ProSPER-82: A prospective phase II trial investigating SpaceOAR hydrogel in patients with prostate cancer receiving dose escalated radiotherapy to 82Gy trial-a radiotherapy planning perspective of clinical implementation.

Abstract

Aim: ProSPER-82: A Prospective Phase II Trial Investigating SpaceOAR® Hydrogel in Patients with Prostate Cancer Receiving Dose Escalated Radiotherapy to 82Gy (ProSPER-82) aims to use Intensity Modulated Radiotherapy (IMRT), following the insertion of SpaceOAR®, to dose escalate men undergoing treatment for clinically localised prostate cancer, aiming to treat to doses of 82Gy in 41 fractions (1). This paper will discuss rectal wall doses achieved for the first 10 patients pre and post. Methods and materials: Additional scans and IMRT plans are required for the study, as described in the trial schema (Fig. 1). A computed tomography (CT) scan pre SpaceOAR® insertion is acquired, in the treatment position (supine, arms on chest, two square sponges under the head, pelvic board with personalised lower half body vacfix). Skin tattoos are placed at setup reference points during this appointment. SpaceOAR® is inserted into the retro prostatic space, introducing a physical gap between the prostate and Results: ARJ wall and rectal wall doses were compared for the pre SpaceOAR® 78Gy plan and the post SpaceOAR® 78Gy and 82Gy plans, at the dose points that current departmental protocol specifies as dose constraints. Figure 3 displays the mean doses for the ARJ wall. The minimum (Fig. 4) and maximum (Fig. 5) doses achieved within the cohort at each dose point were also compared, and the same trend was clearly seen, where in every case analysed, the post SpaceOAR® plans delivered less dose to Conclusion: A comparison of the first 10 patients enrolled into the ProSPER 82Gy trial confirm that SpaceOAR® allows for dose escalation to 82Gy in 41 fractions whilst delivering significantly lower doses to the rectal wall and ARJ wall.