CHICAGOAccording to 1994 patterns of practice, only about 20% of cancer centers in the United States provide 3D conformal radiotherapy to men with prostate cancer, and only 2% of these centers give more than conventional doses of radiation, Gerald Hanks, MD, said at a quality of life and outcomes symposium, sponsored by Northwestern University and Evanston Northwestern Healthcare.
In 1994, less than 2% or 3% of men with localized prostate cancer received high-dose 3D conformal radiotherapy. Using a large-scale database of information on prostate cancer practice patterns, Dr. Hanks found that 93% of conformal radiotherapy treatments were below 7,200 cGy. Yet Dr. Hanks studies have shown that when men with PSA levels between 10 and 20 ng/mL received high-dose radiotherapy (greater than 7,500 cGy), 72% were disease free after 5 years vs only about 50% of men who had lower dose radiotherapy.
For men with PSA levels higher than 20 ng/mL, 45% were disease free at 5 years after receiving high-dose radiotherapy (greater than 7,400 cGy), compared with 18% of men receiving lower radiotherapy doses.
As a result, Dr. Hanks said, at a dose of radiotherapy below 70 Gy, only about 12% to 14% of men with a PSA level of more than 20 ng/mL will be disease free at 5 years, but if the dose is raised to 75 or 80 Gy, the number of disease-free men at 5 years increases to 40% to 50%. So a little difference in dose makes a lot of difference to patients, said Dr. Hanks, chair of the Department of Radiation Oncology, Fox Chase Cancer Center.
Two High-Dose Studies
On the theory that high-dose 3D conformal radiotherapy would improve survival as well as local control of prostate cancer, Dr. Hanks explored radiotherapy dose responses in two groups of men. In a study of 592 men, he evaluated the effects of high-dose (greater than 74 Gy) and lower dose radiotherapy in men who were matched by age, PSA, and Gleason score.
Among the 296 patients who received high-dose radiotherapy, there was a significant difference at 5 years in cancer deaths, absence of distant metastases, and recurrence of disease.
A larger study of 714 patients produced similar results. There were statistically significant differences in the number of distant metastases, biochemical freedom from disease, cause-specific deaths, and overall survival in the 357 men who had high-dose radiotherapy.
Dr. Hanks therefore concluded that cancer centers should replace the conventional dose of radiotherapy with higher dose therapy to provide definitive treatment to men with prostate cancer.
When asked in an interview with Oncology News International if part of the problem is that centers lack the equipment necessary to do high-dose 3D conformal therapy, he said that you can do high-dose therapy without fancy equipment, but it is harder. In the United States, about 250 centers out of a total of 1,500 have CT simulators that allow high-dose therapy to be done more easily, but more important than having the equipment, physicians must have an understanding of the importance of high-dose therapy and be willing to increase the dose in prostate cancer patients.
Dr. Hanks said that he is working with specialty groups, industry, and government to try to put together a series of weekly schools to allow physicians to get hands-on experience with 3D conformal radiotherapy and become more comfortable with the high-dose concept.