What is the initial and continuous treatment for Ductal Carcinoma In Situ (DCIS)?

Treatment of Ductal Carcinoma In Situ (DCIS)

For most patients with DCIS, breast-conserving surgery (lumpectomy) followed by whole-breast radiation therapy is the recommended initial treatment, achieving excellent local control with 10-year breast cancer-specific survival rates of 97-98%. 1, 2

Initial Surgical Treatment

Primary Surgical Options

Breast-conserving surgery (lumpectomy) is the preferred initial approach for the majority of DCIS patients, particularly those with small, mammographically detected lesions. 1 This approach has become standard, with usage increasing from 31% to 54% between 1985-1993. 1

Mastectomy should be performed when:

• Lesions are too large or diffuse to be completely removed without unacceptable cosmetic results 3
• Persistent positive margins despite re-excision attempts, especially with high-grade lesions 3
• Tumor multicentricity is present 1
• Prior chest wall or breast radiation 1, 3
• Patient preference after informed discussion 1

Mastectomy achieves cure rates approaching 100%, with only 1-2% of patients experiencing regional or systemic relapse. 1

Margin Requirements

For DCIS treated with breast-conserving surgery and radiation, negative margins of at least 2 mm are required. 1, 4 This standard is based on meta-analysis showing that margins less than 2 mm are associated with increased ipsilateral breast tumor recurrence compared to 2 mm margins. 1

If margins are less than 2 mm after initial excision, re-excision should be performed to achieve adequate margins. 4

Axillary Management

Sentinel lymph node biopsy is generally NOT recommended for pure DCIS unless mastectomy is planned or the lesion location could compromise future lymphatic drainage patterns. 4 Routine axillary dissection should not be performed in women with DCIS. 3 The inappropriately high rate of axillary dissection (49% initially, declining to 37% by 1993) represents overtreatment. 1

Radiation Therapy

Standard Approach

Whole-breast radiation therapy after breast-conserving surgery is strongly recommended, as it reduces ipsilateral breast tumor recurrence by 50-70%. 4 Data from NSABP B-17 trial with 90 months follow-up demonstrated:

• Invasive recurrence: 3.9% with radiation vs 13.4% without radiation (p=0.000005) 1
• DCIS recurrence: 8.2% with radiation vs 13.4% without radiation (p=0.007) 1
• Overall 8-year ipsilateral breast tumor recurrence: 12.1% with radiation vs 31.7% without radiation 1

Boost radiation provides an additional 50% risk reduction and is indicated for patients with unfavorable risk factors, though may be omitted in low-risk scenarios. 4

Radiation Omission Criteria

Radiation therapy may be considered for omission ONLY in highly selected patients:

• Women over 70 years of age 4
• Low-grade DCIS 3
• Small lesions 3
• Clear pathological margins 3

This represents a Category 2B recommendation (lumpectomy alone), meaning lower consensus and higher risk. 1

Continuous/Adjuvant Treatment

Endocrine Therapy

Adjuvant endocrine therapy should be offered to patients with hormone receptor-positive DCIS to reduce ipsilateral recurrence and contralateral disease risk. 4

For premenopausal women: Tamoxifen is the standard endocrine therapy option. 4

For postmenopausal women: Either tamoxifen or an aromatase inhibitor are options, though tamoxifen is often favored based on side-effect profile. 4

The evidence for tamoxifen in DCIS comes from clinical trials, though the role of hormone receptor status in selecting patients for tamoxifen therapy has not been fully evaluated in the older guidelines. 1

Post-Treatment Surveillance

Postexcision mammography should be performed whenever uncertainty about adequacy of excision remains, particularly when microcalcifications were present on initial imaging. 1, 4

Clips should be placed to demarcate the biopsy area because DCIS may be clinically occult and further surgery may be required pending margin status review. 1

Treatment Algorithm by Risk Category

Low-Risk DCIS (Grade 1, <25% DCIS component, negative margins ≥2mm)

1. Breast-conserving surgery with negative margins ≥2mm 4
2. Whole-breast radiation therapy 4
3. Consider endocrine therapy if hormone receptor-positive 4
4. In women >70 years, radiation may be omitted if ALL low-risk features present 4

Intermediate/High-Risk DCIS

1. Breast-conserving surgery with negative margins ≥2mm 1
2. Whole-breast radiation therapy with boost 4
3. Endocrine therapy if hormone receptor-positive 4
4. If margins <2mm after best surgical attempt, re-excision required 4

Large DCIS (≥4cm)

Lumpectomy remains viable for many patients with DCIS ≥4cm, especially those measuring <6cm, though repeat re-excisions may be required. 5 Success rates: 70% for 4-5.9cm lesions, 33% for 6-7.9cm and ≥8cm lesions. 5

Critical Pitfalls to Avoid

Do not underestimate the importance of achieving adequate surgical margins (≥2mm for DCIS with radiation). 4 Inadequate margins are a primary cause of local recurrence.

Do not omit radiation therapy based solely on low-grade features without considering all risk factors including patient age, margin width, and lesion size. 4

Recognize that approximately 25% of patients with seemingly pure DCIS on initial biopsy will have invasive breast cancer at definitive surgery. 1 This underscores the importance of complete pathological assessment.

Do not perform routine axillary dissection for pure DCIS, as this represents overtreatment with no survival benefit. 1, 3

Do not use subcutaneous mastectomy to treat DCIS, as this is inadequate. 3

Mastectomy should not be followed by adjuvant local radiotherapy or systemic therapy for pure DCIS. 3