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Introduction: Neoadjuvant chemotherapy for invasive breast cancer reduces local disease, improves surgical resectability and evaluates tumor response to treatment. After surgery, pathologists can evaluate treatment response based on pathological yTNM-stage and by residual cancer burden (RCB) score, generated with online calculator by MDAnderson Cancer Center. According to the size and the cellularity of tumor, the number of positive axillary nodes and the largest metastatic deposit, pathologists calculate RCB class as: pathologic complete response (pCR) with no residual cancer (RCB-0), minimal (RCB-I), moderate (RCB-II) or extensive residual cancer (RCB-III). 10-year relapse-free survival for patients with RCB-0 is between 83% and 95%, depending on intrinsic sub-type of breast cancer while for RCB-III is between 21% and 52%. Results: During the last 18 months a 126 patients were evaluated according to the RCB scoring method in University Hospital for tumors, Zagreb. RCB-0 was seen in 23.8%, RCB-I in 6.4%, RCB-II in 32.5%, and RCB-III in 37.3% of patients. Tumor response to treatment, according to hormone receptor status (HR) and HER2 status, is presented in the Table. The best pathologic complete response was achieved in HER2 intrinsic sub-type (60%) and TNBC (40%). pCR RCB I RCB II RCB III No. HR+/HER2- 8% 0% 39.7% 52.3% 63 HR+/HER2+ 28.6% 14.4% 28.5% 28.5% 28 HR-/HER2+ 60% 13.3% 20% 6.7% 15 HR-/HER2- 40% 10% 25% 25% 20 Average age of patients was 53 years. Patients who achieved pCR were much younger than patients in all other groups (47.4 vs. 54.5 years). Four out of 10 axillary nodes were positive in RCB-III class compared with one out of nine in RCB-I or RCB-II group. No difference was observed in residual tumor average size, between class II and III (2.1 vs.2.6 cm), but a difference compared with RCB-I, where the average size of residual tumor was 0.3 cm, was observed. Tumors that responded better to neoadjuvant therapy (RCB- 0), initially had a higher Ki-67 score (46%), compared with 43%, 35% and 33% of tumors with residual burden class I, II and III, respectively. Conclusion: The pathologic response to neoadjuvant chemotherapy has prognostic value in all phenotypes of breast cancer. pCR rates to standard chemotherapy are higher in HER2 positive and TNBC compared with HR positive breast cancer. RCB-I group has similar characteristics as RCB-0 while RCB-III define tumor resistance. The pathologic assessment of residual disease is important to better define prognosis after neoadjuvant chemotherapy. |
