Early-Stage Lung Adenocarcinoma Treated With Stereotactic Body Radiation Therapy: Prognostic Factors for Treatment Outcomes

Abstract

While stereotactic body radiotherapy (SBRT) has been well-established as an effective treatment for early-stage lung cancer, follow-up studies have suggested that the incidence of regional recurrence and distant metastasis can be significant. Given that the histologic subtype of lung adenocarcinoma on either surgical or core biopsy specimens has been recognized as a prognostic factor, we sought to evaluate outcomes after SBRT for early-stage lung adenocarcinoma based on this variable. A review of institutional registries identified 51 consecutive patients (55 lesions) with stage I to IIA lung adenocarcinoma who had undergone definitive SBRT at our institution from August 2009 to August 2016. Potentially prognostic indicators including International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society (IASLC/ATS/ERS) histologic subtypes of lung adenocarcinoma, positron emission tomography (PET) parameters of maximal standardized uptake value (SUVmax), PET volume (volume at 40% of SUVmax), PET volume multiply SUVmax and TLG (total lesion glycolysis), T stage and the pattern of initial presentation (uni- versus multi-focal) as well as pre-SBRT history of malignancy were analyzed to determine if there was an association with local, nodal, regional, distant failure and overall survival rates using logistic regression models. The median follow-up for the entire cohort was 2.17 years. The failure rates of local, nodal, regional, and distant were 5.6%, 19.2%, 25.9% and 24.5%, respectively. The overall survival rate was 71.2%. The PET parameters volume, volume times maximal SUV and TLG as well as T stage (T3 above) were identified as significant predictors (p<0.05) for local control. Any pre-SBRT history of malignancy was significantly associated with higher incidence of distant metastasis. The histologic subtype of adenocarcinoma and presentation of multi-focal lesions were not associated with treatment outcomes (p>0.05, for all). We demonstrated that volume of PET and T stage were significant predictors of local control after SBRT for early-stage adenocarcinoma of the lung. A history of prior malignancy was associated with a high incidence of distant metastasis. We are unable to identify histologic subtype of adenocarcinoma and multi-focal lesions at presentation as prognostic factors.