Integrating TYMS, KRAS and BRAF testing in patients with metastatic colorectal cancer.
AIM
To investigate the impact of thymidylate synthase (TYMS), KRAS and BRAF in the survival of metastatic colorectal cancer (mCRC) patients treated with chemotherapy.


METHODS
Clinical data were collected retrospectively from records of consecutive patients with mCRC treated with fluoropyrimidine-based chemotherapy from 1/2005 to 1/2007. Formalin-fixed paraffin-embedded tissues were retrieved for analysis. TYMS genotypes were identified with restriction fragment analysis PCR, while KRAS and BRAF mutation status was evaluated using real-time PCR assays. TYMS gene polymorphisms of each of the 3' untranslated region (UTR) and 5'UTR were classified into three groups according to the probability they have for high, medium and low TYMS expression (and similar levels of risk) based on evidence from previous studies. Univariate and multivariate survival analyses were performed.


RESULTS
The analysis recovered 89 patients with mCRC (46.1% de novo metastatic disease and 53.9% relapsed). Of these, 46 patients (51.7%) had colon cancer and 43 (48.3%) rectal cancer as primary. All patients were treated with fluoropyrimidine-based chemotherapy (5FU or capecitabine) as single-agent or in combination with irinotecan or/and oxaliplatin or/and bevacizumab. With a median follow-up time of 14.8 mo (range 0-119.8), 85 patients (95.5%) experienced disease progression, and 63 deaths (70.8%) were recorded. The 3-year and 5-year OS rate was 25.4% and 7.7% while the 3-year progression-free survival rate was 7.1%. Multivariate analysis of TYMS polymorphisms, KRAS and BRAF with clinicopathological parameters indicated that TYMS 3'UTR polymorphisms are associated with risk for disease progression and death (P < 0.05 and P < 0.03 respectively). When compared to tumors without any del allele (genotypes ins/ins and ins/loss of heterozygosity (LOH) linked with high TYMS expression) tumors with del/del genotype (low expression group) and tumors with ins/del or del/LOH (intermediate expression group) have lower risk for disease progression (HR = 0.432, 95%CI: 0.198-0.946, P < 0.04 and HR = 0.513, 95%CI: 0.287-0.919, P < 0.03 respectively) and death (HR = 0.366, 95%CI: 0.162-0.827, P < 0.02 and HR = 0.559, 95%CI: 0.309-1.113, P < 0.06 respectively). Additionally, KRAS mutation was associated independently with the risk of disease progression (HR = 1.600, 95%CI: 1.011-2.531, P < 0.05). The addition of irinotecan in 1st line chemotherapy was associated independently with lower risk for disease progression and death (HR = 0.600, 95%CI: 0.372-0.969, P < 0.04 and HR = 0.352, 95%CI: 0.164-0.757, P < 0.01 respectively).


CONCLUSION
The TYMS genotypes ins/ins and ins/LOH associate with worst prognosis in mCRC patients under fluoropyrimidine-based chemotherapy. Large prospective studies are needed for validation of our findings.
['Ntavatzikos|Anastasios|A|', 'Spathis|Aris|A|', 'Patapis|Paul|P|', 'Machairas|Nikolaos|N|', 'Peros|George|G|', 'Konstantoudakis|Stefanos|S|', 'Leventakou|Danai|D|', 'Panayiotides|Ioannis G|IG|', 'Karakitsos|Petros|P|', 'Koumarianou|Anna|A|']
D020413:3' Untranslated Regions D000328:Adult D000368:Aged D000369:Aged, 80 and over D000971:Antineoplastic Combined Chemotherapy Protocols D014408:Biomarkers, Tumor D015179:Colorectal Neoplasms D018450:Disease Progression D018572:Disease-Free Survival D019008:Drug Resistance, Neoplasm D005260:Female D005500:Follow-Up Studies D005820:Genetic Testing D006801:Humans D008297:Male D008875:Middle Aged D009154:Mutation D020641:Polymorphism, Single Nucleotide D011379:Prognosis D048493:Proto-Oncogene Proteins B-raf D016283:Proto-Oncogene Proteins p21(ras) D060888:Real-Time Polymerase Chain Reaction D012189:Retrospective Studies D016019:Survival Analysis D013940:Thymidylate Synthase D016896:Treatment Outcome
TYMS KRAS BRAF Thymidylate synthase Survival mCRC Chemotherapy Polymorphisms Loss of heterozygosity