BACKGROUNDTo evaluate the reversal effect of high dose tamoxifen on multidrug resistance to EP regimen in patients with non-small cell lung cancer.

METHODSA total of 41 patients with NSCLC were studied, who were resistant to EP regimen and were proved to have P-gp protein overexpression. All patients were randomizedly divided into two arms. Reversal group (n=21) received oral tamoxifen 100?mg, 2 times everyday on D1-5, together with EP regimen. Control group (n=20) were only given EP regimen.

RESULTSIn reversal group, complete response occurred in 1 patient, and partial response in 5; disease remained stable in 11 patients, and tumor progression occurred in 4 patients. The response rate was 28.6%(6/21). In control group, no response occurred; 9 patients had stable diseases, and the other 11 progressed. There was a significant difference in response rate between the two groups (P=0.012?1). In reversal and control groups, the median survivals were 8.4 and 4.6 months respectively (P < 0.01), and 1-year survial rates were 38.1% and 35.0% respectively. Reversal of P-gp occurred in 7 cases of reversal group (33.3%),and none in control group (P= 0.005?2) . There was no significant difference in toxicities between the two groups (P > 0.05).

CONCLUSIONSHigh dose tamoxifen can remarkably downregulate the expression of P-gp and partially reverse the multidrug resistance to EP regimen for non-small cell lung cancer.