medwireNews: Advances in adjuvant treatment have made a greater contribution to reducing breast cancer mortality in the USA between 2000 and 2012 than advances in screening, estimate simulation models developed within the Cancer Intervention and Surveillance Network (CISNET).
This was evident for breast cancer overall and for molecular subtypes based on estrogen receptor (ER) and human epidermal growth factor receptor 2 (ERBB2), bar cancers negative for both receptors (ER–/ERBB2–). The degree of association varied according to subtype, however.
“The results from this model analysis confirm the benefits at the population level from the discovery and rapid dissemination over this past decade of several new classes of molecularly targeted therapies, improvements in delivery of standard regimens, and refinements in therapy based on molecular subtype according to ER and ERBB2 status,” say Sylvia Plevritis (Stanford University, California, USA) and colleagues.
From 1975 to 2000, treatment and screening contributed approximately equally to the reduction in breast cancer mortality. And in 2000, CISNET estimated from six independent models that treatment was associated with 56% of the 37% reduction in overall breast cancer mortality among women aged between 30 and 75 years, while the contribution associated with screening was 44%.
With the advancement in both treatment and screening since 2000, including digital replacing plain-film mammography and a greater use of molecularly targeted treatments and taxanes, the estimated reduction in overall breast cancer mortality in 2012 increased to 49% relative to a baseline rate of 63 deaths per 100,000 women.
The estimated screening contribution associated with this reduction was 37%, whereas the contribution associated with treatment was greater, at 63%.
“The larger contribution associated with treatment [versus] screening in 2012 was predicted in 5 of 6 models,” note the researchers in JAMA.
The estimated 63% contribution from treatment comprised 31% from chemotherapy, 27% from hormone therapy, and 4% from trastuzumab.
Among the molecular subtypes studied, ER+/ERBB2– was the most common and was associated with 64% of the reduction in overall breast cancer mortality in 2012. But the ER+/ERBB2+ subtype was associated with the greatest reduction in mortality relative to baseline, at 58%, followed by ER+/ERBB2– at 51%, ER−/ERBB2+ at 45%, and ER−/ERBB2− at 37%.
The relative contributions from treatment and screening also varied according to molecular subtype. They were each associated with a respective 64% and 36% for the ER+/ERBB2– subtype, and a corresponding 69% versus 31% for ER+/ERBB2+, 60% versus 40% for ER−/ERBB2+, and 52% versus 48% for ER−/ERBB2−.
The researchers say that “[b]ecause ER+ cancers are the most prevalent and this group is expected to increase with time, additional advances for this subtype could have the largest effect on reducing the overall population burden of breast cancer.”
They also note, however, that treatment advances are lagging for ER−/ERBB2− cancers and investment into more targeted molecular treatments and better screening to identify groups at high risk for this subtype, such as African American women, “remain important to continue to lower breast cancer death rates.”
By Lucy Piper
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