Open AccessA Model-based method for assessment of salivary gland and planning target volume dosimetry in volumetric-modulated arc therapy planning on head-and-neck cancer
Author(s) -
Honglai Zhang,
Yejie Cao,
J. Antone,
Adam C. Riegel,
Maged Ghaly,
Louis Potters,
A Jamshidi
Publication year - 2019
Publication title -
journal of medical physics/journal of medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.292
H-Index - 24
eISSN - 1998-3913
pISSN - 0971-6203
DOI - 10.4103/jmp.jmp_19_19
Subject(s) - nuclear medicine , radiation treatment planning , medicine , head and neck cancer , salivary gland cancer , radiation therapy , dosimetry , head and neck , cancer , radiology , surgery
This study examined the relationship of achievable mean dose and percent volumetric overlap of salivary gland with the planning target volume (PTV) in volumetric-modulated arc therapy (VMAT) plan in radiotherapy for a patient with head-and-neck cancer. The aim was to develop a model to predict the viability of planning objectives for both PTV coverage and organs-at-risk (OAR) sparing based on overlap volumes between PTVs and OARs, before the planning process. Forty patients with head-and-neck cancer were selected for this retrospective plan analysis. The patients were treated using 6 MV photons with 2-arc VMAT plan in prescriptions with simultaneous integrated boost in dose of 70 Gy, 63 Gy, and 58.1 Gy to primary tumor sites, high-risk nodal regions, and low-risk nodal regions, respectively, over 35 fractions. A VMAT plan was generated using Varian Eclipse (V13.6), in optimization with biological-based generalized equivalent uniform dose (gEUD) objective for OARs and targets. Target dose coverage ( D 95 , D max , conformity index) and salivary gland dose ( D mean and D max ) were evaluated in those plans. With a range of volume overlaps between salivary glands and PTVs and dose constraints applied, results showed that dose D 95 for each PTV was adequate to satisfy D 95 >95% of the prescription. Mean dose to parotid <26 Gy could be achieved with <20% volumetric overlap with PTV 58 (parotid-PTV 58 ). On an average, the D mean was seen at 15.6 Gy, 21.1 Gy, and 24.2 Gy for the parotid-PTV 58 volume at <5%, <10%, and <20%, respectively. For submandibular glands (SMGs), an average D mean of 27.6 Gy was achieved in patients having <10% overlap with PTV 58 , and 36.1 Gy when <20% overlap. Mean doses on parotid and SMG were linearly correlated with overlap volume (regression R 2 = 0.95 and 0.98, respectively), which were statistically significant ( P < 0.0001). This linear relationship suggests that the assessment of the structural overlap might provide prospective for achievable planning objectives in the head-and-neck plan.