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SPINE METASTASIS OF INTRACRANIAL HEMANGIOPERICYTOMA: CASE REPORT OF TWO TREATMENTS

ABSTRACT Objective: To report the use of two techniques (radiosurgery and en bloc vertebrectomy) on the same patient for the treatment of two metastases in different sites of the spine arising from intracranial hemangiopericytoma. Intracranial hemangiopericytomas are rare, comprising approximately 2.4% of meningeal tumors and <1% of all tumors of the central nervous system. Metastases to the spine are even rarer: The largest case series reported in the literature has 5 and 7 cases. Methods: A 37-year-old man diagnosed with intracranial hemangiopericytoma was referred for a metastatic lesion in T12 and underwent en bloc resection using the Tomita technique. Results: The disease evolved with a metastasis to T2 treated by radiosurgery with 1600 cGy. The patient died 1,706 days after the en bloc resection of T12 and 1324 days after the radiosurgery of T2, and no recurrence occurred in these locations due to progression of the systemic diseases (liver and central nervous system). Conclusion: This is the first case reported in the literature in which two different techniques were used to treat metastatic lesions in the spine from an intracranial hemangiopericytoma and is unique for its use of two treatments in the same patient. Level of evidence: V, case report


ABSTRACT
Objective: To report the use of two techniques (radiosurgery and en bloc vertebrectomy) on the same patient for the treatment of two metastases in different sites of the spine arising from intracranial hemangiopericytoma. Intracranial hemangiopericytomas are rare, comprising approximately 2.4% of meningeal tumors and <1% of all tumors of the central nervous system. Metastases to the spine are even rarer: The largest case series reported in the literature has 5 and 7 cases. Methods: A 37-year-old man diagnosed with intracranial hemangiopericytoma was referred for a metastatic lesion in T12 and underwent en bloc resection using the Tomita technique. Results: The disease evolved with a metastasis to T2 treated by radiosurgery with 1600 cGy. The patient died 1,706 days after the en bloc resection of T12 and 1324 days after the radiosurgery of T2, and no recurrence occurred in these locations due to progression of the systemic diseases (liver and central nervous system). Conclusion: This is the first case reported in the literature in which two different techniques were used to treat metastatic lesions in the spine from an intracranial hemangiopericytoma and is unique for its use of two treatments in the same patient. Level of evidence: V, case report Keywords: Spine. Hemangiopericytoma. Radiotherapy. Neoplasm metastasis. Radiosurgery.

INTRODUCTION
Hemangiopericytomas in the bone are rare and are generally the result of the spread of tumors originating in the soft tissues. [1][2][3][4][5] In the spine, they have been described both in the epidural space and the bone, accounting for around 0.6% of primary bone tumors of the spine and sacrum. [6][7][8] Intracranial hemangiopericytomas account for around 2.4% of meningeal tumors and less than 1% of all tumors of the central nervous system (CNS). Although common in most malignant neoplasias, metastases to the spine are extremely rare in intracranial hemangiopericytomas. [8][9][10][11][12] Metastases to the spine may evolve to spinal cord compression syndrome if not treated. [12][13][14][15] Tomita et al. 16 described a globally recognized technique of posterior-approach en bloc resection for the treatment of primary tumors and metastases of the spine, reporting their experience with 20 cases, with pain relief and improvement of neurological deficit in most. Other authors, however, did not achieve the same outcomes when reproducing the technique. 23 There is currently no evaluation and management algorithm available for spine metastases and/or spinal cord compression, 17,18 nor level 1 evidence for intracranial hemangiopericytomas. [15][16][17][18][19][20] We present our experience with one case of intracranial hemangiopericytoma with asynchronous metastases in non-contiguous vertebrae, treated with two techniques (radiosurgery and en bloc vertebrectomy) because of the clinical circumstances of the patient.

Clinical presentation and examination
The study was approved by the institutional research ethics committee: Comitê de Ética e Pesquisa do Instituto do Câncer do Estado de São Paulo -CEP/ICESP -number 876/2016. All the participants signed the Free and Informed Consent Form. A 37-year-old male patient with an intracranial hemangiopericytoma diagnosed 8 years ago was referred to our spine surgery clinic (a public, university referral center for cancer) presenting a lytic lesion in vertebra T12 compatible with metastatic disease during staging (Figures 1 and 2), and complaints of back pain without any neurological deficit. The patient had previously undergone two surgeries for a primary resection and for recurrence in the central nervous system (Figures 3 and 4), and two liver surgeries for the resection of metastatic liver lesions.

