• 5/17/2005
  • Toronto, Ontario, Canada
  • press release
  • Newswire Canada (www.newswire.ca)

Patients being treated with high dose radiation for head and neck cancer in the morning have a lower risk of developing debilitating side effects than patients who receive treatment in the late
afternoon, suggests new research by oncologists at the Toronto Sunnybrook Regional Cancer Centre, the comprehensive cancer program at Sunnybrook and Women’s College Health Sciences Centre.

Funded by the Canadian Cancer Society and the Canadian Institutes of
Health Research, the clinical trial found a condition called mucositis was much less common in patients who received high-dose radiation treatment early in the day compared to the end of the afternoon. Mucositis is damage to the lining of the mouth and throat that is sometimes so severe that treatment must be stopped.

The research presented yesterday at the American Society of Clinical
Oncology Annual Meeting, is the first to show a link between circadian rhythms and the development of mucositis due to radiotherapy.

The study is based on research lead by medical oncologist Dr. Georg
Bjarnason from Sunnybrook & Women’s who is internationally known for his research on circadian rhythms and cancer. “In a previous study on healthy volunteers, we discovered a variation in the cell division cycle of cells in the mouth over a 24-hour period. In the morning, the cells in the lining of the mouth are in a phase of cell division that is relatively resistant to radiotherapy, whereas in the afternoon these cells are in a phase that is quite sensitive,” says Dr. Bjarnason who is also an Associate Professor at University of Toronto. “We used these two previous observations to hypothesize that morning radiation therapy would be less toxic. In this study, the
hypothesis was proven for a subgroup of patients who received the highest dose
of radiation.”

Researchers compared severe oral mucositis in 206 patients in 12 centres across Canada receiving radiation treatment. Patients received their radiationtherapy either in the morning (between 8 a.m. and 10 a.m.) or in the late afternoon (between 4 p.m. and 6 p.m.).

In an unplanned subgroup analysis involving 111 patients receiving a very high dose of radiation researchers found that only 43 per cent of patients who had early morning radiation experienced severe mucositis, compared to 67 per cent of patients who received radiation in the late afternoon. This serious form of mucositis took a longer time to develop in the group of patients treated in the morning (more than 8 weeks vs. 5.7 weeks). Furthermore, among the 53 patients who continued to smoke during the radiotherapy, morning patients experienced 33 per cent less oral mucositis than afternoon patients.

Smoking is known to increase the mucositis associated with radiotherapy. In addition, patients receiving the morning radiotherapy stopped losing weight significantly earlier than the afternoon group.

Radiation therapy for head and neck cancer patients typically lasts from four to seven weeks. About 10 per cent of patients are admitted to hospital when mucositis – equivalent to third degree burns inside the mouth – makes it too painful for them to eat or drink enough to maintain body weight.

“This study suggests that the timing of radiation may be a simple
low-cost strategy to reduce a dose-limiting side effect that up until now has limited our ability to combine radiation with chemotherapy regimens with the potential to improve cure rates,” says co-principal investigator Dr. Bob MacKenzie, Radiation Oncologist at Sunnybrook & Women’s. “This research is likely to lead to studies in other cancer sites where gastrointestinal side effects can be debilitating and sometimes lead to delays or interruptions in radiation treatments.”

“Cancers of the head and neck are often devastating and their treatment is too commonly hindered by serious side effects,” says Dr. Barbara Whylie, CEO of the Canadian Cancer Society. “The results of this clinical trial are an important advance that will help us be more effective in how we treat these patients and help us improve their quality of life.”

“These are important research findings that will significantly improve
the quality of life for many patients undergoing radiation therapy for head and neck cancers”, said Dr. Philip Branton, Scientific Director of CIHR’s Institute of Cancer Research.

Every year in Canada, more than 4,300 people are diagnosed with head and neck cancers with more than 1,500 deaths annually. The clinical trial was coordinated through the National Cancer Institute of Canada Clinical Trials Group, with funding from the Canadian Cancer Society and the Canadian Institutes of Health Research.

The National Cancer Institute of Canada Clinical Trials Group, based at Queen’s University in Kingston, Ontario, is one of the national programs and networks of the Canadian Cancer Society.

The Canadian Cancer Society is a national community-based organization of volunteers whose mission is to eradicate cancer and to enhance the quality of life of people living with cancer.

The Canadian Institutes of Health Research is the Government of Canada’s agency for health research. Its objective is to excel, according to internationally accepted standards of scientific excellence, in the creation of new knowledge and its translation into improved health for Canadians, more effective health services and products and a strengthened Canadian health care system. Composed of 13 Institutes, CIHR provides leadership and support to more than 9,000 researchers and trainees, and research teams in every province
of Canada.