Adaptive biological image-guided IMRT with anatomic and functional imaging in pharyngo-laryngeal tumors: Impact on target volume delineation and dose distribution using helical tomotherapy

doi:10.1016/j.radonc.2007.05.010

Radiotherapy and Oncology

Volume 85, Issue 1, October 2007, Pages 105-115

https://doi.org/10.1016/j.radonc.2007.05.010 Get rights and content

Abstract

Background and purpose

Adaptive image-guided IMRT appears to be a promising approach for dose escalation in pharyngo-laryngeal tumors. In this framework, we assessed in a proof of concept study the impact of anatomic and functional imaging modalities acquired prior and during radiotherapy on the target volume delineation and the dose distribution using helical tomotherapy.

Materials and methods

Ten patients with pharyngo-laryngeal squamous cell carcinoma were treated by concomitant chemo-radiation delivered in 7 weeks. CT, T2-MRI, fat suppressed T2-MRI, and static and dynamic FDG-PET were acquired for each patient before the start of treatment and during radiotherapy, after mean prescribed doses of 14, 25, 35 and 45 Gy. GTVs were manually delineated on CT and MRI images while PET images were automatically segmented by means of a gradient-based method. From these volumes, CTVs and PTVs were derived using consistent guidelines. Simultaneous integrated boost IMRT planning was performed using helical tomotherapy.

Results

GTVs significantly decreased throughout the course of RT for all imaging modalities (p < 0.001). Clinically non-significant differences and high correlations were found between GTVs delineated on CT and MRI, irrespective of the sequence used. By contrast, FDG-PET-based GTVs segmented from pre- and per-treatment images were significantly smaller compared to anatomical imaging modalities, without any difference existing between static and dynamic acquisition. These differences in GTVs translated into parallel reductions of both prophylactic and therapeutic CTVs and PTVs. Resulting FDG-PET-based and adaptive IMRT planning reduced the irradiated volumes by 15–40% compared to pre-treatment CT planning (V₉₀, V₉₅ and V₁₀₀), but did marginally impact on doses to the OAR such as the spinal cord and the parotid glands.

Conclusions

Adaptive IMRT with FDG-PET images has a significant impact on the delineation of TVs and on the dose distribution in pharyngo-laryngeal tumors. Such an approach might thus be considered for dose escalation strategies.

Section snippets

Patient selection

Ten consecutive patients (mean age 57 years; range 45–80 years) with a stage III–IV (1997 AJCC Classification) HN were prospectively enrolled in this study between January 2004 and 2005. From these 10 patients, 7 had hypopharyngeal tumors, 2 had laryngeal tumors and one had an oropharyngeal tumor. Details about the patients’ characteristics are shown in Table 1. All patients were treated by radical concomitant chemo-radiation (forward planning linac-based IMRT with a prophylactic dose of 50 Gy

Comparison between imaging modalities for the primary tumor GTVs delineation before and during treatment (Table 2 and Fig. 1)

The individual patient GTVs before and during treatment for the different imaging modalities are presented in Appendix A. As explained in the Materials and methods section, the first 2 patients did not get any MRI examinations. Thus, this first comparison will only involve the 8 patients who underwent all imaging examinations. On all imaging modalities, the mean primary tumor GTVs significantly decreased during the treatment course (ANOVA, p < 0.001), with a relative tumor reduction at 45 Gy

Discussion

The objectives of the present proof of concept study were to assess the potential value of adaptive multi-modality image-guided IMRT for the treatment of patients with pharyngo-laryngeal squamous cell carcinoma, and in this framework, to determine the optimal imaging modality to use. In summary, in a series of 10 patients with locally advanced pharyngo-laryngeal tumors, the study demonstrated (1) that the re-assessment of the target volumes during treatment with anatomical or functional imaging

Acknowledgements

Xavier Geets was a research fellow of the Belgian national fund for scientific research (FNRS, Fonds National de la Recherche Scientifique, convention # 7.4538.02). This research program was supported by grants from the European Community (BIOCARE research program #LSHC-CT-2004-505785), the Belgian Federation against Cancer (convention #SCIE 2003-23FR) and the Fonds J. Maisin of the Université Catholique de Louvain. This project also benefited from a collaboration with Tomotherapy Inc.

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Adaptive IMRTAdaptive biological image-guided IMRT with anatomic and functional imaging in pharyngo-laryngeal tumors: Impact on target volume delineation and dose distribution using helical tomotherapy

Abstract

Background and purpose

Materials and methods

Results

Conclusions

Section snippets

Patient selection

Comparison between imaging modalities for the primary tumor GTVs delineation before and during treatment (Table 2 and Fig. 1)

Discussion

Acknowledgements

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Int J Radiat Oncol Biol Phys

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Int J Radiat Oncol Biol Phys

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Int J Radiat Oncol Biol Phys

Adaptive IMRT
Adaptive biological image-guided IMRT with anatomic and functional imaging in pharyngo-laryngeal tumors: Impact on target volume delineation and dose distribution using helical tomotherapy