Extracranial doses in stereotactic and conventional radiotherapy for pituitary adenomas

The purpose of this study is to determine the extracranial dose in patients treated for pituitary adenoma with conventional and stereotactic radiotherapy (SRT). Twelve patients receiving treatment with radiation for pituitary adenoma were selected. Six patients underwent SRT, and six patients underwent conventional radiotherapy. Extracranial doses were measured with pre-irradiation annealed lithium fluoride thermoluminscent dosimetry (TLD) chips. The chips were wrapped and placed on the patients' skin, over each eyelid, the thyroid, chest, and scrotum for males and over the suprapubic region for females. Postradiation annealing was done, and the TLDs were read in a TLD reader system. The results were analyzed using the Wilcoxon matched-pairs signed rank test by SPSS, version 6.01. The doses to the thyroid, center, and gonads were significantly higher (74.62 +/- 9.12 mrad, 65.42 +/- 9.35 mrad, and 58.42 +/- 5.36 mrad, respectively) in patients receiving SRT than in conventional radiotherapy portals (69.45 +/- 21.19 mrad, 38.33 +/- 19.44 mrad, and 31.41 +/- 18.25 mrad). But the average doses to the right eye (84.84 +/- 8.80 mrad) and to the left eye (85.68 +/- 5.82 mrad) in the stereotactic group were less when compared with the patients treated with conventional radiotherapy, who received 127.5 +/- 37.90 mrad and 117.29 +/- 34.01 mrad, respectively. In conclusion, SRT is definitely superior to conventional radiotherapy as far as dose to the surrounding normal structures is concerned. The higher extracranial doses in SRT seem to be within the acceptable range; however, the clinical significance of this is still unclear and needs longer followup.