PV QA 1 - Poster Viewing Q&A 1
Purpose/Objective(s): Multiple studies have reported on the efficacy and safety of prostate SBRT for the treatment of prostate cancer (PCa), but none has evaluated SBRT in the context of a periprostatic hydrogel spacer (SpaceOAR; Augmenix) use. We herein report our experience of SBRT with hydrogel to show safe and effective delivery of SBRT.
Materials/Methods: Men with low- or intermediate-risk PCa undergoing SpaceOAR placement followed by linear accelerator-based SBRT to 3625 cGy in 5 fractions at a single institution were included. Patients were evaluated during and after treatment. Follow-up was scheduled at 1 and 4 months after SBRT. Post-treatment PSA measurements were obtained at 4 months, followed by every 3 months thereafter. Acute toxicity was documented per RTOG/EORTC criteria.
Results: A total of 36 men were treated per RTOG 0938 from 2015 to 2017. Median PSA at time of diagnosis was 7.1 (2.7-19.5) ng/ml. Patients underwent SpaceOAR placement a median of 33 (14-56) days prior to SBRT. Median follow-up was 10 (0-29) months, with no PSA failure as per Phoenix definition. Five men with unfavorable intermediate risk PCa received androgen-deprivation therapy. Mean prostato-rectal distance following hydrogel-placement measured 10.25±4.2 mm at prostate midgland. No on-treatment genitourinary (GU) and rectal (GI) toxicity was reported in 44% and 75% of patients, respectively. In 34% of patients, grade 2 GU toxicity (urinary urgency or dysuria) occurred. Of these, 60% experienced symptom improvement or resolution within one month, with the remainder still requiring medication at 6 months. Of men with no or mild GU toxicity during treatment (66%), one third developed grade 2 GU toxicity within one month that persisted for at least six months. At one year, 25% of patients still required medical management for GU symptoms. No toxicity grade ≥3 was recorded. Two men experienced both grade 2 GU and GI toxicity (dysuria, urinary hesitancy, and tenesmus) that resolved prior to completing treatment with methylprednisolone. Following treatment, all men with GI toxicity (grade 1 occurred in 28%, grade 2 in 4%) experienced resolution of symptoms within one month.
Conclusion: Periprostatic hydrogel placement followed by prostate-SBRT resulted in minimal GI toxicity. Nearly half of all men developed grade 2 GU toxicity either during or within one month of treatment. No early PSA failures were recorded. These results indicate that SBRT with periprostatic spacer is a well-tolerated, safe, and convenient treatment option for localized PCa.
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