From Lewis S. Blevins Jr., M.D. cofounder – Lehrer and others published a nice review on the role of stereotactic radiosurgery (SRS) for functioning and nonfunctioning pituitary adenomas. They reviewed several studies focusing on both the beneficial and adverse effects of the treatment of different tumor subtypes.
SRS is designed to target a lesion in a way different from more conventional forms of radiotherapy. SRS is more precise. It is supposed to enable the delivery of high doses of radiotherapy to a lesion and to limit exposure of surrounding tissues to radiation. While conventional radiotherapy may take place over a number of weeks, SRS requires one day and rarely two to three days of treatment.
It is almost impossible to compare conventional radiotherapy to SRS. Response rates and times to responses are different for both forms of radiotherapy. This is potentially related to therapy itself, but it’s probably mostly influenced by treatment bias. For example, patients with larger widespread invasive tumors are probably best treated with conventional radiotherapy. Those with smaller lesions located away from vital structures are good candidates for SRS. The tumors and the forms of radiation are, thus, pretty much like comparing oranges and lemons to peaches and plums.
We have summarized the findings of the paper in order to provide you with “news you can use” in the following graphs.
As you can see, in nearly all patients, regardless of tumor subtype, SRS does a superb job of controlling the targeted lesion and in preventing subsequent growth. Rates of control of excessive hormone secretion in functioning tumors are variable and not as good as is control of tumor growth. In most patients, though early responses have been reported, it takes five to seven years to achieve control of hormone secretion. Many patients require medical management of their hormone hypersecretory states while waiting for the effects of radiation to take place and when radiation has failed to control hormone secretion. Adverse effects may include the partial or complete loss of one or more pituitary hormones, cranial nerve deficits, vascular abnormalities, and even the development of secondary tumors in the radiation-treated area. The latter two complications are probably far more common with conventional radiotherapy.
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