[6049] Invasive lobular breast cancer trends in populations with high versus low use of hormone replacement therapy. Verkooijen HM, Fioretta G, Koot VCM, van der Heiden M, Schipper MEI, Rapiti E, Peterse JL, Bouchardy C, Peeters PHM Geneva University, Geneva, Geneva, Switzerland; Cancer Registry Middle Netherlands, Utrecht, Utrecht, Netherlands; Association of Comprehensive Cancer Centers, Utrecht, Utrecht, Netherlands; University Medical Center Utrecht, Utrecht, Utrecht, Netherlands; Netherlands Cancer Institute, Amsterdam, North Holland, Netherlands Background: Incidence rates of invasive lobular breast cancer have been increasing in several populations and it has been suggested that this might be due to an increased use of hormone replacement therapy (HRT). In the current study we compare lobular cancer incidence trends between two populations, one with low prevalence of HRT use (the Netherlands) and one with high prevalence of HRT use (canton of Geneva Switzerland). Methods: We included all patients diagnosed with invasive breast cancer between 1989 and 2003 in the Netherlands (n=152'428) and in the Swiss canton of Geneva (n=4'909). Histology was categorised as ductal (ICD-O code 8500), lobular (ICD-O codes 8520 and 8522) and other. With generalised linear regression analysis, we modelized incidence trends according to histological subtype. Results: In the Netherlands, the incidence of lobular cancer increased with 3.1% per year (p not significant) and in Geneva with 10.1% per year (p<0.01). In both populations, highest lobular incidence rates were observed between 1998 and 2000 while after 2000, the lobular cancer incidence started to decrease. The incidence of invasive ductal cancer increased significantly and to the same extent in the Netherlands (2.2% per year) and in Geneva (2.5% per year). The incidence of other subtypes significantly decreased in both populations by approximately 3% per year. Conclusion: This study shows that lobular breast cancer incidence increased more sharply in the population with high HRT use than in the population with low HRT use. This supports the hypothesis that the increasing lobular cancer trends can be attributed to HRT. Reduction in the use of HRT, following reports on its detrimental effect on breast cancer risk, seems to have reduced the incidence of lobular breast cancer. San Antonio Breast Cancer Symposium, 12/06 Primary Systemic Therapy of Invasive Lobular Ca: a role for chemo? Abstract #2097 SABCS, 12/06 Long term follow up w/invasive lobular ca Abstract # 1087 SABCS, 12/06 [3065] Invasive lobular br ca Prognostic Factor for Neoadjuvant chemo response & long term outcomes? Abstract #3065 MRI for Lobular Ca - Extent of Local Disease Abstract #3003 SABCS, 12/06 Remember we are NOT Doctors and have NO medical training. This site is like an Encylopedia - there are many pages, many links on many topics. Support our work with any size DONATION - see left side of any page - for how to donate. You can help raise awareness of CAM.