OBJECTIVE:

To evaluate the efficacy and safety of proton stereotactic radiosurgery (PSRS) for acromegaly that is refractory to surgical treatment and medication.

METHODS:

From 1992 to 2003, 22 patients were treated at our institution for persistent acromegaly with use of PSRS. All patients had undergone at least one transsphenoidal surgical procedure without biochemical cure. The median treatment dose delivered during PSRS was 20 (range, 15 to 24) cobalt gray equivalents.

RESULTS:

Follow-up was available for all patients at a median of 6.3 (range, 2.5 to 14.2) years after PSRS. A response to PSRS was observed in 21 of 22 patients (95%). A complete response (CR), defined as sustained (> or =3 months) normalization of insulinlike growth factor-I without medical suppression, was attained in 13 patients (59%). Among patients with CR, the median time to CR was 42 (range, 6 to 62) months. No visual complications, seizures, clinical evidence of brain injury, or secondary tumors were noted on regular magnetic resonance imaging scans. One patient had complete pituitary dysfunction before PSRS and was therefore excluded from evaluation for failure. Of the other 21 patients, 8 (38%) had new pituitary deficits.

CONCLUSION:

These results demonstrate that PSRS is effective for persistent acromegaly, with 59% of patients attaining normal insulinlike growth factor-I levels without use of any medication after a median of 6.3 years. Our findings indicate that radiosurgery results in an expeditious biochemical response with low morbidity.