Abstract P3-14-04: The choice of the indicator lesion impacts on the pCR rate – An analysis of 114 bilateral breast cancer patients treated within neoadjuvant trials

Abstract

Abstract Background: Patients with bilateral breast cancer are usually excluded from participating in clinical trials. The German Breast Group has traditionally included these patients into their neoadjuvant trials. However, little is known about the outcome of the non-indicator lesion. Methods: We prospectively captured the information on bilateral breast cancer in our database and collected retrospectively the information from the original histological and surgical reports on tumor size, nodal status, histology, grading, hormone receptor and HER2 status as well as type of surgery and pathological complete response defined as ypT0 ypN0 and ypT0/is ypN0 because both definitions have been used in our clinical studies. The treating physician decided on clinical presentation, which side to be the indicator lesion on which response was assessed for the purpose of the study. The synchronous carcinoma in the contralateral breast is considered as the non-indicator lesion. Results: From the 6727 patients treated within the Gepartrio, Geparquattro, Geparquinto, and Geparsixto study 157 (2.3%) patients have been identified with the diagnosis of bilateral carcinoma. From the 114 bilateral patients with any information on the non indicator lesion 104 with information on pCR on both sides were used for further analysis. The median age was 51 (range 29-74) years. There were more cT1 (48.5% vs 9.6%, p<0.001) and cN0 (60.0% vs 38.4%, p = 0.004) tumors in the group of the non-indicator lesion compared to the indicator lesion group. In 56% the molecular subtype was identical 86% had a luminal A like tumor of indicator as well as the non-indicator lesion, none of the luminal B-like indicator lesions were identical, 27% of the HER2+/ HR +, 58% in the HER2+/ HR- group and 66% of the triple negative indicator lesions had an identical non indicator lesion. In general the tumor tended to be of lower malignant potential in the non- indicator lesion. Lobular carcinomas (23.4% vs 16.7%, p = 0.205); grade 3 (26% vs 36.7%, p = 0.101), ER positive (72% vs 67%, p = 0.427), HER2-positive (23.9 vs. 35.7%, p = 0.068). Overall the pCR rate (ypT0 ypN) was 20.2% in the non-indicator lesion group vs 13.9% the indicator lesion group (p = 0.276) and ypT0/is ypN0 was 30.8% and 17.6%, respectively (p = 0.0388). 64.4% had no pCR in the indicator as well as the non-indicator lesion, 11.5% had a pCR in the indicator as well as the non-indicator lesion, 4.8% in the indicator alone and 19.2% in the non-indicator alone. Breast conserving surgery was performed more often for non-indicator lesions than for indicator lesions (59% vs 44.4%, p = 0.144). Conclusion: In general the selection for the indicator lesion was based on tumor size, nodal status and inclusion criteria. Probably, some of the indicator lesions would not have qualified for trial participation. The pCR rate including non-invasive residuals was significantly higher for the non-indicator lesions probably due to smaller tumors and less nodal involvement at baseline. However, based on our data bilateral breast carcinomas should not be excluded from neoadjuvant clinical trials. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-14-04.