The Long View

A recent study suggests that the estrogen-receptor (ER)-positive subset of breast cancer may have deeper ramifications than previously suspected (1). “Women who develop ER-positive breast cancer have a remaining long-term risk of fatal disease for more than 20 years,” says study author Linda Lindström, Assistant Professor and Group Leader in the Department of Biosciences and Nutrition at the Karolinska Institutet, Sweden. “We and other researchers have shown that the ER can change when a breast cancer tumor spreads, which affects survival – patients with high intratumoral heterogeneity of the ER were twice as likely to die up to 25 years after diagnosis as patients with low heterogeneity.”

The clinical trial includes patients with low-risk, node-negative, ER-positive breast cancer and is independent of other known tumor markers. Lindström adds, “Patients with luminal A breast cancer and high intratumoral heterogeneity of the ER were also twice as likely to die of their disease.” This finding could help to identify patients at a high long-term risk within the luminal A breast cancer subtype for which patients usually have a good prognosis. Though there is currently no definitive explanation of the underlying mechanisms, the researchers suggest that, given that ER-positive disease is associated with an increased long-term risk of fatal disease, having dormant tumor cells with varying tumor characteristics, as compared with more homogeneous characteristics, may be beneficial for tumor progression and influence patient survival.

If validated, the researchers believe their findings could become actionable in the near future. Lindström says, “We are currently conducting several studies to further understand the long-term risk of fatal breast cancer as determined by patient and tumor characteristics, and we’re also continuing our studies on intratumoral heterogeneity in breast cancer.”