Hi,
I have a 62 year old patient who has a PTEN mutation. She has a history of breast cancer diagnosed in 2010, endometrial cancer and thyroid cancer. She is followed in our breast care clinic with enhanced surveillance, alternating mammogram and breast MRI every 6 months. What is her risk of a second breast cancer? I am debating how long to continue with screening breast MRI.
Thanks for your help.

The risk of a second primary breast cancer in those with PTEN pathogenic mutations is a challenging question. We do know that there is an increased incidence of both multifocality and bilateral involvement observed for both benign and malignant breast disorders with in Cowden patients.

National guidelines (NCCN 2019) do state that for women with a PTEN mutation who are treated for breast cancer and have not had a bilateral mastectomy to screen as you are – with alternating MRI and mammogram. They state that counseling should include the option of risk reducing mastectomy which should include degree of protection, reconstructive options. The family history and residual breast cancer risk with age and life expectancy needs to be considered during your conversation with the patient.

I believe the best study (J Clin Oncol 32:1818-1824. 2014) addressing risk for secondary breast cancers in PTEN female carriers demonstrate a 29% risk to develop a secondary breast cancer within years. This was a multicenter prospective study demonstrating - of the 51 PTEN mutation–positive patients who presented with primary breast cancer, 11(22%) had a subsequent new primary breast cancer and 10-year second breast cancer cumulative risk of 29% (95% CI, 15.3 to 43.7).