Evaluation of Long-Term Outcomes and Toxicity After Stereotactic Phosphorus-32–Based Intracavitary Brachytherapy in Patients With Cystic Craniopharyngioma

Purpose Interstitial brachytherapy based on phosphorus-32 (P-32) has an established role as a minimally invasive treatment modality for patients with cystic craniopharyngioma. However, reporting on long-term outcomes with toxicity profiles for large cohorts is lacking in the literature. The purpose of this study is therefore to evaluate the long-term visual, endocrinal, and neurocognitive functions in what is the largest patient series having received this treatment to date. Methods and Materials We retrospectively evaluated 90 patients with cystic craniopharyngiomas who were treated with stereotactic intracavitary brachytherapy between 1998 and 2010. Colloidal activity of injected radioisotope P-32 was based on an even distribution within the tumor. After treatment, patients were followed-up for a minimum of 5 years and over a mean of 121 months (60-192 months) to assess radiographic and clinical responses. Results The 90 patients included in our study cohort underwent a total of 108 stereotactic surgical procedures for 129 craniopharyngioma-related cysts. Of the included tumors, 65 (72.2%) were associated with a single cyst, 15 (16.7%) were associated with 2 cysts, and 10 (11.1%) tumors had developed septations with 3 to 4 cysts. Stereotactic cyst puncture and content aspiration were used to drain a mean cyst fluid volume of 21.4 mL (1.0-55.0 mL). Each cyst was then instilled for interstitial brachytherapy with colloidal P-32 solution. Based on radiographic follow-up assessments, 56 cysts (43.4%) showed resolution and/or nonrecurrence, which was classified as a complete response to treatment; 47 cysts (36.4%) showed a partial response; and 5 cysts (3.9%) displayed a stable appearance. Treatment resulted in immediate and clinically significant vision improvement in 54 of 63 (86%) symptomatic patients, and this improvement was maintained. Progression-free survival rates at 5 and 10 years were 95.5% and 84.4%, respectively. Conclusions P-32–based interstitial brachytherapy can play an effective role in managing patients with cystic craniopharyngiomas. It can be considered a valid alternative to surgery in select patients with a favorable toxicity profile and long-term clinical outcomes.