Automated contouring of gross tumor volume lymph nodes in lung cancer by deep learning

The precise contouring of gross tumor volume lymph nodes (GTVnd) is an essential step in clinical target volume delineation. This study aims to propose and evaluate a deep learning model for segmenting GTVnd specifically in lung cancer, representing one of the pioneering investigations into automated segmentation of GTVnd specifically for lung cancer.

Ninety computed tomography (CT) scans of patients with stage Ш-Ⅳ small cell lung cancer (SCLC) were collected, of which 75 patients were assembled into a training dataset and 15 were used in a testing dataset. A new segmentation model was constructed to enable the automatic and accurate delineation of the GTVnd in lung cancer. This model integrates a contextual cue enhancement module and an edge-guided feature enhancement decoder. The contextual cues enhancement module was used to enforce the consistency of the contextual cues encoded in the deepest feature, and the edge-guided feature enhancement decoder was used to obtain edge-aware and edge-preserving segmentation predictions. The model was quantitatively evaluated using the three-dimensional Dice Similarity Coefficient (3D DSC) and the 95th Hausdorff Distance (95HD). Additionally, comparative analysis was conducted between predicted treatment plans derived from auto-contouring GTVnd and established clinical plans.

The ECENet achieved a mean 3D DSC of 0.72 ± 0.09 and a 95HD of 6.39 ± 4.59 mm, showing significant improvement compared to UNet, with a DSC of 0.46 ± 0.19 and a 95HD of 12.24 ± 13.36 mm, and nnUNet, with a DSC of 0.52 ± 0.18 and a 95HD of 9.92 ± 6.49 mm. Its performance was intermediate, falling between mid-level physicians, with a DSC of 0.81 ± 0.06, and junior physicians, with a DSC of 0.68 ± 0.10. And the clinical and predicted treatment plans were further compared. The dosimetric analysis demonstrated excellent agreement between predicted and clinical plans, with average relative deviation of < 0.17% for PTV D2/D50/D98, < 3.5% for lung V30/V20/V10/V5/Dmean, and < 6.1% for heart V40/V30/Dmean. Furthermore, the TCP (66.99% ± 0.55 vs. 66.88% ± 0.45) and NTCP (3.13% ± 1.33 vs. 3.25% ± 1.42) analyses revealed strong concordance between predicted and clinical outcomes, confirming the clinical applicability of the proposed method.

The proposed model could achieve the automatic delineation of the GTVnd in the thoracic region of lung cancer and showed certain advantages, making it a potential choice for the automatic delineation of the GTVnd in lung cancer, particularly for young radiation oncologists.