Allelic loss on chromosome 18q as a prognostic marker in stage II colorectal cancer

Background & Aims: Loss of heterozygosity (LOH) on chromosome 18q is frequent in colorectal cancer (CRC) and has been associated with poor prognosis in stage II tumors. This study investigated the frequency of LOH in sporadic CRC and its effect on patient prognosis. Methods: One hundred forty-four patients were screened for LOH at 18q by polymerase chain reaction using three polymorphic microsatellite markers. Results: Nineteen patients were excluded because their tumors showed microsatellite instability in at least one marker. Of the remaining 125 patients, 121 were informative in at least one marker; 45% (54 of 121) showed 18q LOH. Five-year survival was 42% in those with 18q LOH and 73% in those without 18q LOH (P = 0.008). Multivariate analysis showed that tumor side (P = 0.001) and 18q LOH (P = 0.01) were the only independent prognostic factors. Examining markers individually showed that only the loss of D18S474 had a significant influence on survival in patients with stage II CRC (P = 0.016). Conclusions: 18q LOH indicates an unfavorable outcome in patients with stage II ORC. Our results emphasize the importance of the 18q21.1 region, where several tumor-suppressor genes have been mapped. Microsatellite analysis may be useful in identifying high-risk patients who might benefit from adjuvant therapy.