Table 5

Distribution of BRCA2 mutations by disease characteristics and family history in 645 breast cancer cases

CharacteristicsTotal testedBRCA1 MutationsPe (Fisher’s exact test)
Group 1aGroup 2bGroup 3c
n% (95% CI)dn% (95% CI)dn% (95% CI)d
Age at diagnosis
 <4525641.6 (0.4, 4.0)176.6 (3.9, 10.4)93.5 (1.6, 6.6)0.77
 ≥4538930.8 (0.2, 2.2)246.2 (4.0, 9.0)164.1 (2.4, 6.6)
 Total cases64571.1 (0.4, 2.2)416.4 (4.6, 8.5)253.9 (2.5, 5.7)
Family history of breast cancerf
 Noneg59461.0 (0.4, 2.2)366.1 (4.3, 8.3)244.0 (2.6, 6.0)0.21
 First degreeh2913.4 (0.09, 17.8)310.3 (2.2, 27.4)00.0 (0.0, 11.9)i
 Grandmother only400.0 (0.0, 60.2)i125.0 (0.6, 80.6)00.0 (0.0, 60.2)i
 Relative had breast cancer < age 45 yrsj10110.0 (0.3, 44.5)220.0 (2.5, 55.6)00.0 (0.0, 30.8)i0.08
 Relative had breast cancer ≥ age 45 yrs2200.0 (0.0, 15.4)i14.5 (0.1, 22.8)00.0 (0.0, 15.4)i
Family history of ovarian cancerf
 Noneg62371.1 (0.4, 2.3)406.4 (4.6, 8.6)243.8 (2.5, 5.7)1.0
 Yes400.0 (0.0, 60.2)i00.0 (0.0, 60.2)i00.0 (0.0, 60.2)i
  • a Frameshift and splice-site mutations (no nonsense changes were found in this study).

  • b Missense changes, single amino-acid deletions and intronic changes ≤40 bases from coding region.

  • c Silent changes, intronic changes >40 bases from coding region, and changes after the BRCA2 polymorphic stop codon at amino acid 3326.

  • d 95% confidence interval (CI) for proportion of cases with mutations in this group.

  • e P for differences in mutation frequencies among women in different categories of each characteristic.

  • f Family history of cancer was unavailable for 18 women; among these women, 1 had a group 2 mutation and 1 had a group 3 mutation.

  • g Includes 112 women with no family history of cancer in first-degree female relatives, but history was incomplete for one or both grandmothers; also includes 4 women with no family history of cancer in either grandmother, but history was incomplete for one or more first-degree female relatives.

  • h One woman also had maternal grandmother with family history of breast cancer.

  • i One-sided 97.5% confidence interval.

  • j Relative’s age at breast cancer was unknown for 1 woman.