Fractionated Stereotactic Body Radiotherapy (Sbrt) Versus Single Dose Stereotactic Body Radiotherapy In The Treatment Of Primary Lung Tumors: Early Results From A Multi-Institutional Analysis

Stereotactic body radiotherapy (SBRT) is the standard treatment for inoperable early stage lung tumors or when surgery is refused by patients. SBRT is usually delivered in single or multi-fraction regimens, nevertheless only few studies directly compared these two approaches. Clinical outcome and toxicity profile of multi-fraction regimen and single dose SBRT were evaluated in this multi-institutional analysis. Patients affected by medically inoperable early stage lung tumor were treated with two different schedules: 70 Gy in 10 fractions (TF) (BED: 119 Gy 10 ) and 30 Gy in single dose (SD) (BED: 120 Gy 10 ). Toxicities including Common Terminology Criteria for Adverse Events (CTCAE) grade 3 pneumonitis, chest wall pain and esophagitis were evaluated. Seventy-three patients affected by medically inoperable early stage lung tumors were treated from 2012 to 2018 at two Institutions, with SBRT delivered with two biological equivalent schedules: TF (29 patients) and SD (44 patients). Median age was 74 years (range 57-91). Patients were all staged with FGD PET-TC. Sixty (82%) patients had histologically confirmed diagnosis of NSCLC, most tumors were adenocarcinoma (60%) and squamous cell carcinoma (33.3%). Most of them were stage I (86.3%) and stage II (9.6%). Median follow-up was 17 months (range 3-81 months). One- and 2-years Overall survival (OS) was: 69.1% and 38.8% for TF and 85% and 71.3% for SD, respectively. One- and 2-years cancer-specific survival (CSS) was: 89.2% and 66.9% for TF and 92% and 89% for SD, respectively. One- and 2-years local progression-free survival (LPFS) was: 96.2% and 96.2% for TF and 97.5% and 87.8% for SD, respectively. All local progression occurred in lesions >30 mm in the TF group and >25 mm in the SD group. No differences in OS, CSS and LPFS were revealed. There were three cases of grade ≥3 pneumonitis in the TF group and 2 in the SD group. All severe pneumonitis occurred in lesions >30 mm in the TF group and >20 mm in the SD group. No differences in acute and late toxicity between the two groups were detected. TF and SD seems to be equally safe and effective in the treatment of primary inoperable lung tumors. TF schedule seems to be more appropriate for lesion >25 mm, while smaller lesion may benefit more from the SD. A longer follow-up is needed to assess late clinical outcome.