Inflammation in Primary and Secondary Malignancies of the Central Nervous System Using [C-11]-CS1P1

This is a prospective, single-arm interventional imaging study designed to evaluate the investigational PET radiotracer \[C-11\]-CS1P1 in adults with primary or secondary central nervous system malignancies. \[C-11\]-CS1P1 PET may provide complementary information about disease activity, treatment response, and the tumor microenvironment in central nervous system cancers. Eligible participants will be adults with confirmed primary central nervous system tumors (for example, gliomas) or secondary central nervous system involvement (brain metastases or other CNS metastases). After providing informed consent, participants will undergo a baseline \[C-11\]-CS1P1 PET scan in addition to their routine clinical imaging. The PET scan will be performed on a PET/CT or PET/MR scanner following intravenous administration of \[C-11\]-CS1P1, using a standardized acquisition protocol for brain imaging. Participants will be monitored for adverse events related to tracer administration and radiation exposure, which are expected to remain within accepted research limits. Participants will be invited to return for one follow-up \[C 11\]-CS1P1 PET scan within 24 months of the baseline scan, preferably within approximately 6 months after treatment. Follow up imaging will allow assessment of longitudinal changes in \[C 11\]-CS1P1 uptake in relation to treatment and disease course. Clinical management will not be altered by participation in this study. Quantitative PET parameters (for example, standardized uptake values, tumor to background ratios, and volumetric measures) will be derived from tumor and normal appearing brain. Qualitative assessments of tracer uptake patterns will also be performed. These PET measures will be compared with MRI characteristics, treatment history, and available clinical outcomes (including radiographic progression and survival) to explore the potential of \[C 11\]-CS1P1 PET as a diagnostic biomarker of tumor activity and treatment response in central nervous system malignancies. This exploratory study is intended to generate preliminary data that may inform the design of future trials using \[C 11\]-CS1P1 PET in this patient population.