[Seasonal patterns of breast tumor growth in Far North residents]

Earlier, we established a relationship between sex hormone receptor concentration in tumor and 5-year survival, on the one hand, and seasonality, on the other. The parameters showed a distinct 6-month cycle. That pointed to certain environmental factors which could synchronize hormone-dependent tumor process in the breast of women living in the North. The present study is concerned with a relationship of 6-month rhythm of tumor growth and latitude of residence. Said rhythm was reliably identified as a parameter of 5-year survival in the Far North (68 deg. northern latitude, p < 0.001). Maximum values of 5-year survival were registered in those diagnosed with cancer in winter or summer, while those diagnosed in spring or fall had unfavorable prognosis. Northern magnetic storms recur at 6-month intervals and most frequently in spring and fall. Electromagnetic radiation is known to suppress melatonin production and, that might have stimulated tumor process. Therefore, it is most likely that solar electromagnetic radiation might synchronize hormone-dependent tumor process in women resident in the North.