Impact of small prostate size on postimplant prostate dosimetry: analysis of a large community database

Achieving high-quality permanent interstitial brachytherapy in smaller prostates is thought to be more difficult than in larger glands. This study evaluates 4547 implants in a large community database to test this hypothesis.

From January 2003 to October 2010, 4547 prostate brachytherapy implants from a large community database were analyzed. The cohort was divided into three groups based on size, namely smaller (<30cm(3), n=1301), medium (30-40cm(3), n=1861), and large (>40cm(3), n=1385). Postimplant dosimetry, including D90, V100, and V100 by prostate sector, was performed for each implant. Comparison of mean V100 among small, medium, and larger prostate volume cohorts was performed using a one-way analysis of variance test.

For the overall cohort, the D90 was 105% and 104% for monotherapy and boost, respectively. Mean D90 for small prostates was 106% and 104% for monotherapy and boost, respectively. Mean V100 for small prostates was 91.1% and 90.0%, respectively. Coverage for small prostates was as good or slightly better than larger glands. V100 by prostate sector revealed that there were no sectors for which smaller glands had significantly inferior coverage compared with larger glands.

Although smaller prostates may in some respects be more technically difficult to implant than larger glands, a review of community-based brachytherapists reveals that with current implant techniques, good quality implants are readily achievable in men with smaller glands.