Endocrine Abstracts

Introduction: Non functioning pituitary adenomas (NFPAs) are the most common type of pituitary tumors and are often invasive, resulting in high relapse rates. The post-surgical treatment for NFPAs remains a debated issue and include radiation therapy and additional surgery. Several clinical studies have demonstrated that dopaminergic and somatostatin receptors (SSTRs) are widely expressed in NFPAs. Furthermore, recent studies have shown the potential effectiveness of somatostatin analogues in the medical management of NFPAs. Although the data are limited and controversial, NFPAs express SSTR5 and SSTR3 at high levels. Pasireotide, a multireceptor-targeted somatostatin analogue with high affinity for SSTR5, may be beneficial in the management of NFPAs.

Case presentation: We report the case of a 33-year-old female with a history of surgical resection for a macro NFPA in 2010. Despite treatment with cabergoline (0.5 mg once a week), a residual tumor in close proximity to the right cavernous sinus continued to progress on follow-up post-surgery. In 2017, the patient underwent a second endoscopic resection. She did not experience any postoperative pituitary hormone deficits. However, subsequent radiological follow-up scans showed a progressive increase in the size of the residual tumor. In May 2018, the patient was evaluated by the multidisciplinary pituitary board, which suggested performing a PET-CT scan with Gallium that highlighted focal distribution of the receptor tracer on the right side of the sellae. Furthermore, histological revision of the slide showed negative expression of SSTR2A and positive expression of SSTR5. Subsequent radiological follow-up scans showed a progressive increase in the size of the residual adenoma. In December 2020, the patient’s case was re-evaluated by the pituitary board, and radiation therapy was not recommended because of the young age and absence of hypopituitarism. Approval from the Ethics Committee was requested to use Pasireotide LAR as a therapeutic option for compassionate use. In May 2021, the patient started pasireotide LAR 40 mg intramuscular every 28 days. After 18 months of treatment, the residual adenoma showed no further progression on neuroimaging. The patient had good tolerance of the drug with no adverse events.

Conclusion: In this report, we describe a case of a NFPA negative for SSTR2A treated with pasireotide LAR. Our findings suggest that pasireotide LAR may be a treatment option for young patients affected by invasive non-functioning pituitary adenomas positive for SSTR5 who are not candidates for radiation therapy. Clinical studies could expand our single case observations.