ESTRO38 Congress Report

Introduction Clinical Track

The seven-year results from the Dutch HYPRO trial of conventional (39 fraction of 2 Gy) versus hypofractionated (19 fractions of 3.4 Gy) radiotherapy for intermediate- to high-risk prostate cancer showed equivalence for relapse- free and overall survival, and suggested a local control benefit for hypofractionation in patients with Gleason > 7 tumours. The 10-year results of the Austrian ABCSG 8A trial on antihormonal treatment with or without whole breast irradiation (WBI) in low-risk breast cancer confirmed that WBI significantly improved local control and DFS. Finally, themulticenter Dutch/Belgiumphase 3 trial on prophylactic cranial irradiationwith or without hippocampus avoidance in patients with small cell lung cancer provided interesting first results on neurocognitive functions and brain recurrences. Claus Rödel Chair, SAG Clinical Radiotherapy

This year’s ESTRO annual congress featured more than a dozen prospective, randomised phase II or III clinical trials presented either at the randomised clinical trials proffered paper session or the late- breaking proffered paper session. The sheer number is impressive and highlights the ongoing success

CLAUS RÖDEL

of clinicians throughout ESTRO countries to provide high- level evidence for the use of radiation therapy alone or as a treatment component withinmultimodality approaches. Moreover, results of innovative early clinical trials (phase I and II) combining radiotherapy with targeted agents, including immune modulation, were presented for various tumor entities. Technical advances have been made for MR-guided adaptive radiation and high-precision radiotherapy, including SBRT, particularly in the treatment of oligometastatic disease. Five of the prospective randomised clinical trials – obviously a subjective selection – will be presented and discussed in more detail in the following pages. These include an innovative, double-blind randomised trial from the UMCG University Medical Center Groningen, The Netherlands. This group tested parotid gland stem cells-sparing IMRT for head and neck patients, based on previous findings in mice, rats, and humans, which showed that stem and progenitor cells mainly reside in the region of the parotid gland containing the major ducts (van Luijk et al., 2015). The Groningen group subsequently hypothesized that reducing dose to these high stem cell density regions may prevent or alleviate xerostomia. Although they could not show that parotid gland stimulated salivary flow at 12 months (primary endpoint) was significantly improved in the experimental stem cell sparing IMRT arm, this study is a prime example of excellent, hypothesis-driven, well- designed and executed clinical research. Large national and international groups reported their (updated) randomised data on rectal, breast, prostate, and lung cancer at the ESTRO 38 meeting. Three abstracts reported randomised data on rectal cancer therapy. These include the five-year results of the French GRECCAR2 organ preservation trial of chemoradiotherapy followed by local excision versus total mesorectal excision surgery in low T2/T3 rectal cancer patients, supporting the long-term oncologic safety of limited surgery for selected rectal cancer patients with good response after chemoradiotherapy. The GRECCAR2 study is further described in the next section. Bujko et al. provided an update of the Polish randomised phase III study of total neoadjuvant therapy (TNT), i.e. 5x5 Gy followed by consolidation chemotherapy prior to radical surgery, versus long-course chemoradiotherapy in patients with fixed T3 or T4 rectal cancer. After seven years of follow- up, no significant differences were noted for local and distant control, disease-free (DFS) and overall survival. The German Rectal Cancer Study Group (Fokas et al.) presented first results of the randomised CAO/ARO/AIO-12 phase II trial on TNT sequences: Upfront chemoradiotherapy followed by consolidation chemotherapy was less toxic and more effective in terms of pathological complete response rates than the sequence induction chemotherapy followed by chemoradiotherapy and surgery.

Congress report | CLINICAL

5