PP28. THE EFFECT OF PHOTODYNAMIC THERAPY FOR RECURRENT PITUITARY ADENOMAS: A DOUBLE-BLIND RANDOMISED CONTROLLED TRIAL

Abstract

While pituitary tumours are histologically benign lesions, long-term control is difficult to achieve, even in patients who have undergone surgery. Tumour remnants are typically inaccessible, infiltrating the dura or of a consistency that precludes safe removal. Radiotherapy is the mainstay of adjuvant treatment for growing residuum and is able to provide tumour control in the majority of cases, however it is not without limitations and some lesions prove radio-resistant. Photodynamic therapy (PDT) has been employed as an adjuvant therapy in many malignancies and has been endorsed by the American Food and Drug Administration (FDA) for the treatment of oesophageal and non-small cell lung cancer. A photosensitising agent is administered which is then taken up preferentially and retained by tumour cells. It is subsequently activated by administered light of a particular wavelength, in the presence of oxygen. This results in the formation of highly reactive singlet oxygen, which is cytotoxic. The activated oxygen can cause direct cytoplasmic and mitochondrial damage to the tumour cells as well as indirect action through the destruction and collapse of the tumour vasculature. 14 patients with histologically confirmed pituitary adenomas and MRI-proven evidence of disease recurrence were randomised to either IV Photofrin (2mg/ Kg Body Weight) or placebo (0.9% Sodium Chloride, 0.8ml/Kg Body Weight) followed by endonasal light therapy. Patients remained under clinical and radiological surveillance, as per the usual Departmental protocols. 7 patients were randomised each to the PDT and placebo groups. The allocated treatment was received in all cases. The duration of time elapsed since administration of treatment varies as patients were recruited over a 7-year period but is now in the range: 9.8 to 16.4 years post-treatment. 5 of the 14 patients have now died; three in the PDT group and two in the placebo group, none of the deaths were found to relate to the pituitary tumours nor to the treatments administered. There were three of the 14 patients for whom no imaging was available for assessment since the files have been destroyed by the hospital. 7 patients in the placebo cohort and 4 in the PDT cohort had full sets of MRI scans for assessment. Tumour behaviour varied markedly in both cohorts; some lesions showing continued enlargement while others regressed substantially. While the results of this study do not achieve statistical significance, there is no suggestion within the available results that photodynamic therapy is superior to placebo, indeed the placebo group tended to out-perform the PDT group.