By james art Some glioblastoma tumors may respond well to immunotherapy, but there is currently no way to assess this without an invasive brain biopsy – which carries the risk of infection and bleeding.
As a result, biopsies for glioblastomas are rarely performed before surgery to remove the tumor, meaning these patients miss out on improved treatment.
Now there is hope after researchers developed a new imaging technique that could help determine which patients will benefit from immunotherapy drugs without the need for a risky biopsy.
Experts hope the new imaging technique could soon guide personalized treatment for glioblastoma patients, and others called the discovery a “real step forward” for patients.
Glioblastomas are a fast-growing type of brain tumor.
The average survival time after a diagnosis of glioblastoma is 12 to 18 months.
Only 25% of patients survive more than one year and only 5% of patients survive more than five years, according to The Brain Tumor Charity.
The main treatments for glioblastomas are surgery, radiation therapy, and chemotherapy.
But immunotherapy can now be widely used thanks to the development of the new ‘immuno-PET imaging technique’ by scientists at the Institute of Cancer Research, London (ICR).
Higher levels of a protein called PD-L1 have been found in rapidly progressing glioblastoma tumors.
The ICR said this protein acts as the “brakes” of the body’s immune system, so blocking the function of this protein can “prime” the immune system to fight cancer.
Until now, biopsy was the only way to assess PD-L1 levels in a brain tumor.
Scientists have now developed a “radiotracer” that binds to PD-L1, allowing doctors to measure its levels in glioblastoma patients, the authors write in the journal Neuro-Oncology.
The marker has been tested on a small number of patients in Poland.
Eight newly diagnosed glioblastoma patients received the marker, followed by scans at 48 and 72 hours.
The scan showed that the marker successfully bound to PD-L1 positive cells in the tumor and throughout the body.
Five of the patients also received pembrolizumab — a treatment that blocks PD-L1 function — before surgery.
The researchers found that these patients had lower levels of the marker in their tumors – suggesting that the drug works on the PD-L1 protein and removes the “brakes” for the immune system so it can fight the cancer.
In three of the five patients, their cancer stabilized and stopped growing, the ICR said.
The ongoing clinical trial aims to recruit 36 patients diagnosed with glioblastoma to see if pembrolizumab given before surgery is effective.
The researchers will also assess whether PET images with a radioactive tracer can be used to track progress and adjust treatment if necessary.
“This study could revolutionize the treatment of glioblastoma, as we have shown that it is possible to image an immunotherapeutic target with our radiotracer,” said Dr. Gabriela Kramer-Marek, Associate Professor and Head of the Preclinical Molecular Imaging Group at The ICR.
“Being able to scan a patient’s body and see the levels of this target means we can predict patients’ response, see how their immune system is responding to treatment and change treatment when necessary – providing a personalized treatment plan, based on the unique characteristics of their tumor, all without the need for a biopsy before surgery.”
Professor Christian Helin, Chief Executive of The ICR, added: “Glioblastoma is a devastating disease and treatments have not changed significantly for decades.
“Although immunotherapies look like they could be effective, progress has been halted by the lack of a biomarker test to show who might benefit from them, or a way to monitor each patient’s response to treatment.
“It’s fantastic to see advances in technology that mean innovative imaging techniques could soon guide personalized treatment.”
Commenting, Dr Karen Noble, Director of Research, Policy and Innovation at Brain Tumor Research, said: “We are excited by the potential of this new imaging technique to transform the treatment landscape for patients with glioblastoma.
“The ability to identify those who would benefit from immunotherapy without the need for risky biopsies is a big step forward.
“Personalized treatment plans improve the chances that treatment will be effective. Therefore, we welcome these promising results and look forward to seeing how this technique can improve the lives of patients with aggressive brain tumors.
Dr Simon Newman, Chief Scientific Officer at The Brain Tumor Charity, said: “These tumors are notoriously difficult to treat and immunotherapy research has had mixed results due to the tumor’s ability to hide from the immune system.
“However, we are encouraged by the findings of this study, as there is an urgent need for new approaches to monitoring and treating this devastating disease.”
“Immunotherapies are showing progress in other cancers, and we hope to see similar progress in brain tumors.”
“We are pleased to see progress in this area and look forward to following this work as it progresses to larger clinical trials.”