Abstract P3-06-33: Comparison of pathologic response evaluation systems after neoadjuvant chemotherapy among different molecular subtypes of breast cancers

Abstract

Abstract Background: Several ways to assess pathologic response of breast cancer after neoadjuvant chemotherapy (NAC) are currently available. However, clinical usefulness of assessment systems in each molecular subtype of breast cancer is unclear. Therefore, we compared four pathologic response assessment systems predicting patients’ clinical outcome in specific subtypes of breast cancer. Methods: In total, 598 tumors from 590 female breast cancer patients who received anthracycline and taxane-based NAC and subsequent surgery from 2010 to 2012 were analyzed. Molecular subtypes were defined by immunohistochemistry (HER2 and hormone receptor (HR): estrogen receptor and progesterone receptor). Miller-Payne grading, Residual Cancer Burden, Residual Disease in Breast and Nodes and ypTNM stage were evaluated. Results of each assessment system were analyzed for survival with Kaplan-Meier and Cox hazard model. Median follow-up period was 35.2 months (range 21.1-54.4 months). Results: Pathologic complete response was achieved in 4.4% (12/275) of HR+/HER2-, 10.7% (8/75) of HR+/HER2+, 17.8% (16/90) of HR-/HER2+, and 29.7% (47/158) of triple negative (TN) tumors. Results of all four examined assessment systems were significantly correlated with disease-free and overall survival in all tumors. In HR+/HER2- and TN tumors, all systems were associated with disease-free and overall survival. Comparison of pathologic response assessment systems after neoadjuvant chemotherapy for disease-free and overall survivalDisease-free survivalHR+/HER2-HR+/HER2+HR-/HER2+TNMiller Payne gradeHR (95% CI)0.629 (0.429-0.925)0.310 (0.159-0.607)0.647 (0.428-0.977)0.451 (0.343-0.593)P value.018<0.001.039<0.001RCB classHR (95% CI)2.621 (1.398-4.914)2.454 (0.917-6.564)1.696 (0.929-3.094)2.966 (1.982-4.441)P value.003.074.085<0.001RDBN levelHR (95% CI)2.892 (1.642-5.093)2.587 (1.015-6.595)2.189 (1.118-4.286)3.065 (2.108-4.456)P value<0.001.047.022<0.001ypTNM StageHR (95% CI)2.975 (1.606-5.512)2.062 (0.918-4.632)2.004 (1.121-3.582)2.950 (2.152-4.044)P value.001.080.019<0.001Overall survivalMiller Payne gradeHR (95% CI)0.416 (0.222-0.778)0.399 (0.177-0.896)0.633 (0.357-1.124)0.397 (0.294-0.537)P value.006.026.119<0.001RCB classHR (95% CI)8.611 (1.924-38.531)2.971 (0.733-12.032)1.900 (0.771-4.680)2.976 (1.927-4.594)P value.005.127.163<0.001RDBN levelHR (95% CI)11.369 (2.618-49.375)3.042 (0.801-11.550)1.970 (0.805-4.821)3.262 (2.145-4.961)P value.001.102.138<0.001ypTNM StageHR (95% CI)5.812 (1.666-20.270)2.623 (0.851-8.080)1.619 (0.739-3.546)3.040 (2.150-4.300)P value.006.093.228<0.001RCB, residual cancer burden; RDBN; residual disease breast and nodes. Especially in TN, Kaplan-Meier survival curves for disease-free survival were clearly separated by all assessment methods. However, in HR+/HER2+ and HR-/HER2+ tumors, the association of patients’ survival with response assessment results was variable according to the examined systems. Conclusion: By the available pathologic assessment systems after neoadjuvant chemotherapy, HR+/HER2- and TN breast cancers could be effectively classified into groups showing different prognosis. However, for the evaluation of pathologic response of HR+/HER2+ and HR-/HER2+ tumors, the development of effective assessment methods is warranted. Citation Format: In Ah Park, Hee Jin Lee, In Hye Song, Gyungyub Gong. Comparison of pathologic response evaluation systems after neoadjuvant chemotherapy among different molecular subtypes of breast cancers [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-06-33.