Is completion of irinotecan chemotherapy associated with better treatment response in locally advanced rectal cancer?

This study investigated the effectiveness of high completion of irinotecan (Camptosar) chemotherapy before locally advanced rectal cancer surgery. Researchers suggested that the completion of irinotecan chemotherapy was associated with better tumor response in these patients.

Colorectal cancer is the third most common cancer worldwide. Around 2% of these cases are rectal cancer. For locally advanced (spread to the surrounding tissues or lymph nodes) rectal tumors the standard treatment is chemotherapy and radiation therapy followed by surgery. Irinotecan chemotherapy is often used after surgery, to target and kill possible cancer cells left behind after surgery. However, the effectiveness of this drug before surgery is not well known.

Prior studies suggested that the use of irinotecan might increase the tumor response to the treatment. However, this was at the expense of increased toxicity. This is associated with an increased number of patients who do not complete the treatment. Whether incomplete chemotherapy treatment affects irinotecan effectiveness is unclear.

This study included information about 371 patients with locally advanced rectal cancer. All patients received treatment before surgery. Treatment consisted of pelvic radiation therapy and capecitabine (Xeloda) and irinotecan (XELIRI) chemotherapy, followed by surgery. All patients had further chemotherapy after surgery.

38.8% of patients had a low treatment completion (group 1; 1-3 cycles of irinotecan) and 61.2% had a high completion rate (group 2; 4-5 cycles of irinotecan). The treatment response was compared between these two groups.

The complete tumor response rates (includes clinical and pathological response) were 21.5% in group 1 and 33.0% in group 2. The pathological response rates (tumor shrinkage) were 19.4% in group 1 and 26.1% in group 2.

Three different risk groups were identified as low, medium, and high risk. The high-risk group had a high completion rate of 29.2%, the medium group had a rate of 50% and the low-risk group had a rate of 68.9%.

This study concluded that a higher completion rate of irinotecan therapy is associated with better tumor response in locally advanced rectal cancer.

This study was based on medical records. Some information might have been incomplete. This might affect the results.