Objective       To obtain reference data for designing rational irradiation target volume by the characteristics of mediastinal lymph node metastasis in non-small cell lung cancer (NSCLC) patients by positron emission tomography/computed tomography (PET/CT).       Methods       The

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F-FDG PET/CT data of 375 NSCLC patients freshly diagnosed by pathology in our hospital from 2012 to 2015 before treatment were collected. The distribution characteristics of mediastinal lymph node metastasi

s with different lesion location

clinical stage

and pathologic types were analyzed.       Results       PET/CT scanning indicated that in the 207 patients with right lung NSCLC

the metastasis incidences of mediastinal lymph nodes were decreased as the following order

ipsilateral hilar nodes

4R

7

5

2R

10~11L and 6. And for the 168 patients with left lung NSCLC

the highest metastasis incidence of mediastinal lymph nodes was the ipsilateral hilar nodes

followed by 5

7

6

4L

4R and 10~11R. The metastatic rate of zone 7 area was significantly higher in inferior and middle lobe lung than in the superior lobe lung for the patients. There was no significant differences in the mediastinal lymph node metastasis between the squamous carcinoma and adenocarcinoma (P0.05). With the increasing of T stage

the patients were prone to mediastinal lymph node metastasis. There were 88 patients having skip metastasis among the 375 patients

accounting for 23.5%. In the 191 skip metastasis areas

4R

7

5

6 and 2R had higher percentages. Mediastinal lymph nodes metastasis had no correlation with location

pathological type and stage in primary lung lesion P0.05).       Conclusion       PET/CT results indicate that the high risk metastatic areas are different in the right and left NSCLC

and clinical irradiation target volume should include zones 10~11R

4R

7 and 5 for the patients of right lung NSCLC

and 10~11L

5

7

6

4L and 4R.