Impact of the COVID-19 Pandemic on Breast Cancer Mortality in the US

Estimates From Collaborative Simulation Modeling

Oguzhan Alagoz; Kathryn P. Lowry; Allison W. Kurian; Jeanne S. Mandelblatt; Mehmet A. Ergun; Hui Huang; Sandra J. Lee; Clyde B. Schechter; Anna N. A. Tosteson; Diana L. Miglioretti; Amy Trentham-Dietz; Sarah J. Nyante; Karla Kerlikowske; Brian L. Sprague; Natasha K. Stout

Disclosures

J Natl Cancer Inst. 2021;113(11):1484-1494. 

In This Article

Discussion

This collaborative modeling study provides useful information regarding the likely effects of initial pandemic-related disruptions on breast cancer mortality over time. Three independent models found that the cumulative impact of initial pandemic disruptions would be less than a 1% increase in cumulative breast cancer mortality over the next decade. This result is likely to be related to the rapid response of care providers to reinstituting screening and the assumption that women diagnosed with advanced-stage and/or poor prognosis cancers did not experience any delays in chemotherapy initiation. If the pandemic effects on care disruptions persist for 12 months, excess mortality would approximately double.

To our knowledge, no previous modeling study has conducted a comprehensive analysis of the impact of disruptions due to the COVID-19 pandemic on breast cancer mortality in the United States. A prior commentary used a preliminary analysis by 1 of the models used in this study (model W-H) and reported a higher mortality impact than that seen in this study (5391 vs 2487 cumulative excess deaths from 2020 to 2030).[35] However, that early analysis assumed higher reduction in screening (75% vs 50%) and greater delays in diagnosis (delay in diagnosis of all case s vs only symptomatic cases). A modeling study from Canada found that when all scheduled mammograms are skipped for 6 months and are made up gradually, the number of deaths increases by 0.48% by 2029, which is slightly higher than our estimate because we do not assume that all screening stopped during the pandemic.[36] Another study focusing on the United Kingdom estimated that the number of breast cancer deaths could increase by 7.9%-9.6% in 5 years due to the pandemic; however, that study assumed that cancers could not be diagnosed after a screening exam but only through urgent referrals during the pandemic.[37]

Our results suggest that the rapid adaptations of health-care facilities to devise strategies to resume breast cancer screening, diagnosis, and treatment services within a 6-month period greatly mitigated the potential impact on breast cancer mortality.[2,9,13] The overall impact of disruptions in screening and delays in diagnosis of symptomatic evaluation were estimated to be similar, because most women due for routine screening will not have breast cancer. Even small disruptions to diagnostic evaluation of symptomatic women translate to substantial numbers of excess breast cancer deaths as demonstrated in the sensitivity analysis. As such, our results reinforce the importance of prompt evaluation of women with breast cancer symptoms during periods of reduced health-care access and capacity. This is consistent with a recent Breast Cancer Surveillance Consortium study, which found that during periods of reduced capacity, triaging individuals most likely to have cancer, including women with symptoms, could result in detecting the most cancers while performing the fewest examinations compared with a nonrisk-based approach.[38]

Our findings also suggest that excess breast cancer mortality due to reduced access to screening during the pandemic could be mitigated by facilities giving priority to women who missed a screen during the pandemic. Although imaging volumes had returned to normal or above normal by September 2020, there remains a substantial cumulative deficit in screening and diagnostic evaluations compared with prepandemic years.[9,13,39] This deficit may be due to multiple factors, including limited capacity of breast-imaging facilities to accommodate the number of women whose evaluation has been delayed, ongoing concerns from women about the safety of health-care facilities due the continued pandemic, or reduced access to health care due to COVID-19–related loss of employment-based health insurance. Many of these factors are likely to continue to affect receipt of diagnostic and screening services until control of the COVID-19 pandemic is achieved. Thus, the true duration of disruption to breast cancer control activities and the impact on long-term breast cancer mortality may ultimately prove to be more substantial than our current models suggest.

Despite the strength of consistent results from 3 established CISNET models, there are several limitations that should be considered in interpreting our results. First, in the absence of detailed information on breast cancer treatment patterns during the pandemic, we based our treatment assumptions on expert opinion. We assumed that during the pandemic, oncologists rationally limited chemotherapy use among patients least likely to benefit (early stage, ER-positive or HER2-negative disease) and at greatest risk for COVID-19–related complications (women older than 70 years).[27–29] We also assumed that oncologists ensured chemotherapy receipt among poor prognosis subtypes (ER-negative and/or HER2-positive or more advanced stages), assuming the benefit of adjuvant chemotherapy outweighed the risk of death due to COVID-19. Furthermore, because oral endocrine therapies (eg, tamoxifen or aromatase inhibitors) neither compromise the immune system nor require in-person visits for administration, we assumed the pandemic did not disrupt their use. It is possible that there were delays or nonuse of treatment, especially with losses of health-care insurance. In this case, the impact of pandemic-related treatment changes on excess breast cancer mortality may be greater than we expect. More data on cancer treatment patterns and longer follow-up will be essential to refine the mortality projections.

Another limitation is that many aspects of screening behavior and diagnostic evaluation during the pandemic remain poorly understood, including whether patterns in resumption of care are differential by age or perceived cancer risk. For example, disruptions in screening continue as woman are being encouraged to reschedule screening mammography after receiving the COVID-19 vaccination to prevent false-positive callbacks for vaccination-related lymphadenopathy. Additionally, although mammography volumes rebounded over the summer to reach prepandemic levels,[2,9,13] it is not clear what portion of these exams are for missed mammograms or regularly scheduled exams. We tested a range of assumptions about these patterns, and results were similar in magnitude across different scenarios. Moreover, our models did not account for potential disparities in the resumption of breast cancer care services. Our recent work has shown that the recovery of breast cancer–screening and diagnostic services has not been equal for all women, with a slower rebound in use among Hispanic and Asian women as of July 2020.[13] Thus, although the overall impact of the pandemic on cancer outcomes may be small, it may disproportionately affect women in underserved populations and exacerbate health inequities. Therefore, it will be important to focus on resumption of access to screening for racial and ethnic minority women.

Finally, we assumed that future incidence, accuracy of screening and diagnosis, effectiveness of treatment, and other-cause mortality would carry forward at levels before the pandemic. Because these assumptions applied to the scenarios representing both COVID-19 disruptions and usual care, the relative difference in outcomes is unlikely to be affected.

In conclusion, in this collaborative simulation modeling study, we projected a small number of additional breast cancer deaths among US women from 2020 to 2030 due to the COVID-19 pandemic–related disruptions in breast cancer screening, diagnosis, and treatment. Efforts to ensure prompt access to screening, diagnostic evaluation, and treatment should mitigate the impact of the COVID-19 pandemic on breast cancer mortality.

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