Clinical Radiation Oncology
Core concepts
Know site-specific indications, target volumes (GTV/CTV/PTV), dose/fractionation, and normal-tissue constraints for the major diseases: head/neck, lung (NSCLC, SCLC), breast, prostate, GI (esophagus, rectum, anal), CNS, gynecologic, lymphoma, and palliation. Understand concurrent chemoradiation rationale, elective nodal coverage, and when SBRT/SRS is appropriate. Be able to name classic dose levels (e.g., 60 Gy/30 for definitive NSCLC, 50 Gy/25 postoperative breast, 78 Gy prostate, 50.4 Gy anal with mitomycin/5-FU) and key constraints (spinal cord, brachial plexus, parotids, lung V20).
Traps
Questions test whether you know elective vs involved nodal dosing and the difference between definitive and adjuvant intent. Watch for staging that changes management (e.g., limited vs extensive SCLC). Don't over-irradiate the contralateral breast in whole-breast radiation. Distinguish palliative dose (e.g., 8 Gy × 1, 30 Gy/10, 20 Gy/5) from curative. Know that concurrent chemo adds survival benefit in several sites but not all.
Rule of thumb
For palliation, single 8 Gy ≈ 30 Gy/10 for pain; choose based on re-irradiation and logistics. For curative intent, always confirm target dose and critical-organ constraints before finalizing.
Worked example
A patient with limited-stage SCLC: standard is concurrent platinum/etoposide with thoracic RT ~45 Gy/30 fx twice-daily (or 60–70 Gy once-daily), plus prophylactic cranial irradiation after good response. Contrast with extensive-stage, where RT is generally palliative.