(P055) Stereotactic Body Radiation Therapy in Unbiopsied PET+ Pulmonary Tumors

Sujith Baliga, MD, Nathan Bennion, MD, K. Martin Richardson, DABR, RSO, MS, Harry Lomas IV, MD, Kelly Spencer DABMP, MS, Pooya Jahanshahi, MD, John C. Perry, MD, James M. Larner, MD, C. Ronald Kersh, MD, FACR; Riverside Regional Medical Center; University of Virginia

Background: Stereotactic body radiation therapy (SBRT) has been demonstrated to be well tolerated and to offer high rates of local control in patients with inoperable biopsy-proven early-stage lung cancer. However, biopsy is not feasible in many SBRT candidates. Here, we review patient outcomes and toxicity data of unbiopsied positron emission tomography (PET)-positive pulmonary lesions treated with SBRT for presumed non–small-cell lung carcinoma (NSCLC).

Methods: We performed a review of all patients treated between March 2008 and January 2013 who received SBRT for PET+ pulmonary tumors. Criteria for pulmonary tumor diagnosis by PET were defined by high radiographic suspicion of malignancy, based on a hypermetabolic or enlarging lung nodule. The median SBRT dose was 60 Gy delivered in a median of four fractions. Dose was prescribed to a nonuniform planning target volume (PTV), based on the internal target volume (ITV) constructed from a 4D CT scan, allowing for tumor motion and continued alignment of surrounding organs at risk. The treatment plans consisted of noncoplanar static aperture arcs and noncoplanar static fields. Treatments were delivered using 6-MV x-rays with image guidance. Follow-up with PET/CT occurred every 3 months. Toxicity was scored using Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0). The Kaplan-Meier product estimator was used to measure outcomes, such as overall survival (OS), local control (LC), and distant metastasis–free survival (DMFS). The Charlson Comorbidity Index (CCI) was used to assess pretreatment morbidity.

Results: We identified 51 lesions in 51 patients who had a median follow-up of 10 months (range: 2–47 mo). The most common reasons for nonbiopsy included poor pulmonary status (n = 23) and patient refusal (n = 16). The median tumor size was 1.8 cm (range: 0.9–4.8 cm), with 73% located peripherally and 27% located centrally. There were 37 patients with T1 disease and 14 patients with T2 disease. The median age was 77 years (range: 53–90 yr), with a median CCI score of 6 and a median 2-year predicted survival based on CCI of 55%. Median pretreatment % predicted forced expiratory volume 1 (FEV1) and diffusion lung capacity for carbon monoxide (DLCO) were 63.5% and 59%, respectively. The initial median pretreatment standardized uptake value (SUV) was 4.40 and decreased to a median SUV of 1.9 at 10 months. The overall 4-year LC was 80%, and OS was 58%. The 4-year DMFS was 55%. Patients with stage I–IIA disease (n = 47) had an LC of 87% at 4 years. Only 8% of patients had a marginal failure, and 7% had an involved lobe recurrence. There was minimal toxicity, with 7.8% of patients with grade 2 dyspnea and 1.9% of patients with grade 3 fatigue. Serious toxicity, such as pneumothorax, pneumonitis, or bronchial airway obstruction, was not observed.

Conclusions: Our experience suggests that SBRT is a well-tolerated and effective treatment option for patients with PET+ pulmonary tumors who are not candidates for biopsy. Our cohort of medically inoperable patients demonstrated a high rate of LC combined with low toxicity, further supporting the rationale for a prospective randomized controlled study of SBRT in patients who are unable to be biopsied.