I thought I was crazy when I noticed a seasonality to bc metastases

[Lani]

but look here...(again, in mice and not her2 specific...but metastatic bc is often her2 + even when the original tumor was not...and bc in mice syngeneic experiments is usually due to MMTV as I understand it which produces her2+ bc in mice )

Breast Cancer Res Treat. 2007 Oct 14; [Epub ahead of print]
Seasonal modulation of post-resection breast cancer metastasis.

Oh EY, Wood PA, Du-Quiton J, Hrushesky WJ.
Medical Chronobiological Laboratory, Dorn Research Institute, WJB Dorn VA Medical Center, 6439 Garners Ferry Road, Columbia, SC, 29209, USA.
Background Human breast cancer incidence, histopathologic grade, invasiveness, and mortality risk vary significantly throughout each year. In order to better understand this seasonal cancer biology, we investigated the circannual pattern of post-resection breast cancer metastasis, under genetically and environmentally controlled conditions. Methods Over a span of 14 consecutive years, we conducted 22 similar experiments to investigate metastatic biology of breast cancer among 1,214 C3HeB/FeJ female mice. All mice were kept in temperature-controlled environment with 12 h light:12 h dark photoperiod, with food and water freely available, from birth until death. At 10-13 weeks of age, each mouse received 20,000 viable syngeneic mammary cancer cells subcutaneously and the tumor bearing leg was resected 10-12 days after tumor inoculation for potential cure. Once 10% of resected mice were found moribund, due to autopsy proven pulmonary metastases, all remaining mice were sacrificed and metastatic lung nodules were counted. Results The incidence of post-resection pulmonary metastasis was not randomly distributed throughout the year, but peaked prominently in Summer and Winter. Although tumor volume at resection was strongly associated with metastatic potential, a significantly higher probability of pulmonary metastasis was observed if surgery was performed in Summer and Winter, regardless of tumor volume at resection, compared to Spring and Fall. Conclusion These results support the likelihood that human breast cancer seasonality is real and of biological origin. There are implications of this cancer chronobiology for breast cancer prevention, screening, diagnosis, and treatment.
PMID: 17934872 [PubMed - as supplied by publisher]