Geometric changes of parotid glands caused by hydration during chemoradiotherapy

Radiation Oncology

Table 2 Effect of hydration on parotid gland volume and position during chemoradiotherapy

	PG volume change relative to day₋₃ (%)
	CRT		RT		CRT – RT
	Mean	Median	Mean	Median	Mean	Median	p
day₋₃	86.3	87.7	86.7	87.1
day₁ – day₋₃	+2.1	+1.8	−5.1	−4.5	7.2	6.3	<0.001
day₂ – day₋₃	+5.1	+5.4	−5.6	−3.8	10.8	9.2	<0.001
day₃ – day₋₃	+1.4	−1.8	−5.6	−4.7	7.0	2.8	0.016
day₄ – day₋₃	−5.4	−6.9	−7.7	−7.3	2.2	0.4	0.601
day₅ – day₋₃	−4.8	−4.8	−6.8	−6.7	2.0	1.9	0.511
	Medio-lateral distance change between PGs relative to day₋₃ (cm)
	CRT		RT		CRT – RT
	Mean	Median	Mean	Median	Mean	Median	p
day₋₃	−0.24	−0.25	−0.30	−0.31
day₁ – day₋₃	+0.06	+0.04	−0.09	−0.09	0.15	0.13	<0.001
day₂ – day₋₃	+0.12	+0.09	−0.10	−0.08	0.22	0.17	<0.001
day₃ – day₋₃	+0.03	+0.00	−0.09	−0.10	0.12	0.10	0.109
day₄ – day₋₃	−0.08	−0.13	−0.14	−0.11	0.06	−0.02	0.718
day₅ – day₋₃	−0.08	−0.08	−0.12	−0.12	0.03	0.04	0.554

Volume and position were determined from CBCT scans and expressed relative to the planning CT. Baseline volume and position were taken three days prior to start of hydration in the second chemotherapy cycle (week 4). Hydration started around treatment day 21, this day was renamed day 0. Significance (Mann–Whitney U-test) was tested against a control group receiving radiotherapy only. No significant results were found for the distance change between parotid glands in dorso-ventral and cranio-caudal direction
PG(s) parotid gland(s), CRT chemoradiotherapy group, RT radiotherapy alone group

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