Contralateral breast cancer

Between 5-10% of women with primary breast cancer develop contralateral breast cancer.

Accounts for 45% of all second primary malignancies.

Most common second primary malignancies among women diagnosed with breast cancer.

Women with primary breast cancer have a 2-6 fold greater risk of developing a contralateral breast cancer compared with the risk of developing primary breast cancer among women in the general population.

For women with early stage sporadic breast cancer with a minimal 0.5-0.75% annual risk for developing contralateral breast cancer and lifetime risk of 13% and 3.5% for women less than 50 years and greater than 50 years at diagnosis, respectively, there is lack of definitive clinical evidence for the benefit of contralateral prophylactic mastectomy.

The incidence of metachronous contralateral breast cancer that is detected several months after initial breast cancer diagnosis is relatively low at 0.25% to 1% per year.

These cancers are usually detected early and at highly curable stages.

Synchronous occult contralateral breast cancers incidence is only 1-3% in contralateral prophylactic mastectomy specimens.

The Early Breast Cancer Trialists’ Collaborative Group reported the annual rate of contralateral breast cancer is about 0.4% for patients with estrogen receptor positive breast cancer treated with tamoxifen, with a 10 year cumulative risk of contralateral breast cancer of about 4-5%.

Survival studies are comparable in patients with unilateral versus metachronous bilateral breast cancer and is associated with this stage of the first cancer and is consistent with the concept that the initially presenting tumor has a lead time advantage in establishing distant micrometastases.

Contralateral prophylactic mastectomy is unlikely to be associated with any significant survival advantage for the general population of patients with unilateral breast cancer.

In an analysis of 200,000 California cancer registry patients with unilateral non-metastatic breast cancer managed with conservative surgery in 55% of cases, bilateral mastectomy/CPM in 6%, and unilateral mastectomy in 39%: Median follow-up 89.1 months the 10 year survival for the 3 groups was 83.2%, 81.2%, and 79.9% respectively.

Is a new cancer and not a distant metastases.

Prognosis similar to primary breast cancer.

Typically associated with ductal carcinoma which is not seen with a distant metastases.

Risk factors include young age at the time of diagnosis and family history of breast carcinoma.

In patients receiving breast conserving surgery and radiation, the cumulative incidence of contralateral breast cancer is 7% at 10 years.

Patients with inflammatory BC have a higher risk for contralateral breast cancer and than comparably stage patients noninflammatory breast cancer.

Even for women younger than 45 years and with lobular histology the actual contralateral breast cancer rate in 10 years remains less than 7% (Gao et al).

Breast tissue sensitive to radiation carcinogenesis with an inverse risk with age, with a very low risk when radiation exposure is given after the age of 50 years.

The risk of radiation induced breast cancer increases linearly with increasing doses, but decreases at the highest dosage.

BRCA1 and BRCA2 mutation carriers with breast cancer have a strongly elevated lifetime risk of developing a contralateral breast carcinoma.

BRCA1 carriers have an estimated cumulative risk for contralateral breast cancer of 48% by 50 years of age and 64% by 74 years.

BRCA2 carriers have a risk of developing contralateral breast cancers of 37% by age 50 and 52% by age 70 years.

Contralateral prophylactic mastectomy estimated to result in a 90% reduction after a 10 year median follow up in familial breast cancer (McDonnell).

Contralateral prophylactic mastectomy reduces the risk for contralateral breast cancer risk in BRCA1 or BRCA2 mutation carriers by 91%(van Sprundel).

Contralateral prophylactic mastectomy may be unnecessary for patients not likely to develop contralateral disease.

Contralateral prophylactic mastectomy may not be associated with a survival benefit if the risk of systemic metastases from their index cancer may exceed the risk of developing a contralateral breast cancer.

Findings of lobular hyperplasia, atypical ductal hyperplasia, lobular carcinoma-in-situ in the contralateral breast may be surrogate markers for moderate to high risk development of contralateral breast cancer.

The role of collateral prophylactic mastectomy in the management of the average newly diagnosed patient with breast cancer remains controversial.

The incidence of contralateral breast cancer has decreased with adjuvant therapies and the usual incidence of 0.5-0.75% annual incidence is likely exaggerated at this time.

For most patients the risk of developing contralateral breast cancer is much lower than the risk of recurrence of the index cancer.

Fewer than 6% of women with DCIS, develop contralateral breast cancer within 10 years.

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