In this study, 1,277 women diagnosed after age 64 with early-stage breast cancer who had already survived without recurrence for five years were followed an additional five years. The women had originally been diagnosed with breast cancers that were primarily lymph node negative (77%) and estrogen receptor positive (ER+) or unknown (86%). Sixty-one (5%) of the study participants developed a recurrence, of which 25% were local recurrences, 9.8% were regional recurrences, and 66% were distant metastases. Women who had positive lymph nodes, had poorly differentiated tumors, or who had lumpectomies without also having radiation treatment were more likely to have a recurrence than those who had node negative or well differentiated tumors or who underwent mastectomies. Women with ER+ or estrogen receptor unknown tumors who did not receive adjuvant tamoxifen treatment were more likely to have a recurrence than those who were treated with tamoxifen. Although relatively few of the women experienced a late recurrence, most of the recurrences presented as advanced disease. The authors conclude that while the risk of late recurrence is small, it is not negligible even in this group of older women at high risk of death due to other causes.

Breast cancer can recur decades after treatment

While some cancers are considered cured after five years, this is not the case for breast cancer. Many patients with high risk breast cancer characteristics die within the first two to four years. However, although the rate of recurrence declines over time, breast cancer has been known to recur as long as 50 years after surgery. It has not been determined why this is the case.

It may be that some cancer cells that enter the lymph system or general circulation and are deposited away from the primary tumor are resistant to various treatments. Under this theory, such breast cancer cells can exist in two states: solitary dormant cells and active micrometastases that have not yet developed their own blood supplies. Solitary dormant breast cancer cells can exist in a quiescent state, thereby avoiding being eliminated by cytotoxic chemotherapy that might be effective against the same cells when they are in an actively dividing state. Some researchers have suggested that such dormant cells may in fact be breast cancer stem cells, which lack the cell receptors of breast cells and, as such, are insensitive to hormonal therapy. It is unclear what factors would promote awakening of dormant breast cancer cells. It has also been suggested that some active micrometastases may develop barriers that enable them to hide from treatment and from the immune system, although how this might be accomplished also remains to be explained.

One study found that the average risk of recurrence between years five to 12 after initial breast cancer surgery is approximately 4% per year. Other studies have found that the rate of recurrence for early-stage breast cancer after 10 years is 1% to 2% overall. The few studies that have examined the topic have not identified any factors consistently associated with very late recurrence (10 years or longer after initial breast cancer diagnosis). However, estrogen receptor negative (ER-) breast cancer has been found to be more likely to recur early than ER+ tumors, whereas the risk of late recurrence is greater for ER+ tumors. Since the most aggressive types of breast cancer are more likely to recur early, very late recurrences are often very responsive to treatment compared to early recurrences.

Implications for breast cancer survivors

All breast cancer survivors are at risk for late recurrences. However, late recurrences tend to be more treatable than early recurrences. Several studies have reported that early detection of breast cancer recurrences results in significantly better survival compared to late detected recurrences. In particular, survival is better when a recurrence is found by mammography or in patients without symptoms compared to those with symptoms. Therefore, it is important for breast cancer survivors to remain vigilant by continuing their relationships with their oncologists, undergoing regular mammograms or other diagnostic tests, and performing breast self-exams (if possible).