Hypofractionated dose painting IMRT for intermediate to high risk localised prostate cancer: boosting to 68 Gy in 20 fractions


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Joachim Chan1,Thelma Rowntree1,Laura Howard1,John NH Brunt1,Isabel Syndikus1
1Clatterbridge Cancer Centre NHS Foundation Trust

Abstract

Background

CHHiP trial has shown non-inferiority of 60Gy/20# compared to conventional 74Gy/37# for biochemical control at 5 years. Prostate dose-painting (boosting intra-prostatic tumour volumes) may improve biochemical relapse-free survival similar to whole organ dose-escalation, whilst avoiding increased associated toxicity. We present dose painting radiotherapy results for a phase II trial: intermediate to high risk patients treated with 60Gy/20# and concurrent 68Gy boost to intra-prostatic lesions.

Method

Patients had a multi-parametric MRI and 18F choline PET/CT prior to androgen deprivation (ADT), and planning MRI and CT following 2 months' ADT. Registration used fiducial markers. Intra-prostatic boost volumes were outlined by combining visually identified lesions on MRI and PET. Rotational IMRT planning was performed using Pinnacle software (Philips). Patients with unexpected regional lymph node PET uptake also received pelvic radiotherapy with boost. Toxicity evaluation was by CTCv.4.0 and RTOG. Endpoint was acute toxicity at 18 weeks.

Results

53 patients have been planned and treated, 5 with concurrent pelvic radiotherapy. Median age and PSA was 67 years (range 50-77) and 10.0ng/ml (3.9-39.4). 13 patients had intermediate and 40 had high risk disease. Median prostate boost volume for all patients was 13.5ml (range 8.1 to 33.1). Median prostate dose excluding boost was 61.0Gy. Median intra-prostatic boost dose was 68.1Gy. In the pelvic radiotherapy group, lymph node dose of 45 Gy with boost to 50 Gy was achievable, as were normal tissue dose volume constraints (bladder, urethra, rectum and bowel). Grade 2 urinary toxicity at baseline was 12%, increasing to 26% during radiotherapy and 1 patient had grade 3 toxicity (RTOG). At week 18, the results were back to baseline. Bowel toxicity was modest: 12% grade 1 and 5% grade 2 during radiotherapy, 5% with grade 1 and 2 at 18 weeks.

Conclusion

Hypofractionated dose painting schedule of 60Gy/20# with 68Gy boost to intra-prostatic lesions was well tolerated.