2 The procedure
2.1.1 The parotid glands are salivary glands located in front of the ears. Rarely, primary malignant tumours can develop in the parotid glands (although benign tumours are more common). Patients with malignant parotid tumours typically first present with painless, localised swelling on one side of the face.
2.1.2 Conventional treatment for malignant parotid tumours involves surgical excision. Superficial parotidectomy with careful dissection and preservation of the facial nerve is the most common surgical treatment. Superficial parotidectomy can also be used to establish a definitive diagnosis of the tumour. If malignancy is diagnosed, more extensive surgery may be required. Radiotherapy and chemotherapy may also be used in the treatment of malignant parotid tumours.
2.2.1 PDT involves initial administration of a photosensitising agent by intravenous injection. A few days later, the procedure is performed under local or general anaesthetic. A number of needles are inserted into the parotid tumour, either percutaneously or transorally, with the use of ultrasound, computed tomography or magnetic resonance imaging guidance. The required number and length of the needles depend on the size and position of the tumour. A beam splitter is used to divide a primary laser beam of appropriate wavelength into a small number of optic fibres, which are passed through the needles to deliver laser light into the tumour. Light dosimetry calculations are made based on the dose of light required and the output of the laser. After the deepest portion of the tumour has been treated, the needles and laser fibres are pulled back in 1 cm decrements, each withdrawal being followed by further illumination. The illumination of the photosensitive agent results in the formation of high-energy, cytotoxic oxygen molecules.
2.2.2 After administration of the photosensitising agent, patients need to follow a regimen of controlled re-exposure to ambient light over a period of 2 to 3 weeks.
Sections 2.3 and 2.4 describe efficacy and safety outcomes which were available in the published literature and which the Committee considered as part of the evidence about this procedure. For more details, refer to the Sources of evidence.
2.3.1 One report described two patients with refractory parotid tumours treated with PDT. One of these patients, a 42-year-old woman with a stage T4 adenoid cystic carcinoma of the parotid gland, had a complete response to PDT at 4 weeks and was alive and well with no evidence of recurrence at 15-month follow-up. The other patient was described as responding to treatment but no additional information was provided. A second report described a single patient with a parotid tumour, who was still alive 3 years after treatment.
2.3.2 The Specialist Advisers considered the main efficacy outcome to be local tumour control.
2.4.1 No complications attributable to PDT were described for the two patients in the report (see 2.3.1).
2.4.2 The Specialist Advisers considered theoretical adverse events to include photosensitisation that may result in burns to non-treated areas, allergic reactions to the photosensitising agent, nerve and blood vessel damage, bleeding and delayed healing.