Purpose: We report the results of the final phase I/II program in glioblastoma (GBM) multiforme patients using only hyperfractionated irradiation and intravenous iododeoxyuridine (IdUrd).
Methods: For a decade we investigated halogenated pyrimidine radiosensitizers in an effort to exploit the potential for differential uptake of thymidine analogs between proliferating tumor and normal brain tissues. Trials began with bromodeoxyuridine (BrdUrd) but were changed to IdUrd when the latter proved less photosensitizing. A series of dose-escalating pilot trials led to treatment at a maximum-tolerated dose (MTD) of IdUrd of 1,000 mg/m2/d for two separate 14-day courses, one during the initial radiation field and one during the cone down. The radiotherapy also evolved over time and was hyperfractionated in all cases reported. Over 5 years we accrued 45 patients into the final hyperfractionated, 1,000 mg/m2/d scheme. We report here results on only the patients with minimum follow-up of 1 year (90% had at least 2 years of follow-up) or until death.
Results: The results do not indicate a significant benefit for use of sensitizers, as compared with other contemporary and aggressive types of radiation treatment. The median survival has been 11 months, with a 2-year actuarial survival of 9%. As yet, there are no survivors at 3 years. Tumor biopsies at craniotomy showed relatively low sensitizer incorporation.
Conclusion: The failure of radiosensitizers combined with radiation therapy to show major benefit may be due to patient selection but appears also to be related to the combined problems of poor drug penetration/uptake into tumor, tumor-cell heterogeneity, and a high inherent cellular radioresistance of GBM.