Effects of stereotactic surgery after acromegaly – Long-term results from the German Acromegaly Registry

Abstract

Background: The effects of conventional pituitary radiotherapy (RT) have been well described. Currently, conventional radiotherapy has been widely replaced by stereotactic radiosurgery (SRS). In small studies with observation times ranging from 0.5 to 10 years, biochemical remission rates of 20%-85% and hypopituitarism rates of 0%-69% were found with SRS. However, it is known that the full effects of radiotherapy may occur even later after 15 – 20 years. These long-term data are still lacking for SRS. Methods: We included all patients with a follow-up visit at least two years after SRS from the German Acromegaly Registry. We analyzed the rates of remission (by IGF-1 normalization) in Patients not receiving medical therapy at the last visit, the rates of patients still requiring medication, and the rates of hypopituitarism after SRS. We observed the results in the last visit with available information and divided the observation times after SRS into 5-year slots. Results: There were 200 patients with SRS in the Registry (63 Gammaknife, 29 Linac, 8 Cyberknife, 100 not further specified). Among those patients without medication, IGF-1 was normalized in 64% and 95% after 2 – 5 and 10 – 15 years, respectively. The rates of patients requiring medication showed no trend and ranged between 65% and 85% during the whole observation period of 2 – 25 years. The rate of gonadotropic, corticotropic, thyrotropic deficiency was 42%, 30%, and 22%, respectively, after 2 – 5 years and showed a constant increase to 67%, 67%, and 67%, respectively, after 15 – 25 years. Conclusion: Our results on the long-term effects of SRS are disappointing. There is a high rate of patients still requiring medication and the long-term rates of hypopituitarism are higher than described in previous studies of shorter duration.