COVID-19 related change in breast cancer diagnosis, stage, treatment, and case volume: 2019–2021

During the COVID-19 pandemic, health screening and care access were limited to varying degrees with treatment and diagnosis delays depending on local regulation and jurisdiction of health care delivery. In our study of the pandemic impact at our institution in Washington State, we reviewed how breast cancer diagnosis methods, stage at diagnosis, treatment and case volumes were affected by this unprecedented natural disaster-like event and the resulting regulations put in place to curtail COVID-19 spread. We observed a cascade of effects from pandemic related restrictions that affected screening, stage at diagnosis, case volumes, and treatment delays with alternative therapy options enacted in 2020.

In the second quarter of 2020 the impact of COVID-19 closures and restrictions began to take effect at our institution and there was a decrease in breast cancer case volume. In April 2020, mammography screening was stopped while diagnostic mammograms continued on a limited basis dictated by case prioritization directives. During the peak pandemic time, Q2-Q4 of 2020, case volume declined and there was a numeric and proportional decrease in stage 0/I BC relative to stage II-IV BC due to the discontinuation and restriction of non-essential screening in Washington State during the peak pandemic period. In 2021 when mammography screening became more available, the trend reversed to more stage 0 and I, mammography detected breast cancer diagnosed but number of cases were still below 2019 pre-pandemic levels. Neoadjuvant therapy increased during peak-pandemic Q2-Q4 2020 when pandemic restrictions limited care access causing surgery delays and alternative therapies were made available. The most common COVID-19 related alternative treatment observed was pre-operative hormone therapy given to lower stage hormone receptor positive cases due to restrictions on non-urgent surgery. Other treatments affected or delayed were chemotherapy, radiation therapy and treatment planning.

Higher stage II-IV breast cancer diagnosis did not change significantly during the pandemic with a relative proportional increase due to declining number of mammography detected cases stage 0 and I in the peak pandemic time Q2-Q4 2020. In 2021, the relative proportion of stage II-IV BC declined when mammography screening was available and number of stage 0 and I breast cancers increased. In a comparison of only stage II-IV breast cancers, number and proportion of stage II-IV BC did not change significantly over the 3 time periods (data not presented).

Some preliminary studies of the effects of COVID-19 pandemic restrictions on health care access and/or screening for breast cancer have been reported. Decreased mammography screening occurred during the pandemic onset in 2020 [14‐17]. Two studies reported higher proportion of higher stage or symptomatic disease in the 2020 shelter-in-place time period [18, 19]. One study reported increased neoadjuvant therapy [20].

Decline in diagnosed breast cancer case volumes was observed in the US in association with the COVID-19 pandemic in 2020 [21]. In Turkey, a study of a single institution found the volume of breast surgery declined in 2020 [22]. Velazquez et al. tracked screening mammograms at their institution during the 2019–2020 time period and observed a sharp decline in screening mammograms beginning in March 2020 with an increasing number of missed appointments and a slow increase later in 2020 but the number of screening mammograms remained below 2019 baseline levels [14]. In a large study of mammography utilization through 2021, a 40% decrease in mammography was observed nationally in 2020, with rates remaining below normal into 2021, but screening and diagnostic mammography were not differentiated [23]. Similarly, Doan et al. in a study of Medicare enrollee utilization of breast cancer screening found profound decreases in screening starting in March 2020 with continued monthly rate decreases related to increases in national COVID-19 infection rates [24]. Decreases in Medicare cancer screening observed did not resolve after initial pandemic surges.

In the Flanders region of Belgium, breast cancer screening invitation coverage dropped 10% in 2020 but the backlog of invitations was largely resolved in 2021 [25]. The authors concluded a minimal influence on willingness to screen existed but coverage of screening may have been impacted. Duffy et al. assessed the impact of the temporary COVID-19-related cessation of population screening on breast cancer deaths in England. They projected between 148 and 687 additional breast cancer deaths could occur depending on how quickly delays were caught up [26].

In 2020, Guth et al. observed fewer mammography detected breast cancers, more breast cancer detected by self-exam which were palpable on presentation, and fewer DCIS cases between 4/1/2020 and 3/31/2021 [27]. During the time when only essential surgery was allowed, more patients were treated with neoadjuvant chemotherapy and neoadjuvant hormonal therapy. They did not observe an increase in higher stage III and IV breast cancer and observed a decrease in radiation therapy. Zhou et al. observed a significantly lower number of stage I BC and higher amount of stage IV in 2020 after the start of the pandemic [28]. Trojanowski et al. observed a stage shift in 2021 with stage II BC more frequent than stage I and a significant increase in stage III [29].

On April 1, 2020, The American Society of Breast Surgeons issued a guide for use of neoadjuvant endocrine therapy related to surgical delays during the pandemic to assist with triaging breast cancer patients [30]. In 2020, authors Marti et al. and Thompson et al. discussed priorities and options for estrogen receptor positive breast cancer management due to surgical delays [31, 32]. Tonneson et al. observed a 10% increase in neoadjuvant endocrine therapy during the COVID-19 restricted access to care [33]. Habbous et al. observed a 20% increase in neoadjuvant systemic therapy during COVID-19-related care access, both hormonal and chemotherapy [34].

In our cohort, the percentage mammography detected breast cancer cases rebounded to above 2019 levels with a shift to earlier stage cancers very quickly in 2021, although actual number of cases remained below 2019 levels. These findings indicate the impact from delayed screening may have had minimal effect on compliant screeners who quickly made up their missed appointments. The continued lower than usual case volume of both screening mammograms and diagnosed BC cases overall indicate a missing portion of the potential screened population exists.

The 24% decrease in early stage 0 and I breast cancer in peak-pandemic time Q2-Q4 2020 was related to stoppage of mammography screening and limited access in 2020 followed by catch up screening in 2021 with early stage 0 and I breast cancer 34% higher than pre-pandemic year 2019/Q1 2020. However, mammography screening in the United States relies on opportunistic or invitational mammography screening depending on where one receives care, whether the care delivery organization has a reminder system, and type of insurance if one has health insurance. Some guidelines are based on United States Preventive Services Task Force, the American Cancer Society and other organizations recommendations unlike countries with singular organized screening programs [35‐38]. Our institutional radiology department uses American College of Radiology (ACR) guidelines which recommend annual screening starting at age 40 [39]. Screening is therefore predicated on self-initiation of screening mammography or prompting by a care provider or health care system. The continued lower volume of diagnosed breast cancer cases and screening mammograms into 2021 is concerning.