Teaching Case

A 77-year-old female patient presented with a painless left neck mass. Doppler ultrasound and angiography revealed the lesion's highly vascular nature. A diagnosis of hypervascular tumour was made on the basis of findings from imaging studies. Blood and urine tests were unremarkable.

The strongly enhancing mass with a maximum dimension of 3.1cm was located just above the bifurcation of the common carotid artery splaying the internal and external carotid arteries medially and laterally (Fig. 1a). The ascending pharyngeal artery dominated the arterial blood supply, as shown on CECT and angiogram (Fig. 2, 3). Based on clinical findings and imaging, a diagnosis of a carotid body tumour was confirmed. The patient underwent embolisation with significant devascularisation of the lesion (Fig. 4). Surgical procedure was planned but the patient refused post-embolisation surgery and alternatively underwent adjuvant radiotherapy.

For radiation planning, our patient underwent CT with 3 mm slice thickness. Planning target volume (PTV) and critical structures were drawn. PTV consisted of the gross target volume (GTV) plus a 5-mm safety margin (Fig. 5, 6).

Follow-up CT examinations up to 30 months after radiotherapy revealed significant tumour regression, as shown on Figure 1 b, c.

A carotid body tumour (CBT), also called carotid glomus tumour is a slow-growing highly hypervascular tumour arising from paraganglionic cells of the carotid body. It is usually located at the common carotid artery bifurcation. Carotid body tumours are the most commonly seen paragangliomas of the head and neck [1]. Findings obtained by Doppler ultrasound and angiography are usually diagnostic. For exact localization and pre/operative planning a combination of angiography, contrast-enhanced CT, and/or MRI is ideal [1, 2].

Embolisation is an effective treatment that aims to starve CBTs of their blood supply and induce necrosis. A combined endovascular and surgical approach to CBTs has been shown to be an effective treatment of these highly vascularized tumours. However, resection may result in deficits of one or more cranial nerves [1].

Our patient underwent embolisation but she refused post-embolisation surgery because of her age. In the absence of other options, and based on its effectiveness in treating glomus tumours, radiotherapy (RT) was offered. RT is an emerging treatment modality for paraganglioma and represents an alternative to surgery especially for elderly patients and for patients with symptomatic tumours that are considered unresectable or had recurred after resection. RT is generally well tolerated [3-7].

Stereotactic (SRT) or conventional radiotherapy (CRT) can achieve excellent local tumour control rates and relief of symptoms without the morbidity that may be associated with radical surgery. Recent studies show that up to 100% of patients treated with RT achieved tumour control suggesting considering RT for the primary management of paraganglioma. RT can be delivered to CBT patients with no absolute contraindications and independent of size. Tumour size may be the only major limitation of SRT (ideal size <3 cm) [3-7]. For catecholamine-producing paragangliomas surgical treatment maybe more appropriate [8].

Tumour size in our patient was >3 cm, so we decided in favour of CRT. Treatment was delivered by a linear accelerator with 6-MV photons. Daily prescribed dose was 2.0 Gy/fraction, 5 times a week and the cumulative dose was 54.0Gy. PTV was covered by 95% of the prescribed dose (Fig. 5).

The RT was well tolerated except for slight skin erythema after RT which resolved spontaneously after a few weeks. This patient is free of local recurrence to date.

We report a case of carotid body tumour showing good clinical response to radiotherapy in combination with embolisation. This combination is unusual but it can be considered for elderly patients with large tumours who are poor candidates for surgery.