The spacer resulted in clinically and statistically significant reduction in rectal doses for all patients. Advances in knowledge: This is one of the first studies to investigate the efficacy of a hydrogel spacer in prostate SABR treatments. Observed dose sparing of the rectum is predicted to result in meaningful clinical benefit.
The Inhibitor of Apoptosis proteins (IAPs) are a family of proteins that are mainly known for their anti-apoptotic activity and ability to directly bind and inhibit caspases. Recent research has however revealed that they have extensive roles in governing numerous other cellular processes.IAPs are known to modulate ubiquitin (Ub)-dependent signaling pathways through their E3 ligase activity and influence activation of nuclear factor B (NFB). In this review, we discuss the involvement of IAPs in individual hallmarks of cancer and the current status of therapies targeting these critical proteins.
248 Background: Stereotactic Ablative Radiotherapy (SABR) is increasingly used to treat low/intermediate risk localised prostate cancer (PCa). However, data on SABR +/- pelvic nodal irradiation (PNI) in high-risk disease is limited to single institution, single-arm studies. The Stereotactic Prostate Radiotherapy (SPORT) trial examined the feasibility of delivering a randomised trial of SABR ± PNI. The composite primary endpoint to determine feasibility comprised: recruitment rate, technical feasibility, acute toxicity (CTCAE v4.0) and quality of life (QoL)(EPIC). Secondary and exploratory endpoints including late toxicity (RTOG) and QoL and potential biomarkers of toxicity (plasma citrulline and DNA damage in circulating lymphocytes) are also presented. Methods: Men with localised PCa demonstrating one of T3a, Gleason score ≥4+3 or PSA>20 were eligible. T3b and T4 disease were excluded. 30 participants were randomised 1:1 to prostate SABR (P-SABR) or prostate and pelvis SABR (PPN-SABR). The prostate and proximal 1-2cm seminal vesicles received 36.25 Gy in 5 fractions over 29 days (prostate CTV 40Gy). The PPN-SABR arm also received 25 Gy in 5 fractions to the pelvic nodes. All patients had fiducial markers and a rectal spacer gel in-situ. As initial toxicity rates were low, the final 10 men received an additional integrated boost to the dominant intraprostatic lesion of up to 50 Gy, irrespective of randomisation. Results: Feasibility was demonstrated. The target recruitment of 30 men was met (83% high risk). Treatment, including an integrated boost plus PNI, was achievable using strict normal tissue constraints. Acute toxicity and QoL were acceptable (Table: Grade≥2 GU 7%, 27% and GI 0%, 7%; minimal clinically important change (MCIC) in EPIC urinary 40%, 60% and bowel score 33%, 47% in P and PPN arms respectively). At median follow up of 30 months (range 18-42 months), late toxicity and QoL were acceptable (Grade≥2 GU 7%, 20% and GI 0%, 13%; MCIC in EPIC urinary 33%, 67% and bowel score 33%, 67% in P and PPN arms respectively). All toxicity was ≤ grade 2 with the exception of one late grade 3 GU toxicity occurring in the PPN arm. Serum citrulline, a marker of small bowel function, trended towards lower levels in the PPN arm, in keeping with a significantly higher dose delivered to the small bowel in this arm. DNA damage foci in circulating lymphocytes increased at 1 hour after radiation. Foci count and repair correlated to toxicity measures will be presented. Conclusions: A randomised clinical trial comparing P-SABR to PPN-SABR is feasible. There was a suggestion of increased toxicity with PPN-SABR, but this remained acceptable. This data will inform a UK multi-centre phase 2 study. Clinical trial information: NCT03253978 . [Table: see text]
Purpose Boosting dominant intra-prostatic lesions (DILs) has the potential to increase the therapeutic ratio in prostate cancer radiotherapy. In this study, employing 5-fraction stereotactic ablative radiotherapy (SABR) volumetric modulated arc therapy (VMAT) to deliver 40 Gy to the prostate clinical target volume (CTV) while boosting the DIL up to 50 Gy was evaluated for patients before and after rectal spacer insertion. Materials and methods 24 Computed Tomography (CT) scans of 12 prostate cancer patients with unfavourable intermediate or high risk prostate cancer were employed in this study. At least two treatment plans were generated for each patient to compare pre- and post-spacer insertion plans. Plans were evaluated for target coverage, organs-at-risk doses, and the achievable boost dose level. Results The CTV coverage was significantly better in plans with a spacer, V40Gy 98.4% versus 97.0% (p = 0.012). Using spacers significantly reduced rectal dose in all 12 patients in this study. It was possible to boost DIL to 50 Gy to without violating dose constraints in 6 of 12 patients and to 47.5 Gy in 3 patients post-spacer insertion. For 3 patients (25%) it was not possible to boost DIL above 45 Gy even with a spacer in situ. Without a spacer, for 6 patient (50%) clinically acceptable plan were only achieved when the DIL dose was lowered to 45 Gy. In five of these 6 patients the dose limiting structure was the urethra (urethra planning risk volume V45Gy [cc] ≤ 0.1 cc constraint). Conclusions Clinically acceptable plans for 5 fraction SABR, 40 Gy to the prostate CTV, with a SIB to DIL (45–50 Gy) were achieved. The boost dose achieved was DIL location dependent and primarily affected by DIL’s proximity to the urethra. Compared to plans before spacer insertion, higher DIL dose were achieved with spacer in situ for 25% of the patients. Moreover, significant reduction in rectal dose and better target coverage were also achieved for all patients with spacers in situ.
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