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Vol 70, No 4 (2020)
Original article
Published online: 2020-07-27
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Overall and GTV subvolumes tumour control probability (TCP) for head and neck cancer treated by 3D-IMRT with inhomogeneous dose distribution

Leszek Hawrylewicz, Bogusław Maciejewski, Klaus Rudiger Trott, Andrzej Tukiendorf, Leszek Miszczyk, Magdalena Markowska
DOI: 10.5603/NJO.2020.0027
·
Nowotwory. Journal of Oncology 2020;70(4):127-134.

open access

Vol 70, No 4 (2020)
Original article
Published online: 2020-07-27

Abstract

Introduction.  In this study, an original model has been developed to estimate the real TCP that is a product of the TCPs calculated for GTV subvolumes of head and neck cancer based on 3D-IMRT dose planning.

Material and methods.  Retrospective pilot group consist of 16 cases of oropharyngeal cancer in stage T1–2N0 previously treated with 3D-IMRT with at least 3-year follow-up. The total dose (TD) was 60–70 Gy in 2.0 Gy fractions delivered over 42–49 days. Within GTV two subvolumes were marked out: SVA with the planned 100% TD, and underdosed (90–95%) SVB. The TCP for both was calculated using the original formula developed by Withers and Maciejewski.

Results.  During 3-year follow-up, 8 local recurrences (LR) occurred. In about 70% of SVB “dose cold spots” encompassed more than 50% GTV volume. This resulted in the TCPSVB decrease to 60%. Thus, the real overall TCP was much lower than a priori predicted, and in these cases local recurrences occurred.

Discussion.Both cold spot SVB volumes and their dose deficit strongly correlated with a high risk of LR.

Conclusions.In conclusion the magnitude of dose deficit and the size of cold subvolume within GTV have an indepen­dent negative impact on real TCP and demand dose re-planning.

Abstract

Introduction.  In this study, an original model has been developed to estimate the real TCP that is a product of the TCPs calculated for GTV subvolumes of head and neck cancer based on 3D-IMRT dose planning.

Material and methods.  Retrospective pilot group consist of 16 cases of oropharyngeal cancer in stage T1–2N0 previously treated with 3D-IMRT with at least 3-year follow-up. The total dose (TD) was 60–70 Gy in 2.0 Gy fractions delivered over 42–49 days. Within GTV two subvolumes were marked out: SVA with the planned 100% TD, and underdosed (90–95%) SVB. The TCP for both was calculated using the original formula developed by Withers and Maciejewski.

Results.  During 3-year follow-up, 8 local recurrences (LR) occurred. In about 70% of SVB “dose cold spots” encompassed more than 50% GTV volume. This resulted in the TCPSVB decrease to 60%. Thus, the real overall TCP was much lower than a priori predicted, and in these cases local recurrences occurred.

Discussion.Both cold spot SVB volumes and their dose deficit strongly correlated with a high risk of LR.

Conclusions.In conclusion the magnitude of dose deficit and the size of cold subvolume within GTV have an indepen­dent negative impact on real TCP and demand dose re-planning.

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Keywords

3D-IMRT planning; cold spots within GTV; estimates of partial TCPs within GTV subvolumes

About this article
Title

Overall and GTV subvolumes tumour control probability (TCP) for head and neck cancer treated by 3D-IMRT with inhomogeneous dose distribution

Journal

Nowotwory. Journal of Oncology

Issue

Vol 70, No 4 (2020)

Pages

127-134

Published online

2020-07-27

DOI

10.5603/NJO.2020.0027

Bibliographic record

Nowotwory. Journal of Oncology 2020;70(4):127-134.

Keywords

3D-IMRT planning
cold spots within GTV
estimates of partial TCPs within GTV subvolumes

Authors

Leszek Hawrylewicz
Bogusław Maciejewski
Klaus Rudiger Trott
Andrzej Tukiendorf
Leszek Miszczyk
Magdalena Markowska

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