Pathologic assessment of response to chemotherapy in colorectal cancer liver metastases after hepatic resection: which method to use?

BACKGROUND: Patients with metastatic colorectal cancer receive chemotherapy prior liver resection more and more frequently. Histopathologic assessment methods of the resected specimen could evaluate the response to chemotherapy. In this study it is analyzed if these histopathologic changes are specific to preoperative chemotherapy and if these methods have correlation with survival.
METHODS: Sixty three patients with available pathology slides, resected for colorectal cancer liver metastases were enrolled in this study. 46 patients (73%) received neoadjuvant chemotherapy. Five pathological evaluation methods were compared according to the literature: [1] residual tumor cell ratio, [2] tumor regression grade (TRG) scoring system, [3] modified tumor regression grade (mTRG) scoring system with the type of necrosis, [4] pattern of tumor regression and [5] the tumor thickness at the tumor-normal interface (TNI).
RESULTS: Analyzing the pathological methods between the chemotherapy (CTX) and the non-chemotherapy group (NC), we found that that four evaluation methods showed significant and one showed strong correlation with the use of chemotherapy. (Residual tumor cell ratio: p = 0.08; TRG: p <0.01; mTRG: p = 0.03; pattern of tumor regression: p <0.01; TNI: p = 0.02). In the chemotherapy group none of the analyzed pathological methods showed significant correlation with progression free survival (PFS) or with overall survival (OS). Residual tumor cell ratio, TRG and the pattern of tumor cells showed positive but not significant correlation with OS and PFS and a slight difference in the group of patients with TNI <2 mm could be documented.
CONCLUSIONS: Tumor regression grade (TRG) and tumor thickness at the tumor-normal interface (TNI) were the most useful methods for pathological response evaluation and these methods had some correlation with survival. According to these data, authors concluded, that a reproducible and well defined scoring system, based on different histopathological evaluation methods should be developed to predict more accurately the effect of neoadjuvant chemotherapy in CRCLM patients.