Endocrine Abstracts

Introduction: Acromegaly is a rare, progressive disease characterised by excess growth hormone. The recommended treatment is surgery. Radiotherapy and somatostatin analogues are used as adjuncts. The risk of post-radiotherapy osteosarcoma is 0.01% to 0.03% among all irradiated patients. We report a case of radiation-induced osteosarcoma that developed 22 years after radiotherapy for acromegaly.

Case report: In 1997, a 53-year-old gentleman with acromegaly due to an extensive sellar/parasellar/suprasellar tumour was treated with transsphenoidal surgery and radiotherapy, followed by gamma-knife in 2002. At annual reviews, he remained clinically well. His IGF1 was normal on lanreotide and cabergoline. He required hydrocortisone, thyroxine, and testosterone replacement. MRI of pituitary in 2010 and 2015 showed the right parasellar residuum had shrunken, and no residual pituitary fossa tumour compared to 2005. In 2019, he was seen in eye clinic due to headaches, sudden onset 6th nerve palsy. MRI pituitary showed normal sella but an enhancing clival lesion, extending to cavernous sinuses. A CT guided biopsy was non-diagnostic, and the consensus was either post radiation changes or a low-grade tumour. The skull-base MDT proceeded with an endoscopic transnasal biopsy due to worsening headaches and left sided third nerve palsy. The histopathology showed osteoblastic lesion raising suspicion of radiation-induced osteosarcoma, later confirmed by regional sarcoma MDT, but he deteriorated rapidly and died.

Conclusion: Our patient developed rapidly progressive radiation-induced osteosarcoma in the setting of normal IGF1. This case has the longest latency recorded (22 years) for patients developing radiation-induced osteosarcoma following radiation therapy in acromegaly. IGF1 monitoring or visual field surveillance is unlikely to identify this rare complication. Moreover, in treated cases of acromegaly, MRI surveillance is not usual clinical practice unless there is biochemical recurrence. Clinicians should be vigilant in suspecting late development of secondary tumours in patients who received cranial irradiation.