"Functional imaging" on the MRI-scanner indicates the more active part of the tumour in the prostate.
Within a tumour, some cell concentrations may reproduce more actively than others. Research has shown that a tumour that survives a treatment starts to grow from the region that was found to be active previously. In a new set-up of the irradiation technique these "hotspots" receive an extra dose of radiation . The active parts of the tumour are detected on the images produced by MRI (Magnetic Resonance Imaging) and PET-CT (Positron Emission Tomography and Computed Tomography) scanners.
In the adapted treatment plan the linear accelerator delivers a higher radiation dose to the more active parts of the tumour.
Linear accelerator type "Axesse" of Elekta (Sweden).
This accelerator is equipped with a high-resolution multi-leaf collimator (160 leaves, 5 mm leaf width), portal imaging and a Cone Beam CT. The machine is designed for precision irradiation with narrow radiation beams. The newest linear accelerators, such as the Axesse in the Netherlands Cancer Institute (NKI), can be adjusted flexibly and rapidly, which makes it possible to irradiate specific locations inside the tumour with extra intensity up to a dose the "hotspot" cannot survive. At the same time the healthy tissue of the surrounding organs is spared sufficiently to avoid serious side effects. In the past, the side effects were the reason that these high doses could not be given.
Quality control allows high dose delivery . By means of the EPID portal imaging system and the Cone Beam CT-scanner system, the correct delivery of the planned dose and the reaction of the tumour to the treatment are checked during treatment on the machine. This also reveals if an interim adjustment of the treatment is needed. Under such controlled conditions high local doses of radiation are possible which several years ago were still considered dangerous. This increases the chance of cure.
International collaboration.In the fall of 2012 two studies are started in the NKI to investigate the possibility of treating a specific type of cancer according to the "hotspot" principle. The studies are called "FLAME", "Focal Lesion Ablative Microboost for prostatE cancer" and "ARTFORCE", "Adaptive and innovative Radiation Treatment FOR improving Cancer patient's treatment outcomE" . In the FLAME study the effect of a new irradiation technique of prostate cancer is investigated. ARTFORCE is primarily focused on the improvement of the treatment of advanced head and neck and non-small cell lung cancer.
Example of a treatment plan for prostate irradiation
The FLAME study has been designed in the University Medical Centre Utrecht. The NKI and the University Hospital Leuven (in Belgium) participate in this research. Radiation oncologist Floris Pos and medical physicist Uulke van der Heide coordinate the Amsterdam contribution to this study. In 5 years' time the report of the first results is expected.For more information see the link FLAME project
Historical perspective. Almost 30 years ago in 1984, a prostate irradiation was less sophisticated. The example below shows the treatment plan.
Around the prostate the target volume is drawn with a wide margin. The underlying reason is the uncertainty about metastases and the position of the moving prostate. The treated region is increased more by encompassing it by a rectangular high-dose area (volume) that results from a simple 3-field technique. Inside this rectangular volume the radiation dose is as homogeneous as possible at the maximum justified level. A considerable volume of healthy tissue is therefore also irradiated. Vulnerable organs such as the rectum and the bladder receive a large amount of radiation. For example note the difference in the area encompassed by the 60% isodose in the FLAME plan compared to the 1984 plan.
Example of a treatment plan for a head and neck irradiation.
The ARTFORCE study is led from the NKI by Professor Harry Bartelink and radiation oncologist Olga Hamming. Several leading institutes in Europe participate in this study. The standard treatment, in which radiotherapy and chemotherapy are combined, is compared to three other treatment schemes. Based on the diagnostic images from MRI and PET-CT scans it is decided which treatment scheme is the best for each individual patient. The irradiation is adjusted to the behaviour of the tumour and also the chemotherapy is varied.
For more information see the link: ARTFORCE project