Two Studies Assess Benefit of Two Different Drugs Used to Lower the Risk of Colorectal Cancer Returning

May 14, 2005People with stage III, and often stage II, colorectal cancer are given adjuvant chemotherapy (chemotherapy after surgery), to lower the risk that the cancer will return. Two reports from large phase III clinical trials evaluate the benefit of adjuvant chemotherapy in colon cancer.The first study found that adding oxaliplatin (Eloxatin) to standard chemotherapy of leucovorin (Wellcovorin) and fluorouracil (Efudex) lowers the risk that the cancer will return by 21% for people with stage II or III colorectal cancer. Oxaliplatin is already approved by the U.S. Food and Drug Administration (FDA) for use in combination with fluorouracil and leucovorin to treat people with stage III and IV colorectal cancer."Our results suggest that the addition of oxaliplatin to standard therapy is an important option for patients with stage II or III colorectal cancer who need chemotherapy after surgery," said Norman Wolmark, MD, Chairman of the National Surgical Adjuvant Breast and Bowel Project (NSABP) and lead author of the study.In this phase III study, 2,407 patients with either stage II or stage III colorectal cancer received adjuvant chemotherapy with a combination of fluorouracil and leucovorin, with or without oxaliplatin. After almost three years, 76.5% of the patients who received oxaliplatin remained cancer-free, compared with 71.6% of the patients who had not received oxaliplatin.Side effects were similar in the two groups, although 8% of the patients who received oxaliplatin experienced nervous system problems. In addition, diarrhea and dehydration that required hospitalization were more common in the oxaliplatin group (4.7% vs. 2.8%).In the second study, doctors found that irinotecan (Camptosar) slightly improved the effectiveness of the standard chemotherapy drugs used to treat colorectal cancer after surgery for stage II or III cancer, but offered little benefit for stage III cancer alone. Irinotecan is approved by the FDA for use in combination with fluorouracil and leucovorin as initial treatment for people with advanced colorectal cancer and as second-line treatment in people whose colorectal cancer continued to spread after treatment with fluorouracil and surgery.This study evaluated 3,278 people with stage II or III colorectal cancer who received fluorouracil and leucovorin with or without irinotecan for six months. Irinotecan reduced the risk of the cancer returning for people with stage III cancer by 11%, which was not statistically different from the other treatment. When people with stage II or III colorectal cancer were analyzed together, irinotecan lowered the risk of cancer returning by 13%.What this means for patientsBoth studies assess the value of adjuvant chemotherapy in people with early stage colorectal cancer. That is, can chemotherapy after surgery help lower the chance that the cancer returns? These two studies are different in the choice of chemotherapy: oxaliplatin (in the first study) or irinotecan (the second study), and each are given in combination with fluorouracil and leucovorin.The first study confirms the results of an earlier European study that showed that adjuvant chemotherapy with oxaliplatin lowers the risk of the cancer returning for people with stage II or III colorectal cancer by 21%. The second study showed that adjuvant chemotherapy with irinotecan lowered the risk of the cancer returning by 13%, and confirms an earlier study in the United States that showed little benefit with irinotecan. The method of how the drugs were given was also slightly different. The first study used a two-hour infusion of fluorouracil given weekly, rather than a 48-hour prolonged infusion.In conclusion, two large studies have now shown that oxaliplatin lowers the risk of the cancer returning, and two other large studies have shown that irinotecan does not appear to lower this risk. However, many people taking oxaliplatin experience serious side effects to the nervous system, which may not go away after treatment. Patients are encouraged to talk to their doctors about the risks and benefits of adjuvant chemotherapy for early stage colorectal cancer.