By: Dr. Robert D. Timmerman

Radiotherapy is a common and effective cancer therapy. Nearly all cancers can be treated with radiation. In fact, according to the American Cancer Society, about 60 percent of all cancer patients will receive radiotherapy at some point in their overall treatment. Curative intent radiotherapy is used as the initial, primary therapy in 20-50 percent of patients, depending on the diagnosis.

Radiotherapy delivery is painless, and can be tolerated in more frail patients as compared to surgery. Yet radiotherapy has been inconvenient and costly, generally being delivered in multiple daily treatments over many weeks (e.g., 30 or more separate, daily treatments). Implementation of this protracted form of radiation was first introduced in the 1920s in a response to problems related to archaic treatment technology of the time.

Today, with improvements in technology, small fraction daily dosing is no longer an absolute requirement. It remains common, however, because of two important barriers to change: 1. Most doctors providing radiation therapy were trained to give protracted radiotherapy and have comfort with its management, and 2. Hospitals and doctors get paid effectively by the number of treatments delivered. So giving inconvenient, costly, protracted courses of therapy leads to comfortable doctors and higher revenues for radiotherapy cost centers – not exactly patient-centered care.

But the climate is changing – quickly. Pressures include both data and dollars. The opposite of protracted radiation is called hypofractionation. The most pure form of hypofractionation completes a course of therapy in five or fewer treatments and is called stereotactic ablative radiotherapy or SAbR. Some have also called this therapy stereotactic body radiation therapy or SBRT, but SAbR is a better descriptor of the potent treatment. SAbR requires the most advanced technologies to deliver large daily dosing including image guidance, intensity modulation, and rotational therapy capability. Therefore startup costs are higher.

SAbR was first introduced in the 1990s and initially used at larger academic centers having such equipment. But now these capabilities are widespread. Particularly, younger doctors, fresh from residency, have been trained to use SAbR and are comfortable with its requirements and management issues. SAbR is more potent than historical, protracted radiotherapy with local control of targeted tumors on par with best surgery. Also as with surgery, misguiding this potent therapy can lead to severe normal tissue injury. Hence, competency and training in conjunction with modern technology is essential for safe, effective treatment.

Outcomes have been impressive. For example, early stage lung cancer patients treated with three painless outpatient SAbR treatments on an NIH-sponsored multicenter trial were shown in a recent JAMA Oncology article to have 90+ percent targeted tumor eradication with few side effects after long term follow-up.

While SAbR is not cheap, it is generally less costly than protracted courses of conventional radiotherapy. This fact led to its being approved by CMS for treating prostate cancer, a disease with many, generally expensive, treatment options. And SAbR is more effectively utilized by a Cancer Center. As recently as 2004, the average number of treatments per course of radiotherapy was 28, or nearly 6 weeks of daily treatments. Protracted fractionation is inconvenient for patients who have other things to do, but also limits the capacity of the treatment center.

At the University of Texas Southwestern Medical Center in Dallas, Texas, where I practice, we heavily employ SAbR for our patients. Our current number of treatments per course of radiotherapy is 15, about half the national average. That means that with the same capital acquisition costs for radiotherapy equipment and the same cost of labor, we can treat twice as many patients as our competitors. Our capacity is double!

But SAbR wasn’t first conceived to be just a more cost-effective cancer therapy. It was developed amid a desire to improve cancer outcomes. It was first used in the brain (e.g., treatments like the Gamma Knife and the Cyberknife), moved to the lung, then liver, and beyond. Pancreas cancer, kidney cancer and sarcomas have been tested successfully with SAbR.

SAbR is the fastest growing treatment for prostate cancer and is being tested in trials aimed at improving potency preservation compared to surgery or conventional radiation. SAbR is being used in breast cancer where a machine specifically designed for breast SAbR called the Gamma Pod was recently FDA approved. All of these sites were treated with conventional, protracted radiation prior to SAbR. But SAbR is clearly expanding radiotherapy indications.

While radiotherapy has been mostly a palliative treatment in metastatic cancer, SAbR is being tested as part of hopefully curative or life-lengthening treatments for a variety of metastatic cancers. Trials are underway that could transform the field, including randomized trials. When the number of tumors is limited (i.e., oligometastases), SAbR is used to eliminate them all. When systemic therapy is mostly working but a few tumors progress, SAbR is used to consolidate the bad actors. When immunotherapy is indicated, SAbR might be used to “immunize” one or more tumors to accentuate the response. In all cases, SAbR is used with systemic therapy in a collaborative way, playing to the strengths of each therapy while dramatically expanding the indications for radiotherapy.

SAbR is changing radiotherapy, rapidly. Centers without SAbR-trained physicians and equipment are facing considerable competitive disadvantage. SAbR is high-tech and not cheap. But short course, ablative therapy is cost-effective. Fortunately, this is one of the first medical technology innovations that “grew up” during an era where clinical trials were both feasible and expected. Data from these trials is clear. First, SAbR is very potent, yielding exceptional tumor control. The potency also means the therapy can injure normal tissues. Training to properly use SAbR and avoid toxicity is available for guiding physicians, physicists, and care givers. Trials in new indications, including metastatic cancer, are ongoing, which could dramatically increase the number of patients who might benefit. SAbR is transforming radiotherapy, just in time.

About the author: Dr. Robert D. Timmerman is a professor of radiation oncology and neurosurgery and Effie Marie Cain Distinguished Chair in Cancer Therapy Research at the University of Texas Southwestern Medical Center in Dallas, TX.