Novel Ga68-PSMA PET/CT-tracer to Differentiate Between Radiation Necrosis and Tumor Progression in Brain Metastases

Novel Ga68-PSMA PET/CT-tracer to Differentiate Between Radiation Necrosis and Tumor Progression in Stereotactic Irradiated Brain Metastases: a Feasibility Study

This study aims to evaluate the diagnostic potential of 68-Gallium PSMA-PET/CT in stereotactic irradiated brain metastases from non-small cell lung cancer, melanoma and breast cancer.

This prospective phase II diagnostic feasibility study investigates the diagnostic potential of 68-Gallium PSMA-PET/CT in stereotactic irradiated brain metastases from non-small cell lung cancer, melanoma and breast cancer.

Participants will be enrolled in three predefined cohorts per primary tumor type:

1. newly diagnosed brain metastases,
2. definite radiation necrosis, and
3. diagnostic dilemma after radiotherapy.

The goals of this study are:

1. Evaluating PSMA expression using Ga68-PSMA PET/CT in brain metastases of NSCLC, breast cancer and melanoma patients eligible for stereotactic radiotherapy (SRT) or surgery. 2. Evaluating PSMA expression using Ga68-PSMA PET/CT in patients with definite radiation necrosis. 3. Evaluating the use of Ga68-PSMA PET/CT to differentiate progressive brain metastases of NSCLC, breast cancer and/ or melanoma from radiation necrosis by quantifying PSMA activity.

Inclusion Criteria:

For all groups:

• Written informed consent
• Age ≥ 18 years old
• WHO PS 0-3
• Measurable lesion ≥10mm according to RANO BM

For brain metastases groups:

- newly diagnosed brain metastases from either NSCLC (group 1) or melanoma (group 2) or breast cancer (group 7).

For radiation necrosis groups:

- Brain lesion at the location of a formerly brain metastases that has been treated with SRT (> 9 months ago), with the definite diagnosis of radiation necrosis at the location of formerly SRT-treated brain metastases of NSCLC (group 3), melanoma (group 4) and/ or breast cancer (group 8).

For diagnostic dilemma groups:

- Brain lesion at the location of a formerly brain metastases with a diagnostic dilemma of radiation necrosis and recurrent brain metastases of NSCLC (group 5), melanoma (group 6) and/ or breast cancer (group 9).

Exclusion Criteria:

For all groups:

• Known allergy to Ga68-PSMA
• Epileptic seizure less than 7 days before Ga68-PSMA PET/CT scan
• Life expectancy less than 3 months
• Patients with known prostate carcinoma
• Pregnancy