Chemo's benefit in T3 prostate cancer remains to be seen

Chicago-Whether chemotherapy may benefit men with locally advanced prostate cancer is still not known, but it is hoped that clinical trials currently under way may provide some evidence on the potential role of adjuvant or neoadjuvant chemotherapy in this setting.

According to Robert Dreicer, MD, chairman of the department of solid tumor oncology at the Cleveland Clinic, the rationale for investigating the use of chemotherapy in patients with locally advanced prostate cancer is that too many men with this disease fail systemically.

In a presentation at the Perspectives in Prostate Cancer conference here, Dr. Dreicer discussed several trials currently under way to evaluate this question. The first trial to study the impact of adjuvant chemotherapy in this setting is being conducted by investigators from the Southwest Oncology Group-the SWOG 9921 trial-in which patients with locally advanced disease are randomized to 2 years of combined androgen blockade with or without six cycles of mitoxantrone (Novantrone) and prednisone (Deltasone, Meticorten, Orasone, et al) after radical prostatectomy.

To date, the trial has accrued almost 1,000 patients and will assess the impact of this adjuvant chemotherapy regimen on prostate cancer-specific survival and overall survival.

Another trial currently under way in the United States is the TAX 3501 trial, in which men with locally advanced disease are randomized to immediate adjuvant therapy with 18 months of testicular androgen suppression alone or with six cycles of docetaxel (Taxotere), 75 mg/m² every 3 weeks, or to one of these treatment regimens at the time of disease progression. Approximately 1,500 men will be enrolled in the study.

Other phase II studies evaluating the role of chemotherapy in the neoadjuvant setting have shown mixed results, with some evidence of declines in PSA and decreased tumor volume, but also evidence of no pathologic complete response. Most of these studies, however, have included very small patient populations.

Larger studies needed

According to Ian M. Thompson, MD, chairman of the department of urology at The University of Texas Health Science Center at San Antonio, larger studies will be needed to know the value of neoadjuvant chemotherapy in this setting.

"For other diseases, there has been a demonstrated effect [with neoadjuvant chemotherapy], such as in breast cancer," he said. "However, it took thousands of patients and clinical trials to prove this before the standard of care changed. We need these studies completed before we can make that statement in prostate cancer."

Whether any of these trials will show a role for chemotherapy in locally advanced disease remains unknown. Until then, it remains available only to patients enrolled in clinical trials.

"At this time, chemotherapy for locally advanced disease remains investigational," said Dr. Thompson, adding that if chemotherapy does play a role, it probably will be in combination with other therapies, such as targeted therapies.

For Dr. Dreicer, these studies are critical to determine if chemotherapy may be an option for improving outcomes for locally advanced disease.