CHICAGO—In lung cancer patients, stereotactic body radiation therapy achieved a 98% local control rate that persisted over three years in those who were too frail with comorbidities to undergo surgery, according to research presented at ASTRO 2009.
The results support the use of SBRT as standard treatment in patients with early-stage lung cancer who have coexisting serious medical problems, said lead researcher Robert D. Timmerman, MD.
In this phase II RTOG 0236 trial, SBRT failed to achieve local control in only one patient out of 55. Three-year overall survival was 56% in these patients, who had documented comorbidities, such as emphysema, heart disease, and stroke, said Dr. Timmerman, professor of radiation oncology at the University of Texas Southwestern Medical Center in Dallas.
SBRT delivered a dose of 60 Gy to the tumor in three fractions over one week. Conventional radiotherapy for patients whose cancer is inoperable because of their frailty is routinely delivered in 30 fractions over several weeks (abstract 5). Although these results are from a phase II study, they are still very impressive, commented Stephen Hahn, MD, professor of radiation oncology at the University of Pennsylvania in Philadelphia.
SBRT and obesity
In a second study that looked at chest wall and skin toxicity related to SBRT, the researchers determined that obesity and obesity-related diabetes, and not the amount of radiation given, were factors in whether chest wall pain developed in these patients with early-stage lung cancer.
Obese patients who are diabetic are more than three times as likely to develop chest wall pain as are patients who do not have diabetes, said James Welsh, MD, assistant professor of radiation oncology at the M.D. Anderson Cancer Center in Houston.
The study involved 265 patients with tumors within less than 2.5 cm of the chest wall. All patients were treated to a total dose of 50 Gy in four daily fractions of 12.5 Gy.
Of the 265 patients, 132 had tumors within 2 cm of the chest wall. Skin changes developed in 58 (44%) of the 132 patients. Fifty-five percent of the 20 patients in whom chronic pain developed had grade 2-3 pain.
The risk of grade 2 or higher pain was based on the volume of chest wall receiving >30 Gy in the range of 50 cc (abstract 128). "This is a surprising finding, since most side effects of radiation treatment are based on the amount of normal tissue that is treated and the volume of the dose," he said. n