Comprehensive Treatment of Mediastinal Neuroendocrine Tumor: A Case Report

Neuroendocrine tumors in the mediastinum are relatively rare. We report a patient with mediastinal neuroendocrine tumor that was successfully resected after descending stage by drug-eluting embolic transcatheter arterial chemoembolization had been performed. No tumor recurrence was found in the 1-year follow-up after surgical resection.


Introduction
Neuroendocrine tumors (NETs) are thought to arise from cells throughout the diffuse endocrine system.
NETs comprise a broad family of tumors, where the most common are in the gastrointestinal tract, lung, thymus and pancreas. Primary mediastinum is rare. Here, a summary and analysis of clinical data is presented from a patient with giant mediastinal neuroendocrine tumor that was successfully resected after descending stage by drug-eluting embolic transcatheter arterial chemoembolization (DEE-TACE) had been performed. No tumor recurrence was found in the 1-year follow-up after surgical resection.

Case Presentation
A 32-year-old male patient was admitted with symptoms such as chest tightness, chest pain, cough and panic. Computed tomography (CT) had shown that the mediastinum and right lung occupied a space, measuring about 11 cm × 17 cm, with uneven enhancement (Fig. 1a). Then, etoposide and cisplatin chemotherapy were used for 5 cycles. After three months, the CT scan revealed that the tumor was slightly smaller than before, measuring about 10 cm × 14 cm, but uneven enhancement was still seen (Fig. 1b). Multidisciplinary consultation showed that the tumor was huge and close to the pericardium, so it was di cult to remove. Considering the abundant blood supply of the tumor, it was deemed feasible to perform surgical resection after transcatheter arterial chemoembolization.
Using a transfemoral approach, a 5-F Cobra (Cook Medical Products, Bloomington, IN, USA) catheter was used to examine the bronchial artery, internal thoracic artery and phrenic artery for angiography (Fig. 2).
Then the responsible vessels were intubated with 2.7-F PROGREAT® microcatheter (Terumo Interventional Systems, Tokyo, Japan). Through the microcatheter, 40 mg of docetaxel and a vial of 300-500 µm diameter CalliSpheres microspheres (Suzhou Hengrui Callisyn Biomedical Co., Ltd., Suzhou, Jiangsu Province China) loaded with 100 mg of oxaliplatin were injected to occlude each tumor artery until angiographic tumor staining disappeared. Then, the 5-F vertebral catheter (Cook Medical Products, Bloomington, IN, USA) was used to intubate the right internal mammary artery, where the tumor staining area could be visualized by angiography. Embolization was subsequently performed with the above method. It must be noted that the embolic agent should be injected slowly to avoid nontargeted embolization. The patients were given symptomatic treatment after operation to reduce edema and prevent infection.
One month after embolization, CT scan showed a considerable reduction in tumor size and blood supply.
After a further round of DEE-TACE consolidation treatment had been completed, CT scan showed a considerable reduction in tumor size (8.5 cm × 13 cm) and complete necrosis of the tumor (Fig. 1c). After the surgical consultation, the tumor load was signi cantly reduced, so it was decided to move forward with the tumor resection and right upper lobectomy. Postoperative pathology revealed a mediastinal neuroendocrine tumor along with chronic in ammation of the upper lobe of the right lung and interstitial brosis. One month after resection, CT scan showed no residual tumor. The life quality of the patient was signi cantly improved, without chest tightness, chest pain, or other symptoms. At 1-year of follow-up, he had no tumor recurrence.

Discussion
NETs mainly occur in stomach, intestine and pancreas, but primary mediastinum is rare. Because the symptoms and signs of NETs are not typical, the clinical manifestations are complex. Most patients have local spread or distant metastasis when diagnosed and lose the chance for radical operation [1]. The treatment strategy for mediastinal NET is still inconclusive, but surgical resection is still the standard treatment. For patients with highly and moderately differentiated (G1/G2) tumors that cannot be surgically removed and with locally advanced and distant metastases, a combination of systemic and local therapies should be adopted. In this case report, the tumor was considered to be at the G2 stage. An etoposide and cisplatin regimen was used for chemotherapy, but the effect was not good. Considering that the tumor was huge, surrounded by blood vessels, and di cult to surgically remove, embolization was decided to quickly reduce the tumor burden.
Transcatheter arterial chemoembolization (TACE) has been previously used for the treatment of liver cancer, and the technology has been widely used in extrahepatic tumors [2]. Drug-eluting embolic microspheres can be loaded with chemotherapy drugs, and therefore they can embolize the tumor blood vessel bed and while releasing drugs. According to National Comprehensive Cancer Network guidelines for neuroendocrine tumors, etoposide/cisplatin or etoposide/carboplatin are used as rst-line drugs [3].
There is no clear plan for second-line treatment, but uorouracil or capecitabine combined with oxaliplatin or irinotecan can be considered [4]. Furthermore, oxaliplatin is the only platinum drug that can be loaded by CalliSpheres microspheres. Microspheres that ranged 300_500 µm in diameter were chosen to avoid possible stula or dangerous anastomosis.

Conclusion
Neuroendocrine tumors originating from the mediastinum are rarely reported. DEE-TACE down-stage treatment of mediastinal neuroendocrine tumors may be safe and effective.    Angiographic image during the rst DEE-TACE showed the bronchial artery (a), phrenic artery (b) and internal thoracic artery (c) as a tumor-feeding vessel (arrow).