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result(s) for
"Dosimetric gain"
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Long-term evaluation of the safety of a rectal-prostate spacer, the ProSpace® balloon, in patients treated with radiotherapy for prostate cancer
2024
A
bstract
Background
Due to the close proximity of the prostate and rectum, rectal toxicity remains a major problem in patient treated by radiotherapy for prostate adenocarcinoma. One method of increasing the distance between the prostate and the rectum is to use a spacer implanted into the rectoprostatic space. This report describes the long-term outcomes obtained with a new ballon spacer.
Methods
Patients treated with curative radiotherapy for low- or intermediate-risk prostate adenocarcinoma, who underwent insertion of the ProSpace® (BioProtect Ltd, Tzur Yigal, Israel) rectal-prostate balloon spacer, were included. The main objective was to evaluate the dosimetric benefit of the spacer for OARs. The secondary objectives were to evaluate the feasibility and tolerability of ProSpace® balloon placement and to evaluate its long-term therapeutic efficacy and tolerance.
Results
Between October 2013 and March 2015, 16 patients were enrolled in the Pasteur Clinic, Toulouse, France. The median follow-up was 85.5 months. From top to bottom, the space created was a mean of 16.3 mm (range: 11–20.5 mm) at the base of the prostate, 12.1 mm (range: 4–16 mm) at the middle and 8.9 mm at the apex (range: 5–15 mm). On average, rectal volumes receiving a dose of 70 Gy, 60 Gy and 50 Gy were significantly lower after balloon implantation: -4.81 cc (1.5 vs. 6.3;
p
< 0.0005), -8.08 cc (6.4 vs. 14.5;
p
= 0.002) and -9.06 cc (16.7 vs. 25.7;
p
= 0.003), respectively. There were significant differences in coverage after balloon implantation: Median V95% (
p
< 0.0005), median Dmin (
p
= 0.01) and median V98% (
p
< 0.001) were higher after balloon implantation. At 5 years, cumulative gastrointestinal toxicity was grade 1 in 6% (1/16 patients). No toxicity of grade 2 or higher was found. At 5 years, no urinary toxicity grade 3 or 4 toxicity was found. The QoL was not deteriorated.
Conclusions
The use of the ProSpace® balloon seems to be well accepted by patients, allowing a double dosimetric gain: a decrease in doses received by the rectum and an improvement in the coverage of the high-risk PTV. The long-term gastrointestinal toxicity remains low and QoL is preserved in all treated patients.
Journal Article
Can reducing planning safety margins broaden the inclusion criteria for lung stereotactic ablative body radiotherapy?
2021
Introduction Stereotactic ablative body radiotherapy (SABR) is currently indicated for inoperable, early‐stage non‐small cell lung carcinoma (NSCLC). Advancements in image‐guidance technology continue to improve treatment precision and enable reductions in planning safety margins. We investigated the dosimetric benefits of margin reduction, its potential to extend SABR to more NSCLC patients and the factors influencing plan acceptability. Methods This retrospective analysis included 61 patients (stage IA–IIIA) treated with conventional radiotherapy. Patients were ineligible for SABR due to tumour size or proximity to organs at risk (OAR). Using Pinnacle auto‐planning, three SABR plans were generated for each patient: a regular planning target volume margin plan, a reduced margin plan (gross tumour volume GTV+3 mm) and a non‐margin plan. Targets were planned to 48Gy/4 or 50Gy/5 fractions depending on location. Plans were compared in terms of target coverage, OAR doses and dosimetric acceptability based on local guidelines. Predictors of acceptability were investigated using logistic regression analysis. Results Compared to regular margin plans, both reduced margin and non‐margin plans resulted in significant reductions to almost all dose constraints. Dose conformity was significantly worse in non‐margin plans (P < 0.05) and strongly correlated with targets’ surface area/volume ratio (R2 = 0.9, P < 0.05). 26% of reduced margin plans were acceptable, compared to 54% of non‐margin plans. GTV overlap with OARs significantly affected plan acceptability (OR 0.008, 95% CI 0.001–0.073). Conclusion Margin reduction significantly reduced OAR doses enabling acceptable plans to be achieved for patients previously excluded from SABR. Indications for lung SABR may broaden as treatment accuracy continues to improve; further work is needed to identify patients most likely to benefit. Upcoming image guidance and tumour tracking technologies promise to reduce radiotherapy planning safety margins. Here, we investigate the dosimetric gains of margin reductions and their potential to extend stereotactic ablative body radiotherapy (SABR) to more lung cancer patients.
Journal Article