Long-term outcomes of conventionally-fractionated high-precision radiotherapy for craniopharyngioma

Abstract

Although craniopharyngiomas are categorized as benign brain tumors, long-term prognoses have not been satisfactory due to their locational difficulties and invasiveness. Conventinally-fractionated radiation therapy is the standard radiotherapeutic approach for residual or recurrent diseases after surgery, which significantly improves not only local progression-free rates but also survival outcomes. However, long­term results for patients treated with modern high-precision radiotherapy techniques have not been suffi­ciently reported. In this retrospective study, 5-year outcomes of Japanese patients with residual or recur­rent craniopharyngioma treated with high-precision radiotherapy were evaluated. A total of 29 patients with residual or recurrent craniopharyngioma, who were consecutively treated with three-dimensional conformal radiation therapy or streotactic radiation therapy between January 2001 and September 2012, were included in the analyses. The median age was 54 years old (range: 7-78). Five pediatric cases (median: 9 years old, range: 7-15) were included. The number of prior surgeries before radiation therapy was one in 18 cases, two in 9 cases and three in 2 cases. Incomplete resection was per­formed on 28 cases in the most recent surgery before radiation therapy, while gross total resection was achieved in only one patient. Some sort of pituitary hormone deficiency was observed in 28 (97%) cases before radiation therapy. The clinical target volume (CTV) was created by adding a 0-5 mm margin to the tumor bed. The planning target volume was generated by adding a 3-10 mm margin to the CTV. The median prescribed dose at the isocenter was 54 Gy (range: 50.4-54) in a fraction size of 1.8 Gy. The median follow-up period after radiotherapy was 73 months(range: 27-191). Local recurrence was observed in 5 cases and ectopic intracranial recurrence was observed in one patient. Five-year local con­trol, progression-free survival and overall survival rates were 85.3% (95% confidence interval [Cl]: 65.1, 94.2), 81.4% (95% Cl: 60.7, 93.4) and 95.8% (95% Cl: 73.9, 99.4), respectively. No radiation-induced acute toxicity was observed. In one patient, thyroid stimulating hormone replacement treatment was required 67 months after radiation therapy. No other instances of radiation-related late toxicity were observed. High-precision radiation therapy in conventional fractionation could achieve a favorable long-term tumor control rate with minimum complications in Japanese patients with residual or recurrent craniopha­ryngioma. This approach should therefore be considered as the first-choice option in managing residual or recurrent craniopharyngioma after surgery.