ASTRO: Chemo + RT emerges as preferred rectal cancer treatment

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Rectal cancer patients who receive a new combination of chemotherapy combined with five weeks of radiation before surgery have an 88 percent chance of surviving the cancer three years after treatment, according to the results of a trial to be presented at the 53 rd Annual Meeting of the American Society for Radiation Oncology (ASTRO) in Miami, Oct. 2-6.

"The results of the trial allow us to recommend a new pre-operative treatment, the 'Cap50' regimen, in locally advanced rectal cancer. It's safe and reduces the risk of the cancer coming back to less than 5 percent," Jean Pierre Gerard, MD, a radiation oncologist at Centre Antoine-Lacassagne in Nice, France, said in a statement.

Cap50 combines the chemotherapy Capecitabine with five weeks of radiation at 50 Gy.

The primary treatment for cancer of the rectum, which is found in the lower 15 centimeters of the bowel, is surgery. However, there is a risk of cancer re-growth within the bowel and surrounding tissues and recurrence is incurable in the majority of patients. Depending on the location and stage of the cancer,  physicians usually recommend radiation therapy and chemotherapy before surgery. The optimal regimen is still in discussion.

Researchers in the current trial aimed to find the most effective and safe preoperative treatment for rectal cancer by comparing a combination of two different chemotherapies and two different radiation doses. A total of 598 patients with locally advanced rectal cancer were diagnosed and randomly treated across 50 hospitals in France between 2005 and 2008.

In addition to the Cap50 regimen, the researchers also tested Cap45 (Capecitabine and radiation treatment at 45 Gy) and Capox50 (chemotherapies Capecitabine and Oxaliplatin, along with radiation at 50 Gy). At three years after treatment, the Capox50 regimen did not significantly increase the chance of the cancer returning or surviving the disease, compared to the Cap45 treatment. Oxaliplatin, given as part of the Capox50 treatment, was shown to immediately increase side effects, with some cases of severe diarrhea, and was not effective in increasing the chance of local tumor sterilization.

However, the increase of radiation dose from 45 to 50 Gy in five weeks was effective, well-tolerated and did not extend the duration of treatment.

Gerard said the results of the trial, when combined with the results of similar previous trials, showed solid scientific evidence that Cap50 should become the standard treatment for locally advanced rectal cancer.