Can Apparent Diffusion Coefficient (ADC) maps replace Diffusion Tensor Imaging (DTI) maps to predict the volumetric response of meningiomas to Gamma Knife Radiosurgery?

PURPOSE

Noninvasive methods are desired to predict the treatment response to Stereotactic Radiosurgery (SRS) to improve individual tumor management. In a previous study, we demonstrated that Diffusion Tensor Imaging (DTI)-derived parameter maps significantly correlate to SRS response. This study aimed to analyze and compare the predictive value of intratumoral ADC and DTI parameters in patients with meningiomas undergoing radiosurgery.

METHODS

MR images of 70 patients treated with Gamma Knife SRS for WHO grade I meningiomas were retrospectively reviewed. MR acquisition included pre- and post-treatment DWI and DTI sequences, and subtractions were calculated to assess for radiation-induced changes in the parameter values.

RESULTS

After a mean follow-up period (FUP) of 52.7 months, 69 of 70 meningiomas were controlled, with a mean volume reduction of 34.9%. Whereas fractional anisotropy (FA) values of the initial exam showed the highest correlation to tumor volume change at the last FU (CC = - 0.607), followed by the differences between first and second FU values of FA (CC = - 0.404) and the first longitudinal diffusivity (LD) value (CC = - 0.375), the correlation coefficients of all ADC values were comparably low. Nevertheless, all these correlations, except for ADC measured at the first follow-up, reached significance.

CONCLUSION

For the first time, the prognostic value of ADC maps measured in meningiomas before and at first follow-up after Gamma Knife SRS, was compared to simultaneously acquired DTI parameter maps. Quantities assessed from ADC maps present significant correlations to the volumetric meningioma response but are less effective than correlations with DTI parameters.

MRI radiomics in the prediction of the volumetric response in meningiomas after gamma knife radiosurgery

PURPOSE

This report presents the first investigation of the radiomics value in predicting the meningioma volumetric response to gamma knife radiosurgery (GKRS).

METHODS

The retrospective study included 93 meningioma patients imaged by three Tesla MRI. Tumor morphology was quantified by calculating 337 shape, first- and second-order radiomic features from MRI obtained before GKRS. Analysis was performed on original 3D MR images and after their laplacian of gaussian (LoG), logarithm and exponential filtering. The prediction performance was evaluated by Pearson correlation, linear regression and ROC analysis, with meningioma volume change per month as the outcome.

RESULTS

Sixty calculated features significantly correlated with the outcome. The feature selection based on LASSO and multivariate regression started from all available 337 radiomic and 12 non-radiomic features. It selected LoG-sigma-1-0-mm-3D_firstorder_InterquartileRange and logarithm_ngtdm_Busyness as the predictively most robust and non-redundant features. The radiomic score based on these two features produced an AUC = 0.81. Adding the non-radiomic karnofsky performance status (KPS) to the score has increased the AUC to 0.88. Low values of the radiomic score defined a homogeneous subgroup of 50 patients with consistent absence (0%) of tumor progression.

CONCLUSION

This is the first report of a strong association between MRI radiomic features and volumetric meningioma response to radiosurgery. The clinical importance of the early and reliable prediction of meningioma responsiveness to radiosurgery is based on its potential to aid individualized therapy decision making.

FRI0379 VARIATIONS IN THE UTILIZATION OF BILATERAL TOTAL KNEE ARTHROPLASTY IN THE MANAGEMENT OF OSTEOARTHRITIS

Background:

A third of knee osteoarthritis presents with bilateral symptomatic arthritis. In these patients, treatment options include either a staged Unilateral Total knee arthroplasty (UTKA) procedure, or a simultaneous Bilateral TKA (BTKA) procedure. Even though literature regarding outcomes in BTKA procedure has not consistently been favorable, it remains popular in select patients due to use of a single anesthetic, shorter overall surgical time, lower cost and lower overall use of narcotics. African Americans (AAs) have lower utilization and worse outcomes in UTKA literature. It is unclear whether these racial variations extend to BTKA.

Objectives:

We sought to examine BTKA vs UTKA utilization rates and outcomes comparing AA and White patients.

