Outcomes of patients with Nelson’s syndrome after primary treatment: a multicenter study from 13 UK Pituitary centers

Context: Long-term outcomes of patients with Nelson’s syndrome (NS) have been poorly explored, especially in the modern era. 
Objective: To elucidate tumor control rates, effectiveness of various treatments and markers of prognostic relevance in patients with NS. 
Patients, design, and setting: Retrospective cohort study of 68 patients from 13 UK pituitary centers with median imaging follow-up of 13 years (range 1-45) since NS diagnosis. 
Results: Management of Cushing’s disease (CD) prior to NS diagnosis includedsurgery+adrenalectomy (n=30, eight patients had two and one had three pituitary operations), surgery+radiotherapy+adrenalectomy (n=17, two received >1 courses of irradiation, two had ≥2 pituitary surgeries), radiotherapy+adrenalectomy (n=2) and adrenalectomy (n=19). Primary68 management of NS mainly included surgery, radiotherapy, surgery+radiotherapy and observation; 10-year tumor progression-free survival was 62% (surgery 80%, radiotherapy 52%, surgery+radiotherapy 81%, observation 51%). Sex, age at CD or NS diagnosis, size of adenoma (micro-/macroadenoma) at CD diagnosis, presence of pituitary tumor on imaging prior adrenalectomy, mode of NS primary management were not predictors of tumor progression. Mode of management of CD before NS diagnosis was a significant factor predicting progression, with the group treated by surgery+radiotherapy+adrenalectomy for their CD showing the highest risk (HR 4.6; 95% CI, 1.6-13.5). During follow-up, 3% of patients had malignant transformation with spinal metastases and 4% died of aggressively enlarging tumor. 
Conclusions: At 10 years follow-up, 38% of the patients diagnosed with NS showed progression of their corticotroph tumor. Complexity of treatments for the CD prior to NS diagnosis, possibly reflecting corticotroph adenoma aggressiveness, predicts long-term tumor prognosis.