Progress Report on the SSRT clinical trials conducted at the ESRF

Clinical trials are currently being conducted at the ESRF with two types of approaches for the treatment of high-grade brain tumours: 1- one method irradiates the tumours with monochromatic Xrays in the energy range dominated by the photo-electric effect, and 2- the second method, called Micro-beam Radiation Therapy (MRT), and targeting spontaneous tumours in pets, uses an array of very intense, poly-energetic micro-beams (typically 50 microns wide, separated by 400 microns). The first method called Stereotactic Synchrotron Radiation Therapy (SSRT) will be presented in this poster. The current clinical trials program benefits from the ID17 Biomedical beamline setup that had been developed for intravenous coronary arteries imaging. A total of 65 human patients (2000 to 2003) were imaged during that period. A specially designed Patient Positioning System (PPS) had been constructed for clinical trials. Intense monochromatic laminar beams ranging from 25 to 180 keV, and 150 mm wide, 4-5 mm height are available. The SSRT principle combines two cumulative effects. The first one is a local dose enhancement produced by the presence of heavy atoms in the tumour, mainly due to the increased interaction with the monochromatic synchrotron radiation at 80 keV. Pre-clinical tests conducted over a decade have favoured the use of iodine (k-edge = 33 keV) and of platinum compounds, the latter commonly used as anti-cancer agents (k-edge = 78 keV). The second effect, or stereotactic effect, is obtained from the accumulation of the dose deposited in the tumour from up to 10 different coplanar entry ports, whilst the dose deposited in the healthy tissues is kept below the tolerance. Furthermore, the tumours are irradiated through conformal collimators. Obviously, in addition of guaranteeing the value of the dose delivered and at the exact target location, one of the main concerns is to guarantee the patient safety during the irradiation and during the 3-D Xray image guidance procedures performed prior to the irradiation. To this end, a redundant Patient Safety System (PASS) is controlling all the parameters in real-time and would interrupt the beam in less than 4 ms in any case of reaching preset limit values. The first SSRT patient has been treated at the ESRF in June 2012, and at the University Hospital (CHU) in Grenoble. Three to six patients have been and will be treated each year during 6 years to complete this Phase I/II of the clinical trials protocol which aims to prove 1- the technical feasibility of the project, 2- the tolerance by the patient (no unexpected side-effect!), and 3- the patient acceptance of anti-cancer treatment by synchrotron radiation.