[699] Infarct-Like Necrosis: A Distinct Form of Necrosis Seen in Colorectal Carcinoma Liver Metastases Treated with Perioperative Chemotherapy

Hector H Li Chang, William R Leeper, Gabriel Chan, Douglas Quan, David K Driman. University of Western Ontario, London, ON, Canada; University of Montreal, Montreal, QC, Canada

Background: The response of colorectal liver metastases (CRLM) to perioperative chemotherapy (PCx) can be assessed histologically. We classified necrosis in this setting into two types: infarct-like necrosis (ILN) representing therapeutic response to PCx, and usual necrosis (UN) signifying an absence of treatment effect. Tumor regression grading (TRG) is a previously described method that estimates response to PCx by measuring tumor replacement by fibrosis. We devised a modified TRG (mTRG) scoring system that incorporates ILN and compared its prognostic performance against TRG.
Design: A retrospective review was done of all partial hepatectomies performed for CRLM at our center between 2004-10. Cases were classified according to whether UN or ILN was more prominent. UN was defined as patchy necrosis containing nuclear debris and bordered by viable tumor cells; ILN was defined as confluent necrosis surrounded by hyaline fibrosis. UN and ILN were compared with respect to clinicopathologic features, including disease-free survival (DFS) and overall survival (OS). Each case was assigned two tumor regression scores: a TRG score using previously described criteria, as well as a mTRG score in which both ILN and fibrosis were deemed to represent treatment effect. DFS and OS using the two scoring systems were compared.
Results: Of the 109 cases reviewed, 46 received PCx. All 12 cases containing ILN occurred in those treated with PCx. Amongst patients receiving PCx, those with ILN had superior DFS than those with UN (Log-rank test, P < 0.05).

The mTRG score differed from the TRG score in almost all cases containing ILN (11/12). mTRG scores of 1-2 were associated with significantly better DFS and OS than mTRG scores of 3-5 (Log-rank test, P < 0.05). In contrast, use of TRG failed to demonstrate a significant difference in DFS and OS between histologic responders and non-responders to PCx.
Conclusions: ILN represents a therapeutic response to PCx and thus should be distinguished from UN. The prognostic utility of TRG is enhanced when ILN is considered a form of treatment effect.
Category: Gastrointestinal

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 99, Monday Morning


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