Drug-releasing material targets post-surgery tumour tissue
Researchers at Nottingham University believe a polymer originally designed to help heal bones could deliver chemotherapy drugs directly to the site of patients’ brain tumours.
Their study, published in PLOS ONE shows that the biomaterial can be applied to the cavity created following brain cancer surgery and used to release chemotherapy drugs over several weeks.
The university claims also that the targeted nature of the therapy could reduce the toxic effects of chemotherapy drugs on healthy parts of the body.
Study leader Dr Ruman Rahman from the university’s Children’s Brain Tumour Research Centre (CBTRC) said in a statement, : ‘Our system is an innovative method of drug delivery for the treatment of brain tumours and is intended to be administered immediately after surgery by the operating neurosurgeon.
‘Ultimately, this method of drug delivery, in combination with existing therapies, may result in more effective treatment of brain tumours, prolonged patient survival and reduced morbidity.’
Brain tumours are a major cause of cancer-related death in children and adults up to the age of 40, with most relapses occurring when surgeons are unable to remove all of the cancerous cells during surgery.
Alternative systems for delivery of drugs directly to the brain already exist but they are used infrequently because their limited success. This new drug delivery system is the first that can be moulded to the shape of the brain tumour cavity and the first to deliver several different drugs over a clinically meaningful period of time.
The Nottingham polymer formulation is made from two types of micro-particles called PLGA and PEG and has been developed and patented by Prof Kevin Shakesheff, based in the university’s School of Pharmacy. A powder at room temperature, it can be mixed to a toothpaste-like consistency with the addition of water.
The unique properties of the polymer lie in its ability to set into a rigid structure only when it reaches body temperature (37 degrees), a feature suited for use in medical therapies. It was originally developed as a scaffold on to which new bone cells could be grown to speed up the knitting back together of broken bones.
Dr Ruman Rahman at the CBTRC and Dr Cheryl Rahman from the School of Pharmacy spotted the potential for the polymer to deliver chemotherapy drugs directly to patients’ brain tumours. The work was performed at the CBTRC with neurosurgeon Mr Stuart Smith and neuro-oncologist Prof Richard Grundy.
The cavity left by the removal of a tumour would be lined with the polymer while in paste form, which would start to solidify and gradually release the chemotherapy drugs after the incision has been closed. This would directly target any residual cells not initially removed during surgery.
In the lab, the Nottingham scientists were able to successfully demonstrate the slow-release properties of the material by placing paste loaded with three commonly used chemotherapy drugs into a solution of saline and measuring the quantities of the drugs given out by the material over time.
To establish whether the material itself is safe to use on patients in this form of therapy, they used it to create a 3D model onto which they were able to grow brain tumour cells and healthy brain blood vessel cells without any toxicity. They then simulated surgery on a sheep’s brain from an abattoir by moulding the paste around a brain cavity and warming the brain to human body temperature to harden the polymer.
The brain was then scanned using CT and MRI technology to demonstrate that it is still possible to distinguish the polymer from normal brain tissue on a routine brain scan, an aspect crucial for doctors when dealing with follow-up care for brain tumour patients who have undergone surgery.
The team also dealt with concerns that the material could disintegrate and release its chemotherapy contents too quickly during the subsequent radiotherapy which many cancer patients undergo following surgery. By placing the biomaterial loaded with chemotherapy drugs into a head cavity of a medical training dummy and subjecting it to the same duration and intensity of radiotherapy used for brain tumour patients they were able to demonstrate the integrity of the structure.
They then showed that chemotherapy drug etoposide could be effective at destroying brain cancer cells in a mouse when released from the polymer formulation. The next stage of the research will be to extend the study in mice with brain tumours to test whether animals with the drug-loaded polymers survive longer. The team are also investigating the release of other chemotherapeutic drugs that hold promise.
The first clinical test, anticipated in 3 years’ time, will be to devise a multi-centre phase clinical trial which would involve testing the therapy on a small number of patients for whom other clinical treatments have not been successful and would otherwise only be offered palliative care.