Poster Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

ACTH-secreting pituitary carcinoma transformed from Cushing's disease is exceptionally rare and highly aggressive, with limited treatment options. We report the case of a 70-year-old female with ACTH-secreting pituitary carcinoma who demonstrated a durable response to immune checkpoint inhibitors (ICIs) over a 27-month period. 

The patient initially presented with a rapidly growing pituitary carcinoma, which developed following bilateral adrenalectomy for Cushing's disease. The tumor initially responded to six cycles of temozolomide and seven cycles of temozolomide plus capecitabine. However, subsequent imaging revealed multiple brain and pulmonary metastases, along with worsening generalized hyperpigmentation and left oculomotor palsy. After three cycles of combination therapy with ipilimumab and nivolumab, her plasma ACTH levels dramatically decreased from 58,000 pg/mL to 198 pg/mL, accompanied by an improvement in hyperpigmentation (Figure 1). Continued nivolumab therapy further reduced ACTH levels to 44 pg/mL (normal range: 6–60 pg/mL). Follow-up imaging showed a marked therapeutic response, including the complete resolution of chest lesions. While the pituitary tumor and multiple small brain metastases persisted, the patient remains in good condition at 27 months, continuing nivolumab therapy with glucocorticoid and mineralocorticoid replacement. 

This case suggests that ICIs may be a viable therapeutic option for aggressive pituitary carcinoma, particularly in cases resistant to temozolomide. The high tumoral mutational burden induced by prior alkylating agent therapy may have contributed to the robust response to ICIs.