Systemic metastasis in a carotid body tumor: A rare presentation of a rare tumor.

Sir,

A 31-year-old man presented with a small swelling on the left side of his neck and hoarseness in voice since November 2009. History revealed that patient had similar swelling in 2005. He was operated and fine-needle aspiration cytology (FNAC) was suggestive of paraganglioma. Current CECT and MRI of neck were suggestive of a mass in the left carotid space. Fat plane between tumor and carotid vessels was lost. Enlarged lymphnode (1.2 cm) was present in left IJV group. Somatostatin level is highly expressed in some NET, so a recent study has indicated sensitive detection of NETs with somatostatin analogs such as 68 Ga-DOTATATE.[1] DOTATATE PET CT was suggestive of increase uptake in left carotid space, left level 2 and D7 vertebrae. His S. chromogranin level, which is a useful marker for NET, was 89.11 ng/ml at baseline (normal value: 0-40 ng/ml).[2] Patient was considered unresectable and planned for 6-7 cycles of DOTATATE therapy. After two cycles of DOTATATE therapy, he was referred to us for radiotherapy. Repeat DOTATATE scan after two cycles of therapy was suggestive of stable disease. Radiotherapy was delivered by 3D conformal technique. Sixty Gray in 30 fraction primary site and 40 Gray in 20 fractions to D6-D8 vertebrae was delivered (Conventional fractionation). Clinical target volume (CTV) for primary site consisted of Gross tumor volume (GTV) plus 0.5 cm margin and level II and III lymph nodes on left side of the neck. Radiotherapy was planned by three fields: Right anterior oblique, left anterior and posterior oblique. Patient then received four cycles of adjuvent DOTATATE therapy. Repeat DOTATATE scan 8 months after radiotherapy was suggestive of partial response at both primary site and D7 vertebrae.

The vast majority of carotid body tumors also called chemodectomas (CBT) or paragangliomas, are benign; however, some cases appear with visceral metastases.[3] Since 1891, approximately 152 of 1425 carotid body tumors described in the literature were malignant.

Diagnosis of these tumors is based upon history, examination, imaging, and histology.[4] Pre-operative histology is difficult to get due to the highly vascular nature of the tumor. Due to rarity of this tumor, there are no published guidelines for management. Surgery is the commonest modality. Radical lymph node dissection is not justified but sampling of regional lymph nodes has been proposed.[5] Benefit of radiotherapy combined with surgery is controversial as CBT is considered resistant to radiotherapy. It is generally accepted for the treatment of inoperable tumors, incomplete tumor excision or recurrent tumors, as median survival may be significantly improved with adjuvant radiotherapy compared with surgical treatment alone. Chemotherapy using vincristine, dacarbazine, and cyclophosphamide has been used for patients with systemic metastasis but at present, there is insufficient evidence to recommend chemotherapy in these cases.

To conclude, distant metastasis is rare in carotid body tumor. There are no specific guidelines for the treatment in malignant carotid body tumor. Management depends on case to case basis. In the above mentioned case, we highlighted that metastasis can occur even years after treatment of the primary resection of the tumor. So long-term follow-up is mandatory.