En bloc vertebrectomy of T12
The patient underwent en bloc resection of T12 in two stages. In the first surgery, an en bloc laminectomy was performed ( Figure 5). The patient was positioned lying on the stomach, with appropriately placed cushions. An incision was made in the midline; the paraspinal muscle was dissected from the spinous processes and retracted laterally. Pedicle screws were placed two levels above and two    levels below the lesion (T10, T11, L1, and L2) with fixation of the system using two titanium rods. Resection of the costotransverse joint was performed on both sides, followed by blunt dissection of the pleura, detaching it from the vertebra. Next, resection of the T11 spinous process and its inferior articular processes was performed, making room for the passage of a Gigli saw around the pedicles through the intervertebral foramen. After transection of both the pedicles, the posterior elements of T12 were removed in a single block. Temporary fixation was accomplished with two titanium rods. The patient presented no major complications during the postoperative period, only mild pain at the site of the surgical approach, treated with analgesics. In the second surgery, transection of the ribs was performed at the level of the lesion (T12) and the level immediately above (T11) about 4 cm from the costotransverse joint, with ligation of the nerve roots and the segmental arteries of the same levels. We performed blunt dissection around the vertebral body, detaching it from the pleura, creating a plane between the anterior structures (pleura, aorta) and the vertebral body. We passed the Gigli saw through the space created, performing an osteotomy through the inferior terminal plate of the cephalic vertebra and the superior vertebral plate of the caudal vertebra. Once free, the vertebral body was rotated and removed en bloc. We placed an anterior reconstruction cage with a graft from the costectomy. We ended with the final fixation of the system. We also performed ligation of the thoracic duct using metal clips. An accidental injury to the pleura occurred during its detachment from the vertebral body and was repaired. During the entire procedure, we maintained the fixation of the system on at least one side, to reduce the neurological risk. About two months postoperatively, the patient presented significant respiratory discomfort and was hospitalized for pleural effusion (empyema) and diagnosed with chylothorax (Figures 6). He underwent chest drainage for treatment and was put on a lipid restricted diet for two weeks, without any other complications (Figure 7 and 8).
One year and six months following surgery, he underwent revision for symptomatic pseudoarthrosis of the T11-L1 arthrodesis, and made good postoperative progress (Figure 9).

Radiosurgery of T2
In the meantime, the patient presented a new metastatic lesion in T2 (Figure 10), about a year after the first surgery. As the disease was progressing, with new lesions of the liver and the CNS, it was decided to perform radiosurgery on the new lesion with a single dose at 1600 cGy, with no complications.

RESULTS
The patient remained free from recurrence at the sites where the two treatment modalities were performed, until his death, at 1,706 days after the en bloc resection of the lesion in T12, due to the progression of liver disease and clinical complications.

DISCUSSION
The management of hemangiopericytomas remains controversial, with no level 1 recommendation. [1][2][3][4][5] Surgical treatment is the central pillar in the treatment of these tumors. 2 There are no guidelines that indicate the ideal resection margins of metastases, which is even more problematic in the spine, where the margins are often bordered by vital structures. [2][3][4][5][6] In the experience reported, we achieved disease-free margins using the posterior approach en bloc resection technique described by Tomita et al., 16 without any significant neurological damage, and without any motor or sphincter function loss. It is a highly demanding technique with potential risks, and its use is only recommended for patients with metastases without paraspinal extension. 17 Chemotherapy plays a purely palliative role in the treatment of hemangiopericytoma, with poor results reported in the literature. 18 Stereotactic radiosurgery (gamma-knife, cyber-knife), has promising results 18 and radiosurgery can also increase survival and the time free from local recurrence, 19 but does not reduce the risk of distant metastases, which cause significant morbidity and mortality. En bloc resection is a high-risk procedure, with an average duration of 12.1 hours, average bleeding of 3.7 liters, and a complication rate of 36.3% reported in the literature. 20 Our patient had two significant postoperative complications: a profile of chylothorax and symptomatic pseudoarthrosis. Although it did not affect patient survival time, it resulted in higher morbidity, with two additional hospitalizations and a third surgery in addition to the two planned ones. In the lesion of T2, radiosurgery with a single dose of 1600 cGy was chosen, obtaining a good response with 1324 days of follow-up free

CONCLUSION
This is the first case reported in the literature in which two different techniques were used to treat metastatic lesions of the spine from intracranial hemangiopericytoma, unique because the two forms of treatment were used in the same patient. We observed survival free from recurrence for 1706 days, longer than that reported from the original technique (522 days), 16 and comparable to the more recent literature (1873 days in patients with disseminated metastases). 17 In our opinion, both techniques can be effective if executed with precision and discretion, observing the main determinants of success of the treatment, the extent of the disease, and presence of spinal instability, and the neurological and oncological components.

ACKNOWLEDGEMENT
The authors wish to thank dr. Pedro Henrique Xavier Nabuco de Araújo for treating the patient performing the surgical access, and dr. André Tsin Chin Chen for performing radiosurgery. Both provided detailed data about the patients, that allowed this case description.