Evaluation of Long-Term Outcomes of Microsatellite Instability Status in an Asian Cohort of Sporadic Colorectal Cancers.
PURPOSE
Microsatellite instability in colorectal cancer (CRC) and its long-term outcomes remains poorly studied in Asians. We investigate the prognostic significance of microsatellite instability in an Asian population and assess its clinical impact in patients who undergo adjuvant chemotherapy.


METHODS
Six hundred fifty-four consecutive CRC patients who underwent surgical resection between January 2010 and December 2012 were recruited. Survival was estimated using the Kaplan-Meier approach. Univariate Cox proportional hazard models were used to estimate the hazard ratios for variables associated with survival. A subgroup analyses was performed for stage III patients who underwent chemotherapy to evaluate the prognostic significance of microsatellite instability in this group.


RESULTS
Five hundred ninety-one (90.4%) patients were microsatellite stable (MSS) while 63 (9.6%) were microsatellite instable (MSI). Three years recurrence-free survival (RFS) and disease-specific survival (DSS) were 83.7 versus 73.7% (p = 0.295) and 87.1 versus 91.2% (p = 0.307) in MSS and MSI tumors, respectively. Among stage III patients who received adjuvant therapy, MSI status was found to be an adverse prognostic factor for RFS (HR 2.74 (95% CI 1.43-5.26), p = 0.002). This remained significant on multivariate analysis (HR 2.38 (95% CI 1.15-4.93), p = 0.018). Adjuvant chemotherapy was associated with survival benefit for patients with MSS tumors (HR 0.35, 95% CI 0.17-0.69, p = 0.002) but not MSI tumors (HR 0.67, 95% CI 0.08-8.15, p = 0.750).


CONCLUSIONS
MSI status is not a prognostic indicator in the general CRC population but appears to be an adverse prognostic indicator for RFS in stage III CRC patients who received adjuvant chemotherapy.
['Tan|Winson Jianhong|WJ|http://orcid.org/0000-0003-1628-3650', 'Hamzah|Julie Liana|JL|', 'Acharyya|Sanchalika|S|', 'Foo|Fung Joon|FJ|', 'Lim|Kiat Hon|KH|', 'Tan|Iain Bee Huat|IBH|', 'Tang|Choong Leong|CL|', 'Chew|Min Hoe|MH|']
D000368:Aged D000970:Antineoplastic Agents D044466:Asians D017024:Chemotherapy, Adjuvant D015331:Cohort Studies D015179:Colorectal Neoplasms D005260:Female D005500:Follow-Up Studies D006801:Humans D008297:Male D053842:Microsatellite Instability D008875:Middle Aged D009367:Neoplasm Staging D011379:Prognosis D012846:Singapore D016019:Survival Analysis
Outcomes Microsatellite instability Asian Colorectal cancer Prognosis