AOCNP Radiation Therapy Principles and Side Effects 1 — Questions and Answers
Question 1: What is the primary mechanism by which ionizing radiation kills cancer cells?
- Directly disrupting cell membrane integrity
- Inducing DNA double-strand breaks leading to apoptosis or mitotic catastrophe (Correct answer)
- Activating natural killer cells to attack tumor cells
- Inhibiting angiogenesis within the tumor microenvironment
Correct answer: Inducing DNA double-strand breaks leading to apoptosis or mitotic catastrophe
Radiation kills cells primarily through direct and indirect (free radical-mediated) DNA double-strand breaks. Cells unable to repair this damage undergo apoptosis, necrosis, or mitotic catastrophe. Rapidly dividing cells are most sensitive due to less time for DNA repair between divisions.
Question 2: Stereotactic body radiation therapy (SBRT) differs from conventional radiation in that SBRT delivers:
- Lower doses over many fractions (25–35 treatments)
- Ablative doses in 1–5 fractions with high precision (Correct answer)
- Proton beams exclusively
- Whole-body radiation prior to bone marrow transplant
Correct answer: Ablative doses in 1–5 fractions with high precision
SBRT (also called SABR) delivers ablative doses (typically 25–60 Gy) in 1–5 fractions using highly conformal techniques (IMRT/VMAT with image guidance). It is used for early-stage lung cancer, liver metastases, spinal metastases, and other oligometastatic disease.
Question 3: Radiation recall is an acute dermatitis reaction triggered by certain chemotherapy agents administered after prior radiation. Which agent is most classically associated with radiation recall?
- Carboplatin
- Doxorubicin (Adriamycin) (Correct answer)
- Vincristine
- Cyclophosphamide
Correct answer: Doxorubicin (Adriamycin)
Radiation recall is an inflammatory skin reaction in a previously irradiated field triggered by certain drugs, most classically anthracyclines (doxorubicin), gemcitabine, taxanes, and capecitabine. It can occur weeks to years after radiation and may also affect internal organs.
Question 4: Which grading system is used by oncology nurses to assess and document radiation-induced side effects including mucositis and dermatitis?
- Karnofsky Performance Scale
- CTCAE (Common Terminology Criteria for Adverse Events) (Correct answer)
- ECOG Performance Status Scale
- NCI-ODWG grading
Correct answer: CTCAE (Common Terminology Criteria for Adverse Events)
The CTCAE (published by NCI) is the standardized system for grading adverse events in oncology, grading toxicities from 1 (mild) to 5 (death). Radiation-induced dermatitis, mucositis, esophagitis, and other toxicities are all graded using CTCAE criteria.
Question 5: Total body irradiation (TBI) is most commonly used in what context?
- Palliative pain control for bone metastases
- Myeloablative conditioning prior to hematopoietic stem cell transplantation (Correct answer)
- Prophylactic cranial irradiation in small cell lung cancer
- Definitive treatment of localized prostate cancer
Correct answer: Myeloablative conditioning prior to hematopoietic stem cell transplantation
TBI is a component of myeloablative conditioning regimens before allogeneic HSCT for hematologic malignancies. It destroys residual leukemic/lymphomatous cells, suppresses the immune system to prevent graft rejection, and ablates the bone marrow to create space for engraftment.
Question 6: Late radiation toxicity in the pelvis most commonly manifests as which of the following?
- Acute radiation dermatitis
- Radiation proctitis, cystitis, or small bowel injury (Correct answer)
- Immediate hair loss in the field
- Acute nausea and vomiting
Correct answer: Radiation proctitis, cystitis, or small bowel injury
Late pelvic radiation effects (occurring >3–6 months post-treatment) include radiation proctitis (rectal bleeding, tenesmus), hemorrhagic cystitis, small bowel obstruction, fistula formation, and sexual dysfunction. These differ from acute effects and may be permanent or progressive.
AOCNP Radiation Therapy Principles and Side Effects 1
What is the primary mechanism by which ionizing radiation kills cancer cells?