Effect of morphine on growth of metastatic colon cancer in vivo
M. P. Yeager and T. A. Colacchio
Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, Hanover, NH 03756.
Control of colon cancer depends, in part, on intact immune defense
mechanisms. Since opiates are known to affect some components of immune
function, this study was conducted to determine the effect of high-dose
subcutaneous morphine sulfate and of low-dose intrathecal morphine on the
postoperative growth of metastatic colon cancer. Five groups of 15 Fischer
344 rats were given intraportal injections of colon cancer cells as
follows: group 1, control; group 2, daily subcutaneous injections of
20-mg/kg morphine the day before and for 2 days after colon cancer cell
inoculation; group 3, daily subcutaneous injections of saline; group 4,
daily intrathecal injections of 20 micrograms of morphine; and group 5,
daily intrathecal injections of saline. There was a significant decrease in
the hepatic tumor burden in group 2 compared with groups 1 and 3 and a
significant increase in the hepatic tumor burden in groups 4 and 5 compared
with group 1. This study demonstrates that intermittent injections of a
narcotic may decrease the growth of tumor cells that gain access to the
circulation during a surgical procedure. In addition, the results support
the concept that tumor cells entering the circulation during a vulnerable
period of postoperative immunosuppression are more likely to survive as
metastatic tumor.
