Study Author Discusses the Usefulness of the Breast Cancer Index in Assessing Risk of Lobular Breast Cancer Recurrence
Invasive lobular carcinoma (ILC) is the second most common type of invasive breast cancer and has many unique characteristics in terms of presentation, clinical behavior, and response to therapy. Most of our current management recommendations are based on studies involving only a minority of patients with ILC, and there is a great need for continued research focusing specifically on this important problem.
Many questions pertaining to ILC remain unanswered and knowledge regarding the biologic drivers of the behavior of this disease and its response to therapy remains limited.
One of the distinguishing features of ILC is its potential for late recurrence. ILC is almost always hormone receptor positive. In general, when recurrences occur in hormone receptor positive breast cancer, roughly half of these will occur in the first five years after diagnosis, while the other half will occur after five years commonly referred to as late recurrence.
The yearly likelihood of recurrence beyond five years is low, but this yearly risk persists for many years after diagnosis. The risk of late recurrence appears to be proportionally elevated in ILC. Identifying patients who are at higher risk of late recurrence can be particularly important to select patients who are the best candidates to continue hormonal therapies beyond five years. In addition, as new treatments may become available, the ability to individualize treatment decisions and avoid additional toxicity for patients who have a low risk of recurrence may be particularly useful.
In addition to clinical factors (like tumor size, grade, nodal status), there are currently several tests based on gene expression that are routinely used to determine the risk of cancer recurrence. Some data suggests that the performance of some of these tests in ILC (as opposed to IDC) is less robust. Furthermore, while many of these tests have a good ability to predict recurrence within the first 5 years, they are less accurate in predicting late recurrence.
One of these gene signatures, the Breast Cancer Index or BCI, was able to identify patients with a low likelihood of early and late recurrence and predict the benefit of extended endocrine therapy.
The ability of the BCI test to predict late recurrence was initially demonstrated in several clinical studies, mainly including patients with invasive ductal carcinoma. Recently, a group of researchers from four academic institutions evaluated the ability of BCI to offer prognostic information specifically in ILC.
In this retrospective study, BCI gene expression analysis was performed in tumor specimens from 307 patients with ILC with a median follow up of 10 years after diagnosis. BCI analysis classified patients with ILC into risk groups based on risk of overall 10-year, early (0-5 years), and late (5-10 years) distant recurrence. While clinical factors remained important, BCI added additional prognostic information, allowing for a more accurate estimate of prognosis in this population.
While clinical and pathological factors, along with patient’s preferences, remain important determinants in decision making, this study supports integrating additional genomic information when appropriate to help individualize prognosis and inform treatment approaches for patients with ILC.
This study also illustrates the importance of collaboration between different institutions and the need for careful tumor banking in order to continue to make progress in our knowledge about ILC, a disease that affects so many women and to which such limited research attention has been devoted.
Dr. Raquel Nunes is a breast medical oncologist and an Assistant Professor of Oncology in the Division of Women’s Malignancies, Johns Hopkins University.
Patients can ask their clinicians about the BCI test, which is conducted on a patient’s original biopsy tissue.