(CSEMP075) USE OF RADIOTHERAPY FOLLOWING SURGICAL RESECTION OF NON-FUNCTIONING PITUITARY ADENOMAS IN ONTARIO

Abstract:

Introduction:   Non-functioning pituitary adenomas (NFAs) affect 3 to 10% of the population.  Surgery is often first line therapy, with radiotherapy (RT) used to treat incomplete resections, tumor progression, or as first line for inoperable cases.

Purpose:   We describe a population of patients with NFAs in Ontario, as well as the use and timing of RT in this cohort

Method:   Patients with a diagnosis of NFA were identified between January 1999 and December 2018 using administrative health data from the Institute for Clinical Evaluative Sciences. Specifically, radiotherapy data were accrued throughCancer Care Ontario’s Activity Level Reporting (ALR), and the National Ambulatory Care Reporting System (NACRS).,  

Results:   A total of 5,083 patients had surgery for NFA (‘index surgery’).  Mean follow up was 10.87 ± 5.6 years. Out of these patients, 322 (6.3%) received one or more courses of RT.  The most commonly used RT modality was Intensity-Modulated Radiotherapy (IMRT; n = 81; 37.5%).   One hundred ninety-four out of 322 (60.2%) patients who had RT received it directly after index surgery, within a median of 2.4 years (range 0.6 to 5.1 years), and the rest received RT after subsequent repeat surgeries.  Only 40 out of 322 patients (0.8%) received RT within a year.  Ten patients required repeat radiation after their first course; none in this cohort required a third course.  Mean duration between repeat RT courses was 816.3±1113.6 days.  In addition, 728 patients required repeat surgery after index resection, and 123 patients required two or more repeat surgeries.  The need for repeat surgeries was correlated with the use of RT, as 43.2% of patients in the RT group also required repeat surgeries, versus only 12.2% of patients who only had index surgery (p-value = < 0.001). 




Discussion:   Only 6.3% of patients required RT after index surgery in this cohort.  Based on these findings, it seems that use of  RT in Ontario is mainly reserved for cases of tumor  progression, since most patients received RT more than 1 year after index surgery.  Regardless of timing, very few patients required any further interventions following RT, suggesting its effectiveness at controlling tumor progression.  Whether the timing or technique of RT corresponds to differences in long-term outcomes such as hypopituitarism, stroke risk, cognitive impairment, secondary tumors, or increased mortality requires further exploration.