Are direct measures of tumor oxygenation reflective of changes in tumor radiosensitivity following oxygen manipulation?
The present study investigates the correlation between tumor oxygen availability and radiosensitivity following oxygen manipulation. Previous work has shown that tumors may contain both diffusion- and perfusion-limited hypoxic cells. Recently, the combination of nicotinamide (NIC) administration plus carbogen breathing has been proposed as a means of targeting both hypoxic cell subpopulations. Intravascular HbO2 saturations were measured for KHT murine sarcomas following either NIC, carbogen breathing, or the combination, and compared with determinations of tumor cell survival under matched conditions. The percentage of vessels > or = 25% HbO2 increased significantly for both the carbogen and NIC-carbogen combination, while remaining unchanged from controls following NIC. These findings contrast with the survival data, where all treatments showed identical cell survival. A possible explanation is that different proportions of clonogenic versus nonclonogenic cells may be oxygenated by the alternative treatments. Thus direct determinations of alterations in tumor oxygenation may not reflect corresponding changes in radiosensitivity.
Fenton
B M
BM
Department of Radiation Oncology, University of Rochester Medical Center, New York 14642, USA.
Siemann
D W
DW
D000818:Animals; D002245:Carbon Dioxide / Q000627:therapeutic use*; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D051379:Mice; D008809:Mice, Inbred C3H; D009536:Niacinamide / Q000627:therapeutic use*; D010100:Oxygen / Q000627:therapeutic use*; D010108:Oxyhemoglobins / Q000032:analysis* / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D012513:Sarcoma, Experimental / Q000098:blood supply* / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology
D010108:Oxyhemoglobins; D011838:Radiation-Sensitizing Agents; D002245:Carbon Dioxide; D009536:Niacinamide; C011700:carbogen; D010100:Oxygen