Near-complete regression 19 years after Gamma Knife radiosurgery of vestibular schwannoma with massive pseudoprogression: case report

Abstract

<jats:p>Gamma Knife radiosurgery (GKRS) is a frequent treatment choice for patients with small- to moderate-sized vestibular schwannoma (VS). However, pseudoprogression after GKRS is commonly observed, with a reported incidence ranging from 7% to 77%. The wide range of the reported incidence of pseudoprogression reflects the fact that there is no consensus on how it should be diagnosed.</jats:p><jats:p>The authors present the case of a 66-year-old woman who had a 2.5-cm right-sided VS treated with GKRS in 1997. The first posttreatment MRI obtained 5 months later showed that the tumor volume had increased to 9.7 cm<jats:sup>3</jats:sup>. The tumor volume increased further and reached its peak 24 months after treatment at 20.9 cm<jats:sup>3</jats:sup>, which was a 161% increase from pretreatment volume. Thereafter, the tumor shrank gradually and mass effect on the brainstem reduced over time. By 229 months after treatment, the tumor volume was 1.0 cm<jats:sup>3</jats:sup>, equaling 12.5% of pretreatment tumor volume, or 4.8% of peak tumor volume after treatment. This case demonstrates that if a patient remains asymptomatic despite a dramatic increase in tumor volume after GKRS, observation remains an option, because even a very sizable tumor can shrink with near-complete resolution. Patients undergoing GKRS for VS should be counseled regarding the possibility of pseudoprogression, and followed carefully over time while avoiding premature decisions for surgical removal after treatment.</jats:p>

Outcomes of stereotactic radiosurgery in young adults with vestibular schwannomas

“…It can be challenging to differentiate between true tumor progression and pseudo-progression, in particular, for younger patients, where the threshold of salvage surgery may be lowered, as additional resections are generally tolerable in this age group. Recent studies, in contrast to conventional wisdom, have shown that transient expansion may occur later than 2 years post-SRS and the growth rate may occasionally exceed 50% in volume increase [23][24][25]. Thus, tumors not causing disturbing symptoms or brainstem compression may be amenable to observation despite a certain rate of progression.…”

Repeat stereotactic radiosurgery for progressive vestibular schwannomas after previous radiosurgery: a systematic review and meta-analysis

“…Subsequent volumetric measurement is the key to evaluate such progression, while some authors suggested even preradiosurgical radiomics [59]. One should keep in mind that at least 2 years follow-up is usually required [23], avoiding misjudging any temporary tumoral swelling [32]. This should be further judged in the context of presence or absence of patient's symptoms.…”