Morphological changes in vestibular schwannomas after stereotac - tic radiosurgery and retrospective assessment of indications for tumor removal
Authors:   OncoStop Radiation Therapy Center (OncoStop LLC), Moscow, Russia, Ilyalov S. R. ,   Department of Radiology, Radiotherapy, Radiation Hygiene and Radiation Safety named after academicians A. S. Pavlov and F. G. Krotkova Russian Medical Academy of Additional Professional Education of the Ministry of Health of the Russian Federation, Kim D. S. ,   FGAU «National Medical Research Center of Neurosurgery named after Academician N. N. Burdenko» of the Ministry of Health of the Russian Federation, Moscow, Russia, Shishkina L. V. ,   FGAU «National Medical Research Center of Neurosurgery named after Academician N. N. Burdenko» of the Ministry of Health of the Russian Federation, Moscow, Russia, Ryzhova M. V. ,   FGAU «National Medical Research Center of Neurosurgery named after Academician N. N. Burdenko» of the Ministry of Health of the Russian Federation, Moscow, Russia, Banov S. M. ,   FGAU «National Medical Research Center of Neurosurgery named after Academician N. N. Burdenko» of the Ministry of Health of the Russian Federation, Moscow, Russia, Golanov A. V. ,   Department of Radiology, Radiotherapy, Radiation Hygiene and Radiation Safety named after academicians A. S. Pavlov and F. G. Krotkova Russian Medical Academy of Additional Professional Education of the Ministry of Health of the Russian Federation, FGAU «National Medical Research Center of Neurosurgery named after Academician N. N. Burdenko» of the Ministry of Health of the Russian Federation, Moscow, Russia, Usachev D. Yu. ,   FGAU «National Medical Research Center of Neurosurgery named after Academician N. N. Burdenko» of the Ministry of Health of the Russian Federation,Department of Neurosurgery of the Russian Medical Academy of Additional Professional Education of the Ministry of Health of the Russian Federation, Moscow, Russia, Ryzhkin S. A. ,   Department of Radiology, Radiotherapy, Radiation Hygiene and Radiation Safety named after academicians A. S. Pavlov and F. G. Krotkova Russian Medical Academy of Additional Professional Education of the Ministry of Health of the Russian Federation, Moscow, Russia
Published: February 2025

Stereotactic radiosurgery (SRS) of vestibular schwannomas (VS) is an effective and safe treatment method, competitive with microsurgery (MS). However, given the possibility of pseudo-progression, if the tumor continues to grow after SRS, one of the methods of additional treatment is MS, which is associated with an increased risk of dysfunction
of the acoustic-facial group. Given the risks associated with MS, the decision on surgical removal of VS after SRS should be justified, taking into account the timing of the possible course of pseudo-progression.
Material: from 2005 to 2015, 541 patients received radiosurgical treatment on the Gamma Knife device for vestibular schwannoma. In 17 (3.1%) cases out of 541 patients after SRS, microsurgical removal of the VS was performed, of which in 7 cases (41.1%) the only indication for tumor removal was an increase in its volume on average 40.4 months after SRS. A repeated analysis of pathomorphological preparations was performed in 11 patients to assess the signs in the tumors indicating the presence or absence of true tumor growth (recurrence).
Result: in the studied material after SRS, a complete absence of Antony A and Antony B patterns predominated (63.6%),
in the remaining cases their individual elements were detected. Rarefaction of cellular structures was noted in all samples.
Fibrosis of the tumor stroma was noted in all patients, often in combination with foci of angiomatosis. Severe or
focal edema was detected in 81.8%. Thus, it was established that after SRS, despite the continued growth of the tumor, typical post-radiation changes dominate in morphological preparations, indicating the absence of the potential of VS for further true growth.