Hypofractionation

• Definition: larger doses per fraction (>2.5–3 Gy), fewer fractions overall.

• Rationale: tumors with low α/β ratio (e.g., prostate cancer) may benefit.

Stereotactic Body Radiotherapy (SBRT/SABR)

• Definition: very high doses per fraction (6–20 Gy), 1–5 fractions, with precise image guidance.

• Rationale: steep dose gradients, exploiting tumor radiobiology and advanced technology.

Radiobiological basis

• Higher BED delivered to tumor in fewer sessions.

• Challenges: normal tissue sparing and uncertainties in LQ model at high doses.

Clinical relevance

• SBRT widely used for early-stage lung cancer, oligometastases, prostate, liver tumors.