AOCNP Radiation Therapy Principles and Side Effects 5 — Questions and Answers
Question 1: A male patient completes prostate radiation therapy and reports erectile dysfunction 18 months later. The MOST likely etiology of this late effect is:
- Hypothalamic-pituitary axis suppression
- Radiation-induced fibrosis of the neurovascular bundles and penile vasculature (Correct answer)
- Testosterone deficiency from testicular irradiation
- Psychogenic dysfunction secondary to cancer diagnosis anxiety
Correct answer: Radiation-induced fibrosis of the neurovascular bundles and penile vasculature
Late radiation-induced erectile dysfunction is primarily caused by damage to the neurovascular bundles lateral to the prostate and radiation arteritis affecting penile blood flow.
Question 2: Which grading system is most commonly used in clinical trials to standardize reporting of radiation therapy adverse effects?
- RTOG/EORTC Late Radiation Morbidity Scoring
- NCI Common Terminology Criteria for Adverse Events (CTCAE) (Correct answer)
- WHO Toxicity Grading Scale
- Radiation Therapy Oncology Group Acute Morbidity Criteria
Correct answer: NCI Common Terminology Criteria for Adverse Events (CTCAE)
The NCI CTCAE is the standard system used in oncology clinical trials to classify and grade adverse events including radiation-related toxicities.
Question 3: A patient with esophageal cancer develops odynophagia and dysphagia during the third week of concurrent chemoradiation. CT shows mucosal thickening of the esophagus without perforation. What is the most appropriate management?
- Discontinue radiation immediately and restart after 2 weeks
- Provide symptomatic management with viscous lidocaine, analgesics, and nutritional support (Correct answer)
- Perform emergent endoscopy and esophageal stenting
- Switch to hyperfractionated radiation to reduce acute mucosal dose
Correct answer: Provide symptomatic management with viscous lidocaine, analgesics, and nutritional support
Acute radiation esophagitis is expected during chemoradiation for esophageal cancer and is managed symptomatically with analgesics, mucosal coating agents, and nutritional optimization while continuing treatment.
Question 4: In brachytherapy for cervical cancer, the point 'Point A' is used to prescribe dose. Where is Point A located?
- 2 cm lateral and 2 cm superior to the external cervical os
- 2 cm superior to the cervical os and 2 cm lateral to the uterine canal (Correct answer)
- At the intersection of the uterosacral ligaments
- At the bladder neck, 2 cm anterior to the cervix
Correct answer: 2 cm superior to the cervical os and 2 cm lateral to the uterine canal
Point A is defined as 2 cm superior to the cervical os (or vaginal fornix) and 2 cm lateral to the uterine canal, representing the region of the parametria and paracervical triangle.
Question 5: Which of the following radiation sensitizers works by mimicking oxygen and thereby enhancing radiation-induced DNA damage in hypoxic tumor cells?
- Amifostine
- Nimorazole (Correct answer)
- Leucovorin
- Filgrastim
Correct answer: Nimorazole
Nimorazole is a nitroimidazole hypoxic cell sensitizer that mimics oxygen, fixing radiation-induced free radical damage in hypoxic tumor cells that would otherwise be repaired.
Question 6: A patient who received mantle field radiation for Hodgkin lymphoma 20 years ago is now diagnosed with coronary artery disease at age 42. This represents which category of late radiation effect?
- Secondary malignancy
- Radiation-induced cardiomyopathy
- Accelerated atherosclerosis as a radiation late effect (Correct answer)
- Pericarditis constrictiva
Correct answer: Accelerated atherosclerosis as a radiation late effect
Mediastinal radiation accelerates atherosclerosis in the coronary arteries, leading to premature coronary artery disease in Hodgkin lymphoma survivors, a well-recognized late cardiovascular toxicity.
Question 7: When managing a patient with radiation recall dermatitis triggered by docetaxel administered after prior radiation, the MOST appropriate initial intervention is:
- Immediate re-irradiation of the affected area at a lower dose
- Withholding the offending chemotherapy agent and treating with topical corticosteroids (Correct answer)
- Applying silver sulfadiazine cream and continuing chemotherapy at reduced dose
- Performing a skin biopsy to confirm diagnosis before any treatment change
Correct answer: Withholding the offending chemotherapy agent and treating with topical corticosteroids
Radiation recall dermatitis is managed by discontinuing the triggering agent and using topical or systemic corticosteroids; re-challenge decisions are made after resolution based on clinical necessity.
AOCNP Radiation Therapy Principles and Side Effects 5
A male patient completes prostate radiation therapy and reports erectile dysfunction 18 months later.
The MOST likely etiology of this late effect is: