JAMA: SBRT provides tumor control for inoperable lung cancer
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Robert Timmerman, MD, of the University of Texas Southwestern Medical Center in Dallas, and colleagues conducted the Radiation Therapy Oncology Group (RTOG) 0236 trial to test stereotactic body radiation therapy (SBRT) in treating medically inoperable patients with early stage non-small cell lung cancer. SBRT is a noninvasive cancer treatment in which numerous small and highly focused radiation beams are used to deliver potent doses in one to five treatments to tumor targets.
"The main finding in this prospective study was the high rate of primary tumor control (97.6 percent at three years),” wrote the authors. “Primary tumor control is an essential requirement for the cure of lung cancer. SBRT as delivered in RTOG 0236 provided more than double the rate of primary tumor control than previous reports describing conventional radiotherapy."
The Phase 2 study included patients 18 years or older with biopsy-proven peripheral T1-T2N0M0 non-small cell tumors (measuring less than 5 cm in diameter) and medical conditions that would not allow surgical treatment. For 55 patients (44 with T1 tumors and 11 patients with T2 tumors), radiation treatment lasted between 1.5 and two weeks and occurred between May 2004 and October 2006 with a median follow up of 34.4 months.
According to the authors, the primary outcome measured for the study was two-year actuarial primary tumor control; secondary end points were disease-free survival (i.e., primary tumor, involved lobe, regional and disseminated recurrence), treatment-related toxicity and overall survival.
Of all the patients in the study, only one experienced a documented tumor recurrence or progression at the primary site where the three-year primary tumor control rate was 97.6 percent, according to the article.
Three patients had recurrence within the involved lobe; the three-year primary tumor and involved lobe (local) control rate was 90.6 percent. According to the study, combining local and regional failures, the three-year local-regional control rate was 87.2 percent. Disseminated recurrence as some component of recurrence was reported in 11 patients. The three-year rate of disseminated failure was 22.1 percent with eight such failures occurring prior to 24 months.
Disease-free survival and overall survival at three years were 48.3 percent and 55.8 percent, respectively. Median disease-free survival and overall survival for all patients were 34.4 months and 48.1 months, respectively. Seven patients and two patients were reported to experience protocol-specified treatment-related grade three and four adverse events, respectively. No grade five treatment-related adverse events indicating death were reported.
"The RTOG 0236 trial demonstrated that technologically intensive treatments like SBRT can be performed in a cooperative group so long as the proper infrastructure and support are put in place,” the authors concluded. “The RTOG will be building on RTOG 0236 to design a trial to address the rather high rate of disseminated failure observed after treatment, complete a trial to determine a safe and effective dose for central lung tumors and complete a trial to refine the dose of SBRT for peripheral tumors."