Synchronous Breast Cancer
Abstract & Commentary
By William B. Ershler, MD
Synopsis: For patients who have synchronous bilateral breast cancer, overall survival has been shown to be less favorable than for patients presenting with unilateral disease. In the current matched case-control series, overall survival was comparable. Clinicians are advised to prescribe systemic therapy based upon the more aggressive of the two lesions.
Source: Nichol AM, et al. A case-match study comparing unilateral with synchronous bilateral breast cancer outcomes. J Clin Oncol 2011;29:4763-4768.
When two primary cancers are discovered during the evaluation of a patient with possible breast disease, a number of management issues arise for which there is little but clinical judgment on which to rely. Synchronously discovered breast cancers represent about 2% of all newly diagnosed breast cancers, depending on the definition of the term "synchronous" used, and whether invasive metastatic or noninvasive ductal and lobular carcinoma are included.1 In fact, there remains uncertainty whether patients with synchronous bilateral breast cancer (SBBC) have similar or worse outcomes compared with patients with unilateral breast cancer.
Nichol and colleagues examined their large database of breast cancer patients in British Columbia to determine whether survival outcomes for patients with SBBC can be estimated from the characteristics of their individual cancers.
Patients had invasive breast cancer, without metastases or inflammatory disease, and were diagnosed in British Columbia between 1989 and 2000. SBBC patients were those who had bilateral breast cancers diagnosed within 60 days, with clinical or pathologic stage (T1-T4c, N0-3). Excluded were in situ, inflammatory, and metastatic presentations. In total, 207 SBBC cases met the study entry criteria. Using the same exclusion criteria, a contemporaneous cohort of 15,497 potential matches with unilateral breast cancers (T1-T4c, N0-3) also was identified.
By using 10-year breast cancer-specific survival (BCSS) estimates, the higher-risk cancer of each SBBC case was determined and matched with three patients from the unilateral cohort to select 621 high-risk matches. The priority sequence of matching the prognostic and predictive variables was positive lymph node number, primary tumor size, age, grade, lymphovascular invasion, estrogen receptor status, local therapy used, margin status, treating clinic, diagnosis year, and type of systemic therapy used.
With a median follow-up of 10.2 years, the overall 10-year BCSS was significantly higher for the entire unilateral cohort (81%; 95% confidence interval [CI], 81%-82%) than for the SBBC cases (71%; 95% CI, 63%-77%). However, the SBBC cases had significantly higher mean age and stage at presentation. Accordingly, the 10-year BCSS for those 621 patients matched for the prognostic variables (including age and stage) present in the SBBC group was 74% (95% CI, 69%-77%) for the high-risk matches. Thus, BCSS was not significantly different between the SBBC cases and their high-risk matches.
Commentary
Patients who present with synchronous breast cancer as a group have less favorable 10-year survival than those presenting with a single cancer. However, when matched for prognostic variables, there is no significant difference. This finding is different from others in which survival was demonstrably worse for those with SBBC. For example, Verkooijen reported that BCSS was significantly worse for 155 SBBC cases compared with unilateral cancers.2 However, after adjustment for age, social class, and public sector medical care, they concluded that the difference in outcome between their cohorts was due to persistent significant differences between the baseline variables. Hartman determined that BCSS was also significantly worse for 355 SBBC cases compared with unilateral cancers.3 In contrast to Verkooijen's findings, in Hartman's subset of 46 cases with complete treatment information, the 5-year adverse BCSS difference persisted after adjustment for age, year of diagnosis, TNM stage, adjuvant treatment, and estrogen receptor status (hazard ratio, 1.7; 95% CI, 1.2-2.2). In the current study, significant differences in baseline variables between the SBBC cases and the unilateral cohort were demonstrated. The SBBC cases were 9 years older, on average, and had more advanced stage, and these factors contributed to the initial observation that patients with SBBC had worse outcomes compared with patients with unilateral breast cancer. In this case-match study, high-quality matching was made possible by a large registry of breast cancer patients, including 15,497 with unilateral disease.
Synchronous breast cancer is uncommon, but with increased screening compliance and improved imaging techniques, it might be expected to increase. For example in one clinical trial, MRI found additional (i.e., mammographically occult) lesions in 3.1% of contralateral breasts.4 Thus, as enhanced imaging is becoming more commonly employed in the presurgical staging of breast cancer, it is likely we will be encountering the question of optimal management strategies for those with bilateral disease. The current matched-case control study found that SBBC patients had similar outcomes as those with unilateral disease with comparable risk factors. Thus, for patients with SBBC, appropriate systemic therapy should be prescribed according to those histopathological features of the more aggressive of the two malignancies.
References
1. Heron DE, et al. Bilateral breast carcinoma: Risk factors and outcomes for patients with synchronous and metachronous disease. Cancer 2000;88:2739-2750.
2. Verkooijen HM, et al. Survival after bilateral breast cancer: Results from a population-based study. Breast Cancer Res Treat 2007;105:347-357.
3. Hartman M, et al. Incidence and prognosis of synchronous and metachronous bilateral breast cancer. J Clin Oncol 2007;25:4210-4216.
4. Lehman CD, et al. MRI evaluation of the contralateral breast in women with recently diagnosed breast cancer. N Engl J Med 2007;356:1295-1303.
For patients who have synchronous bilateral breast cancer, overall survival has been shown to be less favorable than for patients presenting with unilateral disease. In the current matched case-control series, overall survival was comparable. Clinicians are advised to prescribe systemic therapy based upon the more aggressive of the two lesions.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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