Robert Timmerman, M.D. Answers Questions On: Stereotactic Ablative Radiotherapy (SABR)

Research suggests that giving a powerful dose of radiation, either all at once or a handful of times, is much more biologically deadly – i.e., much more likely to kill tumor – than weaker doses given more often over a period of several weeks, which is the standard method by which conventional radiotherapy is delivered. That is not to say there is not a role for conventional radiotherapy – some types of tumors are well-controlled by a standard course of radiotherapy. However, some tumor types may respond better to SABR. Additionally, SABR treatments are more precise and can spare more normal tissue, making it ideal for treating tumors located near critical structures.

A lesser, but still important, benefit to patients is the reduced treatment time, which can drop from six weeks down to one or two weeks (or less). This can enable patients to move into other phases of treatment, like chemotherapy, if necessary, a little faster.

There are many different factors that go into the decision to use SABR including tumor type, tumor location and size, and how well the patient is doing overall. I am currently very excited about SABR’s usefulness in treating metastatic disease. We used to treat patients with metastases palliatively – that is, to relieve their symptoms in the absence of a cure. With SABR, while we might not entirely cure them, we can ablate metastases and prevent them recurring for a very, very long time. People with cancer are living much longer, and so we are aiming to deliver treatments that are more tolerable and create fewer side effects. For some patients, cancer is not so much a killer that can be destroyed, as a long-term condition like diabetes or AIDS that needs to be managed. These people need treatments that address their quality of life for years afterward.

SABR is an approved treatment for many sites within the body. More and more centers now have the capability to perform this treatment, and we are actively training those interested in learning. We continue to do research to find the most optimal form of our therapies, including SABR. Right now we are engaging in phase I studies to really understand the potency of SABR. What we’re learning is that in some cases we can back off and reduce the amount of radiation given without compromising the survival of the patient, and so reduce potential harmful side effects to the patient.