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AUSTIN -- Following pituitary surgery, radiation for persistent or recurrent acromegaly was shown to be an effective and safe treatment, researchers reported here.

In a retrospective analysis, patients with acromegaly who had undergone pituitary surgery and then received radiation therapy had twice the remission rate seen in those who did not receive radiation (RR 2.1, 95% CI 1.1-4.3, P=0.036), according to Diane Donegan, MD BCh BAO, senior clinical fellow of the Mayo Clinic, and colleagues.

The study reported that patients who underwent radiation treatment and those who did not did not have any significant differences in the requirement for adjuvant medical therapy at the end of the study (38/66 versus 18/28, P=0.5).

The findings of the single-center study were presented at the American Association of Clinical Endocrinologists' annual meeting.

"As many of you know, acromegaly is most commonly due to somatotroph adenoma, and is associated with increased morbidity, mortality, and decreased quality of life, if uncontrolled," Donegan explained during an oral presentation. "If IGF-1 and growth hormone is normalized, then mortality can be similar to the general population."

In order to address this, Donegan noted her research group aimed to assess the outcomes, as well as complications associated with radiation treatment, which is currently considered the third-line therapy for chronic acromegaly. Donegan said radiation treatment is not currently a very common form of treatment, particularly due to associated risk factors, such as cerebrovascular complications and hypopituitarism.

The study included individuals who were diagnosed with acromegaly and failed to achieve remission with surgical treatment. A total of 139 patients were included, who all underwent pituitary surgery, but continued to have abnormal IGF-I levels post-surgery.

Over half of participants underwent radiation treatment (65%, 90 of 139), with the majority exposed to Gamma Knife radiosurgery (86%). After a minimum of six-months following radiation treatment, patients experienced a mean time of 26 month to remission (6 to 223 months).

The groups did differ, Donegan said: the radiation treatment group had significantly larger tumors than those who did not undergo radiation (2 ± 0.9 cm vs 1.4 ± 0.6 cm, P≤0.001). Similarly, radiation-treated patients had a significantly higher incidence of cavernous sinus invasion (60% vs 22%, P= <0.0001).

There were no significant differences for risk of death between both participant groups (P=0.5), although Donegan said there were eight deaths reported throughout the duration of the trial. Other adverse events reported included one instance of stroke in the radiation group, although it was not thought to be due to the treatment.

However, Donegan suggested it is important to consider that "there is a possibility of developing anterior pituitary deficits, which needs to be borne in mind when thinking of the treatment algorithm for individual recurrent or persistent acromegaly." She reported there was an elevated rate of development of new anterior pituitary hormonal deficit without a notable previous history of dysfunction before radiation (28 patients, 33%), most common being adrenal insufficiency.

When a member of the audience inquired about what methods were used to assess participants who developed ACTH deficiency during the study, Donegen responded they did not conduct formal insulin tolerance tests, and instead, analyzed samples of the participants’ cortisol.

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