Doctors often use the medicine irinotecan to treat colorectal cancer. But some patients have irinotecan-refractory colorectal cancer, which means that they are not very responsive to irinotecan therapy. Cetuximab is an antibody that has been shown in previous studies to enhance the effects of of irinotecan in irinotecan-refractory colorectal cancer. In this study, researchers at 56 centers in Europe tried to find out whether cetuximab by it self or a combination therapy of cetuximab and irinotecan could help treat patients with irinotecan-refractory colorectal cancer.

What the researchers wanted to know: Can cetuximab alone or a combination of cetuximab and irinotecan help patients with irinotecan-refractory colorectal cancer?

What they did: Researchers studied 329 patients with irinotecan-refractory colorectal cancer in 11 European countries. Participants had to have received at least one irinotecan treatment that didn't work—the cancer progressed within three months. Researchers randomly assigned 111 patients to receive cetuximab alone and 218 patients to receive a combination of cetuximab and irinotecan. Participants in the cetuximab monotherapy group received injections each week. Participants on the combination therapy received cetuximab injections every week and also received the same amount of irinotecan that they were given during their most recent treatment before the study. For the first 24 weeks, researchers and an independent reviewing committee (who did not know which patients had received which treatment) looked at the tumors every six weeks using CTs and MRIs. After that, they evaluated the tumors every three months. Participants continued the therapy until their disease progressed, they died, or the medicine became too toxic.

What they found: 10.8 percent of patients in cetuximab monotherapy and 22.9 percent of patients in combination therapy improved—half or more of their cancerous lesions went away and no new lesions appeared. Of 329 patients who entered the study, 215 had died by January 2003. Patients on cetuximab monotherapy survived a median of 6.9 months after the start of the study and patients on combination therapy lived somewhat longer—8.6 months was the median lifespan. Researchers also found that patients who had taken oxaliplatin, another colorectal cancer drug, before the study had similar responses to the cetuximab therapy as patients who had not taken oxaliplatin.

What this means to you: A combination of cetuximab and irinotecan seems to be a good choice for patients with irinotecan-refractory colorectal cancer. The price tag for this treatment is pretty steep, though—in an accompanying editorial, another researcher estimated that adding cetuximab to irinotecan roughly triples the cost of therapy.

Caveats: 80 percent of participants in both the combination therapy and the monotherapy developed an acnelike rash during the study. Toxic effects like diarrhea were more common in combination therapy patients, but the incidence of the effects was about the same as in irinotecan therapy.

Find out more: Colorectal cancer network www.colorectal-cancer.net

Read the article: Cunningham, David, M.D. et al. "Cetuximab Monotherapy and Cetuximab Plus Irinotecan in Irinotecan-Refractory Metastatic Colorectal Cancer." New England Journal of Medicine. July 22, 2004, Vol. 351, pp. 337–345.