Radiation therapy is a highly effective cancer therapy that can be delivered either with external beam radiation therapy from a linear accelerator or by brachytherapy which is usually the use of radioactive isotopes. Brachytherapy was the first form of radiation therapy and it had been eclipsed in many sites by the more advanced external beam radiation therapy. However, there has been a renaissance of the use of brachytherapy’s in skin cancers, including cutaneous lymphoma, due to modern brachytherapy’s ability to deliver the most conformal superficial radiation therapy. This is especially important when the contour of the surface to treat is very complex and curvy such as the face, hands, and extremities.
Most of brachytherapy is done using high dose rate afterloader technology. This device houses a single tiny (3mm) radioactive source which is driven by a motor and a cable into applicators that are positioned precisely over the clinical target area. By using computer-based graphic optimization programs, the brachytherapy specialists can essentially paint dose into the area of need with excellent avoidance of normal local tissues at risk. One example of this is a cancer of the nose or eyelid needs to spare the parts of the eye themselves. The applicators are commercially available and consist of a flap of material with catheters spaced evenly through it. It is into these catheters that a single isotope is delivered sequentially for an optimized amount of time to deliver the dose as desired.
For cutaneous lymphoma, brachytherapy has been demonstrated to be highly effective in areas of the scalp, face, neck, axilla, extremities, hands, feet, and genitals. These areas are very difficult to deliver uniform external beam radiation therapy.
A more recent development in the world of brachytherapy has been the advent of electronic brachytherapy. This contrasts with isotopes-based brachytherapy in that the source of the energy is a micro x-ray generator. This is a tiny device again driven by a cable into slightly adapted applicators to deliver an intense local dose of radiation therapy. There have been few prospective randomized trials so far, but the individual clinical case series have shown great promise. One of the contentious areas is that this does not need to fall under the purview and supervision of licensed radiation oncologists in the way that both external beam and brachytherapy do. As such, there are quality assurance issues, as well as oncologic training issues, to be considered both for the dosing to the specific type of cancer, but also the avoidance of dose to nearby organs at risk. You cannot think of quality radiation therapy without the active involvement of a board-certified medical physicist trained in radiation oncology and brachytherapy.
This form of superficial brachytherapy exists in the larger context of significant and very highly effective perspective data in the use of brachytherapy for gynecological, genital, urinary, and a host of other cancers. As such, skin cancers, which historically were first cancer treated with brachytherapy in the early 1900s, have been the latest cancer to be exposed to modern computer planning based brachytherapy, and there is great optimism and evolving research. Cutaneous brachytherapy is for complex cutaneous targets and is a more conformal therapy than external beam therapies in this setting.