Hypofractionated Whole Breast Irradiation (WBI) in Breast Conserving Surgery

  • Hypofractionated WBI continues to increase in its utilization with several regimens available including:
    • The Canadian regimen (42.5 Gy/16 fractions) and 
    • Various UK regimens
  • Ten-year data are now available:
    • With a local recurrence rate of 7% from the Canadian regimen 
    • And no difference in local recurrence or toxicity:
      • Compared with standard fractionation
  • Similar results have been seen with the:
    • UK Standardisation of Breast Radiotherapy (START) A and B trials:
      • Which have found no difference in local recurrence:
        • With fewer treatments and higher doses per treatment compared to standard fractionation
      • The START-B trial:
        • Randomized 2215 women to 40 Gy in 15 fractions or standard 50 Gy in 25 fractions:
        • The 10-year local-regional relapse rate:
          • Was 4.3% for the 40 Gy group and 5.5% for the 50 Gy group
        • Breast shrinkage, telangiectasia, and breast edema:
          • Were significantly less common in the 40 Gy group than in the 50 Gy group
  • In the Canadian trials:
    • 24% of patients were younger than age 50 years
    • 31% had tumors greater than 3 cm
    • 26% were ER-negative
    • 18% had high-grade tumors
    • 42% received tamoxifen
    • 11% received adjuvant systemic therapy of:
      • Cyclophosphamide, methotrexate, and fluorouracil as the standard chemotherapy
  • In the START-A trial:
    • 51% had tumors less than 2 cm
    • 29% of patients had positive lymph nodes
    • Only 35% of patients in this trial received adjuvant systemic therapy
  • Collectively, the hypofractionation trials represent:
    • A more diverse, higher-risk patient population in an era without the benefits of modern systemic therapy
    • This may explain the relatively higher rates of local failure when compared to the accelerated partial breast irradiation group
  • References:
    • Haviland JS, Owen JR, Dewar JA, et al; START Trialists’ Group. The UK Standardisation of Breast Radiotherapy (START) trials of radiotherapy hypofractionation for treatment early stage breast cancer: 10-year follow-up results of two randomised controlled trials. Lancet Oncol. 2013;14:1086-1094.
    • 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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