Dataset Information

Radiation Dose to the Rectum With Definitive Radiation Therapy and Hydrogel Spacer Versus Postprostatectomy Radiation Therapy.

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.

SUBMITTER: Yang DX

PROVIDER: S-EPMC7718530 | biostudies-literature | 2020 Nov-Dec

REPOSITORIES: biostudies-literature

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Radiation Dose to the Rectum With Definitive Radiation Therapy and Hydrogel Spacer Versus Postprostatectomy Radiation Therapy.

Yang Daniel X DX Verma Vivek V An Yi Y Yu James B JB Sprenkle Preston C PC Leapman Michael S MS Park Henry S HS

Advances in radiation oncology 20200915 6

<h4>Purpose</h4>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 def ...[more]

PMID: 33305083

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Project description:PurposeTo assess the efficacy of placing a polyethylene glycol (PEG) spacing hydrogel in patients undergoing proton beam radiation therapy for prostate cancer. This study also aims to assess the effect on rectal radiation dose of prostate-rectum separation in various anatomic planes.Methods and materialsSeventy-two consecutive prostate cancer patients undergoing conventionally fractionated pencil beam scanning proton radiation therapy with and without hydrogel placement were compared. Magnetic resonance images taken after hydrogel placement measured prostate-rectum separation and were correlated to rectal dosing and rectal toxicity. Univariate analysis of clinical variables and radiation dosing was conducted using nonparametric Wilcoxon rank-sum test with continuity correction between groups (hydrogel spacer vs controls). Spearman's rank correlation coefficient assessed relationships between the various anatomic dimensions of perirectal space and rectal radiation dosing.ResultsFifty-one patients had hydrogel placement before therapy and 21 did not. There was a 42.2% reduction in rectal dosing (mL3 rectum) in hydrogel patients (P < .001). Increasing midline sagittal lift resulted in a greater mitigation of total rectal dose (P = .031). The degree of prostate surface area coverage on coronal plane did not correlate with further reductions in rectal radiation dose (P = .673). Patients who had PEG hydrogels placed reported more rectal side effects during treatment compared with those patients who did not (35.3% vs 9.5%, P = .061). At median 9.5-month follow-up, there was no difference in reporting of grade ≤2 rectal toxicity between the 2 groups (7.7% vs 7.1%, P = .145).ConclusionsPolyethylene glycol hydrogel placement before pencil proton beam radiation therapy for prostate cancer reduced rectal radiation dose. The most important factor reducing total rectal dose was the degree of sagittal midline separation created by the PEG hydrogel. This is the largest study with the longest follow-up to investigate hydrogel placement in the proton beam radiation setting.

Project description:PurposeThis phase 1 trial aimed to identify the maximally tolerated hypofractionated dose schedule for postoperative radiation therapy (PORT) after radical prostatectomy. Secondary objectives included biochemical control and quality of life (QoL) measures.Methods and materialsPatients were treated on 1 of 3 dose levels (DLs): 56.4 Gy in 20 fractions (DL1), 51.2 Gy in 15 fractions (DL2), and 44.2 Gy in 10 fractions (DL3). Treatment was delivered to the prostate bed without pelvic nodal irradiation. Dose escalation followed a standard 3 + 3 design with an expansion for 6 additional patients at the maximally tolerated hypofractionated dose schedule. Acute dose-limiting toxicity (DLT) was defined as grade 3 toxicity lasting >4 days within 21 days of PORT completion; late DLT was defined as grade 4 gastrointestinal (GI) or genitourinary (GU) toxicity.ResultsBetween January 2018 and August 2019, 15 patients underwent radiation treatment: 3 on DL1, 3 on DL2, and 9 on DL3. The median follow-up was 24 months. There were no DLTs, and the maximally tolerated hypofractionated dose schedule was identified as DL3. Two of the 15 patients (13.3%) experienced biochemical failure (prostate-specific antigen >0.1). Ten of 15 patients (67%) had grade 2+ acute toxicities, consisting of transient GI toxicities. Three patients experienced late grade 2+ GI toxicity, and 5 patients experienced late grade 2+ GU toxicity. Late grade 3 GU toxicity occurred in 2 patients. There were no grade 4+ acute or late toxicities. There were no significant differences in GI measures of QoL, however, there was an increase in GU symptoms and corresponding decrease in GU QoL between 12 and 24 months.ConclusionsThe maximum tolerated hypofractionated dose schedule for hypofractionated PORT to the prostate bed was determined to be 44.2 Gy in 10 daily fractions. The most frequent clinically significant toxicities were late grade 2+ GU toxicities, which corresponded to a worsening of late GU QoL.

Project description:PurposeWe assessed the feasibility and theoretical dosimetric advantages of an injectable hydrogel to increase the space between the head of the pancreas (HOP) and duodenum in a human cadaveric model.Methods and materialsUsing 3 human cadaveric specimens, an absorbable radiopaque hydrogel was injected between the HOP and duodenum by way of open laparotomy in 1 case and endoscopic ultrasound (EUS) guidance in 2 cases. The cadavers were subsequently imaged using computed tomography and dissected for histologic confirmation of hydrogel placement. The duodenal dose reduction and planning target volume (PTV) coverage were characterized using pre- and postspacer injection stereotactic body radiation therapy (SBRT) plans for the 2 cadavers with EUS-guided placement, the delivery method that appeared the most clinically desirable. Modeling studies were performed using 60 SBRT plans consisting of 10 previously treated patients with unresectable pancreatic cancer, each with 6 different HOP-duodenum separation distances. The duodenal volume receiving 15 Gy (V15), 20 Gy (V20), and 33 Gy (V33) was assessed for each iteration.ResultsIn the 3 cadaveric studies, an average of 0.9 cm, 1.1 cm, and 0.9 cm HOP-duodenum separation was achieved. In the 2 EUS cases, the V20 decreased from 3.86 cm3 to 0.36 cm3 and 3.75 cm3 to 1.08 cm3 (treatment constraint <3 cm3), and the V15 decreased from 7.07 cm3 to 2.02 cm3 and 9.12 cm3 to 3.91 cm3 (treatment constraint <9 cm3). The PTV coverage improved or was comparable between the pre- and postinjection studies. Modeling studies demonstrated that a separation of 8 mm was sufficient to consistently reduce the V15, V20, and V33 to acceptable clinical constraints.ConclusionsCurrently, dose escalation has been limited owing to radiosensitive structures adjacent to the pancreas. We demonstrated the feasibility of hydrogel separation of the HOP and duodenum. Future studies will evaluate the safety and efficacy of this technique with the potential for more effective dose escalation using SBRT or intensity-modulated radiation therapy to improve the outcomes in patients with unresectable pancreatic cancer.

Dataset Information

Radiation Dose to the Rectum With Definitive Radiation Therapy and Hydrogel Spacer Versus Postprostatectomy Radiation Therapy.

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Radiation Dose to the Rectum With Definitive Radiation Therapy and Hydrogel Spacer Versus Postprostatectomy Radiation Therapy.

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