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Original Investigation
December 22, 2016

Association of DNA Mismatch Repair and Mutations in BRAF and KRAS With Survival After Recurrence in Stage III Colon Cancers A Secondary Analysis of 2 Randomized Clinical Trials

Author Affiliations
  • 1Department of Medicine, Mayo Clinic, Rochester, Minnesota
  • 2Department of Oncology, Mayo Clinic Comprehensive Cancer Center, Mayo Clinic, Rochester, Minnesota
  • 3Alliance for Clinical Trials in Oncology Statistics and Data Center, Mayo Clinic, Rochester, Minnesota
  • 4Division of Hematology and Oncology, University of Florida, Gainesville
  • 5Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota
  • 6Division of Medical Oncology, The Ohio State University Comprehensive Cancer Center, Columbus
  • 7Pathology Laboratory, National Surgical Adjuvant Breast and Bowel Project/NRG Oncology, Pittsburgh, Pennsylvania
  • 8NRG Oncology, University of Pittsburgh, Pittsburgh, Pennsylvania
JAMA Oncol. Published online December 22, 2016. doi:10.1001/jamaoncol.2016.5469
Key Points

Question  What is the association of DNA mismatch repair and mutation in the B-Raf proto-oncogene (c.1799T>A [V600E] [BRAFV600E]) or the KRAS proto-oncogene (KRAS) with survival after recurrence in patients with stage III colon carcinoma treated in 2 trials of folinic acid (leucovorin calcium), fluorouracil, and oxaliplatin (FOLFOX)–based adjuvant chemotherapy?

Findings  In a secondary analysis of 2 randomized clinical trials that include 1395 patients with cancer recurrence, tumors with deficient vs proficient mismatch repair had a 30% reduction in mortality. Mutations in BRAFV600E, but not KRAS, were associated with shorter survival after recurrence in the overall cohort.

Meaning  DNA mismatch repair and BRAF mutations can provide prognostic information in patients with tumor recurrence.

Abstract

Importance  The association of biomarkers with patient survival after recurrence (SAR) of cancer is poorly understood but may guide management and treatment.

Objective  To determine the association of DNA mismatch repair (MMR) status and somatic mutation in the B-Raf proto-oncogene (c.1799T>A [V600E]; BRAFV600E) or exon 2 of the KRAS proto-oncogene (KRAS) in the primary tumor with SAR in patients with stage III colon carcinomas treated with adjuvant chemotherapy.

Design, Setting, and Participants  Patients with resected stage III colon cancers were randomized to adjuvant FOLFOX (folinic acid [leucovorin calcium], fluorouracil, and oxaliplatin) chemotherapy with or without cetuximab (North Central Cancer Treatment Group N0147 trial) or adjuvant FOLFOX chemotherapy with or without bevacizumab (National Surgical Adjuvant Breast and Bowel Project C-08 trial). Associations of biomarkers with SAR were analyzed using Cox proportional hazards models adjusted for clinicopathologic features and time to recurrence (data collected February 10, 2004, to August 7, 2015).

Main Outcomes and Measures  The primary study outcome was survival after recurrence of cancer. A secondary outcome measure was the effect of the site of the primary tumor on the association of biomarkers with SAR.

Results  Among 871 patients with cancer recurrence in the N0147 trial (472 men [54.2%] and 399 women [45.8%]; mean [SD] age, 57.8 [11.2] years) and 524 in the C-08 trial (269 men [51.3%] and 255 women [48.7%]; mean [SD] age, 57.0 [11.7] years), multivariable analysis revealed that patients whose tumors had deficient vs proficient MMR had significantly better SAR (adjusted hazard ratio [AHR], 0.70; 95% CI, 0.52-0.96; P = .03). Patients whose tumors harbored mutant BRAFV600E (AHR, 2.45; 95% CI, 1.85-3.25; P < .001) or mutant KRAS (AHR, 1.21; 95% CI, 1.00-1.47; P = .052) had worse SAR compared with those whose tumors had wild-type copies of both genes, although only results for BRAFV600E achieved statistical significance. Significant interactions were found for MMR (P = .03) and KRAS (P = .02) by primary tumor site for SAR. Improved SAR was observed for patients with deficient MMR tumors of the proximal vs distal colon (AHR, 0.57; 95% CI, 0.40-0.83; P = .003), and worse SAR was observed for tumors of the distal colon with mutant KRAS in codon 12 (AHR, 1.76; 95% CI, 1.30-2.38; P < .001) and codon 13 (AHR, 1.76; 95% CI, 1.08-2.86; P = .02).

Conclusions and Relevance  In patients with recurrence of stage III colon cancer, deficient MMR was significantly associated with better SAR, and this benefit was limited to primary tumors of the proximal colon. Mutations in BRAFV600E were significantly associated with worse SAR, and worse SAR for BRAFV600E or KRAS mutant tumors was more strongly associated with distal cancers. These biomarkers have implications for patient management at recurrence.

Trial Registration  clinicaltrials.gov Identifiers: NCT00079274 and NCT00096278

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