Residual cancer burden (RCB) is practical and may be more informative than pathological response following neoadjuvant chemotherapy (NC) for locally advanced breast cancer (LABC)

Abstract

21103 Background: Complete pathological response (pCR) has been considered a reliable endpoint to assess the benefit of NC. However, different pathological responses ranging from near complete response to resistance would likely indicate different prognostic groups. Method: We studied patients with locally advanced breast cancer (LABC) who received NC between 2001–2006 at the University of Cincinnati. Pathological response to therapy was evaluated. In addition, RCB was quantified according to MD Anderson RCB Calculator index that combines pathologic measurements of primary tumor (size and cellularity) and nodal metastases (number and size). We examined the correlation between pCR, RCB, event-free survival (EFS) and over all survival (OS) by Cox regression analyses. Result: Pathological slides of 32 patients were analyzed. Median age 52, 38% white and 62% African American. Stage IIB 12% , Stage IIIA 19%, Stage IIIB 53% and Stage IIIC 16% . 72% invasive ducal, 6% invasive lobular and 22% inflammatory cancer. Forty seven percent of tumors were ER +/or PR+ , 53% ER-/PR-, 28% HER-2 /neu + ( IHC 3+ or FISH HER2 gene to chromosome 17 ration > 2.2). Tumor response was as follows: 22% (n=7) achieved pCR , RCB scores ranged between 0- 4.87. By univariate Cox regression analysis, RCB correlated with EFS {Hazard ratio (HR) 1.57 (95% CI 1.04–2.38), p-value 0.018}, and with OS {HR 1.74 (95% CI 0.91 -3.32), p value-0.09}. However, pCR did not seem to correlate with EFS {HR 0 .24 (95%CI 0.03 -1.86–2.38), p-value .172} or OS {HR 0.03 (95% CI 0–89),p value-0.40}. By multivariate Cox regression analysis, RCB was noted to be an independent predictive variable for EFS {HR 1.59 (95% CI 1.04–2.43), p value-0.033} while pCR was not {HR 0.90 (95% CI 0.52–1.57), p value-0.7. Conclusion: RCB was easily quantifiable and appears to be a better predictor of outcome following neoadjuvant chemotherapy in LABC compared to pCR. Higher RCB scores were associated with higher EFS and lower rate of OS. Prospective trials are needed to further evaluate the role of RCB as an endpoint following NC. No significant financial relationships to disclose.