Contraindications for External Beam Radiotherapy (EBRT)
External beam radiotherapy is absolutely contraindicated in pregnancy, uncontrolled bleeding disorders, active inflammatory bowel disease, prior pelvic irradiation to the same field, and the presence of a permanent indwelling Foley catheter. 1, 2
Absolute Contraindications
Pregnancy: EBRT is strictly contraindicated during pregnancy due to the risk of fetal irradiation causing developmental abnormalities, growth restriction, and increased cancer risk in offspring 1, 3
Uncontrolled bleeding disorders: Active coagulopathy or uncontrolled bleeding diathesis must be corrected before proceeding with radiotherapy, as EBRT carries high bleeding risk 1
Active inflammatory bowel disease: Active proctitis, Crohn's disease, or ulcerative colitis in active flare significantly increases the risk of severe radiation-induced complications including fistula formation and soft tissue necrosis 1, 2
Prior pelvic irradiation: Previous radiation to the same anatomical field creates unacceptable cumulative radiation toxicity and severe tissue damage from overlapping radiation fields 1, 2
Permanent indwelling Foley catheter: The presence of a permanent catheter is incompatible with the precise targeting required for EBRT and increases infection risk 2
Arterial aneurysm near the treatment field: An aneurysm in proximity to the radiation target poses risk of rupture 1
Anatomic obstruction distal to the stone (specific to ESWL for urolithiasis): This prevents stone fragment passage 1
Severe obesity or skeletal malformations (specific to ESWL): These prevent adequate targeting and treatment delivery 1
Relative Contraindications
Inactive inflammatory bowel disease: Inactive ulcerative colitis or Crohn's disease carries an increased risk of disease flare-up following radiation exposure, though recent evidence suggests grade ≥3 toxicity occurs in only 14% of inflammatory bowel disease patients, making this less prohibitive than historically believed 2, 4
Collagen vascular diseases: Conditions such as lupus and scleroderma have traditionally been considered contraindications due to impaired tissue repair, but systematic reviews demonstrate that these patients have only 11.7% risk of grade ≥3 acute toxicity and 6.1% risk of late toxicity, with grade 5 toxicity <1% 2, 4
Very low bladder capacity: This may lead to increased urinary toxicity and reduced quality of life post-treatment, making EBRT delivery challenging 2
Chronic moderate or severe diarrhea: Pre-existing bowel dysfunction may be significantly exacerbated by radiation effects 2
Bladder outlet obstruction requiring suprapubic catheter: This may complicate treatment delivery and increase the risk of urinary complications 2
Multiple prior abdominal/pelvic surgeries: Extensive adhesions and altered anatomy increase the risk of bowel complications 1
Pelvic inflammatory disease history: Prior infection increases tissue sensitivity to radiation 1
Diabetes mellitus: Impaired wound healing and microvascular disease increase complication risk 1
Special Clinical Situations
Genetic skin cancer syndromes: Basal cell nevus syndrome and xeroderma pigmentosum are absolute contraindications for skin cancer radiotherapy due to impaired DNA repair mechanisms 2
Verrucous carcinoma: This histologic subtype is contraindicated for radiotherapy due to documented increased metastatic risk after radiation treatment 2
Prior endobronchial radiation: Previous endobronchial radiation in the same area within 6 months is an absolute contraindication for thoracic EBRT 2
Critical Technical Requirements
EBRT should only be performed at facilities with appropriate technology, physics expertise, and clinical experience, particularly for advanced techniques like intensity-modulated radiotherapy (IMRT) and stereotactic body radiotherapy (SBRT) 5, 2
Proper patient selection and treatment planning are essential to minimize toxicity risk, especially when treating near critical structures such as rectum, bladder, sigmoid, small bowel, spinal cord, and bone 1