| First Author | Urano M | Year | 1998 |
| Journal | Radiother Oncol | Volume | 48 |
| Issue | 2 | Pages | 221-8 |
| PubMed ID | 9783896 | Mgi Jnum | J:52697 |
| Mgi Id | MGI:1330001 | Doi | 10.1016/s0167-8140(98)00010-3 |
| Citation | Urano M, et al. (1998) Are hypoxic cells critical for the outcome of fractionated radiotherapy in a slow-growing mouse tumor?. Radiother Oncol 48(2):221-8 |
| abstractText | PURPOSE: To investigate the significance of hypoxic cells, reoxygenation and repopulation for the outcome of fractionated radiotherapy of a slow-growing subline of a murine fibrosarcoma and to compare the results with those previously obtained from the original fast-growing tumor. MATERIALS AND METHODS: A slow-growing subline, 457- O, was obtained among the tumors that recurred after a single irradiation to the third generation isotransplants of a mouse fibrosarcoma, FSa-II. The single cell suspensions were transplanted into the mouse foot and when the tumors reached an average diameter of 4 mm, they were subjected to one to 20 equal daily y-ray doses given in air (A) or under hypoxic conditions (H). The TCD50 (50% tumor control radiation dose) was calculated according to the tumor control frequency within 180 days. The linear-quadratic plus time model was fitted to these data by logistic regression analysis. RESULTS: The volume doubling time of the 457-O tumors was approximately 2.2 times slower than that of the original FSa-II tumors. The TCD50(H) (single dose) was 52.3 Gy and increased with an increasing number of fractions to a TCD50(H) (20 doses) of 90.8 Gy. This increase of 38.5 Gy was much smaller than that of 149 Gy for the original FSa-II. The TCD50(A) (single dose) and TCD50(A) (20 doses) were 41.3 and 50.6 Gy, respectively. This small difference of 9.3 Gy contrasted with a significant increase of 52.9 Gy for the FSa-II. DISCUSSION: These results suggested no repopulation of 457-O tumor clonogens during the course of up to 20 daily doses, while the original FSa-II tumor cells repopulated substantially. Hypoxic clonogens in the slow-growing tumor reoxygenated but some fractions remained critical. CONCLUSION: The present data together with those obtained from the fast-growing FSa-II suggested that hypoxic clonogens were critical for the outcome of fractionated radiotherapy. Repopulation was insignificant in this slow- growing tumor during five to 20 daily doses. |
