Pituitary Metastases From Differentiated Thyroid Cancers: A Systematic Review.

Background: Pituitary metastasis (PM) from differentiated thyroid cancer (DTC) is extremely rare and may adversely affect outcomes. We aimed to assess the characteristics and outcomes of patients with PM from DTC. Methods: We systematically reviewed the literature on publications on PM and the different DTC histologic types (papillary, follicular, and Hurthle cell cancers). Three databases (PubMed, Embase, and Scopus) were searched for articles published from 1967 to 2022. Survival time was estimated as the period from the first treatment of PM to the time of death or last follow-up. Results: Twenty-five articles comprising 27 cases that met the eligibility criteria were identified using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The median age of the patients was 60 years (23 - 86). A preponderance of females (66.7%) with PM most commonly reported papillary thyroid cancer (55.6%). This was followed by follicular thyroid cancer (37.0%) and Hurthle cell cancer (7.4%). The most common presentations were headache, nausea, and vomiting, with visual symptoms in 44.4%. Diabetes insipidus was an infrequent finding (7.4%). The median time from diagnosis or first treatment of DTC to the diagnosis of PM was 3 years (0 - 25). The most common endocrine abnormality was hyperprolactinemia (63.2%), while the most frequently deficient hormone was luteinizing hormone (50%). The most common treatment modality for PM was a combination of radiotherapy and surgery with or without radio-iodine. At the end of the follow-up, 30% of the patients died. Only 33.3% of the patients achieved complete resolution of symptoms. The overall median survival time was 12 months (3 - 108). There was a moderate inverse correlation between the age of patients and survival, which was, however, not statistically significant (rs = -0.45, P = 0.103). Conclusion: PM from DTC is extremely rare, and Hurtle cell cancer appears to be the least associated with PM. Diabetes insipidus is a rare initial manifestation of PM from DTC. Complete resolution of symptoms is less likely to be achieved in PM from DTC. Older age may confer an increased survival tendency, probably due to more intracranial space volume in older people compared to the younger population. Larger studies are needed to examine the relationship between age and survival in PM from DTC. Also, more observational data are required to determine the predictors of survival and compare the efficacy of the different treatment modalities in patients with PM from DTC.