Abstract P2-05-27: Baseline serum CA15-3 levels are associated with prognosis for breast cancer patients with non-complete pathological response to neoadjuvant chemotherapy

Abstract

Abstract Background: It has been well demonstrated that patients who achieved pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) had a favorable prognosis compared with patients who did not (non-pCR). Even though pCR was not attained, reduction in tumor volume after chemotherapy may be associated with improved prognosis for a certain number of patients. However, the association between residual tumor volume and prognosis is not necessarily consistent. In order to identify substitute markers for breast cancer patients with non-pCR after NAC, we investigated the impact of serum levels of carcinoembryonic antigen (CEA) and carbohydrate antigen (CA15-3) at baseline as well as post-NAC. Patients and Methods: Ninety-six breast cancer patients treated with NAC and operated on at the Hyogo College of Medicine were recruited for this study. Serum CEA and CA15-3 were measured prior to chemotherapy as well as at completion of pre-operative treatment. The optimal cutoff points for CEA (1.55ng/m, normal range: <5.0ng/ml) and CA15-3 (13.25U/ml, normal range: <28.0U/ml) for relapse-free survival (RFS) were determined by analyzing the area under receiver operating characteristic curves in another study involving 613 breast cancer patients. Expression levels of Ki67 in samples obtained at pre- and post-NAC were also determined by means of immunohistochemical staining. Pathological complete response was classified as the absence of residual invasive cancer in the breast and lymph nodes. During a 2.13 years median follow-up period, 15 patients suffered relapse. Results: pCR and non-pCR was attained by 21 and 75 patients, respectively. For the non-pCR patients, serum CEA levels at baseline were classified into high (n=35) and low (n=38) and serum CA15-3 levels at baseline into high (n=31) and low (n=43). RFS of non-pCR patients with high serum CA15-3 levels was significantly worse than of those with low levels (3-year RFS: 0.47 vs 0.93; p=0.0009). RFS for patients with high and low serum levels of CA15-3 after NAC was also significantly different (p=0.037). As for CEA, no significant association with RFS was observed either at baseline or post-NAC. Univariate analysis demonstrated that tumor size and baseline CA15-3 were significant prognostic factors for RFS. Multivariate analysis showed that both tumor size (hazard ratio (HR): 3.88, 95% confidence interval (CI): 1.21-12.35, p=0.023) and baseline CA15-3 (HR: 13.51, 95% CI: 1.74-105.08, p=0.013) were significant and independent risk factors for relapse. As for lymph node metastasis, tumor grade, residual tumor size and pre- and post-NAC Ki67 expression levels of patients with non-pCR showed no significant association with RFS. Conclusion and discussion: High levels of serum CA15-3 at baseline constituted a significantly worse prognosis for breast cancer patients with non-pCR. Tumor size at baseline but not residual size and baseline CA15-3 seems to suitable as a substitute for prediction of outcome for patients with non-pCR. Our findings suggest that these markers may be useful for identifying patients with poor prognosis who may be candidates for additional adjuvant treatment. Citation Format: Fujimoto Y, Imamura M, Higuchi T, Nishimukai A, Yanai A, Miyagawa Y, Murase K, Takatsuka Y, Miyoshi Y. Baseline serum CA15-3 levels are associated with prognosis for breast cancer patients with non-complete pathological response to neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-05-27.