Currently, there are limited methods available in clinical practice to distinguish pseudoprogression after immunotherapy. Most patients rely on follow-up observations to monitor the disease, which does not meet clinical needs. 68Ga-grazytracer is a novel imaging agent targeting granzyme B. By detecting the concentration of granzyme B, it reflects the localization of cytotoxic T cells in the tumor region and their potential ability to kill tumor cells. This study aims to leverage the simplicity, non-invasiveness, visualization, and semi-quantitative advantages of 68Ga-grazytracer PET imaging to evaluate its effectiveness and feasibility in diagnosing pseudoprogression.

Inclusion Criteria:

1. Lung cancer patients who develope lesion enlargement and/or new lesions after treatment with immune checkpoint inhibitors;
2. Pseudoprogression cannot be ruled out in clinical practice;
3. Lung cancer confirmed by pathology or cytology, regardless of pathological type;
4. Fully-informed written consent obtained from patients;
5. Patient ability to comply with protocol requirements;
6. Age 18-75 years;
7. Life expectancy of at least 6 months.

Exclusion Criteria:

1. Patients with serious diseases that the investigator deems unsuitable for participation in the clinical study. Such as severe cardiopulmonary insufficiency, severe bone marrow suppression, severe hepatic or renal insufficiency, etc;
2. Intestinal perforation, complete intestinal obstruction;
3. Active phase of hepatitis B；
4. Pregnant women and women who are potentially pregnant, as well as nursing mothers;
5. Patients with poor compliance.

The patients are enrolled from Department of Respiratory and Critical Care Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine in China.