Methods:

National Inpatient Sample (NIS) - Healthcare Cost and Utilization Project (HCUP) database (2007-2016) was used. We identified all patients ≥ 50 years who underwent elective primary TKA using ICD-9-CM code 81.54 for UTKA and BTKA from January 1, 2012 to September 30, 2015, and ICD-10-CM codes 0SRC0x and 0SRD0x thereafter. Patients with inflammatory arthritis, pathologic fractures, metastatic disease and avascular necrosis were excluded. Major in-hospital complications included post-operative myocardial infarction, prosthetic device complication, surgical wound infection, and venous thromboembolism. Differences in temporal trends in utilization and major in-hospital complications of BTKA vs UTKA were compared between AAs and Whites. Multivariable logistic regression models were used to assess differences in both these trends between AAs and Whites after adjusting for individual (age, sex, Elixhauser comorbidity index, and morbid obesity), hospital level (hospital volume, bed size, region and teaching status) and community level (median household income) variables. Discharge weights were used to enable nationwide estimates. Multiple imputation was performed for missing race variable (11.9%).

Results:

From 2007 to 2016, an estimated 276,194 BTKA (unweighted observations 56,675) and 5,528,429 UTKA (unweighted observations 1,131,329) were identified (Table 1). Females had a higher proportion of TKAs performed (62.1% UTKA vs 55.9% BTKA). Patients had fewer comorbidities (measured by the Elixhauser Index) when undergoing BTKA compared to UTKA. The proportion of BTKA amongst all TKAs declined from 5.53% in 2007-08 to 4.03% in 2015-16. AAs continued to have significantly lower proportion of BTKA utilization compared to Whites (4.68% in AAs vs 6.08% in Whites in 2007-08, whereas 3.28% in AAs vs 4.19% in Whites in 2015-16, adjusted p < 0.001) (Figure 1a). In-hospital complication rates for UTKA and BTKA were significantly higher in Whites compared to AAs throughout the study period (0.77% in AAs vs 0.9% in Whites in 2007-08, whereas 0.69% in AAs vs 0.83% in Whites in 2015-16, adjusted p < 0.001) (Figure 1b). The results were similar after imputation of missing race values.

Conclusion:

In this nationwide sample of patients from 2007 to 2016, we found that AAs have lower utilization rate of BKTA compared to Whites, however the in-hospital complication rates were significantly higher in Whites.

References:

N/A

Table 1.

Weighted frequencies and percentages of demographic characteristics among unilateral TKA vs. bilateral TKA (N = 6, 236, 426).

VariableUnilateral TKABilateral TKAPaN = 5,528,429(Unweighted N = 1,131,329)N = 276,194(Unweighted N = 56,675)Patient CharacteristicsAge, mean (SD)67.4 (0.02)65.0 (0.06)<.0001Sex: Female, n(%)3,429,484 (62.1)154,442 (55.9)<.0001Race, n(%): White4,051,648 (50.9)212,468 (76.9)<.0001 African American352,933 (6.4)14,441 (5.2) Other464,407 (8.4)16,443 (6.0) Missing659,439 (11.9)32,842 (11.9)Morbid Obesity, n(%)401,892 (7.3)20,411 (7.4)0.47Elixhauser Indexd, n(%):<.0001 0716,559 (13.0)41,550 (15.0) 1-44,484,941 (81.1)220,638 (80.0) ≥ 5326,928 (5.9)14,007 (5.1)

Disclosure of Interests:

Bella Mehta: None declared, Kaylee Ho: None declared, Jennifer Bido: None declared, Michael Parks Consultant of: Zimmer Biomet, Linda Russell: None declared, Susan Goodman Shareholder of: Reginosine- Investment, Grant/research support from: Novartis, Horizon, Consultant of: Novartis, Celgene, UCB, Said Ibrahim: None declared

Pretreatment texture analysis of routine MR images and shape analysis of the diffusion tensor for prediction of volumetric response after radiosurgery for meningioma

