The role of fractionated radiotherapy and stereotactic radiosurgery for pituitary adenomas

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Abstract

BACKGROUND

Pituitary adenomas account for 10-20% of primary central nervous system tumors. For nonsecretory adenomas, control of tumor growth and retention of vision are the most important objectives, whereas for nonsecretory adenomas, correction of endocrinopathies becomes a priority. Radiotherapy is indicated for patients whose tumors do not respond to surgery or medical therapies.

OBJECTIVE

To determine the efficacy and safety of fractionated radiotherapy (FRT) and stereotactic radiosurgery (SRS) for patients with pituitary adenoma.

DESIGN AND INTERVENTION

Patients with pituitary adenomas in whom surgical and medical treatment had failed to eradicate the tumor or normalize hormone secretion, or in whom surgery was not appropriate for medical reasons, were included in this retrospective cohort. A total of 125 consecutive patients were treated with FRT or underwent SRS between January 1995 and April 2006. A mean total dose of 50.4 Gy (range 48.54 Gy) was administered as FRT in 64 patients and, following installation of the gamma-knife device in 2002, 61 patients underwent SRS using the gamma-knife technique at a mean marginal dose of 25.1 Gy (range 9.30 Gy). Inclusion criteria for SRS were a maximum tumor diameter of 30 mm and a distance ≥2 mm between the tumor and the optic chiasm. FRT was provided if tumors were located close to the optic apparatus, regardless of tumor size.

OUTCOME MEASURES

The main outcome measures were time to tumor progression and endocrine outcomes.

RESULTS

Patients with pituitary adenomas (54 hormone-secreting and 71 nonfunctioning) were followed up for a mean of 36.8 months (range 2.140 months), and 4 patients (3.2%) had tumor progression (an increase in tumor volume). For the whole group at 2 years and 4 years, progression-free survival rates were 99% and 97%, respectively, and objective response rates were 39.5% and 81.8%, respectively. There was no observable difference in tumor growth control between the groups who had received FRT and SRS. For those patients who had secretory adenomas, receiving either FRT or SRS, the complete remission rate for endocrine parameters was 26.2% at 2 years and 76.3% at 4 years. Complete remission was attained in 14 (43.8%) patients in the SRS group and by 8 (36.4%) patients in the FRT group. Median values for time to complete remission were 26 months in the SRS group and 63 months in the FRT group (P = 0.0068). According to multivariate analysis, the use of SRS versus FRT (P = 0.23) and the type of secretory adenoma (corticotropin versus growth hormone or prolactin-secreting) correlated with outcome (P = 0.005). Hypopituitarism that required hormone replacement therapy developed as a delayed complication in 11 of 95 patients (11.6%) at a median of 84 months.

CONCLUSION

Single-dose radiosurgery produces a more prompt effect than FRT on the hypersecretion of pituitary hormones and can be recommended over FRT in some patients.

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