Radiotherapy is integral to the treatment of pediatric and adult brain, endocrine, and nasopharyngeal tumors, but can induce late endocrine system effects such as hypopituitarism, with potentially profound implications for survivors’ growth, sleep cycle, sexual functioning, osteoporosis risk, and quality of life. Nurses play key roles in assessing and educating patients, and devising and communicating long-term posttreatment patient care and surveillance plans. This column reviews the risks, detection, and management of radiotherapy-induced hypopituitarism.
With new anticancer treatments, such as checkpoint-blockade immunotherapies, novel patterns of late neuroendocrine system dysfunctions, known as endocrinopathies, are emerging among patients with cancer.1 Longstanding patterns of radiation-induced hypopituitarism (RIH) and other endocrinopathies among survivors who have undergone radiotherapy for brain and nasopharyngeal (head-and-neck) tumors might also change with better dose-targeting modalities like intensity-modulated radiotherapy (IMRT) and radiosurgery, which spare healthy tissues.2-7 However, even with IMRT, endocrine organs will still sometimes be exposed to radiation fields, particularly when they are situated near tumor margins, resulting in subsequent endocrine dysfunctions.2,8 Pituitary shielding is not always possible without reducing treatment efficacy, particularly when target tumors occur in the middle cranial fossa.2
“IMRT for tumors away from the H-P axis is not expected to result in pituitary dysfunction, as the H-P axis will be spared from irradiation,” explains Ken H. Darzy, MD, FRCP, MBChB, of Queen Elizabeth II Hospital in Welwyn Garden City, Hertfordshire, United Kingdom. “However, with nearby tumors it may not be possible to spare the H-P axis completely and a degree of pituitary dysfunction may be expected.”
RIH will also continue to be a risk faced by patients treated for pediatric and adult endocrine system neoplasms, such as pituitary adenomas, or prophylactic whole-body or whole-brain irradiation.3,9-11 One recent study found that gamma knife stereotactic radiosurgery for pituitary adenomas yielded superior radiation sparing of hypothalamus tissue compared with IMRT and Linac-based 3D-conformal radiotherapy (CRT), with resulting lower rates of early RIH; 12.5% of patients who underwent radiosurgery experienced one or more hormone deficits after irradiation, compared with 72% of patients who underwent CRT and 50% of patients who received IMRT.7 (A previous study found a long-term new hypopituitarism rate of 30% among patients undergoing stereotactic radiosurgery for pituitary adenomas, after a followup period of up to 150 months.12) Sparing hypothalamus tissue from irradiation was once thought to reduce RIH risk but that no longer appears to be the case.3