OBJECTIVEThe goal of this study was to identify parameters from routine T1- and T2-weighted MR sequences and diffusion tensor imaging (DTI) that best predict the volumetric changes in a meningioma after treatment with Gamma Knife radiosurgery (GKRS).METHODSIn 32 patients with meningioma, routine MRI and DTI data were measured before GKRS. A total of 78 parameters derived from first-level texture analysis of the pretreatment MR images, including calculation of the mean, SD, 2.5th and 97.5th percentiles, and kurtosis and skewness of data in histograms on a voxel-wise basis, were correlated with lesion volume change after a mean follow-up period of 3 years (range 19.5-63.3 months).RESULTSSeveral DTI-derived parameters correlated significantly with a meningioma volume change. The parameter that best predicted the results of GKRS was the 2.5th percentile value of the smallest eigenvalue (L3) of the diffusion tensor (correlation coefficient 0.739, p ≤ 0.001), whereas among the non-DTI parameters, only the SD of T2-weighted images correlated significantly with a tumor volume change (correlation coefficient 0.505, p ≤ 0.05, after correction for family-wise errors using false-detection-rate correction).CONCLUSIONSDTI-derived data had a higher correlation to shrinkage of meningioma volume after GKRS than data from T1- and T2-weighted image sequences. However, if only routine MR images are available, the SD of T2-weighted images can be used to predict control or possible progression of a meningioma after GKRS.

Compression of the middle cerebellar tract by posterior fossa tumors before and after Gamma Knife radiosurgery studied with diffusion tensor imaging

PURPOSE

To investigate if clinically asymptomatic compression of the middle cerebellar tract by extracerebral posterior fossa tumors can produce changes in diffusion tensor imaging (DTI) parameters and if these changes return to normal after Gamma Knife radiosurgery (GKRS).

MATERIAL AND METHODS

In 22 patients (12 female, mean age 53.8 years) with posterior fossa tumors (14 schwannomas and 8 meningiomas), the middle cerebellar tract was tracked using DTI data. DTI parameters, such as fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) within these tracts were determined separately on the tumor side and on the contra-lateral side. As a surrogate parameter of tract compression, we used the distance between a tangential line extending between the anterior, not affected part of the pons and the cerebellum, and the furthest extension of the tumor into the lateral rim of the pons. In a subgroup of 15 patients, DTI parameters were recorded after a follow-up of more than 2 years (mean follow-up time 37.5 months) after GKRS and compared to initial findings.

RESULTS

Before GKRS, all DTI parameters within the compressed tract had increased. The increase in MD correlated significantly with the degree of tract compression (c = 0.443, p < 0.05). Follow-up examinations after GKRS showed reduction in FA and AD, whereas MD and RD increased. After correction for time elapsed after treatment and tumor type, the changes of MD and AD following treatment correlated significantly with the reduction of tract compression, but not with radiation dose.

CONCLUSION

Although without obvious clinical symptoms, disorders of the middle cerebellar tract, as in the case of posterior fossa tumors, persist after reduction of tumor size. Because of the significant correlation between the change of parameters and the reduction of tract compression, initial compression and consequent relief are regarded as the main factors responsible for persistent disorders of the middle cerebellar tract. Radiosurgery dose did not contribute significantly to changes in DTI parameters.

Prognostic value of diffusion tensor imaging parameters for Gamma Knife radiosurgery in meningiomas

OBJECTIVE

Diffusion tensor imaging (DTI) parameters are able to differentiate between meningioma subtypes. The hypothesis that there is a correlation between DTI parameters and the change in tumor size after Gamma Knife radiosurgery (GKRS) was analyzed.

METHODS

DTI parameters were measured using MRI before GKRS in 26 patients with meningiomas. The findings were correlated with the change in tumor size after treatment as measured at the last follow-up (range 12.5–45 months).

RESULTS

Only those meningiomas that showed the highest fractional anisotropy (FA), the lowest spherical index of the tensor ellipsoid (Cs), and the lowest radial diffusivity (RD) either increased or remained stable in terms of volume, whereas all other meningiomas decreased in volume. The correlation between the DTI parameters (correlation values of −0.81 for FA, 0.75 for Cs, 0.66 for RD, and 0.66 for mean diffusivity) and the rate of volume change per month was significant (p ≤ 0.001). Other factors, including original tumor size, prescription dose, and patient age, did not correlate significantly.

CONCLUSIONS

Meningiomas that show high FA values—as well as low Cs, low RD, and low mean diffusivity values—do not respond as well to GKRS in comparison with meningiomas with low FA values. This finding might be due to their higher content level of fibrous tissue. In particular, the meningioma with the highest FA value (0.444) considerably increased in volume (by 32.3% after 37 months), whereas the meningioma with the lowest FA value (0.151) showed the highest rate of reduction (3.3% per month) in this study.