Table 6 Correlation coefficients (r) with corresponding p-values of Pearson’s and Spearman’s correlation test of dose-volumetric parameters of organ-at-risk volumes to modulation complexity score for volumetric modulated radiation therapy and total monitor units for lumbar stereotactic ablative radiotherapy plans

Cauda equine

ΔD_1.5 cc

-0.675

< 0.0001

0.674

< 0.0001

ΔD_0.5 cc

-0.549

0.002

0.569

0.002

ΔD_0.1 cc

-0.535

0.003

0.515

0.005

ΔD_0.035 cc

-0.537

0.003

0.514

0.005

ΔMaximum dose

-0.298

0.116

0.260

0.173

ΔMean dose

-0.802

< 0.0001

0.834

< 0.0001

Cauda equine PRV

ΔD_1.5 cc

-0.505

0.006

0.529

0.004

ΔD_0.5 cc

-0.406

0.030

0.439

0.018

ΔD_0.1 cc

-0.307

0.105

0.323

0.088

ΔD_0.035 cc

-0.255

0.181

0.245

0.200

ΔMaximum dose

0.035

0.857

-0.025

0.899

ΔMean dose

-0.736

< 0.0001

0.774

< 0.0001

Ring_1.5 cm

ΔV_105% (cm³)

-0.717

< 0.0001

0.601

0.001

ΔV_110% (cm³)

-0.697

< 0.0001

0.562

0.002

ΔV_115% (cm³)

-0.457

0.013

0.350

0.063