The influence of infiltrating lobular carcinoma on the outcome of patientstreated with breast-conserving surgery and radiation therapy

Background: The role of conservative surgery and radiation therapy (CS and RT) in the treatment of patients with infiltrating ductal carcinoma is well established. However, the efficacy of CS and RT for patients with infiltra ting lobular carcinoma is less well documented. The goal of this study was to examine treatment outcome after CS and RT for patients with infiltrating lobular carcinoma and to compare the results to those of patients with inf iltrating ductal carcinoma and patients with mixed ductal-lobular histology . Methods: Between 1970 and 1986, 1624 patients with Stage I or II invasive b reast cancer were treated with CS and RT consisting of a complete gross exc ision of the tumor and greater than or equal to 6000 cGy to the primary sit e. Slides were available for review for 1337 of these patients (82%). Of th ese, 93 had infiltrating lobular carcinoma, 1089 had infiltrating ductal ca rcinoma, and 59 had tumors with mixed ductal and lobular feature these pati ents constitute the study population. The median follow-up time for survivi ng patients was 133 months. A comprehensive list of clinical and pathologic features was evaluated for all patients. Additional histologic features as sessed for patients with infiltrating lobular carcinoma included histologic subtype, multifocal invasion, stromal desmoplasia, and the presence of sig net ring cells. Results: Five and 10-year crude results by site of first failure were simil ar for patients with infiltrating lobular, infiltrating ductal, and mixed h istology. In particular, the 10-year crude local recurrence rates were 15%, 13%, and l3% for patients with infiltrating lobular, infiltrating ductal, and mixed histology, respectively. Ten-year distant/regional recurrence rat es were 22%, 23%, and 20% for the three groups, respectively. In addition, the 10-year crude contralateral breast cancer rates were 4%, 13% and 6% for patients with infiltrating lobular, infiltrating ductal and mixed histolog y, respectively. In a multiple regression analysis which included establish ed prognostic factors, histologic type was not significantly associated wit h either survival or time to recurrence. Conclusions: Patients with infiltrating lobular carcinoma have a similar ou tcome following CS and RT to patients with infiltrating ductal carcinoma an d to patients with tumors that have mixed ductal and lobular features. We c onclude that the presence of infiltrating lobular histology should not infl uence decisions regarding local therapy in patients with Stage I and II bre ast cancer.