April 30, 2005
Heat, Radiation Combo Strikes Strong Blow Against Tumors
Hyperthermia boosts effectiveness of radiation, study finds
HealthDay News -- Microwaves are not just for day-old coffee anymore.
Researchers now have strong evidence to suggest that turning up the heat on a cancerous tumor just before radiation therapy appears to destroy the tumor much more often than radiation alone does.
The combined treatment method seems to effectively address breast, chest wall, head, neck and skin cancer in newly diagnosed patients and in those coping with recurring illness.
The heating process -- a noninvasive procedure known as hyperthermia -- relies on microwaves to dramatically elevate tumor temperature to approximately 112 degrees Fahrenheit.
Researchers say that such a thermal assault renders cancerous blood vessel walls more porous, while simultaneously provoking a helpful rise in cellular oxygen levels. In this weakened state, the tumor becomes much more vulnerable to subsequent radiation treatment.
"We're trying to sensitize the tumor cells to the tumor cell-killing potential of other therapies," said study author Dr. Ellen Jones, a Duke University radiation oncologist. "We use it to make these other treatments more effective."
The findings will appear in the May 1 issue of the Journal of Clinical Oncology.
Hyperthermia is not, in itself, a new technology. But 20-year-old studies exploring the potential of a combined hyperthermia-radiation cancer treatment did not reveal much promise at the time.
The new Duke study, however, suggests that control of the heating process has been sufficiently improved to ensure that microwave-increased temperature levels can be properly maintained, delivered and localized within the tumor region.
From 1994 through 2001, Jones and her team followed 108 men and women diagnosed with breast, chest wall, head, neck or skin cancer. The patients were described as having "incurable disease" that gave them a less than 50 percent chance of responding to conventional treatment.
Although the study included patients being treated for both initial and recurring cancer, the largest grouping was comprised of women in whom cancer had recurred in the chest wall following a mastectomy for breast cancer.
The researchers tested the combined treatment effect solely on "superficial tumors" --tumors that extended no more than approximately one inch below the skin. After all the patients underwent an initial hyperthermia treatment, half continued to receive the heat treatment alongside radiation therapy while the rest received only radiation.
The hyperthermia group was treated twice a week for a total of no more than 10 sessions. Each treatment lasted one to two hours, with at least 48 hours between sessions.
Radiation therapies were individualized for each patient, with those patients who had already undergone radiation before the study receiving significantly lower doses than those who had never undergone such treatment.
The researchers found that full tumor shrinkage was achieved in 66 percent of the patients on the combined therapies, and only 42 percent of patients receiving just radiation therapy.
Even more dramatic were the findings concerning those patients with recurring cancer who had already previously undergone radiation. Among these men and women, 68 percent of the patients on combined treatment experienced full tumor shrinkage, compared with 24 percent of the radiation-alone patients.
Among patients who had never received radiation, 65 percent of the combined treatment patients had full tumor eradication, compared with 51 percent of the radiation patients.
The Duke team concluded that hyperthermia appears to be a safe and effective boost to radiation treatment efforts to stem the spread of local tumors -- while noting that side effects, such as skin burns, appeared to be minimal.
They stressed, however, that nothing yet suggests combination therapy will actually improve survival rates overall.
But for cancer patients waging a tug of war with a spreading disease, hyperthermia does offer hope for a markedly better quality of life. Elimination and/or reduction of tumors via combined therapy can significantly reduce pain and discomfort, the researchers noted.
And they further observed that while the combined treatment option can benefit all cancer survivors, patients suffering the most pain -- those engaged in long-term struggles with recurring cancers -- have the most to gain.
Recurrent cases, they noted, usually involve particularly aggressive cancers that have proven resistant to radiation, chemotherapy, and/or surgery. Combining hyperthermia with lower-dose radiation may open treatment doors that are otherwise closed.
Jones said she and her colleagues were actively working to expand on the hyperthermia option by adding chemotherapy to the mix.
"Hyperthermia works," said Dr. Steven Stroup, a radiation oncologist at the Sarah Cannon Cancer Clinic at the Centennial Medical Center in Nashville, Tenn.
"This is absolutely where the field of radiation oncology is going, to improve the effects with regard to tumor control," agreed Dr. David Parda, chairman of the department of Rradiation oncology at Allegheny General Hospital in Pittsburgh.
But he also cautioned that more research is needed to establish the limits of hyperthermia's usefulness.
"The study researchers didn't treat tumors greater than 3 centimeters -- a little more than an inch -- in size," he noted. "So, I really think that it's important for people to be aware that its applicability, so far, is limited to very small tumors. And a lot of recurrent cancers are larger than that. So, widespread applicability would have to be proven with further studies."
For more on cancer treatment options, check out the American Cancer Society.