Table 5.

Contralateral breast cancers among patients treated for unilateral breast cancers

	BRCA1/2 positive	BRCA1/2 negative
Women with a history of unilateral breast cancer	189 cases	892 cases
Contralateral breast cancer onset after genetic testing	8 cases	4 cases
Observation period after genetic testing (average)	0.02–16.8 years (3.0)	0.01–20.2 years (2.2)
Incidence rate	8/567 (persons/person years) 1.4%/year	4/1962 (persons/person years) 0.2%/year
Background
Age of onset of the first breast cancer (average)	Age 19–74 (age 41.7)	Age 22–85 (age 45.4)
Number of exclusion cases due to PM	37 cases	3 cases

PM prophylactic mastectomy