Nuclear medicine has the potential to change the landscape of theranostics in neurooncology, according to a new article published in the February issue of The Journal of Nuclear Medicine (JNM).

With recent advances in techniques to permeate the brain-blood barrier (BBB), the prospect of using radiopharmaceuticals to treat brain tumours, such as meningiomas, gliomas, brain metastases, and pediatric brain tumours, is promising.

“In the last decade, we have observed a huge step forward in treatment options for a wide range of tumours in terms of both survival and quality of life. However, therapeutic approaches to brain tumours remain a challenge, with considerable limitations regarding delivery of drugs,” stated the article’s authors.

“There has been renewed and increasing interest in translating the popular theranostic approach well known from prostate and neuroendocrine cancer to neurooncology. Although far from perfect, some of these approaches show encouraging preliminary results.”

In this state-of-the-art JNM article, authors provided a general overview of the use of theranostics for four areas of neurooncology and provided perspectives on future research needs.

The article focused on meningiomas, gliomas, brain metastases, and pediatric brain tumours.

Meningiomas are the brain tumours for which peptide receptor radionuclide therapy (PRRT) has been most performed.

It is currently used in meningiomas that cannot be treated with surgery or conventional radiation therapy regardless of their grade.

Most of the available data on PRRT in meningiomas are from patients at a late stage of the disease when the efficacy of the treatment is potentially limited.

It might be advantageous, state the authors, to start PRRT earlier in the disease course before patients develop treatment-refractory, progressive, and extensive disease. 

Future studies should include the development of criteria for appropriate use of PRRT in specific subtypes and the determination of efficacy in randomised prospective trials, as well as focus on treatment combinations.

Gliomas are the most common malignant brain tumours, with around 80 percent of tumours considered high-grade.

Many potential theranostic targets for gliomas have been investigated, with variable but mostly discouraging results.

Future studies should focus on patient selection and using multimodal approaches combining theranostic agents with techniques enhancing BBB or blood-tumour barrier (BTB) permeability.

Current therapeutic options for brain metastases consist of a combination of surgery, external radiation therapy, and targeted and immune-modulating therapies.

As primary cancer control is advancing dramatically, brain metastases across many cancer types occur more frequently, and more effective therapies are needed.

Radionuclide therapy for brain metastases has been scarcely investigated; however, an advantage of radionuclide therapy over immune therapy is that the effective targeting of all lesions can be visualised using intratherapy scanning.

Moreover, the effective targeting of brain metastases can be monitored by PET imaging. These features might translate into an advantage over the current standard of care in terms of clinical benefit. 

Pediatric brain tumours are the most frequent solid malignancy in childhood and account for 20 percent of all pediatric tumours.

Surgery is the mainstay in many pediatric brain tumours and can be combined with external radiation therapy or chemotherapy, although this is not ideal for young patients.

A relatively large quantity of literature is available on theranostic approaches to the use of radioligands in pediatric neurooncology; the best-documented and most-promising approach is the use of intracranioventricular 131I-omburtamab for treatment of leptomeningeal disease. 

The main obstacle in neurooncology compared with other solid tumours is getting therapeutics through the BBB and the BTB.

Several strategies have been developed to bypass them, and these potential pathways can allow therapeutics to be directly administered to the tumour or into surgical or anatomical cavities.

“The success of most theranostic agents will depend on the development and clinical implementation of principles that increase the permeability of the BBB,” state the authors. “Here, nuclear medicine techniques can aid and potentially speed development by enabling visualisation and verification of the principle.”

Source: Society of Nuclear Medicine and Molecular Imaging