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Size Matters: A Comparison Of T1 And T2 Peripheral Non-small Cell Lung Cancers Treated With Stereotactic Body Radiation Therapy (SBRT)
Neal E. Dunlap, James M. Larner, Paul W. Read, Benjamin D. Kozower, Christine L. Lau, Ke Sheng, David R. Jones
University of Virginia, Charlottesville, VA
BACKGROUND:
Previous studies of SBRT for non-small cell lung cancer (NSCLC) have combined T1 and T2 tumors and have included both central and peripherally located tumors. The purpose of this study was to compare the outcomes and local control rates of patients with peripheral T1 and T2 NSCLC treated with SBRT.
METHODS:
The records of 40 consecutive patients (median age 73, range 54-87) treated with 3 or 5 fraction lung SBRT for peripheral, biopsy-proven clinical stage I NSCLC from March 2005 to January 2008 at a single institution were reviewed. Thoracic surgeons and radiation oncologists saw all patients and co-designed their treatment plans. SBRT was delivered at a median dose of 60 Gy (range, 42-60) prescribed to cover 95% of the planning target volume. Doses to organs at risk were limited based on the RTOG 0236 treatment protocol. Twelve patients had both pre-and post-SBRT PET-CT scans. Median follow was 11 months (range, 2-35). Survival and local control rates were calculated with the Kaplan-Meier method.
RESULTS:
Median tumor size was 23 mm (range, 9-50) with 27 (67%) and 13 (33%) having T1 and T2 tumors, respectively. Only 7% (3/40) refused surgery with the remainder being medically inoperable. Twenty-three percent of patients developed post-SBRT chest wall pain. Grade I, II, and III pneumonitis developed in 12%, 2%, and 2% of patients, respectively. Median survival was 11 months for the entire cohort. Relative to their pre-SBRT PET-CT scan 66% (8/12) of patients had a decrease in their tumor post-SBRT SUVmax, while 34% had an increase in their tumor post-SBRT SUVmax. Post-SBRT PET-CT scanning did not accurately predict likelihood of local recurrence. Eight patients (20%) developed metastatic disease independent of their T status. Overall survival for T1 tumors at 1 and 2 years was 93% and 65% and for T2 tumors was 75% and 62%. Local control at one year was worse in T2 tumors (70% vs. 100% for T1 lesions). The average time to local recurrence for T1 and T2 tumors was 16 and 7.5 months, respectively.
CONCLUSIONS:
SBRT is well tolerated in inoperable patients with NSCLC. SBRT for T2 NSCLC has a worse intermediate term prognosis and a higher local recurrence rate compared to T1 lesions. In addition, post-SBRT PET-CT scans are not reliable indicators of local control. Tumor size is an important predictor of response to SBRT and should be considered in future clinical trial designs.
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