For prostate cancer, the photosensitising drug is given into the blood stream, through a vein in the arm. For other cancers, especially skin cancer, the drug can be applied directly to the cancer, in a liquid or a cream.
How is the light dose given to the prostate?
Light can be delivered to the prostate from a laser, along thin optical fibres. These optical fibres are put into the prostate within clear hollow plastic needles. The needles are put in under general anaesthetic. The patient lies on his back, with his legs raised and apart. The perineum is cleaned. An ultrasound probe is put into the back passage, so that the prostate can be seen on a monitor screen. A template is put next to the perineum. The template is a grid with holes in it. The template is seen on the ultrasound monitor. Needles are passed through the template into the prostate. The needle is seen on the ultrasound monitor and its position can be moved if necessary. Once the needles are in the right position the optical fibres, which carry light from the laser can be put into the needles. Some needles will be used to carry optical fibres which can detect rather than deliver light.
The fibres that are used are specially designed to deliver light in a cylindrical shape (like a strip light) rather than to shine light from the end, like a torch. This helps to deliver an equal light dose to all parts of the prostate.
Vascular targeted PDT with Tookad uses light in the near infra red range, with a wavelength of 763 nm. This is a longer wavelength than some other drugs. This means that the light can penetrate more deeply into the tissue, and so a larger area can be treated with a single light fibre.
How long does it take?
Vascular targeted PDT takes about 2-3 hours. This is the time taken for the needles to be put into the prostate, all the ultrasound and light measurements made, and the drug and light dose to be given.
