Stereotactic radiosurgery for recurrent skull base polymorphous adenocarcinoma invading the cavernous sinus: illustrative case

Abstract

BAKGROUND Polymorphous adenocarcinomas (PACs) are rare tumors arising from the salivary glands. Radical resection and postoperative radiotherapy are the mainstays of treatment. However, complete tumor resection is not always achievable when the tumor invades the skull base. Stereotactic radiosurgery (SRS) could be a less invasive alternative for treating skull base PACs. OBSERVATIONS A 70-year-old male with a history of surgery for a right palatine PAC presented with right visual impairment, diplopia, and ptosis. Imaging studies revealed tumor recurrence invading the right cavernous sinus (CS). SRS using a gamma knife was performed for this recurrence, prescribing a marginal dose of 18 Gy at a 50% isodose line. Five months after SRS, his symptoms were relieved, and the tumor was well-controlled for 55 months without any adverse events. LESSONS To the best of the authors’ knowledge, this is the world’s first case of recurrent skull base PAC invading the CS that was successfully treated with salvage SRS. Thus, SRS may be an applicable treatment option for skull base PACs.

Role of stereotactic radiosurgery for recurrent skull base acinic cell carcinoma: illustrative case

“…On the other hand, SRS for other salivary gland malignancies were reported with doses of 15 to 20 Gy. 1 , 9 , 10 , 16 Given the potential for long-term survival in cases of AcCC, we considered the possibility that reducing the prescription dose might lower the chances of achieving long-term tumor control and prescribed a higher dose of 20 Gy. Naturally, the exposure of surrounding normal tissues to radiation during treatment is also a concern, underscoring the need for a careful balance between the risks and benefits.…”

“… 7 , 8 Stereotactic radiosurgery (SRS) can be a viable minimally invasive treatment option because it delivers high-dose focused radiation precisely to the tumor in a single fraction. 1 , 9 , 10 However, few studies have examined the efficacy of SRS for AcCC. 1 , 11 Herein, we report a case of recurrent AcCC involving multiple skull base locations, in which tumors had been controlled successfully over 12 years with a combination of safe maximal resection using endoscopic transnasal surgery (ETS), followed by multiple sessions of SRS.…”