Cushing’s disease and aggressive pituitary tumours : Aspects on epidemiology, treatment, and long-term follow-up

Abstract: This thesis focus on clinical and epidemiological aspects of aggressive pituitary tumours/carcinomas and Cushing’s disease. Pituitary carcinomas account for only 0.1-0.2% of the tumours originating from the anterior pituitary gland and are defined solely by the event of distant metastases, whereas aggressive pituitary tumours are defined by their clinical behaviour of rapid/progressive growth despite optimal treatment with surgery, radiotherapy and medical agents. The prognosis for individuals with aggressive tumours/carcinomas has been poor with few treatment options. However, case reports indicated better outcomes after treatment with the alkylating agent temozolomide. In study I and III, we investigated 24 patients (16 aggressive tumours and 8 carcinomas) given treatment with temozolomide. We found an initial response rate (tumour regression ≥30%) in 10/21 evaluable patients, with complete regression in two carcinomas. Favourable response was associated with low tumour expression of the DNA repair protein MGMT; in responders median 9% (range 5-20%) vs non-responders median 93% (50-100%). Our results also indicated a longer survival in patients with low MGMT. Out of 11 patients with MGMT >10%, nine died with an estimated median survival of 26 months (95% CI 14-38), whereas only 1/6 patients with lower MGMT died from tumour progression during a follow-up of median 83 months (range 12-161).One of the patients in study I and III had a corticotroph pituitary carcinoma and in addition, Lynch syndrome (LS), a hereditary cancer-predisposing syndrome caused by germline mutations in DNA mismatch repair (MMR) genes and primarily associated with colon and endometrial carcinomas. In study II, we investigated the characteristics of the pituitary carcinoma and found loss of MSH2 and MSH6 protein expression, consistent with the patient’s germline mutation in MSH2. This was the first published case of a pituitary tumour associated with LS. In addition, we identified all known Swedish patients with LS (n=910) and searched for diagnostic codes consistent with a pituitary tumour in the Swedish national patient register. We found in total three patients with clinically relevant pituitary tumours, the reported prevalence in the background population is around 1:1000.The last two studies in the thesis focused on Cushing’s disease (CD), i.e. an ACTH-secreting pituitary tumour resulting in excess levels of cortisol. CD is associated with multiple comorbidities and increased mortality. The reversibility of comorbidities and mortality risk after remission of cortisol levels have been under debate. Study IV examined psychiatric consequences of CD, measured by the use of psychotropic drugs. 179 patients with CD and a quadrupled matched control group were followed from diagnosis and at 5- and 10-year follow-up. We found that use of antidepressants remained at around 25% of patients with CD, regardless of remission status, at diagnosis and follow-up, whereas drugs for somatic comorbidities decreased. Use of antidepressants, sleeping pills and anxiolytics was higher in patients with CD compared to controls at diagnosis and 5-year follow-up. A cross-sectional analysis of 76 patients in sustained biochemical remission for median 9.3 years showed that 25% were taking antidepressants, a significantly higher use than controls, OR 2.0 (95% CI 1.1-3.8). In addition, patients with CD had a higher use of psychotropic drugs, already in the 5-year period before diagnosis.Study V investigated mortality and causes of death in 371 patients with CD, compared to a quadrupled matched control group. Follow-up was median 10.6 years (IQR 5.7-18.2) after time of diagnosis. Overall mortality was increased in patients with CD, HR 2.1 (95% CI 1.5-2.8) and remained elevated for patients in remission at last follow-up (n=303), HR 1.5 (1.02-2.2). For patients not in remission (n=31), HR was 5.6 (2.7-11.6). Cardiovascular diseases (32/66) and infections (12/66) were overrepresented causes of death in patients with CD. Main conclusions of the thesis:Temozolomide improves outcome in patients with aggressive pituitary tumours/carcinomas and a low MGMT expression in the tumour predicts a favourable outcome. As additional therapies evolve, MGMT will help to tailor the treatment.Germline mutations in MMR genes may contribute to the development and clinical course of pituitary tumours and may be a novel cause of hereditary pituitary tumours.Patients with Cushing’s disease have a high burden of psychiatric health issues that remain despite achievement of biochemical remission, indicating irreversible effects of previous hypercortisolism. Psychiatric symptoms are early and important signs of CD.Efforts to achieve biochemical remission are crucial to reduce mortality in CD. However, patients in remission still have an increased mortality compared to controls. This underscores the need of life-long monitoring and treatment of associated comorbidities in patients with CD.