Accompanying DCIS in breast cancer patients with invasive ductal carcinoma is predictive of improved local recurrence-free survival.

Background: Ductal carcinoma in situ (DCIS) often accompanies invasive ductal carcinoma (IDC). The presence of co-existing DCIS is postulated to present as a less aggressive phenotype than IDC alone.
Patients and Methods: Patients diagnosed with hormone receptor-positive breast cancer receiving mastectomy were evaluated. Only patients without adjuvant radio- and chemotherapy were included to decrease treatment bias on local recurrence (LR).
Results: Of 2239 breast cancer patients, 198 fulfilled the inclusion criteria. The overall LR rate was 11.6%. Tumor stage (p = 0.002), nodal status (pN2 vs. pN0, p = 0.023) and pure IDC compared with IDC-DCIS (p = 0.029) were multivariate independent factors for increased LR risk. Patients with IDC-DCIS were significantly younger (p < 0.001), had smaller tumors (p = 0.001), less lymph node involvement (p = 0.012). The LR rate was significantly increased in patients with pure IDC (p = 0.012). The time to distant metastases was decreased in patients with pure IDC compared with that observed in patients with IDC-DCIS (log rank = 0.030).
Conclusion: Invasive ductal carcinoma accompanied by DCIS is associated with lower LR. The prognostic value of co-existing DCIS in the adjuvant decision-making process may be considered a new independent prognostic marker. This finding needs further studies to evaluate its usefulness in premenopausal women.
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