Radiobiological hypoxia, histological parameters of tumour microenvironment and local tumour control after fractionated irradiation.

Objective: To investigate the relationships between radiobiological hypoxic fraction (rHF), pimonidazole hypoxic fraction (pHF) as well as other histological parameters of the tumour microenvironment, and local tumour control after fractionated irradiation in human squamous cell carcinomas (hSCCs).

Material And Methods: Ten different hSCC cell lines were transplanted into nude mice and rHF was calculated from local tumour control rates after single dose irradiation under normal or clamped blood flow conditions. In parallel, tumours were irradiated with 30 fractions within 6 weeks.

Core needle biopsies for determination of the microenvironment in individual tumours for longitudinal radiobiological studies.

Purpose: We aimed to establish a core needle biopsy technique to investigate the impact on outcome of irradiation of the microenvironment in individual experimental tumours.

Methods: Nude mice bearing FaDu, UT-SCC-5, UT-SCC-14, and UT-SCC-15 tumours (n=67) were injected with pimonidazole hypoxia and Hoechst 33342 perfusion markers. One core needle biopsy was taken from the central part of the tumour under anaesthesia and the rest of the tumour was excised after marking the position of the needle.

Pre-treatment number of clonogenic cells and their radiosensitivity are major determinants of local tumour control after fractionated irradiation.

Objective: The response of tumours to fractionated radiotherapy is determined by many factors including repopulation, reoxygenation, the number of clonogenic cells, and their intrinsic radiosensitivity. However, after single radiation doses given under conditions of clamp hypoxia, the dose to control a tumour locally is dependent only on the number of clonogenic cells and their cellular radiosensitivity. Therefore, these parameters were investigated using local control after single doses given under hypoxia, to predict the outcome of fractionated irradiation.

TCP and NTCP in preclinical and clinical research in Europe.

European research in radiation oncology has a long and successful tradition. The aim of this research is to increase the therapeutic window of radiotherapy by increasing the tumor control probability (TCP) and/or by decreasing the normal tissue complication probability (NTCP). This paper summarizes the basic radiobiological concept underlying treatment optimization by TCP-NTCP data and discusses some of the limitations of currently used models.

TCP and NTCP: a basic introduction.

Radiotherapy is one of the most effective treatments for cancer. The aim of radiotherapy is to achieve a high probability of local tumor control (tumor control probability, TCP) at a low risk of normal tissue complications (normal tissue complication probability, NTCP). This paper gives a brief introduction into dose response relationships for early and late radiation responses and tumor control.