Js. Powell et al., Outcome of radiotherapy for acromegaly using normalization of insulin-likegrowth factor I to define cure, J CLIN END, 85(5), 2000, pp. 2068-2071
Radiation therapy (RT) has traditionally been considered a useful additiona
l therapy for patients with acromegaly not achieving biochemical remission
after surgery. However, recent evidence has suggested that RT is not curati
ve in most patients with acromegaly when normalization of the serum insulin
-like growth factor I (IGF-I) level is used to define remission. Therefore,
we evaluated the success of RT based on IGF-I level in the 47 patients who
received RT as part of their treatment from the cohort of 161 patients wit
h acromegaly seen by us between 1981 and 1999. Four patients in whom no pos
t-RT IGF-I level was available were excluded from the analysis. Of the rema
ining 43 patients, 32 patients received external beam RT, 6 received fracti
onated stereotactic radiosurgery, 4 received gamma-knife RT, and 1 received
proton beam RT. The most recent IGF-I levels in these 43 patients, obtaine
d a mean of 5.2 yr post-RT (range, 0.8-13.2 yr), were compared to age-adjus
ted normal ranges.
IGF-I levels were normal in 17 patients (39.5%) without the addition of med
ical therapy. The percentage of patients with a normal IGF-I level generall
y increased with time post-RT; 27% of patients less than 6 yr post-RT, but
69.2% of patients 6 yr or more post-RT had normal IGF-I levels. Using the m
ore traditional criterion for cure, a random GH measurement, 74% of patient
s had a GH level below 5 ng/mL, and 44% had a GH level below 2.5 ng/mL and
would have been considered in remission based on these criteria.
We conclude that with time RT remains a useful adjunctive treatment for man
y patients with acromegaly. RT should be considered along with appropriate
medical therapy in selected patients who do not achieve normalization of IG
F-I level after surgery or for those resistant to medical therapy.