Endocrine Abstracts

Background: Surgery, sometimes supported by adjunctive radiotherapy (RT), is the treatment of choice for patients with non-functioning pituitary adenoma (NFA). Previous studies have shown that patients treated with pituitary RT have doubling of mortality ratio due to cerebrovascular disease (CVD) but the reason for this excess is unclear. Transcranial Doppler (TCD) can be used to measure blood velocity in the middle cerebral arteries (MCAs) within the circle of Willis and also to conduct cerebral blood-flow autoregulation (CBA) tests. The aim of this study was to determine the impact of RT on CBA in patients treated for NFA and to establish if this could be related to the increased CVD mortality in patients who received RT.

Methods: Thirty-two patients treated for NFA (16 surgery only (8 male), 16 surgery and RT (9 male)) underwent blood flow monitoring using TCD. Patients performed a Valsalva manoeuvre, which gives a measure of autoregulation – A_I–IV. The study was approved by the LREC.

Results: Velocity of MCA blood-flow was significantly greater in patients treated with RT than those treated with surgery alone (left: 66.8 vs 52.6, P=0.01; right: 61.5 vs 51.2, P=0.05). A_I–IV as a measure of CBA was also diminished in the RT treated patients compared with A_I–IV in the surgery only group (120% vs 128%, P=0.09).

Conclusions: Patients treated with RT had increased cerebral blood-flow velocity measured in the circle of Willis. Furthermore, there was a concomitant reduction in CBA in the RT-treated patients. High velocity blood flow is known to cause adverse affects on CBA and contribute to endothelial disease. Our study thus suggests that the higher CVD mortality experienced by patients treated with RT may be partly due to disruption of some of the parameters that contribute to regulation of the cerebral circulation.