Purpose: The purpose of this study is to determine the prognostic significance of overexpression of the HER-2 neu oncoprotein with respect to local relapse following conservative surgery and radiation therapy (CS + RT).
Methods and materials: Twenty consecutive patients who sustained a local recurrence as the first and only site of failure following CS + RT comprised the case population base for this study. Only patients who received no adjuvant systemic chemotherapy or tamoxifen were selected for analysis. Following the identification of 20 consecutive local-relapse patients, the patient database was searched for 20 matching control patients who did not sustain a local relapse. Each control patient was matched to the index case with respect to age, menopausal status, follow-up, primary histology, axillary nodal status, and primary tumor size. Both index cases and the matched control group received full course radiation therapy, to a total dose of 64 Gy to the tumor bed. The paraffin-embedded blocks of the original primary tumor of the local-relapse cases and the primary tumor of 20 matched controls were processed for immunohistochemical staining of the HER-2 neu oncoprotein. Each slide was rated on the 3-point scale, 0 representing no stain, 1+ indicating light staining, and 2+ denoted heavy staining (overexpression).
Results: Of the 20 index cases, with each of the matched controls, 16 were evaluable for analysis. The 4 cases that were eliminated had inadequate paraffin-embedded material in either the case or the match control for adequate staining. By design of the study, the index case group and control group had similar ages (52 years index vs. 51.4 control), follow-up (10.8 years index vs. 10.5 years control), and histologies. For the immunostaining, a value of 2+ was considered to denote high activity and overexpression, and 0 and 1+ were considered negative values. Using these criteria, a total of 9 of the 16 index cases (56%) exhibited overexpression of HER-2 neu oncoprotein, and only 3 of the 16 control cases (18%) demonstrated high immunoreactivity. The difference in immunostaining between the index and control cases was statistically significant by a Pierson chi-square analysis at the p = 0.03 level.
Conclusions: In this matched case-control study, overexpression of the HER-2 neu oncoprotein appears to have prognostic significance with respect to local relapse in the conservatively treated breast. The correlation of overexpression of HER-2 neu by multivariable analysis with other prognostic factors for local recurrence warrants further investigation. The clinical implications of the study are discussed.