Lobular carcinoma in situ increases the risk of local recurrence in selected patients with stages I and II breast carcinoma treated with conservative surgery and radiation.

Background: Lobular carcinoma in situ (LCIS) is a known risk factor for the development of invasive breast carcinoma. However, little is known regarding the impact of LCIS in association with an invasive carcinoma on the risk of an ipsilateral breast tumor recurrence (IBTR) in patients who are treated with conservative surgery (CS) and radiation therapy (RT). The purpose of this study was to examine the influence of LCIS on the local recurrence rate in patients with early stage breast carcinoma after breast-conserving therapy.

Methods: Between 1979 and 1995, 1274 patients with Stage I or Stage II invasive breast carcinoma were treated with CS and RT. The median follow-up time was 6.3 years.

Results: LCIS was present in 65 of 1274 patients (5%) in the study population. LCIS was more likely to be associated with an invasive lobular carcinoma (30 of 59 patients; 51%) than with invasive ductal carcinoma (26 of 1125 patients; 2%). Ipsilateral breast tumor recurrence (IBTR) occurred in 57 of 1209 patients (5%) without LCIS compared with 10 of 65 patients (15%) with LCIS (P = 0.001). The 10-year cumulative incidence rate of IBTR was 6% in women without LCIS compared with 29% in women with LCIS (P = 0.0003). In both groups, the majority of recurrences were invasive. The 10-year cumulative incidence rate of IBTR in patients who received tamoxifen was 8% when LCIS was present compared with 6% when LCIS was absent (P = 0.46). Subsets of patients in which the presence of LCIS was associated with an increased risk of breast recurrence included tumor size < 2 cm (T1), age < 50 years, invasive ductal carcinoma, negative lymph node status, and the absence of any adjuvant systemic treatment (chemotherapy or hormonal therapy) (P < 0.001). LCIS margin status, invasive lobular carcinoma histology, T2 tumor size, and positive axillary lymph nodes were not associated with an increased risk of breast recurrence in these women.

Conclusions: The authors conclude that the presence of LCIS significantly increases the risk of an ipsilateral breast tumor recurrence in certain subsets of patients who are treated with breast-conserving therapy. The risk of local recurrence appears to be modified by the use of tamoxifen. Further studies are needed to address this issue.