The researchers aimed to determine whether women with mutations in breast cancer–associated genes (BRCA1/2 or others) received guideline-concordant care to the same degree as women who lacked deleterious mutations. The authors evaluated guideline concordance with respect to three treatment modalities: surgery (bilateral vs. unilateral mastectomy in women who were eligible for unilateral surgery), radiotherapy after lumpectomy (for women aged less than 70 years with hormonally responsive, ErbB2-negative, stage I cancers), and chemotherapy (among women eligible for consideration of chemotherapy omission)
In alignment with guidelines, many clinicians correctly used genetic test results to guide surgical decisions. For example, 61.7% of women with BRCA mutations underwent bilateral mastectomy, compared with 24.3% who were mutation negative (odds ratio, 5.52). For other pathogenic variants (ATM, CDH1, CHEK2, NBN, NF1, PALB2, PTEN, and TP53), the rate of bilateral mastectomy was still elevated, albeit to a lesser degree (OR, 2.41).
In discord with guidelines, women with BRCA mutations were 78% less likely to receive radiotherapy after lumpectomy (OR, 0.22) and 76% more likely to receive chemotherapy for early-stage, hormone-positive disease (OR, 1.76), suggesting possible trends in under- and overtreatment, respectively. Chemotherapy utilization rates among mutation carriers and noncarriers became more similar after adjustment for clinical and demographic factors.
There are limits on the granularity of the SEER database, such that, if a patient had a mastectomy a year or more after lumpectomy in an effort to avoid radiotherapy, the database would not have reflected that. Clinical factors could have appropriately influenced chemotherapy receipt among patients with mutations, but those additional factors (including patient preference) would not be included in the SEER data.
The authors concluded that research should be conducted to confirm the results of this retrospective, population-based cohort analysis, in an effort to understand the decision-making process and consequences for long-term outcome.
As a consequence of these factors, genetic test results are routinely available to clinicians who may lack formal training in clinical genetics. Whether these results influence the receipt of evidence-based clinical care is uncertain.
The information published by Dr. Kurian and colleagues is inherently limited by the methodology of a SEER database review. Among other limitations, as the authors comment:
Dr. Lyss was a community-based medical oncologist and clinical researcher for more than 35 years before his recent retirement. His clinical and research interests were focused on breast and lung cancers as well as expanding clinical trial access to medically underserved populations.