Hypofractionated Whole Breast Irradiation (WBI) in Breast Conserving Surgery

  • Hypofractionated WBI continues to increase in utilization:
    • Based on data from the Ontario Oncology trial as well as 5- and 10-year data from the UK Standardization of Breast Radiotherapy (START) A and B trials
  • Standardized treatment schedules for hypofractionation typically are:
    • 15 to 16 fractions over 3 to 4 weeks depending on inclusion of a boost
    • The risk of local recurrence in the Ontario trial at 10 years was:
      • 6.7% among the 612 women assigned to standard irradiation compared with 6.2% among the 622 women assigned to the hypofractionated regimen:
        • Absolute difference, 0.5 percentage points; 95% confidence interval [CI], −2.5 to 3.5
      • 71.3% of women in the control group compared with 69.8% of the women in the hypofractionated radiation group had a good or excellent cosmetic outcome:
        • Absolute difference, 1.5 percentage points; 95% CI, −6.9 to 9.8)
    • In the START-B trial:
      • The proportion of patients with local-regional relapse at 10 years did not differ significantly:
        • Between the 40 Gy (hypofractionation) group (4.3%, 95% CI, 3.2–5.9) and the 50 Gy (standard) group (5.5%, 95% CI, 4.2–7.2; hazard ratio, 0.77, 95% CI, 0.51–1.6; P=0.21)
      • There was less breast shrinkage, telangiectasia, and edema in the 40 Gy/15 fraction arm
  • Traditionally:
    • A separation (the distance from the medial to the lateral border of the tangential beam) of:
      • 25 cm was utilized as a cut off:
        • But now a maximum dose of 107% of prescription is used in light of advancements in planning techniques
  • Current evidence-based American Society for Radiation Oncology (ASTRO) guidelines on fractionation recommend hypofractionated WBI be considered in:
    • Patients age 50 years and older:
      • With T1 to T2, N0 disease:
        • Who do not receive chemotherapy
  • It should be noted that the percentage of patients with nodal positivity in these trials was quite low:
    • So the role of hypofractionated regimens in node-positive patients remains unanswered
  • References:
    • Haviland JS, Owen JR, Dewar JA, et al; START Trialists’ Group. The UK Standardization of Breast Radiotherapy (START) trials of radiotherapy hypofractionation for treatment of early stage breast cancer: 10-year follow-up results of two randomised controlled trials. Lancet Oncol. 2013;14:1086-1094.
    • Smith BD, Bentzen SM, Correa CR, et al. Fractionation for whole breast irradiation: an American Society for Radiation Oncology (ASTRO) evidence-based guideline. Int J Radiat Oncol Biol Phys. 2011;81:59-68.
    • Whelan TJ, Pignol JP, Levine MN, et al. Long-term results of hypofractionated radiation therapy for breast cancer. N Engl J Med. 2010;362:513-520.

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