A simple change in the way thousands of breast-cancer patients are treated can have a big impact on preventing the disease from returning, according to Canadian findings presented at the world's largest cancer conference.
By radiating surrounding lymph nodes in addition to the breast, early stage patients were less likely to see the cancer recur, especially in distant parts of the body, suggesting previously undetectable malignant cells were being eradicated.
There was a 35-per-cent reduction in distant cancer recurrence at five years - where the disease turns up somewhere other than the breast - according to figures from Tim Whelan, professor of oncology at McMaster University.
His findings, to be presented Monday at the American Society of Clinical Oncology meeting in Chicago, are so compelling that the Canadian Cancer Society said treatment for early stage patients should be changed as quickly as possible.
"My hope is that it's adopted into clinical change quickly so thousands of women that could significantly benefit from that treatment are offered that option as soon as possible," Christine Williams, director of research for the Canadian Cancer Society, which funded the study, said in a telephone interview. "It's really an innovation rather than an invention, it should be easy to translate."
An estimated 23,400 women are expected to be diagnosed with breast cancer this year and 5,100 are expected to die of it, according to Canadian Cancer Society figures.
The findings would affect an estimated 2,500 breast cancer patients each year, said Dr. Whelan, lead study investigator for the NCIC Clinical Trials Group.
"The reason we wanted to do that is this is a grey area and had been a grey area for some time," said Dr. Whelan of the study, which was conducted at more than 30 Canadian hospitals.
That medical grey zone - how best to treat women with early stage breast cancer who had one to three nodes test positive - has existed for about 15 years, making the best treatment for these patients unclear.
Patients with tumours bigger than 5 centimetres who had more than three axillary lymph nodes with cancer received radiation to the breast and surrounding lymph nodes. The other group - the medical grey zone patients with one to three lymph nodes with cancer - typically received radiation to the breast.
All 1,832 patients in the study that ran from March 2000 to March 2007 in Canada, the United States and Australia, also underwent surgery and chemotherapy or endocrine therapy.
Most surprising to Dr. Whelan, however, was the 35-per-cent reduction in distant cancer recurrence from radiation treatment, which is not typically seen with that type of therapy. Put another way, out of 100 patients treated, five or six would see a benefit from the additional radiation.
As well, there was a reduction in risk of cancer's return to the breast, though a smaller one. Specifically, there was a 42-per-cent reduction in local recurrence at five years, which means out of 100 patients treated, two would benefit.
Though death rates were reduced, they were not statistically significant - a finding that will be followed in the same set of patients over the next few years.
Dr. Whelan said the additional radiation did come with tradeoffs, in the form of lymphedema, excess lymphatic fluid in the arm on the radiated side, which can be a chronic condition for many patients, as well as an increased risk of moderate pneumonitis, a lung inflammation.
Also released at the American Society of Clinical Oncology conference was a study that showed treating healthy women at high risk of developing breast cancer with the drug exemestane can cut their risk of developing the disease by two-thirds. It was published online simultaneously in the New England Journal of Medicine on the weekend.
Michael Wosnick, vice-president of research at the Canadian Cancer Society, called the results "extremely exciting because they have the potential to impact thousands of women."
He said using the drug exemestane, which suppresses estrogen production, offers some women an "important new option" for reducing their risk.
With files from Andre Picard