Stereotactic Radiotherapy for Cushing's Disease and Prolactinoma

Abstract

Stereotactic radiotherapy (SRT) for secretory pituitary adenoma offers precise localization of dose with potential sparing of optic and hypothalamic functions. We collated the indications, treatment parameters, and both the clinical and biochemical results of Stereotactic radiotherapy for ACTH- 1 and prolactin-secreting pituitary adenoma. Between May 1990 and February 1996, nine patients (4 males and 5 females) with a mean age of 31.9 years had fractionated SRT for ACTH- or prolactin-secreting pituitary adenomas (Cushing's disease: n = 5; prolactinoma: n = 3; Nelson's syndrome: n = 1). These 9 patients had subtotal transphenoidal resections before SRT. An additional patient with Cushing's disease had aborted transphenoidal surgery and single-fraction Stereotactic radiosurgery (SRS). Prior to SRT, 4 patients received planned conventional fractionated external beam radiotherapy (XRT) (median dose 33.3 Gy). The median SRT dose was 34.5 Gy (range 14.4–50.4 Gy). The median total radiation dose (XRT plus SRT) for patients receiving fractionated treatment was 47.7 Gy. The median follow-up was 62 months (range 22–91 months). One patient with Nelson's syndrome was lost to follow-up. Of the 9 evaluable patients, none required reoperation for growth of pituitary tumor and all had radiographic control as shown by serial MRI scans. In 4 of the 6 patients with Cushing's disease, treatment resulted in normalization of hormone levels and resolution of symptoms. All 4 patients were able to discontinue medications. In 2 patients, normalization occurred within 4 months of treatment. Two patients with Cushing's disease failed, requiring adrenalectomy. For patients with prolactinoma, treatments resulted in a significant decrease of plasma prolactin levels. All patients treated for prolactinoma became asymptomatic; 2 were able to discontinue bromocriptine and 1 patient had a successful pregnancy. After radiation therapy, 1 patient developed new hypopituitarism. None of the patients developed worsened visual acuity, visual fields, or new neurological deficits. SRT with or without XRT may yield meaningful reductions in hormone levels with concomitant clinical improvement in selected patients with prolactinomas or Cushing's disease. In certain situations, combining conventional XRT with SRT is appropriate. Modifications of the Stereotactic radiation delivery may maximally reduce the hypothalamic dose, thereby possibly reducing the risk of clinical hypopituitarism. This treatment is safe and is without visual or other neurological toxicity.