Data on PET/CT imaging may yield major advance in advanced prostate cancer

August 15, 2007

The AUA take-home messages on management of advanced prostate cancer underscore research interest in better defining the risks and benefits of androgen deprivation therapy (ADT) and provide some encouragement that new methods for treatment and evaluation will be available in the future to fill important gaps.

The use of choline positron emission tomography/computed tomography following primary treatment with prostatectomy was found to have a sensitivity of 91% and a specificity of 50% in detecting clinical recurrence. Separately, single photo emission CT was shown to predict a greater risk of cancer-specific deaths.

Dr. Thrasher noted that, currently, management decisions for men who have a rising PSA after radical prostatectomy or radiation therapy present a therapeutic dilemma because of the inability to accurately determine whether an early recurrence is local or distant. For that reason, the studies showing that the imaging techniques performed with good sensitivity and reasonable specificity for early detection of the site of recurrence are very encouraging.

Patients receiving initial treatment with the immunotherapy sipuleucel-T (Provenge) followed by docetaxel (Taxotere) after progression showed prolonged survival.

Urologists have few treatments to offer patients with androgen-refractory prostate cancer. Therefore, the results of this report showing a survival benefit of combining an investigational form of immunotherapy with docetaxel are encouraging and provide a basis for hope that more options will be shown to have efficacy in the future, Dr. Thrasher told Urology Times.

"Several studies are under way now investigating combinations of immunotherapy, hormone therapy, and/or chemo therapy, and are of great interest because of the paucity of therapeutic choices for men who are no longer responding to ADT. The report also highlights that we can expect to see more of a team approach to prostate cancer management in the future in which radiation oncologists, medical oncologists, and urologists work together, combining their individual expertise to optimize patient care," Dr. Thrasher said.

Several presentations claimed that long-term treatment with ADT carries a risk of cardiovascular complications; others reported deaths from non-cancer causes in about 48% of cases.

Detrimental effects of ADT, including loss of bone mineral density, changes in cognition, and the development of anemia, are already well recognized. These studies lend additional credence to concerns about other harmful consequences of ADT, and they should cause practicing urologists to seriously consider the risks and benefits prior to initiating this therapy, Dr. Thrasher said.

"There has been an increase in the earlier use of ADT for prostate cancer management, such as for downsizing disease or to treat men with PSA recurrence, and that trend has occurred without credible evidence demonstrating benefit," he cautioned. "Urologists need to be careful about prescribing ADT in situations where the indication is questionable, and be thorough in their counseling of patients about the serious side effects of this modality."

After adjusting for non-prognostic factors, one study found that treating patients with ADT for 3 years versus 6 months was not associated with prolonged survival.

There has been significant controversy regarding the duration of adjuvant ADT necessary to achieve a synergistic effect in patients receiving radiation therapy. This report corroborates some previous studies that suggested that a shorter course of ADT may be as effective as treatment over the course of 2 or 3 years, and the results are especially important against the background of accumulating evidence about the risks of ADT.

"The investigators of this report conclude that findings from an ongoing, larger trial from the European Organisation for Research and Treatment of Cancer will provide a more definitive answer about the appropriate duration of ADT. This issue is something practicing urologists should keep on their radar screens, and they should be watching out to see if the radiation oncology community issues revised guidelines on adjuvant ADT," Dr. Thrasher said.