The Molecular Pathology of Cushing Disease: Are We Nearly There?

Corticotroph tumor progression during long-term therapy with osilodrostat in a patient with persistent Cushing's disease

PURPOSE

Corticotroph tumor progression (CTP) or Nelson's syndrome (NS) can occur in patients with Cushing's disease (CD) following bilateral adrenalectomy. It has rarely been observed in patients treated with long-term medical therapy for persistent CD. Osilodrostat (LCI699) is a new steroidogenesis inhibitor of 11β-hydroxylase (CYP11β1) that induced remission of hypercortisolism in 86% of patients with refractory CD in the randomized placebo-controlled trial LINC-3 (NCT02180217).

METHODS

A 40-year-old woman with persistent CD following transsphenoidal surgery was treated with osilodrostat in the LINC-3 trial and was followed with regular hormonal assessments and imaging of residual corticotroph tumor.

RESULTS

Under oral therapy with osilodrostat 10 mg twice daily, urinary free cortisol (UFC) normalized and clinical signs of CD regressed during therapy. However after 4 years of treatment, ACTH levels increased from 73 to 500 pmol/L and corticotroph tumor size increased rapidly from 3 to 14 mm, while UFCs remained well controlled. Surgical resection of an atypical tumor with weak ACTH expression and increased proliferative index (Ki-67 ≥ 8%) resulted in current remission but will require close follow-up.

CONCLUSION

This case highlights the importance of monitoring ACTH and corticotroph tumor size in patients with persistent CD, either under effective treatment with steroidogenesis inhibitors or after bilateral adrenalectomy.

Corticotroph tumor progression after bilateral adrenalectomy (Nelson's syndrome): systematic review and expert consensus recommendations

BACKGROUND

Corticotroph tumor progression (CTP) leading to Nelson's syndrome (NS) is a severe and difficult-to-treat complication subsequent to bilateral adrenalectomy (BADX) for Cushing's disease. Its characteristics are not well described, and consensus recommendations for diagnosis and treatment are missing.

METHODS

A systematic literature search was performed focusing on clinical studies and case series (≥5 patients). Definition, cumulative incidence, treatment and long-term outcomes of CTP/NS after BADX were analyzed using descriptive statistics. The results were presented and discussed at an interdisciplinary consensus workshop attended by international pituitary experts in Munich on October 28, 2018.

RESULTS

Data covered definition and cumulative incidence (34 studies, 1275 patients), surgical outcome (12 studies, 187 patients), outcome of radiation therapy (21 studies, 273 patients), and medical therapy (15 studies, 72 patients).

CONCLUSIONS

We endorse the definition of CTP-BADX/NS as radiological progression or new detection of a pituitary tumor on thin-section MRI. We recommend surveillance by MRI after 3 months and every 12 months for the first 3 years after BADX. Subsequently, we suggest clinical evaluation every 12 months and MRI at increasing intervals every 2-4 years (depending on ACTH and clinical parameters). We recommend pituitary surgery as first-line therapy in patients with CTP-BADX/NS. Surgery should be performed before extrasellar expansion of the tumor to obtain complete and long-term remission. Conventional radiotherapy or stereotactic radiosurgery should be utilized as second-line treatment for remnant tumor tissue showing extrasellar extension.

Cushing's Disease

In patients with Cushing's disease (CD), prompt diagnosis and treatment are essential for favorable long-term outcomes, although this remains a challenging task. The differential diagnosis of CD is still difficult in some patients, even with an organized stepwise diagnostic approach. Moreover, despite the use of high-resolution magnetic resonance imaging (MRI) combined with advanced fine sequences, some tumors remain invisible. Surgery, using various surgical approaches for safe maximum tumor removal, still remains the first-line treatment for most patients with CD. Persistent or recurrent CD after unsuccessful surgery requires further treatment, including repeat surgery, medical therapy, radiotherapy, or sometimes, bilateral adrenalectomy. These treatments have their own advantages and disadvantages. However, the most important thing is that this complex disease should be managed by a multidisciplinary team with collaborating experts. In addition, a personalized and individual-based approach is paramount to achieve high success rates while minimizing the occurrence of adverse events and improving the patients' quality of life. Finally, the recent new insights into the pathophysiology of CD at the molecular level are highly anticipated to lead to the introduction of more accurate diagnostic tests and efficacious therapies for this devastating disease in the near future.