Chronic Radiation Injury

Chronic radiation injury is tissue damage that develops months to years after radiation exposure, from therapy, occupational exposure or accidents. It includes fibrosis, atrophy, telangiectasia, ulceration, necrosis, functional loss of organs, and radiation induced cancer.

Settings. Cancer radiotherapy (late effects in treated fields), interventional radiologists and cardiologists, radiographers, nuclear workers, early radiology and radium workers, and accident survivors.

Deterministic effects. Severity rises with dose and fractions over thresholds, such as skin damage over about 2 Gy, cataract, infertility and organ fibrosis. They occur after a threshold dose.

Stochastic effects. Cancer and heritable effects have no threshold, and risk rises with dose. Latency is 5 to 10 years for leukaemia and longer for solid tumours.

Common syndromes. Chronic radiodermatitis, fibrosis of lung and soft tissue, radiation proctitis and cystitis, enteritis, osteoradionecrosis, myelopathy, hypothyroidism and secondary malignancy.

Occupational limits. Whole body effective dose limits are about 20 mSv/year averaged over 5 years, with no single year over 50 mSv.

Pathophysiology.

Radiation causes endothelial injury, microvascular loss, chronic inflammation with TGF-beta driven fibrosis, and impaired stem cell regeneration. Hypoxia and ongoing oxidative stress perpetuate injury.

Late tissue necrosis follows vascular compromise. Mutations in irradiated cells underlie later cancers.

• Skin: atrophy, telangiectasia, pigmentation, dryness, hair loss, fibrosis, chronic ulcer and nail changes on exposed hands.
• Lung: dry cough and dyspnoea from fibrosis.
• Bowel and bladder: bleeding, urgency, strictures, fistula.
• Bone: pain, exposed bone and pathological fracture.
• Nervous system: myelopathy, brachial plexopathy and cognitive change.

Red flags.

• Non-healing ulcer or nodular skin lesion (radiation induced skin cancer).
• Heavy rectal or urinary bleeding, fistula or obstruction.
• New neurological deficit in the treated field.

• Exposure and treatment history with dose, field and time; dosimetry records.
• Examination of the affected area; biopsy of any suspicious lesion.
• Organ specific investigations: spirometry and CT chest, endoscopy and cystoscopy, MRI for nerve or bone, thyroid and endocrine tests.
• Blood count and chromosomal analysis when exposure is occupational and doses were high.

Differential diagnosis. Recurrent or new cancer in the field, infection, chemotherapy related toxicity, ischaemia, inflammatory bowel disease, autoimmune fibrosis, age related skin change.

• Stop further exposure and review shielding and dose monitoring.
• Skin: emollient, sun protection, avoid trauma; chronic ulcer care; excision of premalignant or malignant lesions.
• Fibrosis: pentoxifylline 400 mg orally three times daily with food for at least 6 months, usually with vitamin E under specialist direction. Maximum 1.2 g daily. Monitor for bleeding, indigestion and blood pressure. Reduce to 400 mg twice daily when creatinine clearance is under 30 mL/min; avoid with recent retinal or cerebral haemorrhage. Evidence is limited.
• Osteoradionecrosis, radiation cystitis and late soft tissue injury: hyperbaric oxygen, 20 to 40 sessions at about 2.0 to 2.4 atmospheres absolute for 90 to 120 minutes, once daily on 5 days each week, directed by a hyperbaric physician. Monitor ears, sinuses and vision.
• Radiation proctitis and haemorrhage: endoscopic argon plasma coagulation; transfusion and iron replacement as needed.
• Strictures and fistulae: surgical or endoscopic treatment by specialists.
• Surveillance for second cancers, with screening of the treated field.

Monitoring. Yearly review of the exposed area and organ function; skin examination every 6 to 12 months for chronic radiodermatitis; surveillance by a specialist for cancers.

Referral and escalation. Oncology and radiation medicine specialists; hyperbaric centre; dermatology for chronic skin injury; occupational physician for dose review and compensation where required.