A 64-year-old female developed the rare complication of undifferentiated malignant sarcoma following stereotactic radiotherapy for a recurrent non-functioning pituitary macroadenoma. This is a complication well recognized by radiation oncologists, oncologists and neurosurgeons, but lesser known to endocrinologists.
The macroadenoma was diagnosed in 1994 when imaging revealed a large sella/supra sella mass with significant invasion into surrounding structures. Only partial resection was possible via transphenoidal surgery. Due to rapid tumour growth, further surgery via craniotomy was performed a year later, followed by stereotactic radiotherapy (37.5 Gy in 15 fractions prescribed to the 80% isodose with a dedicated 6MV linac). Further surgical procedures were required in 2002, 2008 and 2010 via the transphenoidal route. In 2012, after further regrowth the oral chemotherapy agent temozolomide was commenced, with no effect on tumour size. Further surgical debulking was performed in 2013, followed by a further dose of radiotherapy (50.4 Gy in 28 fractions prescribed to the 90% isodose).
In June 2016, serial MRI imaging after the final surgery and irradiation treatment demonstrated no growth of residual tissue. In December 2016, only 6 months later, the patient presented with headache, vomiting and visual changes. Imaging demonstrated marked enlargement of residual tumour, with an irregularly enhancing 36 x 26 x 28mm mass invading the cavernous sinus and numerous surrounding bony structures. Biopsy confirmed a high-grade sarcomatous malignancy and the patient died less than 1 month later.
Radiation induced sarcoma in sellar region is a late, infrequent complication of pituitary radiotherapy.1 These are rapidly growing and aggressively invasive neoplasms with a dismal prognosis. No reported treatment modalities are effective in preventing tumour progression.1,2 Endocrinologists caring for patients with a history of pituitary radiotherapy need to be aware of this complication and include it in the differential diagnosis of sudden and unexpected tumour growth.