Highly-focused stereotactic body radiation therapy (SBRT) can eliminate the targeted tumor while avoiding treatment-related illness and may ultimately improve survival for patients with inoperable non-small cell lung cancer, according to early findings of a Radiation Therapy Oncology Group study published in the March 17 cancer-themed issue of the Journal of the American Medical Association.
Stereotactic body radiation therapy (SBRT) is a noninvasive cancer treatment in which numerous small, highly focused, and accurate radiation beams are used to deliver potent doses in 1 to 5 treatments to tumor targets.
"The primary finding and perhaps most exciting aspect to this prospective study was the high rate of primary tumor control (97.6 percent at 3 years). Primary tumor control is an essential requirement for the cure of lung cancer. Stereotactic body radiation therapy as delivered in RTOG 0236 provided more than double the rate of primary tumor control previous reported for conventional radiotherapy suggesting that this technique could provide a significant step forward in the battle against this type of lung cancer," said Robert Timmerman, MD, of the University of Texas Southwestern Medical Center, Dallas, principal investigator on the RTOG study.
Currently, patients with inoperable early stage lung cancer are generally offered conventional radiation treatment (most commonly given during 20-30 outpatient treatments) or observed without specific cancer therapy. However, study authors indicate that neither of these approaches achieves ideal outcomes.
"Conventional radiotherapy fails to provide long-term control of the primary lung tumor in approximately two-thirds (60 percent to 70 percent) of patients. Most ultimately die specifically from progressive lung cancer with observation, and 2-year survival is less than 40 percent with either approach. Our study suggests that stereotactic body radiation therapy is a new option that produces better outcomes and may represent an updated, and ultimately more successful, approach to the treatment of patients with early stage inoperable lung cancer," said Timmerman.
This is the first North American multicenter, cooperative group study to test SBRT in treating medically inoperable patients with early stage non-small cell lung cancer. Dr. Timmerman and RTOG member investigators enrolled 59 patients to this phase II study that 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. Radiation treatment lasted between 1.5 and 2 weeks. The study opened May 2004 and closed October 2006, with data analyzed through August 2009. The final study population included 55 evaluable patients (44 with T1 tumors and 11 patients with T2 tumors), with a median (midpoint) follow-up of 33.4 months.
The primary outcome measured for the study was 2-year actuarial primary tumor control; secondary end points were disease-free survival (i.e., primary tumor, involved lobe, regional, and disseminated recurrence [the reappearance or return of a cancer in multiple areas of the body]), 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. The 3-year primary tumor control rate was 97.6 percent. Three patients had recurrence within the involved lobe; the 3-year primary tumor and involved lobe (local) control rate was 90.6 percent. Combining local and regional failures, the 3-year local-regional control rate was 87.2 percent. Disseminated recurrence as some component of recurrence was reported in 11 patients. The 3-year rate of disseminated failure was 22.1 percent with 8 such failures occurring prior to 24 months.
Disease-free survival and overall survival at 3 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 (12.7 percent) and two patients (3.6 percent) were reported to experience protocol-specified treatment-related grade 3 and 4 adverse events, respectively. No grade 5 treatment-related adverse events were reported. Higher grades indicate greater severity of adverse event, with grade 5 indicating death.
"While this is a phase II study involving a relatively small patient sample, these results suggest that this technique could greatly improve survival rates for patients with inoperable non-small cell lung cancer. For this group of patients there simply has not been significant advance in survival rates in some time. These results certainly dictate that further study of SBRT is warranted. We are optimistic that the technique holds promise for these patients," said Timmerman
According to Walter J. Curran, Jr., MD, the RTOG Group Chair, and the Executive Director of the Winship Cancer Institute of Emory University, "RTOG 0236 demonstrated that technologically intensive treatments like SBRT can be performed in the cooperative group setting so long as effective quality control measures are in place to assure patient safety. As the preeminent group conducting multi-institutional clinical trials of novel radiation therapy techniques, RTOG is building on these results to improve patient outcomes and quality of life with trials designed to address the rather high rate of disseminated failure observed after treatment, determine a safe and effective dose for central lung tumors, and refine the dose of SBRT for peripheral tumors."
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