[607] Treated Rectal Adenocarcinomas Are Associated with Increased Expression of CK20 and Chromogranin

AM Bellizzi, CD Crowder, WL Marsh, H Hampel, WL Frankel. The Ohio State University Medical Center, Columbus, OH; Brigham and Women's Hospital, Boston, MA

Background: Neoadjuvant chemoradiation (NTx) in stage II/III rectal adenocarcinoma (RA) has become standard of care, associated with less toxicity and better local control than adjuvant therapy. Morphologic changes in these cases, including induction of endocrine differentiation, are well-described, and the immunophenotype of untreated RA (e.g. frequent CK7/CK20 co-expression) is established. Less is known about the immunophenotype of treated RA. This information would be useful, as we occasionally struggle to separate scant residual tumor from benign mimics (e.g. anal glands, endometriosis).
Design: We assembled a group of 64 matched pre-treatment biopsies (bx) and resections (res) from patients receiving NTx for RA. Matched bx and res were placed on a single slide for staining. CK7, CK20, CDX2, and chromogranin immunohistochemistry (IHC) was performed. Cases were assessed for qualitative (yes/no) and quantitative [intensity (0, 1, 2) and percent (0-100)] tumor staining and scores representing the product of intensity and percent calculated. In 14, res demonstrated a complete response (no IHC data for these). Quantitative data was analyzed using Wilcoxon matched-pairs tests, with P's < 0.05 considered significant.
Results: Qualitative and quantitative IHC results are summarized in the tables.

Qualitative Immunohistochemical Results (%)
Biopsy (n=64)Resection (n=50)

Quantitative Immunohistochemical Results (Score ± SD)
Biopsy (n=64)Resection (n=50)P
CK77 ± 2711 ± 360.8
CK2078 ± 63127 ± 52< 0.0001
CDX2181 ± 34158 ± 57< 0.0001
Chromogranin0.7 ± 21.7 ± 3.20.02
score = intensity * quantity; sd, standard deviation

Conclusions: Treated RA is associated with significantly increased CK20 and chromogranin expression compared to pre-treatment controls. Diminution in CDX2 may be explained by focal staining in a few res with little residual tumor (ie. only rare glands). Aside from increased chromogranin expression, the qualitative immunophenotype of treated RA is largely unchanged, with about 15% co-expressing CK7/CK20. Increased CK20 expression represents an unexpected result, and future directions include correlation of this finding with morphology, tumor characteristics, and outcome.
Category: Gastrointestinal

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 80, Tuesday Afternoon


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