Microsatellite instability: Impact on cancer progression in proximal and distal colorectal cancers

Whilst individual planning of treatment and follow-up in every colorectal c ancer case is an increasing demand, prognostic markers are needed for predi cting cancer progression in the primary phase. We studied the effect of rep lication error (RER)-positivity on colorectal cancer progression by analysi ng 255 colorectal cancer specimens by polymerase chain reaction (PCR) and f ragment analysis and correlating the results with the clinical and histolog ical features of the tumour and with patient outcome. RER-positivity was de tected in 12% (28/235) of cases. It was associated with proximal location o f the tumour (P<0.001), poor differentiation (P=0.001) and large tumour siz e (P=0.009). The 5-year cumulative survival rate of the patients with RER-p ositive cancer of the proximal colon was markedly better (100%) than that o f those with RER-negative proximal cancer (74%), whilst in cases of cancer of the distal colon or rectum, RER-positivity (21%) indicated poorer surviv al than RER-negativity (57%). Thus, it is suggested that RER-positivity has an opposite impact on cancer progression in cases of proximal and distal c ancers. RER-positivity appears to indicate improved prognosis only in cases of proximally located cancer, in which it could accordingly be useful as a prognostic marker. (C) 1999 Elsevier Science Ltd. All rights reserved.