Late regrowth of pituitary adenomas after irradiation and/or surgery. Hazard function analysis

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Abstract
A retrospective analysis was performed on all patients with pituitary adenomas treated at the Radiation Oncology Center, Mallinckrodt Institute of Radiology, St. Louis, Missouri. Of 210 patients treated from April 1954 through December 1982, 70 were treated with radiotherapy alone (RT), 121 received immediate postoperative RT (2 to 6 weeks), and 19 received RT following surgical failure. The mean follow‐up time from the date of diagnosis for those patients alive at the time of last follow‐up was 13.0 years (range, 3.0 to 30.0 years). Actuarial progression‐free survival was analyzed up to 30 years. The 10‐, 20‐, and 30‐year progression‐free survival was 80.5%, 73.5%, and 73.5% for those patients treated with irradiation alone and 92.8%, 71.2%, and 44.0% for those treated with immediate postoperative irradiation. The median time to first failure from initial diagnosis by original treatment was 3.8 years for surgery alone, 4.2 years for RT only, and 10.2 years for surgery plus postoperative RT. Analysis for risk of recurrence per 5‐year interval was performed using a hazard function analysis. The risk of recurrence after radiotherapy alone was greatest during the first 5‐year interval after treatment and decreased to zero by 20 years. However, the risk of recurrence after primary surgery and postoperative radiotherapy revealed an increasing risk for recurrence up to 30 years after treatment. The concept of “cure” for pituitary adenomas requires extended follow‐up.