PURPOSE: To characterize prostate swelling and dosimetry in patients with small prostate volumes (PVs) undergoing brachytherapy.
METHODS AND MATERIALS: We studied 25 patients with PV < 25 cc (range, 15.1-24.8) and 65 patients with PV ≥25 cc (range, 25.0-66.2) based on three-dimensional ultrasound contours who underwent brachytherapy monotherapy with intraoperative planning. Postoperative Days 1 and 30 dosimetry was done by CT-MRI fusion.
RESULTS: Small PVs had greater Day 1 swelling than large PVs (32.5% increase in volume vs. 23.7%, p = 0.04), but by Day 30, swelling was minimal and not significantly different (p = 0.44). Small PVs had greater seed and needle densities at implant (p < 0.001). Rectal and urethral doses were nearly identical by Day 30 (small PV rectum receiving 100% of the prescription dose [145 Gy] [V100] = 0.32 cc; large PV rectum V100 = 0.33 cc, p = 0.99; small PV urethra receiving 150% of the prescription dose [145 Gy] [V150] = 0.20, large PV urethra V150 = 0.20, p = 0.91). Swelling at Day 1 created some cool implants (rate dose that covers 90% of the prostate volume [D90 < 140 Gy = 12.0% and 9.4% for the small and large PV groups, respectively, p = 0.71), but Day 30 planning target volume coverage was excellent (rate D90 < 140 Gy = 0% for both groups).
CONCLUSIONS: Although smaller prostates have greater Day 1 swelling, good Day 30 dosimetry can be achieved, making them excellent candidates for 125I seeds (half-life [t½] = 60 days). Smaller prostates may be suboptimal for shorter t½ sources such as 131Cs (t½ = 9.7 days), in which the majority of the dose may be delivered to an edematous gland, unless the planning is adjusted to anticipate the edema.
Written by:
Kovtun KA, Wolfsberger L, Niedermayr T, Sugar EN, Graham PL, Murciano-Goroff Y, Beard C, D'Amico AV, Martin NE, Orio PF, Nguyen PL. Are you the author?
Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
Reference: Brachytherapy. 2013 Aug 1. pii: S1538-4721(13)00282-1.
doi: 10.1016/j.brachy.2013.05.006
PubMed Abstract
PMID: 23911279
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