International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationNatural History of Clinically Staged Low- and Intermediate-Risk Prostate Cancer Treated With Monotherapeutic Permanent Interstitial Brachytherapy
Introduction
Permanent interstitial seed implants are used commonly as monotherapy for men with low-risk, clinically localized prostate cancer. Brachytherapy is used somewhat less frequently as the sole modality for men with intermediate-risk disease. In the larger series the biochemical progression-free survival (bPFS) rate ranges from 80% to 98% for low-risk patients 1, 2, 3, 4, 5, 6, 7, 8 undergoing brachytherapy and from 70% to 97% for intermediate-risk patients 1, 2, 3, 5, 6, 7, 8, 9. However, many men in these series received supplemental external beam radiation and/or neoadjuvant or planned adjuvant androgen deprivation. These series also included men whose implants would be considered suboptimal by today's standards.
The purpose of this report is to explore the natural history of prostate cancer in men who receive brachytherapy as the sole modality. There are obvious short-term advantages to avoiding initial combined-modality treatment, including shorter duration of treatment, exposure to fewer side effects, and lower overall health care costs. However, these advantages disappear rapidly if a significant number of men treated with monotherapy require additional, increasingly morbid salvage therapy because of disease recurrence. Hence understanding the efficacy and durability of high-quality, sole-modality brachytherapy is important.
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Methods and Materials
Between April 1995 and May 2005, 463 patients with low- or intermediate-risk prostate cancer were treated with permanent interstitial seed implants as the sole definitive treatment. Men who received neoadjuvant or planned adjuvant androgen suppression for any reason were excluded from the analysis. In addition, men who received supplemental external beam radiotherapy were excluded. Patients were categorized as low risk if they met all of the following criteria: Gleason score of 6 or less,
Results
Table 1 summarizes the clinical and treatment characteristics of men included in the analysis. Of the 463 men, 319 were low risk and 144 were intermediate risk. In addition to having a higher Gleason score, men in the intermediate-risk group had a higher pretreatment PSA level, higher percentage of positive biopsy cores, and higher clinical stage and were older.
At 12 years, the bPFS, CSS, and OS rates for the group as a whole were 97.1%, 99.7%, and 75.4%, respectively (Fig. 1). Table 2 presents
Discussion
The largest published series to date of sole-modality brachytherapy includes 1,444 low-risk men and 960 intermediate-risk men from 11 institutions (8). The 8-year PSA relapse-free survival rate was 82% for low-risk patients and 70% for intermediate-risk patients. Unfortunately, dosimetric analysis was available for only a subset of this cohort. In the cases when dosimetry information was available, men whose 125I implants had a D90 of 130 Gy or greater (still below current recommendations) (15)
Conclusions
Disease recurrence is very uncommon in clinically staged low- and intermediate-risk prostate cancer patients treated with high-quality brachytherapy monotherapy. For these men, a high-quality implant can achieve results comparable to high-quality surgery in the most favorable pathologically staged patient subgroups. As brachytherapy implant techniques continue to improve and the importance of appropriate dosimetric target coverage continues to disseminate, these results should become
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Conflict of interest: none.