Blindness in patients after external beam irradiation for pituitary adenomas: Two cases occurring after small daily fractional doses

Radiotherapy for non‐functioning pituitary tumours

“…The potential risks of RT are well established but may take many years to develop into clinically relevant complications. Visual impairment due to radiation induced cataract formation or radiation induced optic neuropathy, described in 1·5% of patients treated with pituitary RT in some studies (Millar et al, 1991, Brada et al, 1993Fisher et al, 1993), can be avoided by careful planning of RT with application of a limited total dosage administered through fractionated fields (Jones, 1991). Secondary oncogenesis has been reported following pituitary irradiation (Brada et al, 1992, Tsang et al, 1994; other studies, however, have failed to confirm a clear excess risk of this complication (Jones, 1991;Bliss et al, 1994), hence the true magnitude of the risk remains contentious.…”

“…Following treatment with RT, however, there is a significant risk of varying degrees of hypopituitarism (Snyder et al, 1986;Sheline, 1987;Littley et al, 1989) with Nelson et al, (1989) reporting panhypopituitarism in 50% following pituitary surgery and irradiation. Some studies have also documented visual impairment (Millar et al, 1991), an increased incidence of secondary brain tumours (Al-Mefty et al, 1990;Brada et al, 1992) and cortical scarring (Grattan-Smith & Morris, 1992) following RT. However, the use of carefully planned RT and a limited total dosage administered through fractionated fields do not appear to support such concerns (Jones, 1991).…”

Outcome of fractionated stereotactic radiotherapy in patients with pituitary adenomas resistant to conventional treatments: a 5·25‐year follow‐up study

“…A well‐documented adverse effect of RT is irradiation of surrounding healthy tissues, which has raised safety concerns. Hypopituitarism is seen in up to 50%, 9 and there is increased risk for optic nerve damage, blindness, cerebrovascular disease, second brain tumours and dementia 10–12 . Two studies in patients with acromegaly indicated that excess mortality may be related not only to poor disease control but also to RT 13,14 …”

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“…This number is probably an overestimation as it includes patients who received dose fractions or total irradiation in excess of current recommendation. However, visual loss due to radiation damage can occur even when "safe" doses of are administered [50]. If the total dose is limited to 45 Gy and the daily dose does not exceed 2 Gy, it is likely that the risk of radiation damage to the optic nerve or chiasm will be much lower than the 2% estimate [23].…”