True abscopal effect in a patient with metastatic non-small cell lung cancer

Background Systemic response to local anticancer treatment is a phenomenon called 'abscopal effect'. The immune system is thought to play a pivotal role in its occurrence. To date, several cases have been reported, particularly in patients receiving combined local treatment and immune checkpoint inhibitors. In such cases, it is impossible to discriminate between the effects of local and systemic treatment. Only a few cases of abscopal effect have been described with radiotherapy alone. Case presentation Here, we report on the case of an 81-year-old woman with recurrent metastatic squamous cell carcinoma of the lung with mediastinal tumor bulk, lymph node and bone metastases. The patient refused to undergo systemic treatment, and palliative stereotactic radiotherapy of the mediastinal tumor was performed. At restaging with FDG-PET/CT, the patient presented with a decrease in size and FDG-avidity both of the irradiated site and of the lymph node and bone metastases (which did not receive radiotherapy). At 25 months after radiotherapy, the patient is still in remission at all sites. Conclusions This is a rare case of an abscopal effect after radiotherapy as monotherapy. It is one of the few hitherto reported for lung cancer. Several ongoing studies with a combination of radiotherapy and immunotherapy are seeking to exploit a potential synergy to induce abscopal effects.