In this study, large tumours treated with a combination of chemotherapy and a focused microwave heat treatment shrunk nearly 50 percent more than tumours treated with chemotherapy alone.
"It appears that heating the tumours drastically increased the effectiveness of the chemotherapy. The tumours shrank faster and died faster using the additional microwave hyperthermia on top of the chemotherapy," said Dr. William C. Dooley, director of surgical oncology at the University of Oklahoma and the principal investigator of the study.
In the latest clinical trial, 15 patients received two microwave heat treatments, known as thermotherapy, along with four rounds of chemotherapy before surgery. The goal was to shrink tumours sufficiently to enable a breast-conserving lumpectomy procedure instead of the expected, and more invasive, mastectomy. Surgeons concluded that fourteen of the tumours shrunk enough for this to be possible.
In 1990, Dr. Alan J. Fenn, a senior staff member at MIT's Lincoln Laboratory, adapted the thermotherapy treatment from a system that used focused microwaves to detect missiles and block out interfering enemy signals.
"It's a very simple idea that can be applied to the treatment of many different cancers, including breast cancer," Fenn said.
The microwaves, delivered by two applicators placed near the breast, kill the cancerous tissue while preserving normal breast tissue by targeting tumour cells that contain high amounts of both water and ions, Fenn explained. When the microwave energy passes through the tumour, the water molecules begin to vibrate and generate heat through friction. This process eventually elevates the cancer cells to a "high fever" of at least 108 degrees Fahrenheit in most cases, killing them.
"The treatment is well tolerated," said Dr. Mary Beth Tomaselli, medical director at Comprehensive Breast Centre in Coral Springs, Fla., and a surgeon who was also a co-investigator in the study.
"The patients who have gone through it had minimal side effects and positive results," she added.
Dr. Hernan I. Vargas, associate professor of surgery at UCLA and lead author of the recent study added: "Each one of the treatments adds a little bit. The thermotherapy might be one more tool that helps us fight this disease."
This is the fourth clinical trial of the therapy since 1999. In a Phase-I safety trial using microwave heat alone, researchers found that both small and large breast tumours could be decreased in size between 30 and 60 percent.
In a Phase-II dose-escalation trial for small tumours, scientists increased the amount of heat until 100 percent of the tumour cells were killed, prior to the patients' receiving a lumpectomy.
Next, researchers treated similar early-stage tumours and noticed that after the surgical removal, none of the patients had tumour cells remaining at the edge of the incision. This is important because additional breast surgery and/or radiation therapy are often recommended for patients that have cancer cells close to the edge of the lumpectomy surgical margin.