Prognostic factors of local control and disease free survival in centrally located non-small cell lung cancer treated with stereotactic body radiation therapy
Background: Stereotactic body radiation therapy (SBRT) results in high local control (LC) rates in
patients with non-small cell lung cancer (NSCLC). For central lung tumors, risk-adapted fractionation
schedules are used and underdosage to the Planned Target Volume (PTV) is often accepted to respect
the dose constraints of the organs at risk in order to avoid high rates of toxicity. The purpose of this
study was to analyze the effect of PTV underdosage and other possible prognostic factors on localand disease control after SBRT in patients with central lung tumors.
Material and Methods: Patients with centrally located NSCLC treated with SBRT were included. The
doses were converted into biologically equivalent dose using a/b-value of 10 Gy (BED10). Underdosage
to the PTV was defined as the (percentage of) PTV receiving less than 100 Gy BED10; (%)PTV < 100
BED10. Potential prognostic factors for LC and Disease Free Survival (DFS) were evaluated using Cox
regression analysis.
Results: Two hundred and twenty patients received 12 fractions of SBRT. LC-rates were 88% at
2 years and 81% at 3 years. Twenty-seven patients developed a local recurrence. Both the PTV < 100
BED10 and %PTV < 100 BED10 were not prognostic for LC. Tumor size and forced expiratory volume in
1 second (FEV1) were independently prognostic for LC. Disease progression was reported in 75 patients
with DFS-rates of 66% at 2 years and 56% at 3 years. Disea