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Screening, treatment advances have decreased breast cancer mortality
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Advancements in screening techniques and adjuvant therapy decreased breast cancer mortality between 2000 and 2012, according to results of a model-based analysis.
The estimated reduction in overall breast cancer mortality was 37% in 2000 compared with 49% in 2012, for a total reduction of 12%.
“These numbers represent very positive news for breast cancer patients,” Sylvia Plevritis, PhD, professor of radiology and biomedical data science at Stanford University School of Medicine, said in a press release. “Advances in screening and treatment are saving patients' lives, and this paper quantifies just how much of a difference these advances are making.”
Breast cancer mortality rates have decreased over time in the United States. However, how advancements in molecularly targeted treatments — including chemotherapies — and the transition from plain-film to digital technology for mammography have contributed to molecular subtype-specific breast cancer mortality rates remained unknown.
In 2005, Plevritis and colleagues from the Cancer Intervention and Surveillance Network (CISNET) used 1975 to 2000 data to determine a decrease in mortality from the modeled baseline occurred 50% due to screening and 50% due to treatment.
“Now, over 10 years later, a lot has happened in the field,” Plevritis said. “We've moved from film-based mammography to digital; there are new molecularly targeted treatments and new types of chemotherapy regimens. We wondered whether these advances had changed the relative contributions of treatment and screening on breast cancer mortality.”
Plevritis and colleagues used independent models from six institutions — Dana-Farber Cancer Institute, Erasmus Medical Center, Georgetown University-Albert Einstein College of Medicine, The University of Texas MD Anderson Cancer Center, Stanford University and University of Wisconsin-Harvard — within CISNET to determine the contributions of advanced screening and treatment to reductions in breast cancer mortality.
Specifically, the models compared age-adjusted, overall and ER/HER-2-specific breast cancer relative to mortality rate with the baseline rate — or the rate with the absence of treatment and screening — among women aged 30 to 79 years.
Researchers estimated a 37% (range, 27-42) reduction in overall breast cancer mortality rate relative to the baseline rate of 64 deaths (range, 56-73) per 100,000 women in 2000. Screening contributed 44% (range, 35-60) and treatment 56% (range, 40-65) to this reduction.
The estimated reduction in overall breast cancer mortality rate was 49% (range, 39-58) relative to the baseline rate of 63 deaths (range, 54-73) per 100,000 women in 2012. Thirty-seven percent (range, 26-51) of this reduction stemmed from screening and 63% (range, 49-74) from treatment.
Researchers observed a larger contribution associated with treatment compared with screening in 2012 in five of the simulation models.
Treatment-associated reductions occurred due to chemotherapy (31%; range, 22-37), hormone therapy (27%; range,18-36) and trastuzumab (Herceptin, Genentech; 4%; range, 1-6).
The estimated relative contributions associated with screening and treatment varied by molecular subtype: 36% vs. 64% for ER-positive and HER-2-negative cancer; 31% vs. 69% for ER- and HER-2-positive cancer; 40% vs. 60% for ER-negative and HER-2-positive cancer; and 48% vs. 52% for ER- and HER-2-negative cancer.
The estimated mortality reduction in 2012 appeared largest for the ER- and HER-2-positive subtype — at 58% (range, 46-71) — and lowest for the ER- and HER-2-negative subtype, at 37% (range, 27-46).
These results can help researchers and policymakers who decide how to prioritize new efforts to advance breast cancer treatment and screening, Plevritis said in the release.
“There have been many investments in screening and treatment; we want to know what impact those investments have had in reducing mortality,” she said. “It also helps us think about the future and how to make sure technologies and drugs that are making the biggest difference are disseminated most widely.” – by Melinda Stevens
Disclosures: Plevritis reports a consultant role with GRAIL. Please see the full study for all other authors’ relevant financial disclosures.
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