Pituitary irradiation is a known risk factor for the development of subsequent hormonal dysfunction. However, it has been noted that some patients do not appear to be affected after many years of follow up. The aim of this retrospective study was to identify protective factors from developing radiation induced hypopituitarism (RIH).
Methods: This is a single center study of patients attending the late effects of childhood cancer service in Oxford University Hospitals NHS Foundation Trust. All patients that received at least 18 Gy radiation dose to the pituitary for the treatment of non-pituitary disease as a child and who have been in remission for at least 5 years were included. Up to 26 years of follow up information was available. Out of the 60 patients studied, 20 patients have not yet been diagnosed with any pituitary hormonal deficiencies (mean time since initial therapy of 17.5 years). All patients had pituitary function and clinical assessment annually. We assessed whether sex, age at radiation, tumour type, radiation dose and fraction size were protective factors in this cohort of patients.
Results: A lower radiation dose is protective in the development of RIH (average 37.1 vs 43.9 Gy; P=0.02). However, sex (39% of males vs 22% of females unaffected; P=0.18), average number of fractions (26.5 vs 27.4; P=0.33), age at radiation (9.5 yrs vs 9.9 yrs; P=0.33) and type of tumour were not protective.
Discussion: This single center study with a long follow-up period has identified a lower radiation dose as a protective factor from RIH in a subset of patients treated for childhood cancers. The current literature demonstrates disparity of understanding and has not yet explored this phenomenon. As the population of survivors increase it is essential that further studies take place in order to understand the sequelae of events in these patients.