For most radiation therapy, the intent is to use very high energy x-rays to penetrate deep into the body, giving a higher dose of radiation to the tumor than to the overlying skin. Over the years, the linear accelerators used for treatment have become very large and very powerful.
When treating skin cancer, however, we actually want to deliver most of the radiation dose to the surface, with the intensity falling off with depth as quickly as possible. For this, we need LOW energy x-rays, about the same energy as is used for taking a chest x-ray, but in large quantities.
At Inova Fairfax Hospital we are able to treat superficial basal and squamous skin cancers using a technique called high dose rate (HDR) skin brachytherapy. HDR skin brachytherapy deposits the optimum intensity of therapeutic radiation right at the skin surface, and the intensity falls off very quickly with further skin penetration. This is precisely the distribution of radiation dose that works best for superficial skin cancers. It is ideal for the treatment of small skin cancers, particularly when they occur on the ears, nose, eyelids, or lip where surgery may be deforming. It can also be very useful for skin cancers that lie over bone, such as the shin. In areas where there is ample skin, surgery is usually chosen because it can be done in a single session, but radiation may be an option in some situations.
Each treatment with the superficial unit takes about 30 seconds. Usually, a series of about 6 to 12 treatments over two to three weeks will suffice. There is no sensation, and the only side effect expected is skin reddening.
Larger or deeper tumors may require electron beam therapy, on a linear accelerator. This usually requires a longer treatment course.
Our doctors cooperate closely with dermatologists, and skin cancer specialists who use Mohs surgery, to try to recommend the best treatment for each case.