A prospective study on volumetric and dosimetric changes during intensity-modulated radiotherapy for nasopharyngeal carcinoma patients

Cheng, Ho Ming; Wu, Weiju; Ngan, Roger K.C.; Tang, KW; Chan, Charlie C.L.; Wong, Kevin; Au, Siu-Kie; Kwong, Dora L.W.

doi:10.1016/j.radonc.2012.03.013

Cited by 73 publications

(75 citation statements)

References 30 publications

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“…These changes were increased with the number of fractions delivered, thus, were radiation induced. Similar CTN changes were not observed (,3%) in the spinal cords and NSTs, where radiation doses were substantially lower than those in the GTVs and parotid glands (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) Gy vs 75-65 Gy in maximum doses). The observed CTN change was highly patient specific.…”

Section: Discussionsupporting

confidence: 59%

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Radiation-induced CT number changes in GTV and parotid glands during the course of radiation therapy for nasopharyngeal cancer

Yang

et al. 2016

BJR

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Objective: To investigate the changes in CT number (CTN) in gross tumour volume (GTV) and organs at risk (OARs) during the course of radiation therapy (RT) for nasopharyngeal cancer (NPC). Methods: Daily megavoltage CT (MVCT) data collected from 30 patients with NPC treated with a prescription dose of 70 Gy in 30-33 fractions using helical tomotherapy were retrospectively analyzed. The contours of GTV and OARs on daily MVCTs were obtained by populating the planning contours from planning CT to daily MVCTs with manual editing, if necessary. The changes of GTV and OAR volumes and the histograms of CTN in the GTV and OARs during the course of RT delivery were analyzed. Results: Volumes of GTV and parotid glands were reduced during the course of radiation treatment, with an average shrinkage rate of 0.23% per day (range, 0.02-0.8%) and 1.2% per day (range, 0.2-2.3%), respectively. The mean CTN changes in GTV and ipsilateral and contralateral parotid glands were reduced by 52 6 35 HU, 18 6 20 HU and 17 6 22 HU, respectively. For GTV, the CTN and GTV volume decreases were found to be correlated with each other (p , 0.0001). No noticeable CTN change was found in the spinal cord and non-specified tissue irradiated with low doses. Conclusion: The CTN changes in GTV and parotids are measurable during the delivery of fractionated radiotherapy for NPC, were associated with the doses received (the number of fractions delivered) and were patient specific. Advances in knowledge: The CTN change during radiotherapy is dose dependent and is measurable for NPC.

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Section: Discussionsupporting

confidence: 59%

“…Various ART strategies [7][8][9][20][21][22][23] have been reported to be effective, to correct for the interfraction dosimetric changes during the RT for head and neck cancer. In particular, the offline adaptation has been shown to be practical.…”

Section: Discussionmentioning

confidence: 99%

Radiation-induced CT number changes in GTV and parotid glands during the course of radiation therapy for nasopharyngeal cancer

Yang

et al. 2016

BJR

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“…Charlotte et al reviewed the literature published in the last decade and pointed out that, on average, the PG mean dose increase was 2.2 ± 2.6 Gy as compared to the dose calculated on the planning CT 16. They also emphasized that the largest PG dose increase found by Chen et al and Cheng et al was 10.4 Gy in the sixth week of radiotherapy, and the largest median dose was 7.8 Gy at the 25th fraction 10, 20. These results are approximately consistent with ours.…”

Section: Discussionmentioning

confidence: 97%

“…As for dosimetric variation, the delivered dose may not correspond to the planned dose. Several studies investigated PG dose variation and found great dosimetric changes 10, 12, 20. However, inaccuracies in the calculation of dosimetric change should not be ignored.…”

Section: Introductionmentioning

confidence: 99%

Parotid gland radiation dose‐xerostomia relationships based on actual delivered dose for nasopharyngeal carcinoma

