Abstract PS6-29: A new pathological assessment method to assess residual lesions after neoadjuvant chemotherapy for breast cancer: Residual disease in breast and nodes combined with Ki-67 (RDBN-K)
Authors: Han Ruoqi , Liu Yueping , Ma Yanqi , Liu Zhikun , Li Chunxiao , Geng Cuizhi 
Published: February 2021

Abstract
Purpose The accurate assessment of residual tumor tissue after neoadjuvant chemotherapy (NAC) for breast cancer is closely related to the subsequent treatment and prognosis of patients. Currently commonly used assessment methods, including Miller and Payne system (MPS), Residual Cancer Burden (RCB), and Residual Disease in Breast and Nodes (RDBN) assessment system, etc., have certain limitations in terms of accurate evaluation and determining prognosis. The limitation of MPS lies in the need to review the original tumor biopsy specimen and compare the cell contents of the biopsy specimen and the surgical specimen. The limitation of RCB is that it requires a broader sampling, as well as more time and energy in microscopic examination. Furthermore, determining the number of cells is subjective and differences exist among observers. The limitation of RDBN is its poor correlation with prognosis. Ki-67, as a marker to reflect cell proliferation, is widely used in prognostic judgment of invasive breast cancer and is also an important reference in treatment decision-making. This study aimed to combine the Ki-67 expression status after NAC with RDBN to design a new pathological assessment method, which we called residual disease in breast and nodes combined with Ki-67 (RDBN-K), and to study its significance for the prognosis of patients.Methods RDBN-K = 0.2 (residual breast tumor size in centimeters) + index of involved nodes + tumor histological grade+ index of Ki-67. The residual tumor size, index of involved nodes, and histological grade are the same as RDBN. The index of Ki-67 is scored as 0 for less than 14% and 1 for greater than or equal to 14%. The residual diseases of 723 patients with TNM staging of stage II to stage III who had undergone NAC and surgical treatment were evaluated by RDBN-K. RDBN-K includes 4 risk levels (levels 1-4) according to residual disease magnitude after neoadjuvant chemotherapy. The RDBN-K levels were defined as follows: RDBN-K-1 (equivalent to pCR) is an index of 0, RDBN-K-2 is an index between 0.1 and 3, RDBN-K-3 is an index between 3.1 and 5.3, and RDBN-4 is an index 5.4 or more. At the same time, RDBN was used to evaluate the residual disease of all patients after NAC. This study followed up the survival status of 723 patients. After combining the prognoses, the accuracy and clinical significance of the RDBN and RDBN-K were compared.Results During the follow-up, in the entire cohort, 147 (20.3%) recurrences or metastases were observed; local recurrence was 58 (8.0%), distant metastasis was 103 (14.2%), and 69 (9.5%) patients died. Among the RDBN-2 cases, 40 (5.5%) of 122 cases were reclassified to RDBN-K-3. Among the RDBN-3 cases, 17 (2.4%) of 295 cases were reclassified: 2 cases were reclassified to RDBN-K-4, and 15 cases were reclassified to RDBN-K-2. Among the 220 cases in the RDBN-4 category, 40 (5.5%) were reclassified to the RDBN-K-3 category using the RDBN-K calculation. Over the follow-up period, 13.6% of patients in the RDBN-4 category died, and 15.9% of patients in the RDBN-K-4 category died. RDBN and RDBN-K showed statistically significant differences in the disease-free survival (DFS) and overall survival (OS) of all patients (P values are all less than 0.05). Pairwise stratified analysis showed that the differences in DFS and OS between RDBN-K-3 and RDBN-K-4 (DFS: P = 0.019, OS: P = 0.035) were greater than that between RDBN-3 and RDBN-4 (DFS: P = 0.052, OS: P = 0.214), and the differences in OS between RDBN-K-2 and RDBN-K-3 (P = 0.023) were greater than that between RDBN-2 and RDBN-3 (P = 0.157).Conclusion Compared with RDBN, RDBN-K is more accurate in assessing the residual tumor burden after breast cancer NAC and predicting the prognosis for breast cancer patients, and provides more basis for follow-up intensive treatment of patients.
Citation Format: Ruoqi Han, Yueping Liu, Yanqi Ma, Zhikun Liu, Chunxiao Li, Cuizhi Geng. A new pathological assessment method to assess residual lesions after neoadjuvant chemotherapy for breast cancer: Residual disease in breast and nodes combined with Ki-67 (RDBN-K) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-29.