Pathologic Response of Associated Ductal Carcinoma In Situ to Neoadjuvant Systemic Therapy: A Systematic Review

Area of Science:

• Oncology
• Breast Cancer Research
• Surgical Oncology

Background:

• Traditional assumptions suggested neoadjuvant systemic therapy (NST) for invasive breast cancer did not impact co-existent ductal carcinoma in-situ (DCIS).
• Emerging evidence indicates NST may eradicate DCIS, potentially allowing for less extensive surgical procedures.

Purpose of the Study:

• To systematically review and assess the eradication rate of DCIS following NST for invasive breast cancer.
• To evaluate the impact of neoadjuvant chemotherapy (NACT) and neoadjuvant endocrine therapy (NET) on DCIS.
• To inform surgical decision-making regarding breast resections in patients with DCIS.

Main Methods:

• A systematic literature search was conducted in MEDLINE for studies reporting pathological data on DCIS before and after NST.
• Six studies (N=659) involving NACT and one study involving NET met the inclusion criteria.
• Pooled analysis was performed to determine DCIS eradication rates.

Main Results:

• Post-NACT pathology revealed no residual DCIS in 40.5% of patients (267/659).
• DCIS eradication rates were similar for triple-negative breast cancer (45%) and HER2-positive disease (46%).
• NET eradicated DCIS in 15% of patients (9/59); residual micro-calcifications did not always indicate disease.

Conclusions:

• NST can effectively eradicate DCIS, challenging previous assumptions.
• Extensive DCIS prior to NST should not automatically lead to mastectomy.
• De-escalation to breast-conserving surgery (BCS) should be considered for patients identified by contrast-enhanced MRI.