Atypical Meningioma Radiotherapy

The efficacies of adjuvant stereotactic radiosurgery (SRS) and external beam radiation therapy (EBRT) for atypical meningiomas (AMs) after subtotal resection (STR) remain unclear 1).

In this retrospective cohort study, the authors examine the recurrence rates for atypical meningiomas after resection (with or without adjuvant radiotherapy) and identify which factors were associated with recurrence.

Methods: Of 90 patients with atypical meningiomas who underwent surgery between 1999 and 2009, 71 (79%) underwent gross-total resection (GTR) and 19 (21%) underwent subtotal resection (STR); 31 patients received adjuvant radiotherapy. All tumors were pathology-confirmed WHO Grade II atypical meningiomas. Univariate and multivariate analyses were performed to identify factors associated with recurrence-free survival.

Results: Among 90 patients, 17 developed tumor recurrence (81% recurrence-free survival at 5 years). In the overall group, adjuvant radiotherapy reduced the recurrence rate to 9% from 19% at 5 years (p = 0.048). After STR, adjuvant radiotherapy significantly reduced recurrence from 91% to 20% (p = 0.0016). However, after GTR, adjuvant radiotherapy did not significantly reduce the recurrence rate (16.7% without radiation therapy vs 11.8% with radiation therapy) (p = 1.00). Five factors independently predictive of tumor recurrence included mitotic index, sheeting, necrosis, nonuse of radiation therapy, and STR. Further recursive partitioning analysis showed significant increases in risk for patients older than 55 years with mitoses and sheeting.

Conclusions: Adjuvant radiotherapy was effective at lowering recurrence rates in patients after STR but delivered no significant improvement in patients after GTR. Given that rates after GTR were similar with or without adjuvant radiotherapy, close observation without postoperative radiation therapy may be a viable option for these patients. Patients older than 55 years and those with mitoses noted during pathological examination had a significant risk of recurrence after GTR; for these patients, postoperative radiotherapy is recommended 2).

Conformal, high dose radiotherapy resulted in significant improvement of local control for atypical and malignant meningiomas. Increased local control resulted also in improved rates of survival for patients with malignant meningioma 3).

Role of necrosis

Adjuvant radiation therapy or external beam radiation therapy (EBRT) improved local control after stereotactic radiosurgery STR but only for tumors without spontaneous necrosis. Spontaneous necrosis may aid in decisions to administer adjuvant SRS or EBRT after STR of AMs 4).

Necrosis may be a negative predictor of radiation response regardless of radiation timing or modality 5).

Dawley et al. conducted a retrospective review of all patients with pathologically confirmed atypical meningioma (WHO grade II) treated with primary or adjuvant RT from February 2011 through February 2019. They identified two patients with long-term, grade 3 toxicity. The cases of these patients are described in detail.

Two patients had major complications associated with postoperative RT. Patients 1 and 2 both were treated with postoperative RT for pathologically confirmed atypical meningioma. Patient 1 experienced worsening behavioral changes, cognitive decline, and hydrocephalus following treatment. This required cerebrospinal fluid diversion. Patient 2 developed radiation necrosis with mass effect and cognitive decline. Neither patient returned to his/her initial post-RT status after steroid therapy, and each remained in need of supportive care. Both patients remained free of tumor progression at 52 and 38 months following treatment.

The postoperative management of patients with atypical meningioma continues to be defined, with questions remaining regarding timing of RT, dose, target delineation, and fractionation. Both of the patients in this study received fractionated RT, which included a greater volume of normal brain than more focal treatment options such as would be required by stereotactic radiosurgery (SRS). Further research is needed to compare SRS and fractionated RT for the management of patients with grade II meningiomas. The more focused nature of SRS may make this a preferred option in certain cases of focal recurrence 6).

Atypical Meningioma Radiotherapy Systematic Review.

1) , 6)
Dawley T, Rana Z, Abou-Al-Shaar H, Goenka A, Schulder M. Major complications from radiotherapy following treatment for atypical meningiomas. Neurosurg Focus. 2019 Jun 1;46(6):E5. doi: 10.3171/2019.3.FOCUS1930. PMID: 31153147.
Lee KD, DePowell JJ, Air EL, Dwivedi AK, Kendler A, McPherson CM. Atypical meningiomas: is postoperative radiotherapy indicated? Neurosurg Focus. 2013 Dec;35(6):E15. doi: 10.3171/2013.9.FOCUS13325. PMID: 24289123.
Hug EB, Devries A, Thornton AF, Munzenride JE, Pardo FS, Hedley-Whyte ET, Bussiere MR, Ojemann R. Management of atypical and malignant meningiomas: role of high-dose, 3D-conformal radiation therapy. J Neurooncol. 2000 Jun;48(2):151-60. PubMed PMID: 11083080.
4) , 5)
Sun SQ, Cai C, Murphy RK, DeWees T, Dacey RG, Grubb RL, Rich KM, Zipfel GJ, Dowling JL, Leuthardt EC, Simpson JR, Robinson CG, Chicoine MR, Perrin RJ, Huang J, Kim AH. Radiation Therapy for Residual or Recurrent Atypical Meningioma: The Effects of Modality, Timing, and Tumor Pathology on Long-Term Outcomes. Neurosurgery. 2016 Jul;79(1):23-32. doi: 10.1227/NEU.0000000000001160. PubMed PMID: 26645969.
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