Abstract P3-07-28: Population-based rates of in-situ breast cancer [DCIS] invasive breast cancer [BrINV], and breast cancer [BrCa] mortality [BrMOR] over time. A case for screening mammography? [ScreenMam]
Authors: Ragaz Joseph , Wong Hubert , Qian Hong , Fox Joel , Wilson Kenneth , Coldman Andrew 
Published: May 2015

INTRODUCTION:

The net benefit of ScreenMam has been questioned in recent literature. We report here the 1975-2010 population-based rates of DCIS, BrINV, and of BrMOR in two regions of Canada, British Columbia [BC] vs the Atlantic Provinces of Canada [Atl.P],with unequal adherence (high in BC, low in Atl.P) to ScreenMam and therapy [Th*] guidelines for BrCa [Ref. 1].

METHODS: Annual age-specific rates of DCIS, BrINV, and BrMOR were obtained for 17 age groups (ages 0-4 to 85+) in BC and Atl.P, and averaged over each 5-year periods [1975-1979 up to 2005-2009]. Four birth cohorts were defined within each region: women who in the 1975-79 were aged 30-34 [COHORT 1]; 35-39 [COHORT 2]; 40-44 [COHORT 3] and 45-49 [COHORT 4].

The rates [cases /100,000 person-years] of DCIS, BrINV and BrMOR in 5 year intervals between 1975 and 2009 were followed within each birth cohort and compared between BC and Atl.P in periods 1975-1984 and 2000-2009 [see Table]. Also, age-standardized rates [ASRs] for BrINV incidence and BrMOR were estimated for the entire population, and for ages 50-65 and 65+. The data were obtained from the Public Health Agency of Canada based on the Canadian Cancer Registry database at Statistics Canada.

RESULTS

Table 1. Cases / 100,000 person-years, years 1975-84 vs 2000-09. BrCa Incidence [DCIS, BrINV] and mortality in BC vs Atl. P. within four birth-cohorts.

BC vs. Atl.P [BC – Atl.P]COHORTS*: 1234IN-SITU1975-842 vs 1 [+1]**4 vs 4 [0]8 vs 5 [+3]13 vs 3 [+10]2000-0950 vs 44 [+6]52 vs 46 [+6]52 vs 41 [+11]50 vs 33 [+17]INVASIVE1975-8442 vs 37 [+5]80 vs 66 [+14]134 vs 106 [+24]181 vs 149 [+32]2000-09271 vs 273 [-2]304 vs 327 [-23]325 vs 344 [-19]341 vs 355 [-14]MORTALITY1975-847 vs 9 [-2]13 vs 14 [-1]28 vs 29 [-1]44 vs 46 [-2]2000-0951 vs 54 [-3]65 vs 68 [-3]72 vs 89 [-17]90 vs 110 [-20]**[x] = Difference Cases / 100,000 person-years, BC vs Atl.P: + or –

In BC, the ASR for BrINV incidence increased by 20% between 1985 and 1989, and decreased by 20% between 1990-2007. In the Atl.P, the BrINV rates increased by 40% between 1980 and1998 [i.e.increase to higher extent / over longer time period] and declined by 20% between 1999-2007.

Compared to 1975, corresponding ASRs for mortality show a 47% decline in BC vs 30% for Atl.P [for ages 50-65: 52% vs 46%; for ages 65+: 37% vs 5%, respectively.].

CONCLUSIONS:

1. DCIS: Higher rates in BC than in Atl.P in the older cohorts [3 and 4] during 1975-84 likely reflect earlier clinical use of ScreenMam in BC. Substantially higher rates maintained during 2000-09 likely reflect persistent greater usage in BC.

2. BrINV. In every birth cohort, substantially higher rates in BC than in Atl.P during 1975-1984 but substantially lower rates in 2000-2009 are likely due to detection & Th earlier in life in BC.

3. BrMOR. Rates were similar between the two regions within each cohort during 1975-84 but substantially lower in BC for older cohorts [3 and 4] during 2000-09, likely due to earlier detection and Th in BC, concordant with more substantial ASR reduction of BrMOR observed in BC.

SUMMARY. In view of more ScreenMam in BC, these data suggest that the higher DCIS, but lower rates of BrINV, and more consistent mortality decline in BC than in Atl.P, could all be related - a likely reflection of earlier detection and earlier therapy. The associations of these interactions will be discussed.

*Th : surgery, radiation, Tamoxifen for DCIS; the same + chemotherapy for early BrINV.

Ref.1: Cancer Research: December 15, 2009.

Citation Format: Joseph Ragaz, Hubert Wong, Hong Qian, Joel Fox, Kenneth Wilson, Andrew Coldman. Population-based rates of in-situ breast cancer [DCIS] invasive breast cancer [BrINV], and breast cancer [BrCa] mortality [BrMOR] over time. A case for screening mammography? [ScreenMam] [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-07-28.