Effect of false-positives and women's characteristics on long-term adherence to breast cancer screening.

False-positive results may influence adherence to mammography screening. The effectiveness of breast cancer screening is closely related to adequate adherence among the target population. The objective of this study was to evaluate how false-positives and women's characteristics affect the likelihood of reattendance at routine breast cancer screening in a sequence of routine screening invitations. We performed a retrospective cohort study of 1,371,218 women aged 45-69 years, eligible for the next routine screening, who underwent 4,545,346 screening mammograms from 1990 to 2006. We estimated the likelihood of attendance at seven sequential screening mammograms. Multilevel discrete time hazard models were used to estimate the effect of false-positive results on reattendance, and the odds ratios (OR) of non-attendance for the women's personal characteristics studied. The overall reattendance rate at the second screening was 81.7% while at the seventh screening was 95.6%. At the second screening invitation reattendance among women with and without a false-positive mammogram was 79.3 vs. 85.3%, respectively. At the fourth and seventh screenings, these percentages were 86.3 vs. 89.9% and 94.6 vs. 96.0%, respectively. The study variables associated with a higher risk of failing to participate in subsequent screenings were oldest age (OR = 8.48; 95% CI: 8.31-8.65), not attending their first screening invitation (OR = 1.12; 95% CI: 1.11-1.14), and previous invasive procedures (OR = 1.09; 95% CI: 1.07-1.10). The risk of non-attendance was lower in women with a familial history of breast cancer (OR = 0.97; 95% CI: 0.96-0.99), and those using hormone replacement therapy (OR = 0.96; 95% CI: 0.94-0.97). In conclusion, reattendance was lower in women with false-positive mammograms than in those with negative results, although this difference decreased with the number of completed screening participations, suggesting that abnormal results in earlier screenings more strongly influence behavior. These findings may be useful in providing women with accurate information and in improving the effectiveness of screening programs.

Polyploidization and exit from cell cycle as mechanisms of cultured melanoma cell resistance to methotrexate.

Numerous malignant neoplasias are found to contain varying proportions of high-ploidy cells. Although the role they play in the tumor is poorly understood, several lines of evidence suggest that these cells could be especially resistant to various aggressions, a possibility of great interest in cancer treatment. In the present study, we tested this hypothesis through the analysis of the presence of high-ploidy cells following the administration of the chemotherapeutic agent methotrexate. We also determined the expression of two proliferation markers, PCNA and CDK1, after methotrexate-treatment. Cultured cells from the murine melanoma B16F10 were treated with high doses of methotrexate for seven days prior to determination of DNA content and proliferation markers. Our results showed an obvious increase in the mean ploidy of this population. Specifically, there was a dramatic reduction in the proportion of tetraploid cells (predominant in the original population), and an increase in the proportion of cells with higher ploidies, particularly those whose DNA content was greater than 8c, including some cells with ploidies greater than 16c. Furthermore, there was a reduction in the number of PCNA-expressing cells and the reduction was much more marked in the case of CDK1 that was almost absent in the modal-ploidy treated cells. These alterations concerning ploidy and expression of proliferation markers had completely reverted two weeks after withdrawal of the drug. Our results indicate that methotrexate at a high dosage selects a cell population heterogeneous concerning its ploidy level, composed of one subpopulation of high-ploidy cells and another of modal-ploidy cells that, considering its lack of CDK1 expression, would remain in a latent state to evade the effects of the drug.

Genesis and evolution of high-ploidy tumour cells evaluated by means of the proliferation markers p34(cdc2), cyclin B1, PCNA and 3[H]-thymidine.

Although cell polyploidization is not an infrequent event in mammalian cells and is common in tumours, the mechanisms involved are not well understood. Using the murine B16 cell line as a model, we evaluated the role of some key proteins involved in cell cycle progression: p34(cdc2), cyclin B1 and PCNA. By means of flow cytometry, we showed that both in modal- and in high-ploidy subpopulations, almost all cells were p34(cdc2)-positive. In the modal-ploidy subpopulation only 17.1% cells were cyclin B1-positive and 85.6% PCNA-positive; in contrast, in the high-ploidy subpopulation up to 91.8% cells were cyclin B1-positive and 97.3% cells were PCNA-positive (P < 0.001). Immunofluorescence microscopy showed that PCNA was located in the nucleus; p34(cdc2), both in the nucleus and cytoplasm; and cyclin B1 yielded a cytoplasmic spotted pattern with a perinuclear reinforcement. After a 24-h incubation with 3[H]-thymidine followed by withdrawal of the isotope, high-ploidy cells remained labelled 8 days after thymidine withdrawal, in contrast to modal-ploidy cells. Taken together, our results suggest that polyploid cells are not quiescent, their cell cycle is longer than that of the modal-ploidy population, and they maintain cyclin B1 throughout the cycle, which may contribute to their genesis by impeding the exit from mitosis.

Correlation of DNA content of laryngeal epithelial lesions to degree of malignancy.

PURPOSE: The aim of the present study was to determine the role of DNA content in laryngeal epithelial lesions of different degrees of malignancy. PATIENTS AND METHODS: A total of 53 lesions were studied, which included five benign tumors, 18 dysplasias, and 30 carcinomas of different degrees of differentiation and clinical stage. In all cases, the DNA content was determined by microspectrophotometry of paraffin-embedded Feulgen-stained biopsies. RESULTS: We found significant differences between the DNA-content histograms corresponding to each lesion group studied. Of special interest was the transition from moderate to severe dysplasia (characterized by a striking increase in the G2M-phase cells) and the transition from severe dysplasia to carcinoma (characterized by a brusque change in the modal ploidy of the lesion). CONCLUSION: The determination of DNA content, and study of DNA histogram, will help to assess degree of malignancy in epithelial lesions of the larynx.

Proliferative behaviour of high-ploidy cells in two murine tumour lines.

The presence of high-ploidy cells in malignant tumours has long been documented. However, the biological significance of these cells is not known and there is a great deal of controversy over their proliferative potential. We have analysed the behaviour of these cells in two murine tumour lines, B16F10 melanoma and 3T3A31M angiosarcoma, determining their DNA content by microspectrophotometry and using time-lapse film studies. We have found a discrepancy between the presence of high-ploidy cells in metaphase and the absence of hyperploid telophases. High-ploidy metaphases may be aborted (mitotic polyploidization), prolonged in time or evolve in the form of multipolar, generally tripolar, mitoses. Our results suggest that high-ploidy cells are capable of proliferating, despite certain peculiarities in their cell cycle, and constitute a tumour subpopulation whose role in neoplasia merits further study.