ABR Radiation Oncology Certification
Examination Exam Questions and Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. The standard fractionation for definitive radiotherapy in early-
stage non-small cell lung cancer is typically:
A. 1 Gy x 30 fractions
B. 2 Gy x 30 fractions
C. 3 Gy x 10 fractions
D. 1.8 Gy x 25 fractions
B. 2 Gy x 30 fractions
This fractionation is the conventional regimen used in curative-
intent radiotherapy for early-stage NSCLC.
2. The alpha/beta ratio is most relevant for:
A. Determining chemotherapy dose
B. Understanding tissue radiobiology
C. Imaging quality
D. Surgery timing
B. Understanding tissue radiobiology
The alpha/beta ratio helps predict tissue response to fraction size,
distinguishing early- from late-responding tissues.
3. The main determinant of tumor control probability (TCP) in
radiotherapy is:
A. Dose distribution
B. Tumor size and radiosensitivity
C. Patient age
, D. Chemotherapy schedule
B. Tumor size and radiosensitivity
Tumor control probability depends largely on intrinsic
radiosensitivity and tumor burden.
4. For prostate cancer, hypofractionated radiotherapy involves:
A. Smaller doses per fraction
B. Larger doses per fraction over fewer sessions
C. Continuous low-dose rate brachytherapy only
D. Daily doses less than 1 Gy
B. Larger doses per fraction over fewer sessions
Hypofractionation delivers higher dose per fraction to reduce
overall treatment time while maintaining efficacy.
5. The primary mechanism of cell death from ionizing radiation is:
A. Apoptosis via p53 exclusively
B. DNA double-strand breaks
C. Mitochondrial dysfunction alone
D. Cell membrane disruption
B. DNA double-strand breaks
Radiation primarily kills cells by inducing irreparable DNA damage,
particularly double-strand breaks.
6. In the treatment of glioblastoma, the standard external beam
radiotherapy dose is:
A. 45 Gy in 15 fractions
B. 50 Gy in 25 fractions
C. 60 Gy in 30 fractions
D. 70 Gy in 35 fractions
C. 60 Gy in 30 fractions
This dose-fractionation scheme is standard when combined with
concurrent temozolomide.
, 7. The maximum tolerated dose (MTD) in radiotherapy is:
A. The dose that guarantees tumor cure
B. The highest dose deliverable without unacceptable toxicity
C. Twice the standard fractionation dose
D. The dose that maximizes patient comfort
B. The highest dose deliverable without unacceptable toxicity
MTD balances tumor control against normal tissue toxicity.
8. Which organ is most sensitive to radiation-induced cataract
formation?
A. Retina
B. Cornea
C. Lens
D. Optic nerve
C. Lens
The lens is highly radiosensitive, and cataracts can occur at
relatively low doses.
9. Intensity-modulated radiotherapy (IMRT) primarily improves:
A. Tumor radiosensitivity
B. Dose conformity and normal tissue sparing
C. Fractionation tolerance
D. Chemotherapy synergy
B. Dose conformity and normal tissue sparing
IMRT allows shaping of the dose distribution to match tumor
geometry while minimizing normal tissue exposure.
10. Stereotactic body radiotherapy (SBRT) is best described as:
A. Conventional fractionation
B. High-dose per fraction with precise targeting
C. Low-dose palliative therapy
D. Only used in brain tumors
Examination Exam Questions and Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. The standard fractionation for definitive radiotherapy in early-
stage non-small cell lung cancer is typically:
A. 1 Gy x 30 fractions
B. 2 Gy x 30 fractions
C. 3 Gy x 10 fractions
D. 1.8 Gy x 25 fractions
B. 2 Gy x 30 fractions
This fractionation is the conventional regimen used in curative-
intent radiotherapy for early-stage NSCLC.
2. The alpha/beta ratio is most relevant for:
A. Determining chemotherapy dose
B. Understanding tissue radiobiology
C. Imaging quality
D. Surgery timing
B. Understanding tissue radiobiology
The alpha/beta ratio helps predict tissue response to fraction size,
distinguishing early- from late-responding tissues.
3. The main determinant of tumor control probability (TCP) in
radiotherapy is:
A. Dose distribution
B. Tumor size and radiosensitivity
C. Patient age
, D. Chemotherapy schedule
B. Tumor size and radiosensitivity
Tumor control probability depends largely on intrinsic
radiosensitivity and tumor burden.
4. For prostate cancer, hypofractionated radiotherapy involves:
A. Smaller doses per fraction
B. Larger doses per fraction over fewer sessions
C. Continuous low-dose rate brachytherapy only
D. Daily doses less than 1 Gy
B. Larger doses per fraction over fewer sessions
Hypofractionation delivers higher dose per fraction to reduce
overall treatment time while maintaining efficacy.
5. The primary mechanism of cell death from ionizing radiation is:
A. Apoptosis via p53 exclusively
B. DNA double-strand breaks
C. Mitochondrial dysfunction alone
D. Cell membrane disruption
B. DNA double-strand breaks
Radiation primarily kills cells by inducing irreparable DNA damage,
particularly double-strand breaks.
6. In the treatment of glioblastoma, the standard external beam
radiotherapy dose is:
A. 45 Gy in 15 fractions
B. 50 Gy in 25 fractions
C. 60 Gy in 30 fractions
D. 70 Gy in 35 fractions
C. 60 Gy in 30 fractions
This dose-fractionation scheme is standard when combined with
concurrent temozolomide.
, 7. The maximum tolerated dose (MTD) in radiotherapy is:
A. The dose that guarantees tumor cure
B. The highest dose deliverable without unacceptable toxicity
C. Twice the standard fractionation dose
D. The dose that maximizes patient comfort
B. The highest dose deliverable without unacceptable toxicity
MTD balances tumor control against normal tissue toxicity.
8. Which organ is most sensitive to radiation-induced cataract
formation?
A. Retina
B. Cornea
C. Lens
D. Optic nerve
C. Lens
The lens is highly radiosensitive, and cataracts can occur at
relatively low doses.
9. Intensity-modulated radiotherapy (IMRT) primarily improves:
A. Tumor radiosensitivity
B. Dose conformity and normal tissue sparing
C. Fractionation tolerance
D. Chemotherapy synergy
B. Dose conformity and normal tissue sparing
IMRT allows shaping of the dose distribution to match tumor
geometry while minimizing normal tissue exposure.
10. Stereotactic body radiotherapy (SBRT) is best described as:
A. Conventional fractionation
B. High-dose per fraction with precise targeting
C. Low-dose palliative therapy
D. Only used in brain tumors
