Evaluating volumetric modulated arc therapy planning efficiency and dosimetric impact on non-contoured organ at risk in whole brain radiotherapy: a focus on oral cavity dose distribution

Halis, Hatice; Akbayırlı, Uğur

doi:10.1590/1806-9282.20250188

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Original Article • Rev. Assoc. Med. Bras. 71 (11) • 2025 • https://doi.org/10.1590/1806-9282.20250188 linkcopy

Evaluating volumetric modulated arc therapy planning efficiency and dosimetric impact on non-contoured organ at risk in whole brain radiotherapy: a focus on oral cavity dose distribution

Authorship SCIMAGO INSTITUTIONS RANKINGS

SUMMARY

OBJECTIVE: The aim of this study was to investigate the dosimetric outcomes and planning efficiency of volumetric modulated arc therapy compared to the field-in-field technique for whole brain radiotherapy, with a focus on the oral cavity as a newly defined organ at risk. The study also evaluates the impact of volumetric modulated arc therapy re-optimization on reducing oral cavity doses while ensuring target coverage.

METHODS: Treatment plans for 20 technique for whole brain radiotherapy patients treated with volumetric modulated arc therapy were retrospectively analyzed and re-evaluated using field-in-field and volumetric modulated arc therapy re-optimization techniques. Dosimetric parameters, including D2%, D98%, V30(Gy), homogeneity index, and conformity index, were compared for the planning target volume. Mean and maximum doses to the oral cavity and bilateral lenses were assessed.

RESULTS: Volumetric modulated arc therapy provided superior conformity (CI 0.82±0.07) and homogeneity (HI: 1.05±0.00) compared to field-in-field (CI 0.65±0.13, HI: 1.06±0.10) with significant differences (p<0.001). However, volumetric modulated arc therapy resulted in higher mean and maximum oral cavity and lens doses. Volumetric modulated arc therapy re-optimization significantly reduced oral cavity doses (p<0.001) while maintaining similar target coverage and dosimetric performance to volumetric modulated arc therapy.

CONCLUSIONS: Volumetric modulated arc therapy improves dose conformity and homogeneity compared to field-in-field but increases doses to non-contoured organ at risk. Volumetric modulated arc therapy re-optimization effectively lowers oral cavity doses without compromising target coverage, underscoring the importance of identifying and addressing non-standard organ at risk. These findings highlight volumetric modulated arc therapy's clinical advantages, particularly in high-demand settings, while emphasizing the need for optimizing organ at risk to reduce toxicity.

KEYWORDS:
Brain neoplasms; Secondary; Intensity-modulated; Radiotherapy planning; Mouth; Radiation effects

Structure parameter	DVH goal	Max acceptable criteria
PTV D98%	>2,850 cGy	>2,800 cGy
PTV D2%	<3,250 cGy	<3,300 cGy
Lens (individually) mean dose	<600 cGy	<1,000 cGy
Oral cavity	ALARA*	ALARA*

Target metric	FIF mean	VMATt mean	VMATro mean	Statistical significance
D2% of PTV (cGy)	3,119.86±21.70	2,984±62.94	3,129.53±14.66	p>0.005
D98% of PTV (cGy)	2,852.88±49.51	2,859.38±137.89	2,853.28±54.47	p>0.005
V30(Gy) of PTV (%)	69.12%±13.14	83.92%±7.41	78.36%±7.89	FIF vs. VMATt: p<0.001 VMATt vs. VMATro: p>0.005
Homogeneity index (HI)	1.06±0.10	1.05±0.00	1.06±0.013	p>0.001
Conformity index (CI)	0.65±0.13	0.82±0.07	0.78±0.079	FIFvs. VMATt/VMATro: p<0.001; VMATt vs. VMATro: p>0.001
Oral cavity mean dose (cGy)	151.33±30.53	381.87±239.26	104.25±19.97	FIF vs. VMATt: p=0.002 FIF vs. VMATro: p<0.001 VMATt vs. VMATro: p<0.001
Oral cavity maximum dose (cGy)	691.87±201.14	1,202.60±436.69	256.15±71.05	FIF vs. VMATt: p=0.002; FIF vs. VMATro: p<0.001; VMATt vs. VMATro: p<0.001 FIF vs. VMATro: p<0.001; VMATt vs. VMATro: p<0.001
Right lens mean dose (cGy)	509.36±22.90	520.71±17.71	342.24±56.57	FIF vs. VMATro: p<0.001 VMATt vs. VMATro: p<0.001
Left lens mean dose (cGy)	525.63±67.01	530.08±16.35	328.37±48.59	FIF vs. VMATro: p<0.001; VMATt vs. VMATro: p<0.001

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Associação Médica Brasileira R. São Carlos do Pinhal, 324, 01333-903 São Paulo SP - Brazil, Tel: +55 11 3178-6800, Fax: +55 11 3178-6816 - São Paulo - SP - Brazil
E-mail: ramb@amb.org.br

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[TFN1] ALARA: as low as reasonably achievable; DVH: dose volume histogram; PTV: planning target volume.

[TFN2] ^*
ALARA—indicating that doses should be minimized without compromising treatment efficacy.