The study was led by Eric L. Chang, M.D., associate professor in the Department of Radiation Oncology at The University of Texas M. D. Anderson Cancer Center.
Over the last decade, SRS, which uses high-doses of targeted x-rays, has gained acceptance as an initial treatment for tumours that have spread to the brain.
SRS is also commonly used in combination with WBRT, radiation of the entire brain, to treat tumours that are visible and those that may not be detected by diagnostic imaging.
"Determining how to optimize outcomes with the smallest cost to the quality of life is a treatment decision every radiation oncologist faces," said Chang.
"While both approaches are in practice and both are equally acceptable, data from this trial suggest that oncologists should offer SRS alone as the upfront, initial therapy for patients with up to three brain metastases," Chang added.
In the seven-year study, the researchers observed 58 patients presenting with one to three newly diagnosed brain metastases who were randomized to receive SRS followed by WBRT or SRS alone.
Approximately four months after treatment, 49 percent of patients who received WBRT experienced a decline in learning and memory function compared to 23 percent in those patients who received SRS alone.
"This is a case where the risks of learning dysfunction outweigh the benefits of freedom from progression and tip the scales in favour of using SRS alone. Patients are spared from the side effects of whole brain radiation and we are able to preserve their memory and learning function to a higher degree," said Chang.
"Here the research suggests patients who receive SRS as their initial treatment and then are monitored closely for any recurrence will fare better," Chang added.
The findings of the phase III randomized trial were presented at today's 50th annual meeting of the American Society for Therapeutic Radiology and Oncology.