Postoperative radiation therapy for pituitary adenoma

Background: We evaluated the efficacy of postoperative radiation therapy (R T), prognostic factors for local control probability, dose response relatio nship and treatment sequelae in 75 patients with pituitary adenoma. Materials and methods: A total dose of 48-60 Gy (median: 50 Gy) was deliver ed with a conventional fractionation schedule after surgery. Of 75 patients , 55 (73%) were followed for more than 5 years and 27 (36%) were followed f or more than 10 years with a median of 95 months. Results: Five- and 10-year local control probabilities were 87.1% and 85.0% , respectively. Univariate analysis revealed that age (p = 0.007), tumor vo lume smaller than 30 cm(3) (p = 0.018) and the absence of prolactin secreti on (p = 0.003) were significantly favorable prognostic factors for local co ntrol probability. After multivariate analysis combining these 3 factors, t umor volume smaller than 30 cm(3) (p = 0.017) and age (p = 0.039) were stat istically significant. Patients with prolactinoma greater than 30 cm(3) sho wed particularly poor local control rates. No significant improvement of th e local control rate was detected with increasing total irradiation doses b etween 48 and 60 Gy (p = 0.29). The most common side effect was hypopituita rism, and there were no severe sequelae such as optic neuropathy or brain n ecrosis. Conclusion: Except with prolactinoma, the dose of postoperative RT for pitu itary adenoma should not exceed 50 Gy. Large prolactinoma, however, was ver y difficult to control with the irradiation doses between 50 and 60 Gy, and would be good candidates for stereotactic radiosurgery or stereotactic rad iation therapy.