The expression of the MDR1 gene, a multidrug resistance gene, was pros
pectively determined in 113 primary colorectal carcinoma specimens and
correlated with clinical data including survival durations of the pat
ients. MDR1 RNA was detected in 65% of the carcinomas. No expression o
f the MDR2 gene was seen. MDR1 gene expression was independent of age
and sex of the patients, size and histologic grading of the tumour, ly
mph node involvement and distant metastasis. Kaplan-Meier analysis rev
ealed that the durations of both relapse-free survival and overall sur
vival were not different between patients with MDR1 RNA positive tumou
rs and those with MDR1 RNA negative tumours.