FRACTIONATED STEREOTATIC RADIOSURGERY IN THE EXTRACONAL METASTASIS OF NEUROENDOCRINE TUMOR – CASE REPORT AND REVIEW OF LITERATURE

Case report: A 28-year-old male patient presented persistent diarrhea. Clinical investigation revealed tumoral images in the liver, pancreas, bones, and retroperitoneum, suggesting neoplastic involvement. Biopsy of the liver was performed, showing a highgrade neuroendocrine tumor (NET). During the systemic treatment based on chemotherapy, the patient developed severe ocular pain, refractory to analgesics, and bilateral eye mobility restriction. Magnetic resonance imaging (MRI) of the orbits showed bilateral extraconal expansive lesions in the right medial rectus and left lateral rectus muscles, measuring 10x11x11mm and 9x9x12 mm, respectively. We proposed a fractionated stereotactic radiosurgery (SRS) treatment with 25 Gy in five fractions. Intensity-modulated radiotherapy was employed. The patient evolved with an improvement of symptoms and preserved visual acuity confirmed by eye campimetry. An MRI performed five months after treatment showed a complete response of the lesions and discrete thickness of the right medial rectus muscle. Discussion: The actual epidemiology of NET metastases is unknown. A retrospective analysis showed that the most commonly affected site is the liver. The primary site that more often evolves to metastatic disease is the small intestine, followed by the pancreaticobiliary system. We reviewed the literature, retrieving eight articles containing case reports or series of cases of orbital involvement for metastatic TNE. Only one publication containing a sequence of cases presented SRS as a therapeutic approach, but only for unilateral involvement. The patient received treatment in five fractions, without information on the dose, progressing with the improvement of diplopia and proptosis. Follow-up revealed a stable disease. Partial resection followed by radiotherapy, use of image-guided radiotherapy (IGRT), and systemic therapy was also described therapeutic possibilities. Final Comments: Extraconal NET metastases are rare and therefore challenging in its management. The morbidity of the disease and treatment should be considered, limiting in the vast majority of cases the possibility of extensive resections. In this scenario, local therapies such as SRS and systemic therapies constitute valid therapeutic possibilities, reinforcing the importance of a multidisciplinary approach.