Injection of hydrogel spacer increased maximal intrafractional prostate motion in anterior and superior directions during volumetric modulated arc therapy-stereotactic body radiation therapy for prostate cancer

Sawayanagi, Subaru; Yamashita, Hideomi; Ogita, Mami; Takenaka, Ryosuke; Nozawa, Yuki; Watanabe, Yuichi; Imae, Toshikazu; Abe, Osamu

doi:10.1186/s13014-022-02008-3

Table 3 Multivariate analyses for maximum intrafractional displacement

From: Injection of hydrogel spacer increased maximal intrafractional prostate motion in anterior and superior directions during volumetric modulated arc therapy-stereotactic body radiation therapy for prostate cancer

	Regression coefficient (95% CI)	P value^a
Superior MID
Age (continuous)	− 0.012 (− 0.036–0.012) per year	0.31
Spacer injection		0.014^†
Non-spacer	Reference
Spacer	0.546 (0.118–0.975)
Rectum volume (continuous)	0.001 (− 0.001–0.013) per cc	0.80
Monitoring time (continuous)	0.001 (− 0.003–0.005) per second	0.66
Inferior MID
Age (continuous)	0.026 (− 0.003–0.055) per year	0.082
Spacer injection		0.31
Non-spacer	Reference
Spacer	− 0.263 (− 0.783–0.256)
Rectum volume (continuous)	− 0.011 (− 0.025–0.002) per cc	0.10
Monitoring time (continuous)	0.000 (− 0.005–0.005) per second	0.99
Left MID
Age (continuous)	0.011 (− 0.015–0.038) per year	0.39
Spacer injection		0.70
Non-spacer	Reference
Spacer	0.089 (− 0.382–0.560)
Rectum volume (continuous)	0.000 (− 0.012–0.013) per cc	0.98
Monitoring time (continuous)	0.000 (− 0.005–0.004) per second	0.84
Right MID
Age (continuous)	0.008 (− 0.015–0.031) per year	0.48
Spacer injection		0.23
Non-spacer	Reference
Spacer	0.245 (− 0.161–0.652)
Rectum volume (continuous)	0.002 (− 0.008–0.013) per cc	0.67
Monitoring time (continuous)	0.002 (− 0.001–0.006) per second	0.22
Anterior MID
Age (continuous)	0.008 (− 0.020–0.036) per year	0.57
Spacer injection		0.0074^†
Non-spacer	Reference
Spacer	0.692 (0.199–1.185)
Rectum volume (continuous)	0.001 (− 0.012–0.014) per cc	0.84
Monitoring time (continuous)	0.002 (− 0.003–0.006) per second	0.50
Posterior MID
Age (continuous)	0.004 (− 0.042–0.049) per year	0.87
Spacer injection		0.35
Non-spacer	Reference
Spacer	− 0.375 (− 1.174–0.424)
Rectum volume (continuous)	− 0.012 (− 0.033–0.009) per cc	0.24
Monitoring time (continuous)	0.002 (− 0.006–0.009) per second	0.65
Maximum intrafractional vector length
Age (continuous)	0.023 (− 0.040–0.085) per year	0.46
Spacer injection		0.42
Non-spacer	Reference
Spacer	0.441 (− 0.664–1.547)
Rectum volume (continuous)	− 0.010 (− 0.039–0.019) per cc	0.48
Monitoring time (continuous)	0.002 (− 0.008–0.012) per second	0.69

Abbreviations: MID maximum intrafracitonal displacement, CI confidence interval
^aBy multiple regression analysis
^†Statistically significant

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