hypofractionation

Hypofractionation is a radiotherapy approach in which a higher dose per treatment session is delivered in fewer sessions than conventional schedules. This contrasts with hyperfractionation, which uses smaller doses per fraction given more than once daily, and with standard regimens that use moderate doses per fraction over several weeks. The intent is to shorten the overall treatment time while maintaining tumor control and acceptable toxicity.

The rationale for hypofractionation relies on the radiobiology of the tumor and surrounding normal tissues, often described by the alpha/beta ratio. Tumors and late-responding normal tissues with low alpha/beta ratios may respond favorably to larger fraction sizes, but late side effects can increase if normal tissues are sensitive to high doses per fraction. Therefore, hypofractionation requires careful treatment planning, image guidance, and strict dose constraints tailored to the tumor site and patient.

In breast cancer, hypofractionated schedules delivering roughly 40 Gy in 15 fractions over three weeks have become widely used and have shown tumor control and toxicity comparable to conventional, longer regimens in many studies. In prostate cancer, several large trials have demonstrated non-inferiority of hypofractionated regimens—commonly around 60 Gy in 20 fractions over four weeks—with similar biochemical control and acceptable toxicity, leading to broad adoption in many clinics. Hypofractionation is also employed in palliation, such as for bone metastases, where single or short-course regimens provide rapid symptom relief.

Practical implementation involves contemporary planning, image guidance, and motion management. Selection depends on tumor type, location, stage, and patient factors. Guidelines continue to evolve as trials expand hypofractionation to additional cancers and follow-up data clarify long-term outcomes, with the overarching aim of maintaining efficacy while improving convenience and access.