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. 2021 Aug;10(15):5175-5190.
doi: 10.1002/cam4.4079. Epub 2021 Jun 22.

A Study to Assess the Dosimetric Impact of the Anatomical Changes Occurring in the Parotid Glands and Tumour Volume during Intensity Modulated Radiotherapy using Simultaneous Integrated Boost (IMRT-SIB) in Head and Neck Squamous Cell Cancers

Arunima Ghosh  1 , Seema Gupta  1 , Danial Johny  1 , Vivek Vidyadhar Bhosale  2 , Mahendra Pal Singh Negi  2
Affiliations

A Study to Assess the Dosimetric Impact of the Anatomical Changes Occurring in the Parotid Glands and Tumour Volume during Intensity Modulated Radiotherapy using Simultaneous Integrated Boost (IMRT-SIB) in Head and Neck Squamous Cell Cancers

Arunima Ghosh et al. Cancer Med. 2021 Aug.

Abstract

Background: Anatomical variations in head and neck cancer during IMRT leads to volume shrinkage, results in dosimetric variations in tumour and normal tissue including parotid glands, with a risk of radiation toxicities.

Methods: 30 patients with a stage II-IV head and neck squamous cell carcinoma (HNSCC) were treated with definitive IMRT-SIB and concomitant chemotherapy. Volumetric and dosimetric variations were evaluated during the period of IMRT by recalculating and obtaining dose-volume histograms of re-contoured target volumes and parotid glands on repeat CT scans taken multiple times during treatment (CT1, CT2, CT3 and CT4).

Results: Result showed significant (p < 0.001) mean decrease in both primary and nodal tumors volume with time whereas increase (p < 0.01 or p < 0.001) in respective V100 (%) and D2% (Gy). The mean parotid gland dose increased (p < 0.01 or p < 0.001) with time, whereas parotid gland volume and distance between plan isocenter and centre of mass of parotid glands decreased (p < 0.05 or p < 0.001) with time. Patient's mean weight and neck circumference both decrease (p < 0.001) with time whereas ECOG score increase (p < 0.001) with time. The mucosal toxicity increased significantly (p < 0.001) with time. The change in both weight and neck circumference showed significant (p < 0.001) and direct (positive correlation) association with change in parotid gland volume.

Conclusion: If the PTV and normal anatomy are changing with time, adaptive IMRT would be beneficial radiation dose delivery where possible.

Keywords: adaptive radiation; dosimetric variation; head neck cancer; imrt; parotid gland; volumetric variation.

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Conflict of interest statement

There is none.

Figures

FIGURE 1
FIGURE 1
A, Axial CT sections of a T2N0 soft palate carcinoma. Dose distribution of Plan 1 on CT1 (left) and on CT4(right). Patient lost about 6 kgs during treatment. The parotid glands decreased in size during treatment. The 30 Gy (light green) and 20 Gy (light yellow) isodose lines shifted closer to lateral border of the parotid glands in CT4 compared to CT1. B,. DVH comparison between CT1(formula image) and CT4 (formula image)
FIGURE 2
FIGURE 2
A, Coronal CT sections of a 55‐years‐old carcinoma pyriform fossa (T1N3b) patient. The gradual decrease in GTV primary (maroon), GTV nodal (pink) and bilateral parotid gland volumes can be appreciated. The low dose isodose curves [20 Gy (light yellow) and 30 Gy (light green)] can be seen covering more areas of right parotid gland in CT4 compared to CT1 and CT2. b. Comparative DVH of CT1 (‐‐‐‐‐‐‐) and CT2 (formula image) c. Comparative DVH of CT1 (‐‐‐‐‐‐‐) and CT4 (formula image)
FIGURE 3
FIGURE 3
Correlation between changes in weight and neck circumference over the time
FIGURE 4
FIGURE 4
(A) Correlation between weight and H‐Parotid gland volume over the time (B) Correlation between weight and distance between plan isocenter and COM of H‐Parotid gland over the time (C) Correlation between weight and L‐Parotid gland volume over the time (D) Correlation between weight and BOTH‐Parotid glands volume over the time
FIGURE 5
FIGURE 5
(A) Correlation between neck circumference and H‐Parotid gland volume over the time (B) Correlation between neck circumference and distance between plan isocenter and COM of H‐Parotid gland over the time (C) Correlation between neck circumference and L‐Parotid gland D mean over the time (D) Correlation between neck circumference and L‐Parotid gland volume over the time (E) Correlation between neck circumference and BOTH‐Parotid glands volume over the time (F) Correlation between neck circumference and distance between plan isocenter and COM of BOTH‐Parotid glands over the time
See this image and copyright information in PMC

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