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Adv Radiat Oncol. 2020 Sep 15;5(6):1225-1231. doi: 10.1016/j.adro.2020.08.015. eCollection 2020 Nov-Dec.
ABSTRACT
PURPOSE: Management options for localized prostate cancer include definitive radiation therapy (RT) or radical prostatectomy, with a subset of surgical patients requiring adjuvant or salvage RT after prostatectomy. The use of a peri-rectal hydrogel spacer in patients receiving definitive RT has been shown to reduce rectal doses and toxicity. However, in the postprostatectomy setting, a hydrogel spacer cannot be routinely placed. Therefore, we sought to compare rectal dosimetry between definitive RT with a hydrogel spacer versus postoperative RT.
METHODS AND MATERIALS: We identified patients with prostate cancer who underwent conventionally fractionated RT. Rectal dosimetry was evaluated between 2 groups: definitive RT with a hydrogel spacer (79.2 Gy, group 1) and postoperative RT (70.2 Gy, group 2). Rectal dosimetry values were tabulated and compared using Mann-Whitney U test. We implemented a Bonferroni correction to account for multiple comparisons (threshold P < .005). Linear regression analysis evaluated predictors of candidate rectal dose-volume parameters.
RESULTS: We identified 51 patients treated during years 2017 to 2018; 16 (31%) and 35 (69%) patients were included in groups 1 and 2, respectively. The rectal volume receiving ≥65 Gy (V65) was significantly lower in group 1 (median, 2.1%; interquartile range, 0.9%-3.1%) than in group 2 (10.7%, 6.6%-14.5%) (P < .001). Use of a hydrogel spacer in the definitive setting was independently associated with lower V65 (P < .001). Similar results were found for V60, V55, V50, and V45 (P < .005 for all).
CONCLUSIONS: Rectal dosimetry is more favorable for definitive RT (79.2 Gy) with a hydrogel spacer compared with postoperative RT (70.2 or 66.6 Gy). This may inform shared decision-making regarding primary management of prostate cancer, especially among patients at high risk of needing postoperative RT after prostatectomy.
PMID:33305083 | PMC:PMC7718530 | DOI:10.1016/j.adro.2020.08.015
