Progressive Visual Failure in Acromegaly Following External Pituitary Irradiation

Abstract

Four out of twenty-three acromegalic patients selected for treatment with external megavoltage pituitary irradiation between 1961 and 1975 developed progressive visual failure. They had received megavoltage external irradiation through multiple portals from a cobalt-60 unit over a period of 3 weeks. Visual deterioration began 2 months to 6 years after irradiation. In two patients the optic nerves were explored. In both, post-mortem later confirmed radiation damage to the optic nerves and hypothalamus. In one case there was also necrosis of the right frontal lobe with necrosis and inflammation of the bone surrounding the pituitary fossa. In the two other patients, extensive clinical and neuroradiological investigation excluded the presence of a suprasellar mass as a cause for this visual failure and a clinical diagnosis of radiation necrosis was made.

Recent developments in the treatment of acromegaly

“…The advantage of low immediate morbidity and no mortality has to be considered. Radiation damage to the optic nerves and hypothalamus may occur even after a delay of several years [2]. Similar effects with only slightly higher control rates and a lower incidence of pituitary deficits were reported for the treatment with alpha-particles [23] or proton beam [19].…”

Efficacy and safety of CyberKnife radiosurgery for acromegaly

“…Even if biochemical control is attained, normalization of GH levels may take a decade or more. Moreover, conventional fractionated RT is associated with complications caused by local tissue exposure to radiation, including hypopituitarism, cranial nerve neuritis, visual-field defects, possible cognitive disturbances or increased cerebrovascular disorders, radiation-induced gliomas, and delayed brain necrosis [9,[21][22][23][24][25][26][27][28][29][30]. In summary, conventional RT is effective in only a subset of patients, and may cause significant short and long-term complications.…”

Current and Future Strategies in Radiotherapy of Childhood Low-Grade Glioma of the Brain

“…In a total of 1,202 patients undergoing surgery followed by radiotherapy or radiotherapy alone, only 20 cases (1.6%) of radiation-induced late effects were observed (Table 2) [6]. Fractionated doses in excess of 2.0 Gy, however, are associated with an increased risk of late complications [2,3,31] (Table 2). …”