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Gamma irradiation effects on human growth hormone producing pituitary adenoma tissue. An analysis of morphology and hormone secretion in an in vitro model system.

Irradiation-induced effects on pituitary cell morphology and secretion of growth hormone (GH) and prolactin (PRL) have been analysed using an in vitro system. Specimens for organ culture were obtained from three patients with pituitary tumours causing acromegaly but with different clinical activity of disease. Specimens were followed in vitro 1 h - 6 days after single-dose gamma irradiations (60Co) with 70, 100 and 150 Gy, respectively. These doses are used in clinical work for the stereotactic radiosurgery of pituitary adenomas. Considerable fluctuations in hormone secretion/release occurred during the first 24 h after irradiation. Following 70 Gy single dose, the GH secretion increased slightly a few days after irradiation, having been at a minimum level 24 h after exposure. When using dose of 100 and 150 Gy, however, no such increased secretion with time after irradiation was indicated. All three tumors showed individual differences concerning irradiation-induced morphological damage. Only a minor variation occurred between specimens from the same tumour. In specimens from all tumours, irrespective of dose, minor morphological changes were observed 3-5 h after irradiation. Thereafter an individual response to irradiation became apparent. One tumour displayed maximum cell damage 24 h after irradiation with 70 Gy, showing severe oedema and damage to cell organelles. The other two adenomas were only slightly damaged following irradiation with 70, 100 and 150 Gy. Numerous morphologically normal or near-normal cells were found in all specimens from the three tumours 6 days after irradation. An individual sensitivity to irradiation of pituitary tumours in vitro is documented. The great number of surviving pituitary tumour cells one week after irradiation--many with an intact ultrastructure and containing hormone granules--indicated an initial high degree of radioresistance.

Acromegaly↗
PubMed1994

An audit of selected patients with non-functioning pituitary adenoma treated by transsphenoidal surgery without irradiation.

OBJECTIVE: To determine whether the rate of tumour regrowth in patients with non-functioning pituitary tumour treated by transsphenoidal surgery and selected for observation without post-operative irradiation is acceptably low, and to identify a group of patients who could appropriately avoid pituitary irradiation. SUBJECTS: One hundred and thirty-two patients treated by transsphenoidal surgery, of whom 98 did not undergo post-operative irradiation. These 98 were selected as having had apparently complete surgical removal, and as lacking features of tumour invasion or rapid growth; 73 of them are being followed by serial pituitary imaging to detect tumour regrowth. RESULTS: Forty-two patients who have been imaged on two or more occasions or more than two years after operation have shown no sign of tumour regrowth; 25 of them have been imaged at 3 or more years after operation, 13 at more than 5 years, and 4 at more than 10 years. Eight patients have shown regrowth as judged by imaging, although only one had pressure symptoms at the time; 5 out of 6 of these recurrences were found within 5 years of operation (two cannot be timed). The unirradiated group of 73 patients showed 90% recurrence-free survival at 5 years (95% confidence limits 80-100%). CONCLUSIONS: Provided that careful surgery and meticulous recall mechanisms for imaging can be ensured, patients so selected may be given the information contained in these results and offered the choice of follow-up by imaging alone, without pre-emptive irradiation. We recommend that they should be imaged 6-8 weeks post-operatively, then at either 6 or 12 months depending on the appearance, and then every 3-5 years for at least 15 years. By this means, many patient-years of good health and relative medical independence can be gained, together with some financial saving.

Adenoma↗