DCIS

Role of RT after BCS in DCIS

  • NSABP B17
    • DCIS with negative margins
      • XRT vs No XRT
    • F/U 8 years
    • Recurrence of DCIS→ XRT makes it HALF
      • 8.4% vs 13.4%
        • IBTR recurrence rate is ~4% per year
  • Predictors of recurrence:
    • Moderate to marked comedo-necrosis
    • Positive margins
  • Cancer-specific survival for DCIS → 95%
Options of Local Therapy
  • Mastectomy→ 98% cure regardless of age, size and grade
  • Indications
    • If lesion is too large for clear margin
    • Multicentric
    • Best measure: magnification mammogram; MRI over and underestimates
  • Partial Mastx + RT
  • Partial Mastx alone

How to choose the therapy?!

  • extent of the DCIS (size)
  • Consider risk of local recurrence with each form of treatment

How do we know XRT is beneficial after excision of DCIS?

There are 4 trials :
Risk of recurrence : with RT → no RT

  • European ( EORTC)
    • 26% → 15%
  • UK-Australia-New Zealand
    • 14% → 6%
  • Swedish
    • 22% → 7%
  • NSABP
    • 32% → 16%
What is important to know about these four trials?
  • All decreased the risk by half
  • 50 Gy to the whole breast /25 fractions
    • No boost dose
  • Only 9% in NSABP and 5% in EORTC got boost
    • But in young patients it is generally recommended just based on data of invasive ca
  • No difference in OS
  • Risk of axillary recurrence regardless of use of Tamoxifen is , 0.1%
  • No Tamoxifen except UK/ANZ
  • 50% of recurrences were invasive
  • Risk reduction in both invasive and in situ

What about Tamoxifen?

  • 80% of DCIS → ER+
  • In UK/ANZ → two-by-two randomization
    • RT versus none and tamoxifen versus none
  • No benefit invasive recurrence ( ipsi or contra )
  • But risk reduction 34% in in situ recurrence
    • So why do we recommend TAMOXIFEN in DCIS?
  • NSABP B24 trial
    • 1,804 patients → RT + Sx
    • Tamoxifen 20 mg daily vs placebo
    • 5 years
    • Breast Ca event → 13.4% vs 8.2%
    • What factors affect risk of recurrence?
      • Age
      • 40 and younger; 60 and older
      • Grade
      • Palpable ( Clinical presentations of DCIS)

Who may not require RT?

  • Negative margin > 1 cm
    • A prospective trial attempt to prove this —> BUT 12% rate of recurrence (30% invasive ) ==> study closed early
    • Eastern Cooperative Oncology Group (ECOG)
        • A prospective, single-arm study
        • Excision alone in selected patients with DCIS
        • If Low- or intermediate-grade DCIS
          • 3 mm > DCIS < 2.5 cm
        • If High grade
          • DCIS < 1cm
        • Margin > 3 mm
        • 579 patients
        • Local recurrence rate —> 6.1%
          • 101 patients with high-grade DCIS ( median tumor size of 7 mm )
            • 5-year local recurrence rate —> 14.8%
            • Maybe worth not giving RT in low-intermediate grade
              • but after 10 years of follow-up no differences in the rate of local failure on the basis of grade were seen