Shirnett Williamson, M.D., medical director of Radiation Oncology and CyberKnife for Capital Health, shares the latest technological and procedural advances in her field, which is having an impact on treating cancer.
What have been the biggest advances in radiation oncology in recent years?
Image-guided radiation therapy is what I would consider one of the biggest advances in recent years in the field. We are able to use more precise imaging such as Cone Beam CT scans, which allow us to image a tumor just before we treat it to make sure we are not missing anything and allows smaller margins for treatment. This in turn allows higher doses to tumors and lower doses to other normal structures, so we lessen the side effects and have greater tumor control. We are also able to use kilovoltage xrays to localize treatment areas daily as well for better tumor control and smaller margins.
Another advance would be using altered fractionation to treat tumors such as hypofractionated treatments, whereby higher doses are used and we are able to have the same outcome, less number of days of treatment and less or similar side effects. An example is using cyberknife where only five treatments are given.
The mammosite or breast brachytherapy is also relatively new over a few years whereby a balloon device is placed in the breast tumor cavity at the time of surgery then patients come twice a day over a week for treatments to the tumor cavity.
Is targeted radiation proving effective?
Targeted radiation is very effective. Because of advanced imaging techniques to diagnose tumors and also to image tumors on our treatment machines, we are able to provide more precise treatments with techniques such as IMRT (intensity modulated radiation therapy) and Arc therapy as well as cyberknife. This allows higher doses, more conformality to the tumors being treated and lesser side effects but effective outcome. An example is head and neck cancers where studies using IMRT indicate better survival. Brachytherapy is another method of targeted radiation whereby a radioactive source is placed directly at the tumor and this enables again higher dose with less toxicity. This is particularly beneficial for cancers in body cavities and has been used for many years because of its effectiveness.
What is CyberKnife?
The Cyberknife is a robot made by the company Accuray. It provides focused radiation treatment and allows us to administers stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT). This consists of multiple beams of radiation being administered to a tumor using a very high dose with great precision within 1 mm of accuracy. We are able to treat and retreat tumors of many sites such as brain and spine, lungs, pancreas, prostate, lymph nodes and so forth. This system continuously images during treatment so as to ensure accuracy and it is frameless as opposed to some other radiosurgery systems that may have head frames screwed onto patient’s skulls. The shape also allows it to be more flexible compared to other regular linac radiation systems and so allows treatment from many more angles. A regular radiation machine may deliver up to 12 beams and cyberknife up to 100 beamlets or more at times and this ensures more conformability and so a higher dose and less toxicity.
What are the best remedies for the side effects of radiation?
The side effects of radiation are dependent on the body part that is being treated. These remedies will be supportive in nature to heal the normal cells while we administer treatment to cancer cells in a particular area. For example, skin reactions are common if we target the skin and so we would prescribe skin creams. We can sometime cause nausea if we treat the stomach and would give anti-nausea medication; diarrhea if we treat the rectum and would give anti-diarrheal medication. Once a patient is having radiation, then they are usually told ahead of time the possible side effects to look out for and the doctor usually sees the patient during a course of treatment and prescribes appropriate medications as necessary.