Modulated radiotherapy can cut treatment time for cancer of the rectum without increasing toxicity

This radiotherapy procedure involves the administration of higher daily doses of radiation but with a total dose equivalent to conventional ones. In this way the treatment time is cut by 30%, without a rise in side effects and with very high rates of pathological response.

These were the results of the study undertaken by a team of doctors at the University Hospital of Navarra, recently published in the specialist scientific journal, “International Journal of Radiation Oncology, Biology, Physics” of the American Society for Therapeutic Radiotherapy and Oncology. Involved in the research was a medical team from the area of digestive system tumours, led by Doctor José Javier Aristu, specialist at the Oncological Radiology Service. The article in the North American journal is the first published in the world giving clinical results from the application of preoperational modulated radiotherapy in tumours of the rectum.

Novelty for cancer of the rectum

IMRT (Intensity-Modulated Radiation Therapy) is a radiotherapy technique in which the administration of the radiation doses for the patient is effected by means of a lineal accelerator equipped with a system of multilaminas. Depending on the characteristics of the region that has to be irradiated, the planning system is capable of adapting high radiation doses to the shape of the target volume, enabling adjustments to be made to the morphology of the area to be treated in an individualized manner.

To date, the application of this procedure had been fundamentally limited to tumours located in the head, neck and prostrate gland. “This technique had been used in more confined tumours, more limited and smaller. We have now also begun to apply it to tumours of the rectum given that the conventional treatment, combining chemotherapy and radiotherapy, may cause high levels of toxicity”, explained Doctor Aristu.

The main goal in administering modulated radiotherapy in the treatment of cancer of the rectum, lies in excluding the greatest possible proportion of healthy tissue from the field of radiation, mainly the intestines, bladder and the healthy section of the rectum. We have shown that treatment using conventional radiotherapy and chemotherapy simultaneously causes about a 30% enteritis rate (inflammation of the intestine). However, in the study, we observed that the application of modulated radiotherapy reduces the rate of enteritis practically to the minimum in the patient who is being treated for bowel cancer. Moreover, on limiting the radiation to the tumoral mass and thus affecting healthy tissue less, it was possible to increase the daily dosage and cut the overall treatment time by approximately 30%, while the total dose administered is equivalent to two conventional treatments.

Study in phase I-II

This research, initially undertaken with 20 patients with cancer of the rectum, is in study phase I-II, the main purpose of which is to find the highest dose that can be applied using modulated radiotherapy in combination with chemotherapy. According to Doctor Aristu, the research showed for the first time that a radiation dose equivalent to that administered using conventional techniques can be applied using IMRT – in less time and with very promising rates of pathological response.