Lou

Huang

et al. 2018

J Applied Clin Med Phys

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Xerostomia induced by radiotherapy is a common toxicity for head and neck carcinoma patients. In this study, the deformable image registration of planning computed tomography (CT) and weekly cone‐beam CT (CBCT) was used to override the Hounsfield unit value of CBCT, and the modified CBCT was introduced to estimate the radiation dose delivered during the course of treatment. Herein, the beams from each patient's treatment plan were applied to the modified CBCT to construct the weekly delivered dose. Then, weekly doses were summed together to obtain the accumulated dose. A total of 42 parotid glands (PGs) of 21 nasopharyngeal carcinoma patients were analyzed. Doses delivered to the parotid glands significantly increased compared with the planning doses. V20, V30, V40, Dmean, and D50 increased by 11.3%, 28.6%, 44.4%, 9.5%, and 8.4% respectively. Of the 21 patients included in the study, eight developed xerostomia and the remaining 13 did not. Both planning and delivered PG Dmean for all patients exceeded tolerance (26 Gy). Among the 21 patients, the planning dose and delivered dose of Dmean were 30.6 Gy and 33.6 Gy, respectively, for patients with xerostomia, and 26.3 Gy and 28.0 Gy, respectively, for patients without xerostomia. The D50 of the planning and delivered dose for patients was below tolerance (30 Gy). The results demonstrated that the p‐value of V20, V30, D50, and Dmean difference of the delivery dose between patients with xerostomia and patients without xerostomia was less than 0.05. However, for the planning dose, the significant dosimetric difference between the two groups only existed in D50 and Dmean. Xerostomia is closely related to V20, V30, D50, and Dmean.

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“…The dosimetric effects of changes in body contour, e.g., due to weight change, have been studied for head and neck1, 2 and prostate cancer patients 3, 4. For tumor sites in the upper abdomen, including the pancreas, no studies were found.…”

Section: Introductionmentioning

confidence: 99%

Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

Horst

Houweling

Tienhoven

et al. 2017

J Applied Clin Med Phys

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Pancreatic tumors show large interfractional position variation. In addition, changes in gastrointestinal gas volumes and body contour take place over the course of radiation therapy. We aimed to quantify the effect of these anatomical changes on target dose coverage, for the clinically used fiducial marker‐based patient position verification and, for comparison, also for simulated bony anatomy‐based position verification. Nine consecutive patients were included in this retrospective study. To enable fraction dose calculations on cone‐beam CT (CBCT), the planning CT was deformably registered to each CBCT (13–15 per patient); gas volumes visible on CBCT were copied to the deformed CT. Fraction doses were calculated for the clinically used 10 MV VMAT treatment plan (with for the planning target volume (PTV): D98% = 95%), according to fiducial marker‐based and bony anatomy‐based image registrations. Dose distributions were rigidly summed to yield the accumulated dose. To evaluate target dose coverage, we defined an iCTV +5 mm volume, i.e., the internal clinical target volume (iCTV) expanded with a 5 mm margin to account for remaining uncertainties including delineation uncertainties. We analyzed D98%, Dmean, and D2% for iCTV +5 mm and PTV (i.e., iCTV plus 10 mm margin). We found that for fiducial marker‐based registration, differences between fraction doses and planned dose were minimal. For bony anatomy‐based registration, fraction doses differed considerably, resulting in large differences between planned and accumulated dose for some patients, up to a decrease in D98% of the iCTV +5 mm from 95.9% to 85.8%. Our study shows that fractionated photon irradiation of pancreatic tumors is robust against variations in body contour and gastrointestinal gas, with dose coverage only mildly affected. However, as a result of interfractional tumor position variations, target dose coverage can severely decline when using bony anatomy for patient position verification. Therefore, the use of intratumoral fiducial marker‐based daily position verification is essential in pancreatic cancer patients.

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A prospective study on volumetric and dosimetric changes during intensity-modulated radiotherapy for nasopharyngeal carcinoma patients

Cited by 73 publications

References 30 publications

Radiation-induced CT number changes in GTV and parotid glands during the course of radiation therapy for nasopharyngeal cancer

Radiation-induced CT number changes in GTV and parotid glands during the course of radiation therapy for nasopharyngeal cancer

Parotid gland radiation dose‐xerostomia relationships based on actual delivered dose for nasopharyngeal carcinoma

Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

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