COMPUTER-ASSISTED MORPHONUCLEAR CHARACTERIZATION OF RADIOTHERAPY-INDUCED EFFECTS IN MXT MOUSE MAMMARY ADENOCARCINOMAS SURVIVING EARLIER RADIOTHERAPY

Purpose: To present the effects of different radiotherapeutic treatmen ts on the morphonuclear characteristics and growth of the MXT mouse ma mmary adenocarcinoma. Methods and Materials: We collected MXT tumor ce lls by means of fine-needle aspirations during various radiotherapeuti c treatments and analyzed the morphological aspects of the cell nuclei by means of the digital cell image analysis of Feulgen-stained nuclei , In addition, we studied the morphonuclear aspects of cells from MXT tumors that had been radioresistant cell enriched, These radioresistan t cell-enriched tumors involved MXT tumors that had survived one or tw o previous radiotherapies, The radiotherapy-induced effects on the mor phonuclear characteristics were monitored by means of both monovariate (one-way variance) and multivariate (principal components and step-wi se linear discriminant) analyses. Results: The monovariate analyses sh owed that radiotherapy significantly influenced the values of the para meters relating to nuclear size (nuclear area-NA), the frequency of sm all dense chromatin clumps (short run length emphasis-SRL) in the nucl ei, and the overall chromatin condensation level (local mean-LM). The global effect corresponded to a decrease in the overall chromatin cond ensation level in the radioresistant cell-enriched MXT tumors, This de crease occurred concomitantly with an increase in the frequency of the small dense chromatin clumps in the nuclei and a decrease in the nucl ear area, The multivariate analyses showed that it was possible to qua ntitate the proportion of ''radiosensitive-like'' and ''radioresistant -like'' cell nuclei in the various MXT tumor types under study. Conclu sions: The development of certain morphonuclear parameters, that is, t he NA, the SRL, and the LM, could be proposed to predict the response of human tumors to radiotherapy as, indeed, could the quantitation of the proportion of radioresistant cells.