High dose rate brachytherapy as prostate cancer monotherapy reduces toxicity compared to low dose rate palladium seeds.

PURPOSE

We evaluated the potential for differing acute and chronic toxicities between 2 monotherapy methods of image guided conformal brachytherapy, high dose rate (HDR) brachytherapy alone and low dose rate (LDR) permanent palladium seeds.

MATERIALS AND METHODS

A total of 149 patients with biopsy proven, early stage prostate cancer were consecutively treated with interstitial brachytherapy as the sole method of treatment at William Beaumont Hospital between 1999 and 2001. Of the 149, 65 patients were treated with HDR using 192 iridium (192Ir), and 84 patients were treated with LDR using 103 palladium (103Pd). The majority of patients had clinical stage II, T1c or T2a disease, pretreatment prostate specific antigen less than 10 ng/ml and Gleason score 6 or less. Neoadjuvant hormones were used in 36% of patients for gland volume optimization. All treatments were performed transperineally with trans-rectal ultrasound guidance and fluoroscopy for verification of needle/seed positions. The HDR dose was 38 Gy delivered in 4 fractions, 2 times daily during 2 days. The LDR dose was 120 Gy. Acute and chronic toxicities were scored according to the Common Toxicity Criteria scale, version 2.0.

RESULTS

Median followup for all patients was 35 months. The 2 treatment groups were well-balanced with respect to age, clinical stage, prostate specific antigen, Gleason score, use of neoadjuvant hormones, pretreatment genitourinary symptoms, implanted gland volume and length of followup. Biochemical control (American Society for Therapeutic Radiology and Oncology definition) was 97% and 98% for LDR and HDR, respectively. HDR brachytherapy alone was associated with decreased acute rates of grade 1 to 3 dysuria (67% versus 36%, p <0.001), urinary frequency/urgency (92% versus 54%, p <0.001) and rectal pain (20% versus 6%, p = 0.017). These differences remained significant when patients who received prior hormonal therapy were excluded from analysis. Selected chronic toxicities were also decreased with HDR, including long-term urinary frequency and urgency, 32% (HDR) vs 56% (103Pd), p = 0.004. There were no differences in the rates of chronic dysuria, urinary incontinence, retention or hematuria. Urethral stricture rates were 8% in the HDR alone group vs 3% for 103 Pd (p = 0.177). The 3-year actuarial impotence rate was 45% for the LDR group and only 16% for HDR. The majority of complications were grade 1. No grade 4 toxicities were encountered in either group. HDR decreased treatment cost by 19%.

CONCLUSIONS

While HDR (192 iridium) and LDR (103Pd) monotherapy maintained the same biochemical control, the use of HDR brachytherapy as monotherapy was associated with decreased rates of acute urinary frequency, urgency, dysuria and rectal pain compared to LDR. Chronic urinary frequency, urgency and grade 2 rectal toxicities were also decreased with HDR. A dramatic decrease (66%) was noted in the rate of sexual impotency with HDR. In addition, patients treated with HDR did not remain radioactive after treatment. There was a decrease in cost from not purchasing seeds per patient. HDR monotherapy as prostate cancer treatment resulted in the same biochemical control with much lower toxicity. It is an accepted, convenient, cost-effective method of prostate brachytherapy for patients with favorable risk prostate cancer.