Radiotherapy for Pituitary Adenomas May Increase Risk for Secondary Brain Tumors, Study Shows

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by Alice Melao |

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Patients with Cushing’s disease or other pituitary tumors who undergo radiotherapy after surgery have a higher chance of developing secondary brain tumors, a new study shows. Such patients should be followed for longer periods, and by multidisciplinary clinical teams, ensuring proper and prompt care.

The study, “Secondary Intracranial Tumors Following Radiotherapy for Pituitary Adenomas: A Systematic Review,” was published in the journal Cancers.

Benign tumors in the pituitary gland, which often lead to Cushing’s disease, account for approximately 8 percent of brain tumors.

The first line of treatment for pituitary adenomas is surgical excision, but when drugs and surgery fail, radiotherapy is considered.

Despite considerable evolution on radiotherapy techniques, pituitary tumor patients may suffer side effects from radiation therapy, including long-term neurological complications and secondary malignancies.

“Pituitary irradiation is one of the important treatment options for functioning and non-functioning adenomas,” the researchers wrote. “Radiotherapy is administered in the case of incomplete resection, invasive tumors, or tumors showing resistance to treatments. The use of radiotherapy is well established and effective in delaying tumor regrowth.”

To assess the incidence of secondary malignancies in patients with pituitary tumors treated with radiotherapy, researchers at the Kyoto Prefectural University of Medicine in Japan reviewed data from 137 case reports published between 1959 and 2017.

The analysis included 48 neuroepithelial tumors, 37 meningiomas, and 52 sarcomas. Among them there were 10 cases of prolactin-producing adenomas, 37 cases of acromegaly due to growth hormone-producing adenomas, four cases of Cushing’s disease, and one patient whose tumor produced both prolactin and growth hormone. Also, 57 patients had non-hormone producing adenomas, and 28 had tumors of undetermined function.

On average, secondary tumors appeared 15.2 years after radiation therapy. Patients with Cushing’s disease, however, developed secondary tumors within a shorter period of time: seven years.

It is not clear if the hormones produced by benign pituitary adenomas can contribute to the development of other brain tumors. But in Cushing’s disease patients, the immune system is commonly hampered as a result of excessive secretion of glucocorticoids, which could explain the development of secondary tumors. However, this correlation has not been fully explored.

Modern radiotherapy techniques have significantly reduced the levels of radiation needed to achieve therapeutic results, as well as the amount of radiation reaching surrounding tissues. Still, the authors consider the development of secondary brain tumors in these patients following radiotherapy should be taken into consideration.

“Consistent and long-term aftercare is basically required in the case of pituitary adenomas not only to detect a possible radiation-induced tumor, but also to check the tumor control and to detect long-term damage to the optic pathway and the pituitary function,” the researchers wrote.

The researchers also suggest that follow-up should be conducted in specialized centers with a multidisciplinary team, which should include radiation therapists, neurosurgeons, endocrinologists, and ophthalmologists.