Repopulation of Tumour Cells during Radiotherapy Is Doubled during Treatment Gaps

Rafal Tarnawski,Andrzej Wygoda,Krzysztof Skladowski,Anna Mucha,Andrzej Swienrniak

doi:10.1080/10273660008833056

Abstract

The aim of this work is to analyse the proliferation of tumour cells in the treatment gapduring the radiotherapy for head neck cancer.Material and Methods: The clinical material is based on records of head and neck patients treated by radiotherapyalone in our institution. The effect of radiotherapy was assumed to be described by a linearquadratic model. The patient data were fitted directly to the radiobiological model and theparameters were estimated using maximum-likelihood procedures.Results: According to our model results of treatment were significantly correlated with Normalised Total Dose of radiation, the tumour progression (according to TNM), the overall treatment time and the gap duration. The laryngeal cancers had better prognosis then cancers of oroand nasopharynx. When the treatment time is prolonged without treatment interruptions 0.36 Gylday is lost due to the repopulation of tumour cells. During the treatment gap proliferation is faster and 0.67 Gylday is lost.Conclusion: Proliferation of tumour cells is faster during the treatment gap then during the days with irradiation.

Highlights

The aim of radiation therapy (RT) is to deliver a dose of radiation to a tumour volume with as minimal damage as possible to the surrounding normal tissue resulting ideally in tumour cure, prolongation of survival, with high quality of life standard
The clinical observation of the growth of unirradiated cancers showed the relatively long doubling times of tumour volumes, many studies showed that the prolongation of the overall treatment time resulted in worse results of radiation therapy, and the doubling time of tumour cells might be reduced during RT to 5 days
According to the mixture model the results of treatment were significantly correlated with Normalised Total Dose (NTD), the tumour progression, the overall treatment time, and the gap duration

Summary

Introduction

The aim of radiation therapy (RT) is to deliver a dose of radiation to a tumour volume with as minimal damage as possible to the surrounding normal tissue resulting ideally in tumour cure, prolongation of survival, with high quality of life standard. 0 42-55 cases 0 56-68 cases 80 0 >68 cases Both retrospective and some prospective randomised clinical studies showed the importance of treatment time for local control of disease [I-31. The clinical observation of the growth of unirradiated cancers showed the relatively long doubling times of tumour volumes (median 30 days), many studies showed that the prolongation of the overall treatment time resulted in worse results of radiation therapy, and the doubling time of tumour cells might be reduced during RT to 5 days. The only possibility to estimate repopulation of tumour cells is measurements of radiation dose required to balance proliferation during one day prolongation of treatment [4]

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