Hypofractionation Emerges as Standard, but Not Yet for Every Patient

Andrew Smith
Published: Monday, Jul 08, 2013
Tim Whelan, MSc, FRCPC
Tim Whelan, MSc, FRCPC

Professor, Department of Medicine
Associate Member, Department of Clinical Epidemiology & Biostatistics
Director, Supportive Cancer Care Research Unit
Juravinski Cancer Centre McMaster University Hamilton, Ontario, Canada

Recently published clinical trial results support new radiation therapy protocols for many breast cancer survivors⎯protocols that could greatly improve collective outcomes despite working little better than existing standards of care, according to Tim Whelan, MSc, FRCPC.

Whelan analyzed the results of the Ontario Clinical Oncology Group (OCOG) trial he led and additional British studies of hypofractionation during the 30th Annual Miami Breast Cancer Conference, which Physicians’ Education Resource (PER)® hosted in Miami Beach, Florida, in March. Hypofractionation is used as a general term for radiation regimes that reduce therapy duration by packing moderately large doses of energy (2.1 Gy−3 Gy) into each day’s treatment.

The studies began more than a decade ago, when researchers started testing alternatives to the long radiation treatments that physicians have used after breast-conserving surgery for more than 30 years: 50 Gy of radiation divided in 25 “fractions” of 2 Gy, and delivered every weekday for five weeks.

“We now have a mountain of evidence, a full 10 years of data on thousands of patients, so we really can feel comfortable in concluding that hypofractionation should indeed become the standard of care for many groups of breast cancer survivors,” Whelan said in an interview. “It will save patients large amounts of time and money while delivering outcomes and side effect profiles that are at least as good as the current standard—and possibly somewhat better.”

The British studies, known as the START A and B trials, tested various hypofractionation programs in 4451 women who had been diagnosed with invasive breast cancer and undergone primary surgery.

In the OCOG trial, 1234 patients were randomized to receive either 50 Gy administered in 25 fractions over five weeks or 42.5 Gy delivered in 16 fractions over three weeks. After 12 years’ median follow-up, the probability of local recurrence was 6.7% for those who received the standard radiation therapy versus 6.2% for those who received the hypofractionated dose (hazard ratio [HR] = 0.95; CI, 0.63-1.46), Whelan said in his presentation.

Table. Radiation Regimen Trial Results

Study Radiation Treatment Arms Patients (No) Median Follow-up (years) Recurrence(%)
OCOG 42.5 GY/16 Fr/3 wk
50 Gy/25 Fr/5 wk
12 6.2
START A 39 Gy/13 Fr/5 wk
41.6 Gy/13 Fr/5 wk50 Gy/25 Fr /5 wk
9.3 8.7
START B 40 Gy/15 Fr/3 wk
50 Gy/25 Fr/5 wk
9.9 4.3

aLocal recurrence in OCOG; locoregional for START trials
Fr indicates fractions; Gy, gray; OCOG, Ontario Clinical Oncology Group; START, Standardisation of Breast Radiotherapy.
Adapted from Whelan T. Should hypofractionation be the new standard after BCS? Presented at: 30th Annual Miami Breast Cancer Conference; March 7-10, 2013; Miami Beach, FL.

Moreover, the cosmetic outcome by time and treatment was nearly identical among the two groups, with 71% of 216 evaluable patients in the standard therapy group achieving an excellent or good outcome, compared with 70% or 235 evaluable patients with the same outcomes.

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