P-241VANISHING PRIMARY LUNG CARCINOMA FOLLOWING IRRADIATION OF THE METASTASIS: THE ABSCOPAL EFFECT

Abstract

Objectives: A new phenomenon also known as abscopal effect refers to a regression of metastatic lesions distant from the primary site of radiotherapy. Localized radiotherapy has been shown to induce abscopal effect in several types of cancer, including melanoma, lymphoma, and renal-cell carcinoma. However, clinical reports of abscopal effect in non-small-cell lung carcinomas are extremely rare. Case description: A 68-year old male patient was admitted to our clinic with dyspnoea. A computed tomography (CT) scan of the chest revealed an 8-mm lesion located at superior segment of lower lobe in the right lung. Transthoracic fine needle aspiration revealed squamous cell carcinoma. Cranial magnetic resonance imaging disclosed a pons metastasis. The patient had cranial radiotherapy. A mediastinoscopy was performed and it revealed no N2 disease. A second positron emission tomography (PET)-CT suggested the disappearance of right lower lobe nodule (i.e., no nodule and no radioactive fluorodeoxyglucose uptake). Revision of the evaluation of the lung nodule confirmed its squamous cell pathology. Six months later, new chest CT showed a right lower lobe nodule 1 cm in size. PET imaging also showed slightly increased radioactive fluorodeoxyglucose uptake of the lesion. We performed superior segmentectomy of the right lower lobe and lymph node dissection. The specimen was reported as adenocarcinoma with a predominant lepidic pattern. He was recurrence-free up to the 19-month follow-up. Conclusions: Regression of tumour cells after the radiation of a distant metastatic site is known as the Abscopal effect, suggesting stimulation of anti-tumour immunity by irradiation of tumour cells. The phenomenon should be considered in lung cancer patients with metastasis who have had irradiation for metastatic tumour.