therapy and jaw-stretching exercises.
Functional and Endocrine Support
Speech and swallowing rehabilitation is necessary to address dysphagia and manage aspiration risk. Thyroid function is monitored with blood tests (TSH levels) every six to twelve months, and hormone replacement is prescribed when hypothyroidism is confirmed. Overall care should also include nutritional support and psychological support.