Deformable registrationAssessment by a deformable registration method of the volumetric and positional changes of target volumes and organs at risk in pharyngo-laryngeal tumors treated with concomitant chemo-radiation
Section snippets
Patient selection
The set of images used was acquired in a previously reported study [23]. Briefly, 10 patients with stage III-IV (1997 AJCC Classification) H&N squamous cells carcinoma (SCC) were imaged before (pre-treatment) and weekly during (per-treatment) concomitant chemo-RT. Patients’ characteristics are shown in Table 1. All patients were treated by radical concomitant chemo-RT (70 Gy in 7 weeks for the therapeutic PTVs and 50 Gy in 5 weeks for the prophylactic PTVs; concomitant chemotherapy with
Metric analysis
All volumes were calculated from the contoured axial slices using IMRE-viewer. The slopes of the relative change in volume over time for each organ and each patient were calculated using linear regression analyses. Then the mean slope for each volume was calculated and bilateral paired t-test for parametric data, and the Wilcoxon Signed-Rank test for non-parametric data were performed. CT-based and PET-based slopes were compared to each other using the bilateral paired t-test for parametric
Volumetric analysis
The mean relative slopes of the volume variations, confidence intervals and performed statistical tests are described in Table 2.
The GTVT,CT, GTVT,PET and GTVN,CT decreased throughout fractionated RT (Fig. 2), at a mean rate of 3.2 (p < 0.01, paired t-test), 3.9 (p = 0.005, Wilcoxon) and 2.2% (p = 0.018, Wilcoxon) per treatment day, respectively . This decrease in GTVs translated in a parallel decrease of the corresponding CTVther,T,CT, CTVther,T,PET and CTVther,N,CT of 2.6 (p < 0.001, paired t-test),
Discussion
The collected data show that during fractionated concomitant chemo-RT for locally advanced H&N SCC marked volumetric and positional modifications occur in TVs and OARs. These changes most likely resulted from tumor response resulting in changes in patients’ anatomy, as well as a consequence of patients’ morbidity encountered during treatment, e.g. weight loss. In this study as in other published data, the volume decrease with dose was fitted assuming a linear relationship [7]. This is likely an
Conclusions
Major volumetric and positional changes in TVs and OARs were observed during fractionated concomitant chemo-RT treatments. Such modifications affect the parotid glands, the submandibular glands, the prophylactic and the therapeutic CTVs for both the primary tumors and the lymph nodes. Such volumetric and positional modifications are likely to affect the dose distribution, and thus support the evaluation of adaptive dose re-planning solutions.
Acknowledgements
Pierre Castadot is a Research Fellow with the F.N.R.S. (Fonds National de la Recherche Scientifique). John A. Lee and Xavier Geets are Postdoctoral Researchers with the F.N.R.S. (Fonds National de la Recherche Scientifique). Nicolas Christian is a research fellow with the F.R.I.A. (Fonds pour la formation à la Recherche dans l’Industrie et dans l’Agriculture).
This work is supported by a grant from the Belgian Federation against Cancer (convention #SCIE 2003-23FR), by a grant from the
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