Patients who undergo stereotactic radiosurgery for benign indications do not appear to be at increased risk of malignant transformation, new findings show.
“Although prospective cohort studies with longer follow-up are warranted to support the results of this study, the available evidence suggests the long-term safety of stereotactic radiosurgery and could support physicians counselling patients on Gamma Knife stereotactic radiosurgery,” Dr. Amparo Wolf of the University of Western Ontario in London, Canada, and colleagues conclude in The Lancet Oncology, online November 22.
Cases of patients developing new tumors after intracranial radiosurgery have been published, but larger studies with longer-term follow-up have not been conducted, the authors note.
To investigate, they looked at 4,905 patients treated at five international radiosurgery centers in the U.S. and Europe for arteriovenous malformations, trigeminal neuralgia or benign intracranial tumors with Gamma Knife surgery. All had at least five years of follow-up data, and none had received radiotherapy previously.
During a median follow-up of 8.1 years, suspected malignant transformation occurred in two of 3,251 patients with benign tumors (0.0006%, incidence 6.87 per 100,000 patient years).
One patient developed a new intracranial malignancy (0.0002%, 2.26 per 100,000 patient years), which was considered treatment-related because it occurred within the radiation field.
Two patients developed intracranial malignancies that were not within the radiation field.
Overall, the incidence of radiosurgery-associated malignancy was 6.8 per 100,000 person years, similar to the risk of developing a malignant tumor in the central nervous system for the general population of the U.S. and parts of Europe, which ranges from 3.1 to 9.1 per 100,000 patient-years, the authors note.
“Based on the results of this study, for patients who are having either primary or salvage stereotactic radiosurgery for a histologically benign brain tumour, the risk of neoplastic transformation or the risk of having a new radiation-induced intracranial malignancy after radiosurgery is low and similar to that of the annual incidence of primary CNS tumours in the general population, even at long-term follow-up (more than 10 years),” they conclude.
“We agree with Wolf and colleagues that the overall risk of secondary cancers appears reassuringly low at 10 years, and this concern alone should not preclude stereotactic radiosurgery when warranted,” Dr. Alejandro Berlin and colleagues of the University Health Network in Toronto write in a comment accompanying the study.
“With an expected long survival of patients with benign conditions, it is prudent to advocate for properly quantified longer-term outcomes (>15-20 years) to guide judicious decision making and surveillance strategies,” they add.