A Single-Center Experience in Brachytherapy for Treatment-Refractory Nonsecreting Pituitary Adenomas

Introduction: Recurrent pituitary adenomas are challenging lesions. The typical second-line treatment is radiotherapy. Stereotactic radiosurgery and fractionated external beam radiotherapy are the modalities of choice. Pituitary adenomas refractory to photon radiation present a challenging clinical dilemma. There is no strong evidence to support a standard third-line therapy. At our institution, in select cases, we utilize brachytherapy as the third-line treatment option. We present our experience with the use of brachytherapy with I-125 seeds for multiple recurrent pituitary adenomas.

Methods: Eight patients with surgery- and radiation-refractory nonsecreting pituitary adenomas were treated with I-125 brachytherapy at our institution from April 2010 to June 2019. The primary end point was tumor control. The secondary point was vision preservation.

Results: All patients underwent endoscopic, endonasal implantation of I-125 seeds, with four patients having additional seeds implanted via craniotomy. The median number of seeds implanted was 2 per patient. In seven patients, the seeds were placed with frame-based stereotactic navigation to a preplanned target. In one patient, the seeds were placed using frameless stereotactic navigation via an endoscopic, endonasal approach. The median number of prior surgeries per patient was 2 (range: 1–3). The median number of prior radiotherapy treatments per patient was 1 (range: 0–2). Four patients were treated to a dose of 100 Gy early in the experience (2010–2012), and four patients were treated to a dose of 50 Gy thereafter (2013–2019). Overall, tumor control rate was 100% at a mean follow-up of 47.2 months (range: 3–124 months). All patients treated to 100 Gy demonstrated imaging evidence of radiation necrosis in the brainstem or mesial temporal lobe at a mean of 23 months after treatment. Two patients treated to 100 Gy experienced visual decline. No patients treated to 50 Gy demonstrated imaging evidence of radiation necrosis or visual decline.

Conclusion: Brachytherapy with I-125 seeds is a viable third-line treatment option for multiply recurrent pituitary adenomas. A dose equivalent of 50 Gy appears to have the optimal balance of tumor control while minimizing side effects.