Results of Newer Radiation Treatments for Prostate Cancer

Newer radiation treatments--brachytherapy and conformal radiotherapy--werediscussed at a symposium at the 1996 meeting of the American Society forTherapeutic Radiology and Oncology (ASTRO) in Los Angeles.

Brachytherapy

Kent Wallner, MD, of Memorial Sloan-Kettering who has been implantingradioactive seeds for eight years, reported that tumor control rates withimplantation are quite similar to the rates achieved with radical prostatectomy--atleast over a 6-year period following the therapy. "Of course, theseresults need to be verified, but I think that radioactive seed implantationwill very soon begin playing a more prominent role in the treatment ofprostate cancer," he said.

The treatment has a number of advantages. It can be performed on anoutpatient basis; it allows most men to go back to work within a few days;and it appears to preserve potency. All of the men under age 60 who wereable to achieve erection before seed implantation remained potent 5 yearsafter treatment, while 80% of those over 60 retained their ability to haveerections.

Three-Dimensional Conformal Radiotherapy

Gerald E. Hanks, MD, chairman of radiation oncology at Fox Chase CancerCenter in Philadelphia, described the results of a study in which 233 menwere treated with three-dimensional conformal radiotherapy (3D-CRT). Thesuccess rate at five years, as measured by a stable PSA level, was comparableto that of men treated with surgery at Johns Hopkins and M. D. Anderson.The 3D-CRT caused fewer side effects and preserved sexual function betterthan traditional radiation therapy, Dr. Hanks said.

Dr. Zvi Fuks, chairman of radiation oncology at Memorial Sloan-Kettering,who conducted the 3D-CRT study along with Dr. Hanks, discussed the possibilityof increasing the dose of radiation by 10%. "The increase may be possiblebecause 3D-CRT gives greater protection to healthy tissue," notedDr. Fuks.

Dr Malcolm Bagshaw, professor emeritus at Stanford University Schoolof Medicine, who pioneered the use of external-beam and linear acceleratortreatment, observed that "the standard dose of 70 Gy is really quitea high dose in its own right. It is possible to increase the dose, butto what extent we don't really know yet. It would be important to increasethe dose as high as can be achieved without increasing unwanted side effects.I think that for the time being, when a dose of 70 Gy is exceeded, it shouldbe achieved in a clinical trial by people who are treating with a well-developedprotocol and escalating the dose very cautiously.

Improvements in Traditional Radiotherapy

"We're seeing an absolute technical explosion in the developmentof linear accelerators, computer control of linear accelerators, betterways to plan the treatment and better ways to calculate the dosage,"noted Dr. Bagshaw. Treating prostate cancer patients who are consideredgood candidates for radical surgery with external-beam radiation instead,is yielding the same long-term survival (15 years and longer) as surgery,he said.

Traditional radiotherapy may also have new applications. A pair of studiesdetermined that traditional therapy could be effective for early-stagedisease. The Cleveland Clinic study of 400 men with early-stage prostatecancer indicated that regardless of whether surgery or radiation was chosen,the same percentage in each group were recurrence free after 5 years. Atthe University of Michigan, Ann Arbor, 93 men who were candidates for prostatesurgery were treated with traditional therapy instead. Five years aftertreatment, almost 99% showed signs of recurrence, a rate identical to thatfollowing surgery.