Stereotactic Body Radiation Therapy In Patients With Immune Suppression

Stereotactic Body Radiation Therapy (SBRT) is commonly used to treat patients with early stage non-small cell lung cancer (NSCLC) with high local tumor control. Anti-tumor immune response is thought to play an important role in patients treated with SBRT. In concordance with this, we hypothesize that patients on immunosuppressive therapy will have poor outcomes after SBRT with regard to local tumor control, disease progression, and survival. A retrospective review of 244 consecutive patients treated with SBRT from January 2007 through July 2013 was performed. Patients were identified who were treated with immunosuppressive therapy prior to and during therapy. All patients had biopsy proven stage I NSCLC with a Karnofsky performance status ≥ 70. Patients were treated by institutional standard fractionation schemes with Biologically Equivalent Dose greater than 100 Gy. Thirteen patients treated with SBRT on immunosuppressive therapy were identified. Eight patients had autoimmune disease, 3 had lymphoma, and 2 patients had prior renal transplant. Local control was 62% at 3 years. Progression free survival at 1, 2, and 3 years was 62%, 46%, and 0% respectively. Mean progression free survival was 11.5 months. Overall survival was 44% at 3 years; however all surviving patients at 3 years had disease progression. Median overall survival was 12 months. There were no grade 3-5 treatment related toxicities. Although patients on immunosuppressive therapy tolerate SBRT treatment with minimal acute toxicity; they have poor local control and progression free survival compared to historical controls. Overall survival appears to be marginally worse than historical rates in medically inoperable patients treated with SBRT. In this small cohort of patients, local control of early stage NSCLC in patients on immunosuppression therapy is much less than previously reported data. This supports the hypothesis that immune response plays an important role in tumor cell death in patients treated with SBRT for early stage NSCLC.