This article is more than 5 years old. Information may no longer be current.
Least aggressive form of breast cancer poses risks years later
Women diagnosed with the least aggressive form of breast cancer are still at a risk for death from the disease even after 10 years of follow-up treatment, according to study results.
Breast cancer tumors often are divided into four subtypes.
Luminal A — the least aggressive and most common subtype — accounts for 42% to 59% of all breast cancers, according to background information in the study. Luminal B typically occurs in younger women and accounts for about 10% of all breast cancers. Basal-like subtype typically occurs in younger women and African-American women, and HER-2–enriched subtype is characterized by high-grade tumors and poor outcomes.
Knowledge regarding the effectiveness of adjuvant therapy treatment by breast cancer tumor subtype is limited.
The purpose of the study was to investigate the effect of breast cancer subtypes and treatment on survival in a cohort followed for more than 20 years.
Reina Haque, PhD, MPH, research scientist in the department of research and evaluation for Kaiser Permanente Southern California, and colleagues evaluated 934 women recently diagnosed with breast cancer. Median patient age at the time of diagnosis was 59 years.
Median follow-up was 13.3 years, and maximum follow-up was 21 years.
The most common breast cancer subtype among study participants was luminal A (66%), followed by basal-like breast cancer (22%), HER-2 enriched (7%) and luminal B (5%).
During the study period, 23.9% of patients died due to breast cancer and 19.8% died due to other causes. A total of 39.7% of patients completed follow-up and 16.6% exited the health plan.
According to results from the study, breast cancer mortality rates were twofold among women with luminal B and HER-2–enriched tumors compared with patients with luminal A subtype.
Women with luminal A subtype had the longest survival, according to researchers. Women with HER-2–enriched and luminal B subtypes had shorter survival times (P<.0001).
Deaths occurred earlier for women with basal-like tumors compared with those with luminal A breast cancer.
Survival declined during the first 3 to 4 years of follow-up for HER-2–enriched and luminal B subtypes, followed by a slowing of the decline in subsequent years of follow-up. Basal-like subtype showed a similar rate of decline as the HER-2–positive subtypes during the first 2 to 2.5 years, followed by a steady decline to about 13 years of follow-up.
“Interestingly, the curve for luminal A continues to decline steadily after 10-years of follow-up, suggesting that the risk of late mortality persist in this group,” Haque and colleagues wrote.
Luminal A subtype was the only subtype that continued a steady decline in survival during the 20-year period with little leveling off in the later years, according to the study results.
The findings should encourage doctors to consider molecular subtypes when determining treatment for patients with breast cancer. Patients with luminal A breast cancer could benefit from extended treatment, ultimately improving their chances of long-term survival, according to the researchers.
“Future studies should examine how the association with between molecular subtypes and survival varies by race/ethnicity, particularly in minority women who are more likely to have aggressive tumor subtypes, as well as identity factors to enhance survival in women with luminal A tumors,” Haque and colleagues concluded.
Perspective
Back to TopWe generally think of luminal A patients as having excellent outcomes, but we’ve already known that they can recur very late. More aggressive cancers tend to recur early, but once the patient reaches 5 to 10 years without recurrence, the recurrence rate is quite low. This study — with a long median follow-up of more than 13 years — tells us is that even the good prognosis group (luminal A) continues to recur over time, although a majority of these patients did not receive hormonal therapy. That does not necessarily mean we should treat them more aggressively, as chemotherapy tends to lower the annual hazards for recurrence only in the first few years.
We need to better understand predictors of late recurrence. Several recent studies have identified gene profiles associated with late recurrence, and this may identify novel targets for this group of patients. For now, our only handle on this group of patients is to test more prolonged hormonal therapy, and we eagerly await results of completed trials comparing 5 to 10 years of aromatase inhibitor therapy. In the future, it is possible that a new generation of new therapies — or lifestyle interventions — that can be given safely for prolonged periods will emerge that can attenuate late recurrences.
Collapse