This study aimed to assess the therapeutic impact and diagnostic accuracy of 18F-DOPA PET/CT in patients with glioblastoma or brain metastases. Gliomas and metastases are the most common malignant brain tumors. Brain metastases arise in 10–40% of systemic cancers with non-small cell lung cancer being the primary tumor in about half of the patients

Patients with histologically proven glioblastoma or brain metastases were prospectively included in this monocentric clinical trial (IMOTEP). Patients were included either due to clinical suspicion of relapse or to assess residual tumor infiltration after treatment. Multimodality brain MRI and 18F-DOPA PET were performed. Patients’ data were discussed during a Multidisciplinary Neuro-oncology Tumor Board (MNTB) meeting. The discussion was first based on clinical and MRI data, and an initial diagnosis and treatment plan was proposed.

18F-DOPA PET

Secondly, a new debate was conducted based on the overall imaging results, including 18F-DOPA PET. A second diagnosis and therapeutic plan were submitted. A retrospective and definitive diagnosis was obtained after a 3-month follow-up and considered as the reference standard. The MNTB prospectively investigated one hundred six cases. All patients with brain metastases (N = 41) had aclinical suspicion of recurrence.

The addition of 18F-DOPA PET data changed the diagnosis and treatment plan in 39.0% and 17.1% of patients’ cases, respectively. Concerning patients with a suspicion of recurrent glioblastoma (N = 12), the implementation of 18F-DOPA PET changed the diagnosis and treatment plan in 33.3% of cases. In patients evaluated to assess residual glioblastoma infiltration after treatment (N = 53), 18F-DOPA PET data had a lower impact with only 5.7% (3/53) of diagnostic changes and 3.8% (2/53) of therapeutic plan changes.

The definitive reference diagnosis was available in 98/106 patients. For patients with tumor recurrence suspicion, the adjunction of 18F-DOPA PET increased the Younden’s index from 0.44 to 0.53 in brain metastases and from 0.2 to 1.0 in glioblastoma, reflecting an increase in diagnostic accuracy. 18F-DOPA PET has a significant impact on the management of patients with a suspicion of brain tumor recurrence,

either glioblastoma or brain metastases, but a low impact when used to evaluate the residual glioblastoma infiltration after a first line radio-chemotherapy or second-line bevacizumab.The assessment of tumor metabolism with amino-acid PET can detect high- and low-grade brain tumors independently of the blood-brain barrier breakdown. Thus, it is complementary to MRI, the current imaging gold-standard . Previous studies have demonstrated the usefulness of amino acid PET for the diagnosis, treatment monitoring, and prognostic evaluation of patients with high-grade gliomas and brain metastases.