The Residual Cancer Burden (RCB), a standardized measure of residual disease in pathologic resection specimens following neoadjuvant chemotherapy, was found to be prognostic of long-term survival across all three phenotypic subtypes when it was applied to five breast cancer cohorts totaling 1,158 patients from a single institution, investigators report in the Journal of Clinical Oncology.
If the findings of this retrospective cohort analysis are validated in other cohorts, it would indicate that assessing patients’ RCB index could add “meaningful information to pretreatement clinical and pathologic information and posttreatment yp stage [American Joint Commission on Cancer stage],” said W. Fraser Symmans, MD, of the University of Texas M.D. Anderson Cancer Center, Houston, and his associates.
Residual disease is categorized into four groups: an index of zero (RCB-0) reflects a complete pathologic response to neoadjuvant treatment, RCB-I indicates minimal residual disease, RCB-II indicates moderate residual disease, and RCB-III indicates extensive residual disease. The investigators reviewed pathology specimens to determine the RCB index in a cohort of 219 patients followed for 13 years, a cohort of 262 patients followed for 9 years, a cohort of 342 patients followed for 7 years, a cohort of 132 patients followed for more than 16 years, and a cohort of 203 patients followed for 7 years.
They found that the RCB index predicted the risk of relapse or death across all five cohorts, regardless of other clinical and pathologic variables such as tumor stage or grade, patient age, and type of surgery (J Clin Oncol. 2017 Jan 30. doi: 10.1200/JCO.2015.63.1010).
RCB also was predictive regardless of whether patients had triple-negative disease, HR-positive/HER2-negative disease, HER2-positive disease treated with paclitaxel plus combined fluorouracil, doxorubicin, and cyclophosphamide alone, or HER2-positive disease treated with paclitaxel plus combined fluorouracil, doxorubicin, and cyclophosphamide plus trastuzumab.
In two especially high-risk groups of patients – those with triple-negative breast cancer and those with HER2-positive breast cancer – RCB was the only or the most important predictor of survival. Approximately half of the patients with triple-negative disease had an index of RCB-0 or RCB-I and a good prognosis, while those with an RCB-II or RCB-III index had poor survival, Dr. Symmans and his associates said.