This evidence-based series was developed by the Breast Cancer Disease Site Group (DSG) of Cancer Care Ontario's (CCO's) Program in Evidence-based Care (PEBC). The series is a convenient and up-to-date source of the best available evidence on the management of ductal carcinoma in situ (DCIS) of the breast, developed through systematic review, evidence synthesis, and input from practitioners in Ontario.
In the surgical management of DCIS, the choice between mastectomy and breast-conserving surgery (BCS) should be dependent upon patient preference and the results of clinical, mammographic, and pathologic evaluation. Mastectomy is indicated for patients at high risk of recurrence with BCS and radiation. High-risk factors include large size tumours (>5 cm), particularly those with positive margins. While optimal margin widths for patients having BCS and radiation are not specifically known, close lateral margin widths of <1 mm have been associated with higher local recurrence rates in some studies. Patients with smaller areas of DCIS with resection margins <1 mm or positive resection margins are also at a higher than average risk of recurrence. Mastectomy with the option of reconstruction is also an acceptable choice for women preferring to maximize local control. Given the importance of breast conservation for the patient and the potential for salvage, BCS and radiation is an equally acceptable option for eligible women with DCIS.
There are currently three prospective randomized trials that support the routine use of radiation following BCS for patients with DCIS of the breast. Radiation resulted in reduced rates of breast recurrence (both invasive and non-invasive) and mastectomy. Patients should be made aware of the duration of radiation and its toxicity before making a choice between total mastectomy and BCS. All three studies used the dose-fractionation schedules of 5000 cGy in 25 fractions in five weeks, which should be considered the standard; however, the Ontario Clinical Oncology Group (OCOG) randomized trial in patients with invasive breast cancer showed that the shorter fractionation schedule of 4250 cGy in 16 fractions was as effective as and no more toxic than 5000 cGy in 25 fractions. The guideline developers could find no radiobiological evidence to suggest that DCIS responds differently to radiation than invasive disease. The Breast Cancer DSG therefore felt it would be reasonable to offer this shorter fractionation schedule to those women with DCIS who preferred the convenience of a shorter overall treatment time.
None of the randomized studies in DCIS added a boost to the tumour bed. Randomized trials of boost versus no boost in patients with invasive disease have shown a decrease in local recurrence rates when a boost of 1000 to 1600 cGy is added, particularly in younger women or those with close or positive resection margins. Some DCIS studies have shown increased recurrence rates in younger women and those with close resection margins who received standard postoperative whole breast radiation without a boost. The Breast Cancer DSG therefore felt it reasonable to consider the addition of a boost to the tumour bed in those DCIS patients who are felt to be at higher than usual risk of recurrence with standard whole breast radiation alone, provided the patients are willing to accept the possibility of a somewhat poorer cosmetic outcome.
Identifying a group of patients treated with BCS for DCIS who do not require adjuvant radiotherapy is not yet possible. Current data suggest that age, tumour size, margin status, grade, and comedo-type necrosis are important predictors for local recurrence. These studies suggest that there may be different risk groups for local failure (e.g., low, intermediate, and high) where different treatments may be more desirable—low risk, BCS alone; moderate risk, BCS plus radiation; and high risk, total mastectomy plus or minus reconstructive surgery. Further evidence is necessary before making firm recommendations and prospective randomized trials looking at this question are ongoing. Until then, it is recommended that pathologic descriptions including assessment of size, margin status, nuclear grade, and evidence of comedo necrosis be reported more consistently. Patients interested in BCS alone should be made aware of what is currently known about the potential benefits and toxicities of post-lumpectomy radiation.
The National Surgical Adjuvant Breast Project (NSABP-24) study showed an overall decrease in invasive and in situ disease with the addition of tamoxifen to surgical excision followed by radiation, but most of the benefit appeared to be in younger women and those with positive or unknown resection margins. The United Kingdom Coordinating Committee on Cancer Research (UKCCCR) study showed no benefit with the addition of tamoxifen, but the study population consisted mostly of women over 50 years of age with clear resection margins. There was an observed benefit in the subset of women less than 50 years of age and also in those who did not receive radiation. Therefore, the Breast Cancer DSG felt that five years of tamoxifen is an option for DCIS patients, particularly in women less than 50 years of age, those with positive resection margins who refuse further surgery, and those who refused or are unable to have radiation but want to avoid mastectomy. Patients and physicians need to consider the potential toxicities of tamoxifen as well as the possible benefits.
