Speaker
Description
The aim of the Danish randomized HERAN2 trial is to examine if heterogeneous and hypofractionated proton radiotherapy can improve survival compared with X-ray radiotherapy in patients with locally advanced NSCLC who are not candidates for standard chemoradiotherapy. Patients selected for proton therapy are treated at the Danish Center for Particle Therapy and hereby, we present our treatment strategy and experience from the first pilot patients in the protocol.
The patients are positioned in standard fixation with arms up when possible, and for all patients, a 4DCT scan without contrast, a 3DCT with contrast and a PET-CT scan are obtained for treatment planning. Delineation and treatment planning is performed on the average scan. Respiratory motion is included by delineation of the gross tumour volume (GTV) on all phases of the 4DCT with a subsequent rigid accumulation into an iGTV on the average phase. The iCTV is hereafter defined by a 5 mm isotropic margin to the iGTV.
The gross tumour volumes of primary tumours (GTV-T) and lymph nodes with a diameter >3cm are prescribed a mean dose of up to 66Gy in 24 fractions, 5 fractions per week while the remaining targets (GTV-N and CTV) are covered by 95% of 50 Gy. The dose escalation is limited by constraints to the surrounding organs at risk (OAR).
Treatment plans are created in the Varian Eclipse treatment planning system v16.1 using robust multi-field optimization and the Monte Carlo dose calculation algorithm, AcurosPT. The plans consist of 3-6 fields and robust optimization is performed using 14 scenarios; 4.5% range uncertainty combined with 5 mm and 0 mm setup uncertainty along the major axis. Respiration (excluding interplay effect) is accounted for by coverage of the iCTV and 4D robust evaluation on all the respiratory phases. A workflow for evaluation of the interplay effect is currently being developed for the pilot patients, and will be used to determine if repainting is necessary.
Patients are setup with daily CBCT image guidance using a soft tissue match on the target volume. A thorough adaptive strategy based on daily imaging and weekly surveillance scans is mandatory for all patients, and re-planning is performed if dosimetric or geometric changes exceeds the clinic-specific tolerances.
