Giant pituitary adenomas: role of radiotherapy

Between 1970 and 1989, 31 patients with a diagnosis of giant pituitary adenoma were referred to the London Regional Cancer Center. Giant pituitary adenoma was defined in terms of extension in excess of 40 mm from the midpoint of the jugum sphenoidale. The diagnosis was made surgically in 30 patients and clinically in one. Tumor extent and dimensions were obtained from operative reports and/or radiological scans computed tomography or magnetic resonance imaging. Mean follow-up was 8 years. Initial treatment consisted of surgery alone (4 patients), radiotherapy alone (2 patients) and combined surgery-radiotherapy (25 patients). One patient underwent a needle biopsy for histological confirmation and was grouped with the radiotherapy alone subset. Four of the six patients who received single modality treatment failed initial treatment (three surgery and one radiation). In contrast only 3 of the 25 patients treated with combined surgery-post-operative radiotherapy progressed despite the fact that all patients had gross residual disease post-operatively and that 43% of these patients received radiotherapy based on the post-operative rather than the pre-operative tumor extent. With subsequent salvage, overall tumor control amongst the 31 patients was 93.5%. Complications in general were minimal although one acromegalic patient sustained a unilateral internal capsular cerebrovascular accident year post treatment. In summary, combined modality treatment with initial surgical debulking followed by radiotherapy in the dose range of 4500-5000 cGy over 25 fractions yields tumor control rates in giant pituitary adenomas similar to those of smaller pituitary adenomas without undue morbidity.