Even the least lethal form of breast cancer can reappear and turn deadly years after a woman’s last treatment, according to a study by Kaiser Permanente.
“Impact of Breast Cancer Subtypes and Treatment on Survival: An Analysis Spanning Two Decades,” says that women with luminal A tumors are still at risk for death more than 10 years after diagnosis. These women could “benefit from extended treatment to improve their chances for long-term survival,” says Reina Haque, PhD, MPH, the study’s lead author, who works in the research and evaluation department of Kaiser Permanente Southern California. The study is published in the journal Cancer, Epidemiology, Biomarkers & Prevention.
The 21-year study tracked about 1,000 Kaiser beneficiaries. It separates cases by four molecular subtypes: luminal A, luminal B, the basal-like subtype, and the HER2-enriched subtype. Luminal B and the basal-like subtype tend to occur in young women and have a poor prognosis. HER2-enriched subtype also has a poor prognosis.
The Kaiser Permanente Southern California beneficiaries were diagnosed with breast cancer between 1988 and 1995 and were tracked through 2008. The study says that “women with HER2-enriched and luminal B tumors had a two-fold increased adjusted risk of breast cancer mortality compared with women with luminal A tumors....”
However, the study adds that “Despite its markedly higher survival probabilities in earlier years of follow-up, luminal A subtype was the only subtype that continued a steady drop in survival over the 20-year period with little leveling off in later years.”
The study also notes that the fact that the subjects belong to a health plan led to a more thorough collection of data and, hopefully, better survival rates.
“...[T]he managed care setting afforded a rare opportunity for very long-term follow-up of breast cancer patients,” the study says. “Health plan membership sustainment was high, with more than four of every five members continuing membership until either death or the end of the 21-year follow-up period.” In total, 223 women out of the 934 who were tracked died from breast cancer.
The health plan link even rated a mention when the study listed some drawbacks.
“Another limitation was the lack of treatment data for recurrences.” However, the authors say because the cohort consisted of a fully insured population with long-term sustained membership, it’s unlikely that survival rates were affected by recurrences of breast cancer.