Prostate Cancer Therapies May Not Be Equal

ORLANDO—Men with low- and intermediate-risk early-stage prostate cancer who received external-beam radiation therapy (RT) did not live as long as those who were treated with brachy-therapy or radical prostatectomy, researchers said at ASCO's 2007 Prostate Cancer Symposium (abstract 293). The reason for the finding is still unclear and is being investigated, said lead author Jay P. Ciezki, MD, of the Department of Radiation Oncology, Cleveland Clinic.

"Despite previous work promoting equivalence among the three major treatment modalities for prostate cancer, there is now evidence that they may not have identical long-term outcomes relative to overall survival," he commented. The study represents the first time the effect of the three treatment strategies on overall survival has been assessed.

The researchers analyzed 5-year overall survival among 2,285 patients with low- or intermediate-risk prostate cancer who were treated at the Cleveland Clinic from 1996 to 2003: 662 patients were treated with brachytherapy, 570 with external-beam RT, and 1,053 with radical prostatectomy.

"This is the group of patients one most commonly sees in practice, the low- and intermediate-risk patients who make up 80% of all patients being diagnosed," Dr. Ciezki commented. He stressed that the study measured overall survival rather than softer endpoints, such as biochemical relapse-free survival.

To make the analysis more robust, other confounding factors that could affect survival were included in the analysis: age, comorbidities as defined by Charlson score (a validated comorbidity index), socioeconomic status, race, body mass index, coronary artery disease, hypertension, dyslipidemia, initial PSA, biopsy Gleason score, clinical stage, use and duration of androgen deprivation therapy, alcohol use, and smoking.

Patients treated with brachytherapy had the greatest comorbidity burden, as evidenced by a mean Charlson score of 0.62. Mean Charlson scores were 0.34 for external-beam RT patients and 0.20 for radical prostatectomy patients.

5-Year Results

After 5 years, 93.8% of the men who received external-beam RT were still alive, compared with 95.7% of those who received brachytherapy and 97.7% of those who underwent radical prostatectomy (P = .0003). After controlling for confounding factors, brachytherapy and surgery were found to be equally effective, while external-beam RT remained less effective (P = .0158).

Smoking, increasing Charlson score, and age were also independently associated with reduced overall survival.

"We are not sure why we are seeing this, and the comorbidities did not explain the difference," Dr. Ciezki said. "We are now analyzing our results to see if we can detect a pattern as to the cause of death. If we find that there is a pattern, we can start generating hypotheses about the treatment, but we cannot say anything about this now."