AOCNP Radiation Therapy Principles and Side Effects 4

Question 1

A patient undergoing pelvic radiation for cervical cancer reports diarrhea, cramping, and rectal bleeding 6 weeks after completing treatment. What is the most likely diagnosis?

Accepted Answer

Chronic radiation enteritis

Answer

Symptoms appearing weeks to months after completing pelvic radiation are consistent with chronic radiation enteritis, which can develop from 6 weeks to years post-treatment.

Question 2

Which dosimetric parameter best predicts the risk of radiation-induced pneumonitis in a lung cancer patient receiving thoracic radiotherapy?

Accepted Answer

Mean lung dose (MLD)

Answer

Mean lung dose (MLD) is one of the strongest predictors of radiation pneumonitis risk, with higher MLD correlating with increased incidence.

Question 3

A patient with head and neck cancer develops trismus 8 months after completing chemoradiation. Which structure's fibrosis most directly causes this complication?

Accepted Answer

Temporomandibular joint and masticatory muscles

Answer

Trismus results from radiation-induced fibrosis of the masticatory muscles and temporomandibular joint, causing limited mouth opening.

Question 4

Stereotactic body radiation therapy (SBRT) for a peripheral lung tumor uses a biologically effective dose (BED) of 100 Gy or more. This high BED is thought to achieve tumor control partly through which mechanism beyond direct DNA damage?

Accepted Answer

Ablation of tumor vasculature causing indirect tumor cell death

Answer

High-dose-per-fraction SBRT is believed to destroy tumor vasculature, causing indirect tumor cell death through ischemia in addition to direct cytotoxicity.

Question 5

During radiation therapy planning, what does the term 'R50' measure in SBRT?

Accepted Answer

The ratio of the 50% isodose volume to the planning target volume

Answer

R50 (conformity index) is the ratio of the 50% isodose volume to the PTV, used to evaluate the conformality and fall-off of SBRT plans.

AOCNP - Advanced Oncology Certified Nurse Practitioner Practice Test

AOCNP - Advanced Oncology Certified Nurse Practitioner Practice Test

AOCNP Radiation Therapy Principles and Side Effects 4