While much breast cancer research is focused on high risk breast cancer types such as triple negative, HER2 overexpressing (HER2+) and inflammatory breast cancer, many women have less aggressive disease. In fact, there is a large minority of breast cancer patients that have a low risk of relapse during the first five years.
Characteristics of low risk breast cancer
Generally speaking, breast cancer with all of the following characteristics and treatment factors has a very low risk of recurrence (under 2%) during the first five years after diagnosis:
- Estrogen and progesterone receptor positive (ER+/PR+)
- Tumor was found by screening mammography, could not be felt by hand
- Small tumor size (under 2 cm)
- Lymph node negative
- Single tumor (not multicentric, multifocal or diffuse)
- Clear surgical margins
Risk of late relapse is highest for ER+ disease
Risk of breast cancer recurrence persists for decades, especially for ER+/PR+ breast cancer, which is more subject to late relapse (after seven years) than triple negative or other more aggressive disease. One study reported that while the risk of recurrence was lower at first for ER+ compared to ER- disease, ER+ tumor status was more detrimental after 7.7 years. While relapse during the first five years is associated with variables such as large number of positive lymph nodes, poorly differentiated tumor, or radiotherapy, the few studies that have examined very late recurrence (10 years or longer after initial breast cancer diagnosis) have not found that similar factors are linked to it. Positive hormone receptor status appears to be the only attribute consistently associated with very late recurrence.
Early detection of late breast cancer recurrences can confer a survival advantage. For example, it has been shown that survival is better when a recurrence is found by mammography or in women without symptoms compared to those with symptoms. Therefore, it is important for early-stage breast cancer survivors to remain vigilant by continuing their relationships with their oncologists, undergoing regular mammograms or other diagnostic tests, and performing regular breast self-exams.
Latest research identifies low-risk tumor characteristics
The study referenced at the beginning of this news article was designed to identify the pathologic features of breast cancer with a low risk of recurrence. The study included 715 invasive breast cancer cases with tumors up to 5.0 cm in size. Study participants were divided into two risk categories: low-risk and moderate/high risk. The 79 tumors designated low risk were non-palpable (could not be felt by hand), lymph node negative, and detected only by mammographic screening. The remaining 636 tumors were classified as moderate/high risk.
The low-risk tumors were found to be characterized by estrogen and progesterone receptor positive status (ER+/PR+), HER2- status, as well as ck5/6 negativity, EGFR negativity and p53 negativity (the latter three are different measures of aggressiveness). Approximately 68% of the low-risk tumors were of the luminal A subtype, compared to 53% of the moderate/high risk tumors. Luminal A tumors are normally ER+ or PR+, HER2- and tumor grade 1 or 2. Among the 42 study participants with a mammogram-detected, non-palpable, PR+/HER2- cancer of up to 5.0 cm, the 15-year distant recurrence-free survival rate was 100 %. The authors conclude that small breast cancers detectable by mammogram alone that are PR+ and HER2- have a very low risk of recurrence. Some of these cases may represent examples of over diagnosis.