[Impact of PET/CT on precise radiotherapy planning for non-small cell lung cancer].

Objective: To investigate the impact of PET/CT on the clinical staging, target volume delineation and precise radiotherapy (PAR) planning for patients with non-small cell lung cancer (NSCLC).

Methods: PET/CT scanning was performed in 58 histologically proven NSCLC patients for radical radiotherapy or surgery. The clinical staging of all patients was determined by PET/CT according to 1997 World Health Organization (WHO) staging system. The gross tumor volume (GTV) was delineated and three-dimensional conformal radiotherapy (3D-CRT) planning was established with identical parameters based on CT image and PET/CT fused image, respectively. The indexes including volume of GTV (V(GTV)), percentage of the total lung volume which received more than 20 Gy (V(20)), mean lung dose (MLD), tumor control probability (TCP), normal tissue complication probability (NTCP), and dose to spinal cord (Ds) were selected and evaluated. The quality of the two plans and the impact of PET/CT on PAR planning was compare and analyzed.

Results: 1. PET/CT image results changed the clinical stages in 21 of 58 (36.2%) patients with 14 upstaged and 7 downstaged, therefore, the management decisions were modified in 16 (27.6%) patients. 2. Among 32 patients who underwent surgery, PET/CT staging result was consistent with pathologic staging in 29 with one false negative and 2 false positive in lymph node staging. The sensitivity of PET/CT was 96.9% and accuracy 90.6%. 3. The differences of indexes including V(GTV) (P = 0.004), V(20) (P = 0.000) and MLD (P = 0.004) between the two radiotherapy plannings were statistically significant, whereas, the Ds, TCP and NTCP (left lung, right lung, skin and spinal cord) was not.

Conclusion: 1. The impact PET/CT on clinical staging of NSCLC and PAR planning was remarkable. 2. PET/CT is more consistent with pathology in staging than CT and, therefore, is an important compensatory staging measure. 3. Compared with CT, PET/CT can reduce the V(GTV) in patients with atelectasis and obstructive pneumonitis when contouring the target volume, so can provide better protection for normal surrounding lung tissue. On the other hand, PET/CT is more sensitive in detecting mediastinal lymph node metastasis than CT, and the V(GTV) can be more precise and guaranteed. 4. Radiopneumonitis may be more effectively prevented because of significant decrease in V(20) and MLD by more precise planning based on PET/CT results. 5. PET/CT not only can provide satisfactory Ds, TCP and NTCP within clinical demand, but also more precise delineation of the radiation target volume and precise radiotherapy planning for NSCLC.