INITIAL CLINICAL-RESULTS OF LINAC-BASED STEREOTACTIC RADIOSURGERY ANDSTEREOTACTIC RADIOTHERAPY FOR PITUITARY-ADENOMAS

Purpose: To retrospectively evaluate the initial clinical results of s tereotactic radiosurgery (SRS) and fractionated stereotactic radiother apy (SRT) for pituitary adenomas with regard to tumor and hormonal con trol and adverse effects of the treatment. Subjects and Methods: Forty -eight patients with pituitary adenoma who underwent SRS or SRT betwee n September 1989 and September 1995 were analyzed. Of these, 18 receiv ed SRS and 30 received SRT, The median tumor volumes were 1.9 cm(3) fo r SRS and 5.7 cm(3) for SRT. Eleven of the SRS and 18 of the SRT patie nts were hormonally active at the time of the initial diagnosis. Four of the SRS and none of the SRT patients had a history of prior radiati on therapy. Both SRS and SRT were performed using a dedicated stereota ctic 6-MV linear accelerator (LINAC), The dose and normalization used for the SRS varied from 1000 cGy at 85% of the isodose line to 1500 cG y at 65% of the isodose line. For SRT patients, a total dose of 4500 c Gy at 90% or 95% of the isodose line was delivered in 25 fractions of 180 cGy daily doses. Results: Disease control-The three year tumor con trol rate was 91.1% (100% for SRS and 85.3% for SRT), Normalization of the hormonal abnormality was achieved in 47% of the 48 patients (33% for SRS and 54% for SRT), The average time required for normalization was 8.5 months for SRS and 18 months for SRT, Adverse effects-The 3-ye ar rate of freedom from central nervous system adverse effects was 89. 7% (72.2% for SRS and 100% for SRT), Three patients who received SRS f or a tumor in the cavernous sinus developed a ring enhancement in the temporal lobe as shown by follow-up magnetic resonance imaging. Two of these cases were irreversible and were considered to be radiation nec rosis, None of the 48 patients developed new neurocognitive or visual disorders attributable to the irradiation. The incidence of endocrinol ogical adverse effects were similar in the two groups, resulting in 3- year rates of freedom from newly initiated hormonal replacement of 78. 4% (77.1% for SRS and 79.9% for SRT). Conclusion: Considering the rela tively high incidence of morbidity observed in the SRS group, we recom mend SRT as the primary method of radiation therapy for pituitary tumo rs. When treating a lesion in the cavernous sinus with SRS, special at tention should be paid to dose distribution in the adjacent brain pare nchyma, Longer follow-up is necessary before drawing any conclusions a bout the advantages of these techniques over conventional external bea m radiation therapy. (C) 1998 Elsevier Science Inc.