The Effectiveness of the Prescribed Dose of the Gamma Knife Radiosurgery in Treating Secretory Pituitary Adenomas
Abstract
Background: Pituitary adenomas are one of the most common primary central nervous system tumors. Approximately half of the pituitary adenomas secrete distinct pituitary hormones. Because of their pathophysiologic endocrine secretion and anatomic location near critical neural/vascular structures, hormone-secreting pituitary adenomas require defined optimum management that can include relief of mass effect and biochemical remission. Gamma Knife radiosurgery is a well-established method to treat selected targets in the brain. Leksell Gamma Knife is not a knife in the mean of the word. Instead, very precisely focused beams of radiation that directed to the treatment area in the brain. The treatment procedure is simple, painless, and straightforward, allows to minimize the dose of radiation to nearby critical structures.
Aims: The primary goal of the research is to gain control of adenoma growth (Size control), hormonal control. Also, this research aspires to achieve highly decreases in adenoma size, so the fast recovery means short treatment duration, and then arrive to completely adenoma disappearance, and also to make radiosurgery performed only once.
Patients and methods: This is a cohort (prospective) design study including fifty patients (27 females & 23 males) with secretory pituitary adenomas who were attending at the Gamma knife center of Neurosciences Hospital, Baghdad/Iraq at four months period from July to October 2019 to treated by Gamma Knife radiosurgery, with prescribed doses at 50% from 6Gy to 30Gy. Thirty-eight patients with prolactin-secreting adenoma (76%) (Female 21 and male 17), ten patients with Growth hormone secretory adenoma (20%) (4 females and six males), two patients with Cushing secretory adenoma (4%) (2 females) (Adrenocorticotropic hormone (ACTH) secreting adenoma). Twenty-one patients (42%) underwent a removal operation for adenoma pre-GKR two patients with more than one removal operation.
Results: This study shows that the rate of disappearance of the adenoma was 7/50 post GKR, with prescription doses at 50% 12Gy, 14Gy, and 4patients at 20Gy, 22Gy. The adenoma shrinkage incidence ranged from (6 Gy to 30 Gy) in 36/50 patients with prescription doses of 50 percent. The adenoma control (stable) rate was 3/50 with 50percent 10Gy, 20Gy, and 22Gy prescription doses. Just 5/50 patients have seen a small expansion in the size of adenomas. In 24 of 50 post-GKR patients, elevated hormones decreased to normal levels. The elevated hormone levels in 18 of 50 patients have decreased post-GKR levels to levels lower than those pre-GKR levels.
Conclusions: Finally, our findings indicate that radiosurgery from the gamma knife (GKR) appears to be a safe and successful alternative primary therapy for pituitary adenomas patients.
Gamma Knife radiosurgery (GKR) is also a useful adjuvant type of therapy for selected patients with residual or recurrent pituitary adenomas and those with an unacceptable risk of microsurgery. The past pituitary surgery (microsurgery) coupled with Gamma Knife radiosurgery tends to be more effective in the cure of patients with pituitary macroadenoma. In this research, there are different doses used and all were enough to change the size of adenomas and the level of hormones. However, this study also found that fast recovery varies from patient to patient depending on whether or not patients with pituitary adenoma underwent an operation, the duration of the previous surgery in the hypophysis, the position of adenoma if they pressed on their optic nerve, optic chiasm or brain stem, also depending on the size of the pre-GKR adenoma. The optimal dose was thus difficult to assess. To this, this study finds a way to predict pituitary adenoma size shrinkage per month based on the prescribed doses.
