Abstract Context: Aggressive pituitary tumours causing Cushing’s Disease are very rare, difficult to treat, and usually resistant to conventional therapy. There is growing evidence for the use of temozolomide (TZM), an alkylating chemotherapeutic agent, as first line chemotherapy in tumours resistant to repeated neurosurgery, radiotherapy and adrenalectomy. Objective: To present the response to TMZ in a rare case of an aggressive pituitary tumour in the course of Cushing’s Disease and to review the literature referring to similar cases. Patient: In this report, we present the case of a 61 year old male patient who was diagnosed with Cushing’s Disease in the course of a pituitary invasive macroadenoma in 2011. The patient underwent 4 transphenoidal non-radical neurosurgeries (2012,2013) with rapid tumour progression, repeated non-radical bilateral adrenalectomy (2012, 2013) and stereotactic radiotherapy, and gamma knife surgery (2013, 2015). Histopathological examination revealed macroadenoma with high cell polymorphism and the presence of Crooke's cells, Ki- < 2%. Since 2015 the patient has been treated with 6 cycles of TMZ (320 mg per day for 5 consecutive days, 28-day cycle) with clinical and biochemical improvement and stabilized tumour size and no side effects. TMZ was continued for up to 9 cycles with a stable serum level of cortisol and ACTH being observed. However, clinical symptoms like headaches, visual field impairment, and finally hearing loss started to progress from the eighth cycle. After the ninth cycle of TMZ, there was a sudden increase in the size of the tumour, impairment of the cortisol and ACTH level, marked deterioration of the clinical status with the recurrence of severe headaches, narrowing of the visual field and hearing loss. At the beginning of 2016, a sudden clinical status and sight deterioration, strong headaches, drop of the right eyelid with widening of the pupil were observed. The patient died in February 2016. Lessons: The case of our patient suggests that the response to the TMZ treatment monotherapy in aggressive pituitary tumour causing Cushing’s Disease could be partial and restricted to 7-8 cycles followed by rapid progression of the tumor mass. Therefore, further research should be carried out with regard to new methods to extend the responsiveness and duration of TMZ treatment and to investigate predictors of responsiveness.

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