Endocrine Abstracts

Background: Suitable postoperative radiotherapy (RT) of nonfunctioning pituitary macroadenomas (NFMAs) is still controversial, subjected to rapid technical and medical progress.

Patients and methods.: We studied 87 patients with NFMA to identify factors affecting tumor control such as the time of RT and tumor pathology. Partial pituitary surgery was performed either by transfrontal (30 patients) or transsphenoidal (57 patients) approach. An immunoperoxidase (avidin biotin technique) analysis for anterior pituitary hormones was performed, revealing 41 null cell adenomas, 22 gonadotropinomas, 13 silent plurihormonal (nongonadotroph) and 11 silent unihormonal adenomas (ACTH, GH or PRL). Tumor recurrence after surgery was defined as a minimum 25% increase of either diameter by serial imaging studies, initially performed at 3 months after surgery and 6 months after RT.

Results: After partial surgery, high voltage RT (mean dose 50.5 Gy) was given to 35 out of 87 patients with a follow-up of 7.5±4.3 years. Recurrence rate was registered in 38% patients (33/52) without RT and 11.4% patients (4/35) after postoperative RT (P<0.001). Tumor relapse in the first year after surgery was noticed in 4/13 silent plurihormonal (nongonadotroph) tumors and in 2/11 silent unihormonal immunoreactive adenomas (for ACTH or PRL) and only in 2/41 null cell and 1/22 gonadotroph adenomas. Immediate postoperative RT showed a significant benefit on the tumor reccurence. Patients who received postoperative RT earlier than one year (18/35) showed a low rate of recurrence, as compared to patients with later RT (χ², P<0.05). Regression analysis showed that the early postoperative radiation therapy is independently associated with a lower risk of relapse.

Conclusion: It is tempting to suggest as an optimal time for radiotherapy, the first year post partial-surgery of pituitary macroadenomas. The relapse rate increases gradually along 5 years in patients who were not irradiated.