title: Chromosomal copy number alterations are associated with tumor response to chemoradiation in locally advanced rectal cancer.
abstract: Rectal cancer response to chemoradiation (CRT) varies from no response to a pathologic complete response (pCR). Identifying predictive biomarkers of response would therefore be useful. We assessed whether chromosomal copy number alterations (CNAs) can assist in predicting pCR. Pretreatment tumor biopsies and paired normal surgical tissues from the proximal resection margin were collected from 95 rectal cancer patients treated with preoperative CRT and total mesorectal excision in a prospective Phase II study. Tumor and control DNA were extracted, and oligonucleotide array-based comparative genomic hybridization (aCGH) was used to identify CNAs, which were correlated with pCR. Ingenuity pathway analysis (IPA) was then used to identify functionally relevant genes in aberrant regions. Finally, a predictive model for pCR was built using support vector machine (SVM), and leave-one-out cross validation assessed the accuracy of aCGH. Chromosomal regions most commonly affected by gains were 20q11.21-q13.33, 13q11.32-23, 7p22.3-p22.2, and 8q23.3-q24.3, and losses were present at 18q11.32-q23, 17p13.3-q11.1, 10q23.1, and 4q32.1-q32.3. The 25 (26%) patients who achieved a pCR had significantly fewer high copy gains overall than non-pCR patients (P = 0.01). Loss of chromosomal region 15q11.1-q26.3 was significantly associated with non-pCR (P < 0.00002; Q-bound < 0.0391), while loss of 12p13.31 was significantly associated with pCR (P < 0.0003; Q-bound < 0.097). IPA identified eight genes in the imbalanced chromosomal regions that associated with tumor response. SVM identified 58 probes that predict pCR with 76% sensitivity, 97% specificity, and positive and negative predictive values of 91% and 92%. Our data indicate that chromosomal CNAs can help identify rectal cancer patients more likely to develop a pCR to CRT.
authors.affiliation: Department of Surgery, City of Hope, 1500 E. Duarte Road, Duarte, CA 91010, USA.
authors.forename: Zhenbin
authors.initials: Z
authors.lastname: Chen
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.forename: Wenyan
authors.initials: W
authors.lastname: Li
authors.forename: Kun
authors.initials: K
authors.lastname: Qu
authors.forename: Xutao
authors.initials: X
authors.lastname: Deng
authors.forename: Madhulika G
authors.initials: MG
authors.lastname: Varma
authors.forename: Alessandro
authors.initials: A
authors.lastname: Fichera
authors.forename: Alessio
authors.initials: A
authors.lastname: Pigazzi
authors.forename: Julio
authors.initials: J
authors.lastname: Garcia-Aguilar
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology / Q000628:therapy*; D000328:Adult; D000368:Aged; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D003131:Combined Modality Therapy; D055028:Comparative Genomic Hybridization; D056915:DNA Copy Number Variations; D005260:Female; D052138:Genes, Neoplasm; D056726:Genetic Association Studies; D005819:Genetic Markers; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D012372:ROC Curve; D012004:Rectal Neoplasms / Q000235:genetics* / Q000473:pathology / Q000628:therapy*; D016896:Treatment Outcome
chemical_list: D005819:Genetic Markers