Extracranial doses in stereotactic and conventional radiotherapy for pituitary adenomas

Abstract

Aim To determine the extracranial dose in patients treated for Pituitary adenoma with Conventional and Stereotactic Radiotherapy. Materials and methods Twelve patients receiving treatment with radiation for Pituitary adenoma in the year 2001 were selected at random for the study. Of these six received Stereotactic Radiotherapy while the remaining six were treated using conventional Radiation therapy portals. Extracranial doses were measured with pre-irradiation annealed Lithium fluoride TLD chips. The chips were wrapped and placed on the patients? skin, over each eye lid, thyroid, chest and scrotum for males and over the suprapubic region for females. Post-radiation annealing was done and the TLD?s were read in TLD reader system. The results were analysed using the Wilcoxon Matched ?Pairs Signed Rank Test by SPSS Ver 6.01 Results The dose to the thyroid, pelvis and gonads were significantly higher (74.62, 65.42, 58.42 mR) in patients receiving Stereotactic Radiotherapy than in Conventional Radiotherapy portals (69.45, 38.33, 31.41 mR).But the average dose to the right eye (84.84 mR) and left eye (85.68 mR) in Stereotactic group was less when compared to the patients treated with Conventional Radiotherapy, who received 127.5mR and 117.29 mR respectively. Conclusion SRT is superior to conventional RT in as far as Being able to limit the dose to the tissues surrounding the tumour . The doses to extracranial structures in SRT are marginally more than in conventional Radiotherapy. Though they seem to be within the acceptable range, their clinical significance is still unclear and needs longer follow-up.