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.
