Background
Radiationâinduced tumor immunity (RITI) influences primary tumor growth and development of metastases in preclinical cancer models with conventional radiotherapy. Antigenâspecific immune responses have also been shown for prostate cancer treated with radiotherapy. We examined whether RITI can be induced in patients with nonâsmall cell lung cancer (NSCLC) following proton radiotherapy.
Methods
Preâ and postâradiotherapy plasma samples from 26 patients with nonmetastatic NSCLC who received radiotherapy between 2010 and 2012 were evaluated by western blotting for IgG and IgM bands to assess RITI response to tumor antigens from lung cancer cell lines. Statistical analysis was used to evaluate any correlation among IgG or IgM and clinical outcomes.
Results
Twentyâone patients received proton therapy at 2 GyRBE/fraction (nâ= 17) or 6â12 Gy/fraction (n = 4); five received photon therapy at 2â2.5 GyRBE/fraction. Compared with the pretreatment baseline, new IgG or IgM binding was detected in 27% and 50% of patients, respectively. New IgG bands were detected in the 25â37 kD, 50â75 kD, and 75â100 kD ranges. New IgM bands were detected in the 20â25 kD, 25â37 kD, 37â50 kD, 50â75 kD, and 75â100 kD ranges. There was no difference in IgG and/or IgM RITI response in patients treated with photons versus protons, or in patients who received SBRT compared to standard fractionation (Pâ>â0.05). There was no difference in overall survival, metastasisâfree survival, or local control based on IgG and/or IgM RITI response (Pâ>â0.05).
Conclusion
RITI can be induced in patients with NSCLC through upregulated IgG and/or IgM. RITI response was not associated with proton versus photon therapy or with clinical outcomes in this small cohort and should be examined in a larger cohort in future studies.