NEW YORK (Reuters Health) – High-potency, stereotactic body radiation therapy (SBRT) may improve survival for patients with medically inoperable early stage lung cancer, results of a multicenter phase 2 trial suggest.

Patients with severe comorbidities can’t tolerate surgery for early lung cancer, and even with conventional radiotherapy, 2-year survival is less than 40%, the researchers explain. SBRT involves numerous small, highly focused radiation beams that deliver potent doses to tumor targets. Small, single-center studies indicate that frail patients tolerate this treatment well.

First author Dr. Robert Timmerman and associates used SBRT to treat 55 patients with peripheral T1-T2 N0M0 non-small cell tumors measuring no more than 5 cm in diameter. Patients received 18 Gy per fraction in three fractions administered over about 2 weeks.

The median follow-up was 34.4 months (38.7 months among survivors).

As reported in the March 17 Journal of the American Medical Association, the 3-year primary tumor control rate was 97.6%. Only one patient had a documented recurrence at the primary site, and there were no marginal recurrences.

SBRT “provided more than double the rate of primary tumor control than previous reports describing conventional radiotherapy,” the investigators note.

The 3-year local-regional control rate was 87.2%, with a 3-year rate of disseminated failure of 22.1%. Overall, 14 patients had recurrence of cancer.

Disease-free survival at 3 years was 48.3%, and overall survival was 55.8%.

Twenty-six patients died during follow-up. However, autopsies were performed on only a few patients, and nine died of unknown causes.

Regarding the rate of disseminated failure, the authors say that “either better whole-body staging to identify patients with occult metastatic disease, or effective adjuvant therapies to eradicate such disease are necessary to improve the outcomes.”

The authors say treatment-related morbidity was “moderate.” Protocol-specific grade 3 adverse events occurred in seven patients and grade 4 events in two patients. These included a decline in forced expiratory volume in the first second (FEV1), hypocalcemia, hypoxia, pneumonitis, and pulmonary function test decreases. In addition, six patients had adverse events attributable to SBRT that were not protocol-specified.

Dr. Timmerman, from the University of Texas Southwestern Medical Center, Dallas, and his associates note that their study was the first North American cooperative group trial of SBRT. They say that the infrastructure they established for this research “will eventually allow evaluation of relationships between dosimetry, compliance, and adverse events with longer follow-up…from completed trials.”

Reference:
JAMA 2010;303:1070-1076.