ESTRO 2024 Congress Report

The ESTRO 2024 congress delivered interesting findings in the field of stereotactic body radiotherapy (SBRT) for prostate cancer (PCa). Professor Piet Ost presented the results of the trial of salvage treatment oligorecurrent nodal PCa metastases (STORM), which is a phase II randomised, superiority trial. Patients diagnosed with PET-detected pelvic nodal oligorecurrence after radical local treatment were randomised into two arms: A (metastasis-directed therapy (MDT) + six- months of androgen-deprivation therapy (ADT)) or B (external elective nodal radiotherapy (ENRT) + MDT + six months of ADT). In the case of radiotherapy, SBRT (3x10Gy) was used for arm A, with a simultaneous integrated boost in arm B. Surgery was the MDT choice in only 11 patients (6%). The primary endpoint was metastasis-free survival (MFS) and the secondary endpoint was late toxicity. A total of 196 patients were randomly assigned to MDT or to ENRT. Patients were diagnosed with a single node, two nodes or three to five nodes in 110 (58%), 49 (26%) and 28 (15%) patients respectively. The biochemical recurrence-free survival (RFS) rate was 47% for MDT vs. 69% for ENRT (hazards ratio (HR): 0.55, 95% confidence interval (CI): 0.34-0.87, p=0.01). The regional RFS was 70% for MDT vs. 90% for ENRT (HR: 0.32, 95%CI 0.15-0.67, p=0.002). Data maturity for MFS is awaited; nevertheless, the MDT vs. ENRT debate seems to have been concluded in favour of ENRT in this context.

Dr Alison Tree reported the acute toxicity results from the phase III PACE-C trial, in which SBRT was compared with moderate hypofractionation (MHRT) in patients with intermediate- or high-risk PCa. A total of 1208 patients were randomised (1:1) to SBRT or MHRT; all were planned to receive six to 12 months of ADT. The SBRT dose was 36.25Gy/five fractions in one to two weeks, whereas MHRT was 60Gy/20 fractions in four weeks. Toxicity assessed as Radiation Therapy Oncology Group level G2+ was not significantly different for gastrointestinal (GI) or genitourinary (GU) events. There were differences in G2+ GI toxicity in terms of common terminology criteria for adverse events: MHRT 9.9% vs. SBRT 15.4% (p=0.004) but not GU: MHRT 28.2% vs. SBRT 33.3% (p=0.053). Efficacy and incidence of late toxicity data are awaited.

Dr Cédric Draulans presented the five-year results of the trial of extreme hypofractionated focal lesion ablative microboost in PCa (hypo-FLAME) trial, which evaluates the usefulness of focal boost SBRT in men with intermediate- and high-risk PCa. A total of 100 patients were included in this phase II trial. A majority (75%) of the patients were classified as having high-risk PCa, and ADT was prescribed to 62% of all the patients. All were treated with doses of 35Gy in five weekly fractions with an integrated boost of up to 50Gy to the tumours defined according to multi-parametric MRI. Dose constraints to the normal tissues were prioritised over the aimed boost dose, and the median mean dose delivered to the visible tumour nodule(s) was 44.7Gy. The estimated five-year biochemical disease-free survival rate (95% CI) was 93% (86-97%). The prevalence of G2+ GU and GI toxicity was 12% and 4%, respectively. The reported cumulative incidence of late grade 3 toxicity was 2% for GU and 1% for GI toxicity.

The sessions on re-irradiation were also of particular interest, especially one session that was dedicated to prostate cancer and another to innovations in the designs of re-irradiation clinical trials. The community's efforts must continue to provide high-quality and prospective data.

Prof David Pasquier MD, PhD

Academic Department of Radiation Oncology, Centre Oscar Lambret

Lille University, France