Target volume definition of lung cancer between PET-CT and CT-based dosimetric planning.

Background: Lung cancer is the most common cancer worldwide with an incidence and mortality of 12.4% and 18.7%, respectively. Positron emission tomography-computed tomography (PET-CT) helps in both downstaging T criteria and upstaging disease by detection of distant extrathoracic or nonregional nodal metastases.

Aim: The study is intended to compare target volume definitions between PET-CT and CT-based dosimetric planning for lung carcinoma patients on specific treatment planning parameters like tumor volumes and the number and location of involved nodes.

Methodology: It was a prospective observational study done on 50 histologically proven, non-small-cell lung carcinoma patients. Two sets of target volumes were contoured independently - one based on the fused PET-CT images and the other based on CT alone.

Results: The gross tumor volume on CT-based contours was 130.84 cc and that with PET was 95.84 cc, with an overall mean reduction of 35 cc on PET-CT as compared to CT, which was statistically significant with a P value of 0.004. A similar trend was seen with clinical target volume with a P value of 0.005. There was no significant difference seen in the normal tissue dose, represented by V20 (P = 0.418), mean lung dose (P = 0.185), and mean esophageal dose (P = 0.142) between PET-CT and CT-derived plans.

Conclusion: FDG-F18 PET-CT is a valuable tool in the management of patients with non-small-cell lung cancer. It demonstrated advantages in reducing radiation doses to critical organs compared to CT, suggesting improved sparing of normal tissues while maintaining effective tumor targeting.