Background:Many women who are at increased risk of breast cancer due to a mother or sister diagnosed with breast cancer aged under 40 do not currently qualify for surveillance before 40 years of age. There are almost no available data to assess whether mammography screening aged 35-39 years would be effective in this group, in terms of detection of breast cancer at an early stage or cost effective.
Methods:A cohort screening study (FH02) with annual mammography was devised for women aged 35-39 to assess the sensitivity and screening performance and potential survival of women with identified tumours.
Findings: 2899 women were recruited from 12/2006-12/2015. These women underwent 12086 annual screening mammograms and were followed for 13365.8 years. A total of 55 breast cancers in 54 women occurred during the study period (one bilateral) with 50 cancers (49 women) (15 CIS) adherent to the screening. Eighty percent (28/35) of invasive cancers were ≤2cm and 80% also lymph node negative. Invasive cancers diagnosed in FH02 were significantly smaller than the comparable (POSH-unscreened prospective) study group (45% (131/293) ≤2cm in POSH vs 80% (28/35) in FH02 p<0.0001), and were less likely to be lymph-node positive (54% (158/290, 3 unknown) in POSH vs 20% (7/35) in FH02: p=0.0002. Projected and actual survival were also better than POSH. Overall radiation dose was not higher than in an older screened population at mean dose on study per standard sized breast of 1.5mGy.
Interpretation: Mammography screening aged 35-39 years detects breast cancer at an early stage and is likely to be as effective in reducing mortality as in women at increased breast cancer risk aged 40-49 years.