Colon Cancer Treatment May Be More Toxic Than Thought
"I would have to say that we were surprised," says O'Connell. "We think that the higher-than-expected death rates maybe due to the fact that we had a lot more patients included in the trials -- there were nearly 2,100 patients in these trials, whereas the original study had approximately 680 patients in it." The larger number of participants "may have allowed us to identify more precisely this relatively uncommon but very serious early toxic reaction: the early death."
Cancer expert Leonard Saltz, MD, says that the way these deaths were identified so quickly shows that the system is working. "The safety system we have in the cooperative groups ... is a system where the data is monitored carefully to look for unexpected developments," he says. "When you have such a serious unexpected event as early death, to pick that up at a very early level allows us to put the breaks on, stop and think, and protect the people involved in the study. That is what happened here." Saltz, an associate attending physician at New York's Memorial Sloan-Kettering Cancer Center, is the lead investigator in the Cancer and Leukemia Group B trial.
The next step is to figure out what this means and how to keep moving forward, says Saltz. "We have to bear in mind that [Camptosar] is still a very important drug and a good drug in the treatment of colon cancer," he tells WebMD.
Previous studies, he says, have shown Camptosar improves survival. "Now we have new information that we have to digest and analyze, in terms of these early deaths. We have to learn how to improve on what we have without abandoning it. ... Why did we see more deaths on these follow-up studies than in the first study? Nobody knows," Saltz says.
Indeed, the researchers aren't sure what is causing the high toxicity rate, but they note that 12 of the 14 patients who died in the North Central Cancer Treatment Group trial had several severe side effects in common, including dehydration resulting from diarrhea, nausea, and vomiting, an abnormally low number of a certain type of white blood cells, and blood infections. In the Cancer and Leukemia Group B trial, many of the deaths were related to blood clotting abnormalities.