R037

A Single Centre Assessment of Pituitary Radiotherapy

GS Seyan¹, A Falconer², NM Martin¹

¹Imperial Centre for Endocrinology, Imperial College Healthcare NHS Trust, London.

²Department of Clinical Oncology, Imperial College Healthcare NHS Trust, London.

Abstract:

This was a retrospective study of the efficacy and side effects achieved by fractionated external beam pituitary radiotherapy at a single centre (Charing Cross Hospital, ICHNT).

Tumour size and presence of hypophyseal axes were compared before and after pituitary radiotherapy. Thirty-eight patients with pituitary adenomas were studied (19 males): 15 non-functional adenomas (NFA), 18 growth hormone (GH) secreting adenomas, four adrenocorticotrophic hormone (ACTH) secreting adenomas and one prolactinoma. Median radiotherapy dose was 50 (45-50) Gy and median fractions 30 (25-30).

Tumour growth was controlled in 93.9% of cases. Pituitary axis dysfunction occurred in the following order: prolactin, ACTH, TSH, FSH/LH, GH.

There was a median follow-up time for acromegalic patients of 81 (32-115) months.  In acromegalic patients (n = 18), radiotherapy significantly reduced GH burden (nadir GH on an oral glucose tolerance test (OGTT) (3.4 (2.6-5.6) [pre-radiotherapy] vs 1.6 (0.9-2.7) mcg/L [post-radiotherapy], p<0.001) and age-adjusted IGF-1 (94.5 (60.8-119.1) [pre-radiotherapy] vs 60.6 (32.9-78.5) nmol/L [post-radiotherapy], =18, p<0.001). However, using strict criteria for cure (nadir GH on OGTT <0.6mcg/L and normal age-adjusted IGF-1), radiotherapy induced remission in only two acromegaly patients over a median follow up time of 36 (1-72) months.

This study can conclude that fractionated external beam radiotherapy is effective at controlling growth of pituitary adenomas and reducing GH burden in acromegaly. Contrary to historical reports, this study demonstrates early loss of prolactin and ACTH axes following pituitary radiotherapy.