ESTRO38 Congress Report

Clinical

3. PROSTATE Hyprofractionated vs conventional radiotherapy for prostate cancer: 7 yr results from the HYPRO trial (E38-1311)

Luca Incrocci, Kim C. de Vries, Ruud C. Wortel, Esther Oomen-de Hoop, Wilma D. Heemsbergen, Floris J. Pos

Erasmus MC Cancer Institute, Rotterdam, The Netherlands Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands

Context of the study In the early 90’s multiple studies hypothesised an α/β for prostate cancer as low as 1.5 Gy. This opened the way for several hypofractionation trials such as the CHiPP, PROFIT, RTOG 0415 and HYPRO. These trials tried to answer the question whether it is safe to use hypofractionation in low and intermediate-high risk localized prostate cancer. Long term results (5-10 years) show that hypofractionation is safe for both outcome and toxicity. National and international guidelines consider hypofractionation now as the new standard of care for localized prostate cancer. Overview of abstract Patients with intermediate-high risk prostate cancer were randomly assigned to either hypofractionated radiotherapy (64·6 Gy, 19 fractions/3·4 Gy, three fractions/week) or conventionally fractionated radiotherapy (78·0 Gy, 39 fractions/2·0 Gy, five fractions/week). The HYPRO trial did not show inferiority in toxicity, nor superiority in relapse free survival at 5 year. The use of long-termandrogen deprivation therapy in 66% of the patients might have obscured a potential benefit of hypofractionated radiotherapy at 5-year follow-up. We update here the outcome results at 7 years. What were the three main findings of your research? 1. At 7-year follow-up relapse free survival and overall survival demonstrated no difference between hypofractionation versus conventional fractionation. 2. None of the examined subgroups seemed to have an advantage of hypofractionation in term of relapse free survival. 3. A trend toward better local control was found after hypofractionation. Local control was statistically significant superior in patients with Gleason ≥8 tumors. What impact could your research have? The HYPRO trial is the biggest randomized trial which included intermediate and high risk prostate cancer, showing its safety in terms of relapse free survival in this group of patients. Our results show a better local control in patients with Gleason score ≥8 prostate cancer, although the study was not powered for this question. In this group of patients it may be beneficial to give a radiobiological higher dose to the prostate. Due to novel imaging techniques at present it is easier to diagnose patients who have only local disease. Therefore, excluding N+M+ patients, this effect might even be bigger. Is this research indicative of a bigger trend in oncology? The randomized hypofractionation trials have opened the trend to reduce the number of fractions in external beam

radiotherapy for prostate cancer, not only convenient for the patients but also enabling to make better use of hospital resources. Multiple new (ultra)hypofractionation trials are now being conducted, such as the HYPO-RT-PC and the PACE-B trial, that reduce the number of fractions to 4 or 5. The preliminary results of these trials, mainly in low and intermediate risk patients, are promising. In the past the question has been how low the α/β ratio for prostate cancer might be. Now, the question is how far we can go in reducing the number of fractions.

CLINICAL | Congress report

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