Omission of Adjuvant Irradiation Following a Partial Mastectomy

  • Multiple groups have attempted to define a favorable subgroup of women:
    • In whom the omission of adjuvant irradiation following a partial mastectomy is reasonable
  • One study (CALGB 9343):
    • Randomized women:
      • Ages 70 years and older:
        • Clinical stage I (T1, N0, M0) disease 
      • To tamoxifen for 5 years versus tamoxifen plus whole-breast irradiation
      • Patients with estrogen receptor-negative tumors:
        • Were excluded
      • Most tumors were 2 cm or less, and surgical margins were required to be negative (defined as the absence of tumor at the inked margin)
      • Adjuvant whole-breast irradiation:
        • Significantly reduced the risk of local or regional failure:
          • From 10% to 2% at 10 years
        • There were no significant differences in:
          • Distant disease-free survival or overall survival between the groups
  • The PRIME II trial:
    • Enrolled 1326 patients:
      • Ages 65 years and older:
        • With T1 to T2, node-negative tumors and clear margins
    • Following breast-conserving surgery:
      • Patients received endocrine therapy and were randomized to:
        • Adjuvant radiation therapy or no further treatment
    • At 5 years:
      • Those undergoing radiation demonstrated a reduction in local recurrence:
        • 4.1% vs 1.3% with no difference in survival
  • Typical breast tangents, without targeted nodal irradiation, would be appropriate for a patient with pN0 disease
  • Adjuvant irradiation:
    • Reduces the risk of ipsilateral breast tumor recurrence regardless of whether the margins are positive:
      • A positive margin, however, significantly increases the risk of local failure despite irradiation
  • References:
    • Hughes KS, Schnaper LA, Bellon JR, et al. Lumpectomy plus tamoxifen with or without irradiation in women age 70 years or older with early breast cancer: long-term follow up of CALGB 9343. J Clin Oncol. 2013;31:2382-2387.
    • Hughes KS, Schnaper LA, Berry D, et al. Lumpectomy plus tamoxifen with or without irradiation in women 70 years of age or older with early breast cancer. N Engl J Med. 2004;351:971-977.
    • Kunkler IH, William LJ, Jack WJ, Cameron DA, Dixon JM; PRIME II investigators. Breast-conserving surgery with or without irradiation in women aged 65 years or older with early breast cancer (PRIME II): a randomised controlled trial. Lancet Oncol. 2015;16:266-273.
    • Moran MS, Schnitt SJ, Giuliano AE, et al. Society of Surgical Oncology-American Society for Radiation Oncology consensus guideline on margins for breast-conserving surgery with whole-breast irradiation in stage I and II invasive breast cancer. Int J Radiat Oncol Biol Phys. 2014;88:553-564.

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