Consensus and controversies on delineation of radiotherapy target volume for a patient with locally advanced non-small cell lung cancer

Objective To investigate the consensus and controversies on the delineation of radiotherapy target volume for patients with locally advanced non-small cell lung cancer (LA-NSCLC). Methods Questionnaires including 15 questions on the delineation of radiotherapy target volume of NSCLC were sent to 12 radiation departments in China in November 2015. A patient with LA-NSCLC was selected by Fudan University Shanghai Cancer Center, and simulation CT images and medical history data were sent to the 12 radiation departments. Twelve radiation oncologists from the 12 radiation departments showed and explained the delineation of radiotherapy target volume of their own, and the patient was discussed by all experts in the sixth multidisciplinary summit forum of precise radiotherapy and chemotherapy for tumor and lung cancer. Results All receivers of the questionnaire answered the questions. The standard lung window width/level for the delineation of lung cancer was 800-1600/-600 to -750 HU, and the mediastinum window was 350-400/20-40 HU. Respiratory movement was measured by stimulator, 4D-CT, and stimulator+ 4D-CT with 2-5 mm expansion based on experience. The primary clinical target volume (CTV) was defined as gross target volume (GTV) plus 5-6 mm for squamous carcinoma/5-8 mm for adenocarcinoma. The metastatic lesion of mediastinal lymph nodes was delineated as 5 mm plus primary lesion in 6 departments and as primary lesion in another 6 departments. Of the 12 departments, 10 applied 5 mm of set-up error, 1 applied 3 mm, and 1 applied 4-6 mm. For V20 of the lungs, 10 departments defined it as<30%, 1 as<35%, and 1 as 28%. Nine departments defined the radiation dose of concurrent chemoradiotherapy (CCRT) for LA-NSCLC as 60 Gy in 30 fractions, 62.7 Gy in 33 fractions in 1 department, 50-60 Gy in 25-30 fractions in 1 department, and 60-70 Gy in 25-30 fractions in 1 department. For the delineation of target volume for the LA-NSCLC patient treated with CCRT, the primary planning target volume (PTV) was defined as GTV plus organ movement (IGTV) and set-up error (GTV→IGTV→PTV) in 3 departments, as CTV plus organ movement (ITV) and set-up error (GTV→CTV→ITV→PTV) in 8 departments, and as CTV plus set-up error/IGTV plus 5-6 mm for squamous carcinoma/5-8 mm for adenocarcinoma (CTV) and set-up error (GTV→CTV→PTV/GTV→IGTV→CTV→PTV) in 1 department. For the delineation of PTV in the mediastinal lymph node, GTV→IGTV→PTV was performed in 3 departments, GTV→CTV→ITV→PTV in 8 departments, and GTV→CTV→PTV in 1 department. For 10%-100% patients with LA-NSCLC, the radiation field needed to be replanned when 38-50 Gy was completed. There was no unified standard for the optimal standardized uptake value (SUV) of positron emission tomography (PET)-computed tomography (CT) simulation and delineation. Seven departments had applied magnetic resonance imaging (MRI) simulation and 10 departments had applied stereotactic body radiation therapy (SBRT) for the treatment of early-stage NSCLC. For the delineation of PTV for early-stage NSCLC (T1-2N0M0), GTV→IGTV→PTV was performed in 5 departments, IGTV→PTV in 3 departments, and GTV→CTV→ITV→PTV in 2 departments. In all the 12 departments, peripheral early-stage NSCLC was given 6.0-12.5 Gy/fraction, 3-12 fractions and central early-stage NSCLC was given 4.6-10.0 Gy/fraction, 5-10 fractions. The results of discussion on the delineation of target volume for the patient were as follows: respiratory movements should be measured by 4D-CT or simulator; the lung window width/level is 1600/-600 HU and the mediastinal window width/level is 400/20 HU; the primary controversy is whether the involved-field irradiation or elective nodal irradiation should be used for the delineation of CTVnd in the mediastinal lymph node. Conclusions Basic consensus is reached for the delineation of target volume in LANSCLC in these aspects: lung window width/level, respiratory movements and set-up error, primary lesion delineation, the radiation dose in CCRT, and the optimal time for replanning the radiation field. There are controversies on the optimal SUV in the delineation of target volume based on PET-CT simulation, the optimal dose fractionation in SBRT for early-stage NSCLC, and the delineation of CTVnd. Key words: Carcinoma, non-small cell lung/radiotherapy; Delineation; Consensus