Pretreatment ADC predicts tumor control after Gamma Knife radiosurgery in solid vestibular schwannomas

Emerging strategies for the prediction of behaviour, growth, and treatment response in vestibular schwannoma

Vestibular schwannoma (VS) can present several management challenges for the clinician. Their unpredictable potential for growth creates uncertainty regarding when active treatment should be initiated, and once growth is confirmed which treatment option should be adopted, notably surgery or radiotherapy, and in particular stereotactic radiosurgery (SRS). The obvious benefits of SRS would ideally come with the ability to reliably predict long-term radiosurgery response/failure. Differentiation from temporary post-treatment phenomena such as transient tumour expansion or reactive swelling remains an unmet need. More powerful again would be the pre-treatment identification of which tumours will respond to radiosurgery and which will not. Over the past decade, there has been emerging interest in the development of non-invasive biomarkers, including imaging, for predicting growth and treatment response in VS. Alongside clinical radiographic predictors for VS growth such as extracanalicular tumour location and growth in the first year, studies have shown potential promise for advanced MRI and blood-based biomarkers that capture pathophysiological mechanism behind VS growth. Emerging interest in radiomics-based analyses of routinely acquired MRI, and the use of physiological imaging techniques such as dynamic-contrast enhanced MRI for pre- and post-treatment evaluation of tumour microvasculature and microstructure holds promise for revolutionizing this area. This article explores the current state of identifying VS growth at initial presentation, predicting treatment response to SRS and detecting early treatment failure, and finally the potential for developing more personalized patient selection for drug therapies, including bevacizumab, as well as emerging novel therapeutics for these tumours.

Stereotactic Radiosurgery for Vestibular Schwannoma - A Case-Based Practice Guide From the Radiosurgery Society

PURPOSE

Vestibular schwannomas (VS) are the most common benign intracranial nerve sheath tumors. Surgery and radiation therapy - particularly stereotactic radiosurgery (SRS) - are the primary treatment options. SRS is the dominant treatment for small- and medium-sized VS and selected larger tumors due to its excellent local control rates and favorable safety profile compared with surgery. However, careful treatment planning is essential, taking into account patient preferences, tumor location and size, symptoms, and anticipated treatment-related toxicity.

METHODS AND MATERIALS

Four clinical VS scenarios have been selected to illustrate the use of SRS, including a unilateral small intracanalicular VS, a large VS with cystic components, reirradiation with SRS after local tumor recurrence, and bilateral VS in the setting of neurofibromatosis type 2-related schwannomatosis.

RESULTS

SRS is an effective and safe treatment modality for the majority of VS cases, requiring careful treatment planning and a thorough understanding of potential limitations and challenges.

CONCLUSIONS

This case-based practice guide aims to provide a concise overview of the treatment of VS with SRS. We present and discuss 4 different clinical scenarios of VS to highlight the pitfalls and best practice recommendations.

Apparent diffusion coefficient and magnetic resonance imaging characteristics in predicting response to radiosurgery in patients with vestibular schwannomas

OBJECTIVE

Predicting treatment response in patients with vestibular schwannomas (VSs) remains challenging. This study aimed to evaluate the use of pre-treatment normalized apparent diffusion coefficient (nADC) values and magnetic resonance (MR) imaging characteristics in predicting treatment outcomes in patients with VSs undergoing radiosurgery.

METHODS

The MR images of 44 patients with VSs who underwent radiosurgery at our institution were retrospectively reviewed, and the patients were categorized into tumor control (n = 28) and progression (n = 16) groups based on treatment response after treatment initiation, with a median follow-up duration of 29.5 (13-115) months. Pre-treatment nADC values for the whole tumor and solid portion of the tumor were assessed for predictive significance. MRI characteristics were analyzed, including hemorrhage status, tumor morphology, and post-treatment loss of central enhancement. Interobserver reliability was also evaluated.

RESULTS

Early post-treatment enlargement was associated with tumor progression (p = .024). The mean pre-treatment nADC values for the solid part of the tumor were significantly higher in the tumor control group than in tumor progression group (1.32 vs 1.05, p = .005). The receiver operating characteristic curve analysis revealed a mean nADC of 1.18 as an optimal cutoff, with sensitivity and specificity of 76.2% and 86.7%, respectively, in predicting treatment response.

