EFFECT OF IMPLANT DOSE VOLUME AND SURGICAL RESECTION ON SURVIVAL IN ARAT GLIOMA BRACHYTHERAPY MODEL - IMPLICATIONS FOR BRAIN-TUMOR THERAPY/

OBJECTIVE: This study sought to investigate the effects of implant dos e/volume and surgical resection on survival in a rat glioma brachyther apy model, Two doses were investigated to determine a suitable therape utic range, METHODS: We performed two experiments. Three treatment gro ups and one control group of male F-344 rats bearing 9L brain tumors 1 2 days after tumor inoculation were used in the first experiment. Day 12 tumors were an average of 4 to 6 mm in diameter. Animals treated wi th brachytherapy received a tumor dose of 80 Gy delivered to a 5.5-mm- radius volume. Total macroscopic tumor removal was achieved by microsu rgical techniques. A subsequent experiment compared the survival of tu mor-burdened rats treated with an implant dose of 60 Gy delivered to a 5.5-mm-radius volume with a control group. RESULTS: Surgery alone pro duced an increased life span of 28.6% over control animals treated wit h sham surgery and dummy seed implants, a statistically significant in crease in survival (P = 0.0023, log-rank test), Brachytherapy alone pr oduced the most significant increase in survival over control animals (P = 0.0001, log-rank test; median survival not attained with an impla nt dose of 80 Gy delivered to a 5.5-mm-radius volume; and P = 0.0001, increased life span 121% with an implant dose of 60 Gy delivered to a 5.5-mm-radius volume). This was not improved by the addition of surgic al tumor removal. CONCLUSION: We have demonstrated a relationship betw een implant dose/volume and survival of tumor-burdened rats in this mo del that is not improved by the addition of tumor removal. Implication s for brain tumor brachytherapy are discussed.