External irradiation of macroinvasive pituitary adenomas with telecobalt: a retrospective study with long-term follow-up in patients irradiated with doses mostly of between 40-45 Gy.

PURPOSE

Published dose recommendations for radiotherapy in patients with pituitary macroadenomas vary. Therefore, we retrospectively analyzed the results in our patients from the treatment period 1973-1992.

METHODS AND MATERIALS

From a total of 89 patients with macroinvasive adenomas, 66 received radiation therapy immediately following subtotal surgical removal (combined treatment modality), and 22 were irradiated as primary treatment or after surgical recurrence. Only one patient was reirradiated. The surgical interventions have been performed by the same surgeon. For the majority of patients (79 out of 89) with a mean follow-up of 8.1 years (0.5-19 years) the total tumor dose ranged between 40-45 Gy at a dose per fraction of 1.8-2.25 Gy. All patients had bilateral opposed fields with telecobalt. Eleven patients had an additional arc rotation.

RESULTS

The 10-year progression-free survival for all 89 patients independent of treatment modality was 88.1%. The 10-year progression-free survival for patients treated by surgery and adjuvant radiation therapy (40-45 Gy at 1.8-2.25 Gy, 60 out of 79) was 90.3%, and for radiation therapy alone (40-45 Gy at 1.8-2.25 Gy, 19 out of 79), 100% (p = 0.32). The prognostic factors for progression-free survival were the subtype of adenoma, the presence of visual symptoms at the time of diagnosis, the suprasellar extension, and the initial hormone levels. The presence of infiltration of adenoma cells in the basal dura or in the mucosa of the sinus sphenoidalis do not represent prognostic factors showing the special biological behavior of pituitary adenomas. Signs of x-ray-induced cerebral necrosis have not been observed in any patient. Long-term visual complications developed in four patients. This could be due to scar formation in the treated region, which can compress the optic nerve and provoke disturbance similar to an empty-sella syndrome. The latter occurred prevalently years after treatment, even though surgical methods of sellar plugging were used. The incidence of hypopituitarism after combined treatment modality at time of last follow-up (irradiated between 40-45 Gy at 1.8-2.25 Gy) was low (36%, 21 out of 60).

CONCLUSION

In patients with pituitary macroadenomas, radiotherapy with a total dose of 40-45 Gy at 1.8-2.25 Gy per fraction resulted in a high local tumor control without serious morbidity.