Dataset Information

Anatomical change during radiotherapy for head and neck cancer, and its effect on delivered dose to the spinal cord.

ABSTRACT:

Background and purpose

The impact of weight loss and anatomical change during head and neck (H&N) radiotherapy on spinal cord dosimetry is poorly understood, limiting evidence-based adaptive management strategies.

Materials and methods

133 H&N patients treated with daily mega-voltage CT image-guidance (MVCT-IG) on TomoTherapy, were selected. Elastix software was used to deform planning scan SC contours to MVCT-IG scans, and accumulate dose. Planned (D_P) and delivered (D_A) spinal cord D_2% (SCD_2%) were compared. Univariate relationships between neck irradiation strategy (unilateral vs bilateral), T-stage, N-stage, weight loss, and changes in lateral separation (LND) and CT slice surface area (SSA) at C1 and the superior thyroid notch (TN), and ?SCD_2% [(D_A - D_P) D_2%] were examined.

Results

The mean value for (D_A - D_P) D_2% was -0.07?Gy (95%CI -0.28 to 0.14, range -5.7?Gy to 3.8?Gy), and the mean absolute difference between D_P and D_A (independent of difference direction) was 0.9?Gy (95%CI 0.76-1.04?Gy). Neck treatment strategy (p?=?0.39) and T-stage (p?=?0.56) did not affect ?SCD_2%. Borderline significance (p?=?0.09) was seen for higher N-stage (N2-3) and higher ?SCD_2%. Mean reductions in anatomical metrics were substantial: weight loss 6.8?kg; C1LND 12.9?mm; C1SSA 12.1?cm²; TNLND 5.3?mm; TNSSA 11.2?cm², but no relationship between weight loss or anatomical change and ?SCD_2% was observed (all r²?ConclusionsDifferences between delivered and planned spinal cord D_2% are small in patients treated with daily IG. Even patients experiencing substantial weight loss or anatomical change during treatment do not require adaptive replanning for spinal cord safety.

SUBMITTER: Noble DJ

PROVIDER: S-EPMC6358720 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Anatomical change during radiotherapy for head and neck cancer, and its effect on delivered dose to the spinal cord.

Noble David J DJ Yeap Ping-Lin PL Seah Shannon Y K SYK Harrison Karl K Shelley Leila E A LEA Romanchikova Marina M Bates Amy M AM Zheng Yaolin Y Barnett Gillian C GC Benson Richard J RJ Jefferies Sarah J SJ Thomas Simon J SJ Jena Raj R Burnet Neil G NG

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology 20180723

<h4>Background and purpose</h4>The impact of weight loss and anatomical change during head and neck (H&N) radiotherapy on spinal cord dosimetry is poorly understood, limiting evidence-based adaptive management strategies.<h4>Materials and methods</h4>133 H&N patients treated with daily mega-voltage CT image-guidance (MVCT-IG) on TomoTherapy, were selected. Elastix software was used to deform planning scan SC contours to MVCT-IG scans, and accumulate dose. Planned (D<sub>P</sub>) and delivered (D ...[more]

PMID: 30049455

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Project description:BackgroundTo evaluate the possible advantages of a simple spinal cord (SC) dose-limiting three-dimensional conformal radiotherapy (3D-CRT) technique in comparison to conventional two-dimensional (2D) techniques and other 3D-CRT techniques for spinal bone irradiation.MethodsFor 41 spinal target volumes, seven different techniques were evaluated, using a standard schedule of 30 Gy in 10 fractions. The SC dose-limiting 3D-CRT technique 1F2S-18MV using a single posterior field (F) supplemented by two anterior segment fields (S) and 18-MV photon beams was compared to two conventional 2D techniques (a single posterior field, PA, and two opposed anterior-posterior fields, APPA), three other 3D-CRT techniques (a single posterior field supplemented by four segment fields, 1F4S; two wedged fields, WD, and the SC dose-limiting variant using 6 MV, 1F2S-6MV) along with the original clinically applied plans.Results1F2S-18MV demonstrated notably better results for all target volume parameters compared to the conventional 2D techniques (p < 0.001). Limitation of the SC dose was significantly superior with 1F2S-18MV in comparison to PA and APPA (SC Dmean: 28.9 ± 0.4 vs. 30.1 ± 0.6 Gy and 30.1 ± 0.4 Gy; SC Dmax: 30.9 ± 0.7 vs. 32.5 ± 1.0 Gy and 31.8 ± 0.7 Gy; SC D1cm3 : 30.1 ± 0.6 vs. 31.7 ± 0.9 Gy and 31.1 ± 0.6 Gy; p < 0.001). Likewise, lower mean SC doses with 1F2S-18MV were observed in comparison to the more treatment time-consuming 3D-CRT techniques (1F4S, WD) and the original plans without relevant compromises on the dose homogeneity in the target volume and the dose exposure to the other OARs.ConclusionIn treatment planning of spinal metastases, simple variants of 3D-CRT-techniques like 1F2S-18MV can offer a significant dose limitation to the SC while providing a sufficient dose coverage of the target volume. Especially in patients with favorable life expectancy and potential need for re-irradiation, such SC dose-limiting 3D-CRT techniques may be a reasonable approach.

Project description:Doses actually delivered to the parotid glands during radiation therapy often exceed planned doses. We hypothesized that the delivered doses correlate better with parotid salivary output than the planned doses, used in all previous studies, and that determining these correlations will help make decisions regarding adaptive radiation therapy (ART) aimed at reducing the delivered doses.In this prospective study, oropharyngeal cancer patients treated definitively with chemoirradiation underwent daily cone-beam computed tomography (CBCT) with clinical setup alignment based on the C2 posterior edge. Parotid glands in the CBCTs were aligned by deformable registration to calculate cumulative delivered doses. Stimulated salivary flow rates were measured separately from each parotid gland pretherapy and periodically posttherapy.Thirty-six parotid glands of 18 patients were analyzed. Average mean planned doses was 32 Gy, and differences from planned to delivered mean gland doses were -4.9 to +8.4 Gy, median difference +2.2 Gy in glands in which delivered doses increased relative to planned. Both planned and delivered mean doses were significantly correlated with posttreatment salivary outputs at almost all posttherapy time points, without statistically significant differences in the correlations. Large dispersions (on average, SD 3.6 Gy) characterized the dose-effect relationships for both. The differences between the cumulative delivered doses and planned doses were evident at first fraction (r=.92, P<.0001) because of complex setup deviations (eg, rotations and neck articulations), uncorrected by the translational clinical alignments.After daily translational setup corrections, differences between planned and delivered doses in most glands were small relative to the SDs of the dose-saliva data, suggesting that ART is not likely to gain measurable salivary output improvement in most cases. These differences were observed at first treatment, indicating potential benefit for more complex setup corrections or adaptive interventions in the minority of patients with large deviations detected early by CBCT.

Dataset Information

Anatomical change during radiotherapy for head and neck cancer, and its effect on delivered dose to the spinal cord.

Background and purpose

Materials and methods

Results

Publications

Anatomical change during radiotherapy for head and neck cancer, and its effect on delivered dose to the spinal cord.

Similar Datasets

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