CONCLUSION

The mean nADC values for the solid part of the tumor demonstrated predictive value for treatment response, with implications for treatment planning. Notably, early post-treatment enlargement was correlated with tumor progression. Incorporating these findings into clinical practice may refine treatment strategies for patients with VSs undergoing radiosurgery.

Surgical and radiosurgical outcomes for Koos grade 3 vestibular schwannomas

This study aimed to reveal the preferred initial treatment for Koos grade 3 vestibular schwannomas (VS). We performed a two-institutional retrospective study on 21 patients with Koos grade 3 VS undergoing resection at Yokohama Medical Center and 37 patients undergoing radiosurgery at Yokohama Rosai Hospital from 2010 to 2021. Tumor control, complications, and functional preservation were compared. The median pre-treatment volume and follow-up duration were 2845 mm3 and 57.0 months, respectively, in the resection group and 2127 mm3 and 81.7 months, respectively, in the radiosurgery group. In the resection group, 16 (76.2%) underwent gross total resection, and three patients (14.3%) experienced regrowth; however, no one required additional treatment. In the radiosurgery group, the tumor control rate was 86.5%, and three cases (8.1%) required surgical resection because of symptomatic brainstem compression. Kaplan-Meier analyses revealed that tumors with delayed continuous enlargement and large thin-walled cysts were significantly associated with poor prognostic factors (p = 0.0027, p < 0.001). The pre-radiosurgery growth rate was also associated with the volume increase (p = 0.013). Two cases (9.5%) required additional operation due to complications such as post-operative hematoma and cerebrospinal fluid leaks in the resection group, whereas temporary cranial neuropathies were observed in the radiosurgery group. Two patients (9.5%) had poor facial nerve function (House-Brackmann grading grade 3) in the resection group, while no one developed facial paresis in the radiosurgery group. Trigeminal neuropathy improved only in the resection group.Radiosurgery can be considered for the treatment of Koos grade 3 VS for functional preservation. However, resection may also be considered for patients with severe trigeminal neuropathy or a high risk of volume increments, such as large thin-walled cysts and rapid pre-treatment growth.

Volumetric apparent diffusion coefficient (ADC) histogram metrics as imaging biomarkers for pretreatment predicting response to fertility-sparing treatment in patients with endometrial cancer

OBJECTIVES

To investigate the feasibility of volumetric apparent diffusion coefficient (ADC) histogram analysis for prediction of fertility-sparing treatment (FST) response in patients with endometrial cancer (EC).

METHODS

Pretreatment data of 54 EC patients with FST were retrospectively analyzed. Treatment response at each follow-up was pathologically evaluated. The associations of ADC histogram metrics (volume, minADC, maxADC, meanADC; 10th, 25th, 50th, 75th and 90th ADC percentiles; skewness; kurtosis) and baseline clinical characteristics with complete response (CR) at the second and third follow-ups, two-consecutive CR, and recurrence at the final follow-up were evaluated by uni- and multivariable logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was used for diagnostic performance evaluation.

RESULTS

Compared with non-CR patients, CR patients had significantly higher minADC and 10th and 25th ADC percentiles at the second follow-up (P = 0.008, 0.039, and 0.034, respectively) and higher minADC, older age, lower HE4 level, and higher overweight rate at the third follow-up (P = 0.001, 0.040, 0.021, and 0.004, respectively). Patients with two-consecutive CR had a significantly higher minADC than those without (P = 0.018). There was no association between ADC metrics or clinical characteristics and recurrence (all P > 0.05). MinADC yielded the largest AUC in predicting CR (0.688 and 0.735 at the second and third follow-up, respectively) and the presence of two-consecutive CR (0.753). When combined with patient age and HE4 level, the prediction of CR could be further improved at the third follow-up, with an AUC of 0.786.

CONCLUSION

Pretreatment minADC could be a potential imaging biomarker for predicting FST response. Clinical characteristics may have incremental value to minADC in predicting CR.