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Aims: The initial aims were to use recently available observations of glioblastomas (as part of a previous study) that had been imaged twice without intervening treatment before receiving radiotherapy in order to obtain quantitative measures of glioma growth and invasion according to a new bio-mathematical model. The results were so interesting as to raise the question whether the degree of radio-sensitivity of each tumour could be estimated by comparing the model-predicted and actual durations of survival and total numbers of glioma cells after radiotherapy., Materials and Methods: The gadolinium-enhanced T1-weighted and T2-weighted magnetic resonance imaging volumes were segmented and used to calculate the velocity of radial expansion (v) and the net rates of proliferation (rho) and invasion/dispersal (D) for each patient according to the bio-mathematical model., Results: The ranges of the values of v, D and rho show that glioblastomas, although clustering at the high end of rates, vary widely one from the other. The effects of X-ray therapy varied from patient to patient. About half survived as predicted without treatment, indicating radio-resistance of these tumours. The other half survived up to about twice as long as predicted without treatment and could have had a corresponding loss of glioma cells, indicating some degree of radio-sensitivity. These results approach the historical estimates that radiotherapy can double survival of the average patient with a glioblastoma., Conclusions: These cases are among the first for which values of v, D and rho have been calculated for glioblastomas. The results constitute a 'proof of principle' by combining our bio-mathematical model for glioma growth and invasion with pre-treatment imaging observations to provide a new tool showing that individual glioblastomas may be identified as having been radio-resistant or radio-sensitive.

Aims: Delays between surgery and the delivery of radiotherapy may allow brain tumours to grow beyond the planned radiotherapy fields and therefore reduce the effectiveness of radiotherapy. This pilot study aimed to ascertain whether significant growth of brain tumours occurs between post-biopsy imaging and the start of radiotherapy., Materials and Methods: Two estimates of tumour volume were obtained from contrast-enhanced magnetic resonance images obtained within 3 days of surgical debulking/biopsy (postoperative), and shortly before starting radiotherapy (pre-radiotherapy). The postoperative and pre-radiotherapy volumes were compared to assess tumour growth and expansion of the tumour margin. The enhancing tumour volume was measured on a workstation using two methods: tracing the area of the lesion on each slice on which it appeared and summing the volume in each slice, and by measuring the largest diameters in three planes. The ease of use and intra-operator variability of the two methods were compared., Results: The median time between postoperative and pre-radiotherapy scans was 31.5 days (range 15-53 days). Both methods found that statistically significant tumour growth occurred between postoperative and pre-radiotherapy imaging. The tumour area method found median postoperative volume of 42,849 mm3 (range 4843-148,047 mm3), and median pre-radiotherapy volume of 49,382 mm3 (range 9327-150,850 mm3) and a median growth of 35.07% (range 0-105%). The enhancing tumour margin on the pre-radiotherapy scan overlapped the margin of the postoperative scan by a maximum of 20 mm. Our study found that the diameter method gave lower estimates of tumour growth than the area method. The diameter method was inaccurate when tumours were small or irregularly shaped., Conclusion: As a 2-3 cm margin is usually included around the tumour when planning radiotherapy, it seems unlikely that the visible tumour actually grew outwith the planned radiotherapy fields. However, cells beyond the tumour margin visible on imaging could be outside the planned radiotherapy field. This paper highlights difficulties in determining the most appropriate time for baseline radiotherapy planning imaging to be carried out.