Adjuvant Radiation Therapy For DCIS

• The National Surgical Adjuvant Breast and Bowel Project (NSABP) B-17 phase III randomized clinical trial and three other prospective randomized clinical trials and their follow-up studies:
  • Have demonstrated and continue to show the benefit of radiation therapy (RT) following breast-conserving surgery for patients with DCIS:
    • With a significant 50% reduction in IBTR
• In a report by Wapnir et al. on long-term outcomes of the NSABP B-17 and B-24 trials:
  • Patients who only received lumpectomy:
    • Had a local recurrence rate of:
      • 19.4% compared with 8.9% in the lumpectomy plus RT group at 15 years of follow-up:
        • Demonstrating a 52% reduction in the risk of IBTR
• Similarly, European Organization for Research and Treatment of Cancer (EORTC) 10853:
  • Showed a risk reduction of 48% with the addition of radiotherapy to locally excised DCIS

• The Radiation Therapy Oncology Group (RTOG) 9804 trial:
  • Evaluated the impact of RT after breast-conserving therapy (BCT) in patients with mammographically detected low-risk DCIS as defined by:
    • Size less than 2.5 cm
    • Unicentric
    • Low- and intermediate-grade
    • Margins > 3 mm
  • The primary endpoint of ipsilateral local failure was:
    • 0.9% in the RT arm versus 6.7% in the observation arm
• The E5194 trial:
  • Included a similar patient population of 665 patients placed into two cohorts: 
    • Low- and intermediate-grade DCIS with a tumor size less than 2.5 cm or high-grade DCIS with a tumor size less than 1 cm
  • All patients were treated with BCT yielding greater than 3 mm margins without RT with a median follow-up of 12.3 years
  • These results demonstrated tumor size and cohort to be significant predictors of developing an ipsilateral breast event:
    • 14.4% for the low-risk cohort versus 24.6% for the high-risk cohort
  • This risk continued to increase without plateau through the follow-up period, necessitating further follow-up to determine long-term outcomes
• Differences in the IBTR rates between these studies:
  • May be due to the effect of tamoxifen use:
    • Which was not controlled in either trial
    • Which is known to reduce the risk of IBTR in combination with RT after BCT as shown by the NSABP B-24 trial
• Together, the results of both RTOG 9804 and E5194:
  • Support the individualized treatment of DCIS:
    • Based on identification of patients at low risk for IBTR determined by:
      • Pathologic and clinical features that may omit RT
• A 12-year follow-up study of RTOG 9804 demonstrated:
  • That the 12-year cumulative incidence of local recurrence (LR) was:
    • 2.8% with RT and 11.4% with observation alone
  • The 12-year cumulative incidence of invasive LR was:
    • 1.5% with RT and 5.8% with observation alone
• References:
  • Wapnir IL, Dignam JJ, Fisher B, Mamounas EP, Anderson SJ, Julian TB, et al. Long-term outcomes of invasive ipsilateral breast tumor recurrences after lumpectomy in NSABP B-17 and B-24 randomized clinical trials for DCIS. J Natl Cancer Inst. 2011;103(6):478-488.
  • EORTC Breast Cancer Cooperative Group; and EORTC Radiotherapy Group; Bijker N, Meijnen P, Peterse JL, et al. Breast-conserving treatment with or without radiotherapy in ductal carcinoma-in-situ: ten-year results of European Organisation for Research and Treatment of Cancer randomized phase III trial 10853—a study by the EORTC Breast Cancer Cooperative Group and EORTC Radiotherapy Group. J Clin Oncol. 2006;24(21):3381-3387.
  • McCormick B, Winter K, Hudis C, Kuerer HM, Rakovitch E, Smith BL, et al. RTOG 9804: a prospective randomized trial for good-risk ductal carcinoma in situ comparing radiotherapy with observation. J Clin Oncol. 2015;33(7):709-715.
  • Solin LJ, Gray R, Hughes L, Wood WC, Lowen MA, Badve SS, et al. Surgical excision without radiation for ductal carcinoma in situ of the breast: 12-year results from the ECOG-ACRIN E5194 Study. J Clin Oncol. 2015;33(33):3938-3944.
  • 5. McCormick B. Randomized trial evaluating radiation following surgical excision for “good risk” DCIS: 12-year report from NRG/RTOG 9804. Int J Radiat Oncol Biol Phys. 2018;102(5):1603.

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