Study: Knowing about an inherited BRCA mutation improves outcomes for women with breast cancer

IN-DEPTH REVIEW OF RESEARCH

Study background:

Inherited mutations in BRCA1 and BRCA2 are linked to a high lifetime risk of breast, ovarian and related cancers. However, some women are not diagnosed with an inherited BRCA mutation until after their breast cancer diagnosis. This happens most often in people with no strong family history (perhaps due to small family size or few female relatives with the mutation). These women would have had general guidance about breast cancer surveillance and prevention.

In contrast, women who know that they have an inherited harmful mutation in BRCA1 or BRCA2 would be counseled about surveillance and prevention options. They can choose to increase surveillance for breast cancer or consider risk-reducing bilateral mastectomy (RRBM) to reduce their risk. However, the majority of people with BRCA mutations decline RRBM.
 

Researchers of this study wanted to know:

Whether women who knew that they inherited a harmful BRCA1 or BRCA2 mutation and declined RRBM had improved outcomes compared to women who were unaware that they had inherited a harmful BRCA1 or BRCA2 mutation (and therefore did not consider RRBM or other risk-reducing choices).

Populations looked at in this study:

This study looked at medical information for 105 women diagnosed with an inherited BRCA mutation seen at the Sha'are Zedek Medical Center in Israel from 2005 to 2016. In this study, 83% of women were of Ashkenazi Jewish heritage. The average age at time of breast cancer diagnosis was 50 years.

Study design:

Researchers collected previous medical information from records in the Israeli Cancer Registry,  including information about cancer staging, tumor type and characteristics, family history, method of cancer detection, type of treatment and survival.

All patients had counseling for surveillance and prevention based on standard guidelines for those with known BRCA mutations, including the option of risk-reducing bilateral mastectomy (breast removal) and risk-reducing salpingo-oophorectomy (ovary and fallopian tube removal).

Study findings:  

• 42 of 105  women (40%) were aware of their BRCA mutation before their breast cancer diagnosis (pre-diagnosis group).
• 63 of 105  women (60%) were unaware of their BRCA mutation until after their breast cancer diagnosis (post-diagnosis group).

The majority of women in the pre-diagnosis group were diagnosed at earlier stages and required less treatment compared to women in the post-diagnosis group.

• Among women in the pre-diagnosis group:
  • 64% had their breast cancer detected by MRI.
  • 86% had early-stage cancer (stage 0-1: 86%, stage II-IV: 14%).
  • 64% chose to have bilateral mastectomy at the time of their tumor surgery.
  • 85% had lymph node biopsy without further surgery, while only 7% needed more invasive lymph node surgery.
  • 55% did not require chemotherapy after surgery. None required chemotherapy before surgery.
     
• Among women in the post-diagnosis group:
  • 63% had their breast cancer detected by their own physical exam or clinical exam by a healthcare provider.
  • 61% were diagnosed with later stages of cancer (stage 0-1: 39%, stage II-IV: 61%).
  • 78% chose to have unilateral mastectomy at the time of their tumor surgery.
  • 51% had lymph node biopsy without further surgery, while 35% needed more invasive lymph node surgery.
  • Only 5% did not require chemotherapy after surgery. 22% required chemotherapy before surgery.

Women in the pre-diagnosis group had better overall survival.

• • 2 of 42 (5%) women in the pre-diagnosis group died.
  • 16 of 63 (25%) women in the post-diagnosis group died.
  • This corresponds to an estimated survival rate at 5 years after diagnosis of 94% for the pre-diagnosis group and 78% for the post-diagnosis group.
     
• Women in the pre-diagnosis group had a stronger family history of cancer and were better off socio-economically than women in the post-diagnosis group.

Some features did not differ between women in the pre-diagnosis group and the post-diagnosis group.

• Among both groups, about 64% of the women had a BRCA1 mutation and 36% had a BRCA2 mutation.
• The two groups of women had a similar number of tumors with different grades, hormone-receptor status and HER2 status.
   

Strengths and limitations:

Strengths:

• Women in the pre-diagnosis and post-diagnosis groups were well-matched for age at diagnosis and for the percentage of women with mutations in each BRCA gene. This suggests that the women in each group had similar general features. This is a goal of most scientific studies, that groups are similar apart from the features being tested. Statistical analysis was done to determine what other factors might be similar or different between these two groups of breast cancer patients. The statistical analysis was appropriate for this type of study.
• Also, because all patients were seen at one healthcare institution, the care and guidance about breast cancer risk would be consistent.

Limitations:

• A limitation of this study was that it was based on past medical records. This type of retrospective study depends on the medical records containing relevant information. Only women who eventually were diagnosed with breast cancer were included. It is possible that other women who did not develop breast cancer but who knew or did not know their BRCA status may have differed in other ways that were not tested.
• Another limitation of this study was the relatively small sample size of patients (105 women). In such a small study, it is possible that the differences observed might not hold up in a larger study. The study’s statistical analysis suggests that it is reliable, but repeating it with larger numbers would help validate the results. The small size of the study prevented researchers from making any conclusions about the effect of risk-reducing bilateral salpingo-oophorectomy (ovary and fallopian tube removal) on outcomes.
• This study took place in Israel. There may be differences in healthcare, genetic counseling and guidance for people in the U.S. with BRCA mutations. It is unknown whether such differences might alter these findings. Given the differences in insurance and medical coverage in Israel and the United States, the women who knew that they had an inherited BRCA mutation and declined RRBM may have declined for reasons that are different than women in the U.S.

Context:

Women with BRCA mutations who chose to have risk-reducing bilateral mastectomy had improved outcomes. It was not known whether knowing about an inherited BRCA mutation among women who had not yet had a breast cancer diagnosis would be helpful. This is the first report of a survival advantage among women who knew their BRCA status and declined risk-reducing bilateral mastectomy.

Conclusions:

The researchers state:

"These results provide further support for BRCA1/BRCA2 screening in unaffected women, particularly in populations such as Ashkenazi Jews with high BRCA1/BRCA2 carrier rates."

Knowing about an inherited BRCA1 or BRCA2 mutation before a breast cancer diagnosis is linked to earlier diagnosis, less aggressive treatment and better overall survival. While this study did not directly test why women who knew about their BRCA mutation had better outcomes, it does suggest that increased surveillance with MRI may be beneficial for women with BRCA mutations.

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Posted 10/26/20