Effect of implant dose/volume and surgical resection on survival in a rat glioma brachytherapy model: implications for brain tumor therapy.
OBJECTIVE
This study sought to investigate the effects of implant dose/volume and surgical resection on survival in a rat glioma brachytherapy model. Two doses were investigated to determine a suitable therapeutic range.


METHODS
We performed two experiments. Three treatment groups and one control group of male F-344 rats bearing 9L brain tumors 12 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 with brachytherapy received a tumor dose of 80 Gy delivered to a 5.5-mm-radius volume. Total macroscopic tumor removal was achieved by microsurgical techniques. A subsequent experiment compared the survival of tumor-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 produced an increased life span of 28.6% over control animals treated with sham surgery and dummy seed implants, a statistically significant increase in survival (P = 0.0023, log-rank test). Brachytherapy alone produced the most significant increase in survival over control animals (P = 0.0001, log-rank test; median survival not attained with an implant 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 surgical tumor removal.


CONCLUSIONS
We have demonstrated a relationship between implant dose/volume and survival of tumor-burdened rats in this model that is not improved by the addition of tumor removal. Implications for brain tumor brachytherapy are discussed.
Bampoe
J
J
Division of Neurosurgery, Toronto Hospital, University of Toronto, Ontario, Canada.
Glen
J
J
Mackenzie
I
I
Porter
P
P
Bernstein
M
M
D000818:Animals; D001918:Brachytherapy; D001921:Brain / Q000473:pathology; D001932:Brain Neoplasms / Q000401:mortality / Q000601:surgery* / Q000628:therapy*; D003131:Combined Modality Therapy; D004307:Dose-Response Relationship, Radiation; D005910:Glioma / Q000401:mortality / Q000601:surgery* / Q000628:therapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D008866:Microsurgery; D009368:Neoplasm Transplantation; D051381:Rats; D011916:Rats, Inbred F344; D016019:Survival Analysis