Clinical Results Of Stereotactic Body Radiation Therapy (Sbrt) For Stage Ib (T2an0m0) Non-Small Cell Lung Cancer (Nsclc)

SBRT is becoming a standard treatment for patients with stage I NSCLC who are inoperable or refuse surgery. In stage I NSCLC, however, stage IB tumors are more difficult to control than stage IA tumors. We started SBRT in July 2006 using the linear accelerator system equipped with micro-multi-leaf collimators and an accurate patient setup system. Based on the new TNM classification (UICC 7th), clinical results of SBRT for stage IB NSCLC were analyzed in this study. Enrolled were 100 patients with NSCLC (81 men and 19 women) with a median age of 80 years (range, 59-89) treated from July 2006 to March 2013. All patients had stage IB (T2aN0M0) cancer. Eighty-eight lesions were histologically confirmed; 47 were adenocarcinoma (AD), 32 were squamous cell carcinoma (SCC), and 9 were NSCLC. All cases were medically inoperable or had a high age. The CTV was delineated using CT images taken at 3 phases (expiratory, inspiratory, and free breathing). The PTV margin was 3-7 mm. Three coplanar and 4 non-coplanar beams were used. The PTV was covered with 95% or higher isodose lines. Median PTV volume was 61 cc (range, 32-122). The SBRT dose was either 48-52 Gy in 4 fractions over 2 weeks (78 lesions) or 56-64 Gy in 8 fractions in 3 weeks (22 lesions). The median follow-up period was 42 months (range, 6-94) for living patients. The 3- and 5-year overall survival rate was 58% and 38%, respectively. The 3- and 5-year cause-specific survival rate was 80% and 72%, respectively. The 5-year local control rate was 83% and the progression-free rate was 56%. We assessed the 5-year survival, cause-specific survival, local control, progression-free, and radiation pneumonitis (RP) rates according to gender, age, PS, treatment period, histology, PTV volume, lung V20, fraction size, and BED. The 5-year survival rates of female patients, patients with high PS, and those treated after April 2010 were significantly higher than those of other patients (p=0.029, 0.021, and 0.005, respectively). The 5-year local control rate was significantly higher in AD than SCC patients (91% vs 67%, p=0.015), while the other rates did not differ significantly. Patients receiving higher doses (BED > 110 Gy) achieved a higher local control rate than lower dose patients (p=0.027), while there was no difference due to the fraction size. Grade 2 or higher RP occurred in 16%. RP rates did not differ according to the other factors. Re-irradiation was performed in 5 patients after local failure, and 4 achieved tumor control again. Novalis SBRT is safe and efficient for stage IB NSCLC. High dose treatment may be important for SCC patients, while AD patients may require adjuvant chemotherapy in light of the high rate of distant metastasis. Re-irradiation for local failure could achieve local tumor control.