A longitudinal evaluation of early anatomical changes of parotid gland in intensity modulated radiotherapy of nasopharyngeal carcinoma patients with parapharyngeal space involvement

Zhang, Yingting; Lin, Chuyong; Wu, Jianhua; Jiang, Xiaobo; Lee, Shara W. Y.; Tam, Shing Yau; Wu, V.

doi:10.1002/jmrs.209

Cited by 15 publications

(18 citation statements)

References 24 publications

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“…According to a previous report, one major advantage of using adaptive strategies is to prevent doses to the parotid glands . Some studies have reported that body weight loss is related to shrinkage of these glands, and that they shrink more as the mean dose to the gland increases . Capelle et al reported that the reduction in the diameter of the neck caused the mean dose to the parotid gland to increase .…”

Section: Discussionmentioning

confidence: 99%

Analyses of integrated EPID images for on‐treatment quality assurance to account for interfractional variations in volumetric modulated arc therapy

Matsushita

Nakamura

Sasaki

et al. 2020

J Applied Clin Med Phys

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Purpose: To investigate the effects of interfractional variation, such as anatomical changes and setup errors, on dose delivery during treatment for prostate cancer (PC) and head and neck cancer (HNC) by courses of volumetric modulated arc therapy (VMAT) aided by on-treatment electronic portal imaging device (EPID) images.Methods: Seven patients with PC and 20 patients with HNC who had received VMAT participated in this study. After obtaining photon fluence at the position of the EPID for each treatment arc from on-treatment integrated EPID images, we calculated the differences between the fluence for the first fraction and each subsequent fraction for each arc. The passing rates were investigated based on a tolerance level of 3% of the maximum fluence during the treatment courses and the correlations between the passing rates and anatomical changes.Results: In PC, the median and lowest passing rates were 99.8% and 95.2%, respectively. No correlations between passing rates and interfractional variation were found. In HNC, the median passing rate of all fractions was 93.0%, and the lowest passing rate was 79.6% during the 35th fraction. Spearman's correlation coefficients between the passing rates and changes in weight or neck volume were − 0.77 and − 0.74, respectively.Conclusions: Analyses of the on-treatment EPID images facilitates estimates of the interfractional anatomical variation in HNC patients during VMAT and thus improves assessments of the need for re-planning or adaptive strategies and the timing thereof.

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Section: Discussionmentioning

confidence: 99%

Analyses of integrated EPID images for on‐treatment quality assurance to account for interfractional variations in volumetric modulated arc therapy

Matsushita

Nakamura

Sasaki

et al. 2020

J Applied Clin Med Phys

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“…In our centre, planning staff have historically placed less importance on the optimisation of the ipsilateral parotid, with the belief that once the dose exceeds tolerance, there is no substantial benefit in small improvements in dose. Zhang et al and Ren et al explain the importance of parotid sparing to negate the potential for shrinkage and medial migration of the glands during treatment increasing dose. Keeping the dose to the parotids as low as possible has been shown to have a direct impact on the development of xerostomia, functional recovery of the glands and quality of life.…”

Section: Discussionmentioning

confidence: 99%

Parotid sparing in RapidPlan Oropharynx models: To split or not to split

O’Toole

Bromley

et al. 2020

J of Medical Radiation Sci

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Introduction Differences in knowledge and experience, patient anatomy and tumour location and manipulation of inverse planning objectives and priorities will lead to a variability in the quality of radiation planning. The aim of this study was to investigate whether parotid glands should be treated as separate or combined structures when using knowledge‐based planning (KBP) to create oropharyngeal plans, based on the dose they receive. Method Two separate RapidPlan (RP) models were created using the same 70 radical oropharyngeal patients. The ‘separated model’ divided the parotids into ipsilateral and contralateral structures. The ‘combined model’ did not separate the parotids. The models were independently validated using 20 patients not included in the models. The same dose constraints and priorities were applied to planning target volumes (PTVs) and organs at risk (OARs) for all plans. An auto‐generated line objective and priority was applied in both models, with parotid mean dose and V50 doses evaluated and compared. Results Plans optimised using the combined model resulted in lower ipsilateral mean doses and lower V50 doses in 80% and 75% of cases, respectively. Fifty‐five per cent of plans produced lower mean doses for the contralateral parotid when optimised using the combined model, while lower V50 doses were evenly split between the models. Conclusion Combining the data for both parotids into one RP model resulted in better ipsilateral parotid sparing. Results also suggest that a combined parotid model will spare dose to the contralateral parotid; however, further investigation is required to confirm these results.

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“…They were reflected by the increase of Δ%V, DSC and TVD from pre-treatment to 30 th fraction, respectively. The shrinkage of parotid glands during radiotherapy has been reported in previous studies 16,17 and it was mainly caused by the loss of gland parenchyma and acinar cell atrophy due to high dose radiation. 18,19 The volume reduction of the parotid gland subsequently changed its shape and therefore resulted in a similar trend in DSC as for Δ%V.…”

Section: Discussionmentioning

confidence: 99%

Pattern of geometric changes of parotid gland in conventional and intensity-modulated radiotherapy in nasopharyngeal cancer patients

et al. 2018

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Introduction: This study compared the pattern of radiation induced parotid changes between conventional (ConRT) and intensity modulated radiotherapy (IMRT) in nasopharyngeal carcinoma patients. Methods: 56 adult NPC patients treated with IMRT (n = 28) and conventional radiotherapy (n = 28) were recruited. CT scans were acquired before radiotherapy, at 10 th , 20 th and 30 th fractions, and 3 months after treatment. Parotid gland was delineated in the corresponding CT slices and its mean dose was calculated. The volumetric and geometric changes of the parotid gland at various time intervals were compared against the pre-treatment structure set. The pattern of changes was compared between the two techniques. Results: The mean parotid dose of IMRT (37.5 ± 9.5 Gy) was significantly lower than ConRT (49.1 ± 7.4 Gy). The parotid gland volume, DICE similarity coefficient and lateral dimension of patient head gradually decreased during the radiotherapy course and partially recovered in 3 months post-treatment. The differences between two groups were not significant until at 3 month after treatment, where IMRT showed significantly better volume recovery. Conclusion: Similar parotid gland size and location changes were observed during the treatment course in both ConRT and IMRT. However IMRT demonstrated better parotid volume recovery after treatment.

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A longitudinal evaluation of early anatomical changes of parotid gland in intensity modulated radiotherapy of nasopharyngeal carcinoma patients with parapharyngeal space involvement

Cited by 15 publications

References 24 publications

Analyses of integrated EPID images for on‐treatment quality assurance to account for interfractional variations in volumetric modulated arc therapy

Analyses of integrated EPID images for on‐treatment quality assurance to account for interfractional variations in volumetric modulated arc therapy

Parotid sparing in RapidPlan Oropharynx models: To split or not to split

Pattern of geometric changes of parotid gland in conventional and intensity-modulated radiotherapy in nasopharyngeal cancer patients

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