Transcriptomic analysis of pretreated rectal cancer biopsies and association to the tumor regression score.

To determine a preditcive marker of treatment resistance for rectal cancer, we have employed a microarray gene profiling analysis on pretreated rectal biopsies and compared with their response to therapy as defined by the American Joint Commission on Cancer (AJCC) and the American College of Pathologists. Frozen rectal cancer biopsies utilized for the transcriptomic analysis were from 33 patients seen between 2006 and 2009 at Cleveland Clinic Main Campus in Cleveland, Ohio. After collection of biopsie and diagnosis, patients generally underwent surgery with curative intent approximately 8–12 weeks after completion of neoadjuvant chemoradiotherapy with 5-fluorouracil as radiation sensitizer and 50.4Gy in 25 fractions. The resected tumor is assessed by pathologists to determine AJCC score.