title: Influence of irradiation of a primary tumor on the labeling index and estrogen receptor index in a distant tumor focus.
abstract: The present investigation reaffirms our observation that removal of a C3H mouse mammary adenocarcinoma results in a perturbation of tumor cells in a metastatic focus. An increase occurs in the proportion of cells undergoing DNA synthesis (labeling index, LI), and a decrease occurs in the proportion demonstrating estrogen receptor (ER index; ERI). The changes are transient but of sufficient duration and magnitude to produce an increase in the size of a distant tumor. This study was conducted to determine whether cytoreduction of a primary tumor by irradiation would produce a similar change in metastatic tumor cells and whether preoperative radiation would obtund the effect of primary tumor removal. The administration of a maximum tolerated dose of radiation (50 Gy) to a primary tumor produced a significant (p less than 0.001) increase in LI and decrease in ERI of a lesser magnitude than that observed following surgical removal of the primary tumor, but still sufficient to enhance the growth of a metastatic focus. Whereas, there was almost a 50% increase in LI in a metastasis 1 and 3 days following removal of a primary tumor the increase was only 13% three days after radiation. There was a 20% decrease in ERI 3 days following radiation and a 37% decrease at that time following tumor removal. Preoperative irradiation of a primary tumor 1, 3, or 5 days prior to tumor removal, obtunds the increase in LI and decrease in ERI following operation. Radiation the day before surgery was most effective because the changes in a distant focus occurring as a result of the radiation and of the surgery were prevented. The clinical relevance of these observations deserves further consideration.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000528:radiation effects; D004261:DNA Replication / Q000528:radiation effects*; D005260:Female; D007700:Kinetics; D008325:Mammary Neoplasms, Experimental / Q000032:analysis / Q000473:pathology / Q000532:radiotherapy*; D051379:Mice; D008809:Mice, Inbred C3H; D009362:Neoplasm Metastasis; D011960:Receptors, Estrogen / Q000032:analysis / Q000528:radiation effects*
chemical_list: D011960:Receptors, Estrogen