Breast cancer diagnoses plummeted during first year of pandemic, finds study

Several studies have described the distinct ways the COVID-19 pandemic adversely impacted cancer care, but less is known about the specific ways the pandemic disrupted breast cancer, the most common non-skin cancer diagnosed in women.

Research evaluating data from the American College of Surgeons (ACS) National Cancer Database (NCDB) shows that breast cancer was not immune to pandemic-related stressors, with researchers finding that there was a 15-20% decrease in newly diagnosed breast cancer cases reported to Commission on Cancer (CoC) sites in 2020 compared to 2019.

The results, published in Cancer Medicine, describe one of the first large-scale studies to examine the rates of breast cancer diagnoses during the first year of the COVID-19 pandemic; the results also have implications for how physicians and policymakers can address issues that may arise due to the diagnostic delays that occurred during the pandemic, the authors said.

"I think what's notable is that the drop in breast cancer diagnoses was consistent across all regions of the country, all age groups, and all different races. It was not an isolated event," said Katharine Yao, MD, FACS, senior author of the study and Chair of the ACS National Accreditation Program for Breast Centers (NAPBC).

"The results of this study tell us that during the pandemic, patients weren't coming in for evaluation of breast findings and for screening mammograms, and that's very likely why we saw fewer cancers diagnosed in 2020."

The NCDB, a clinical oncology database jointly operated by the CoC and American Cancer Society, captures approximately 74% of all newly diagnosed cancers in the U.S. Researchers also used U.S. Census data to determine the number of women and men in the general population over the study period. In total, they analyzed data from 1,499,806 patients with stage 0-IV breast cancer across 1,328 CoC sites.

Other key study findings

• While the researchers found that the decrease was seen for both women and men and across nearly all patient age groups, races, and ethnicities, the decrease was most dramatic for females aged 50–59 years (16.1% decrease) and 60–69 years (17.4% decrease). The authors noted two possible reasons for why these age groups were most vulnerable during the pandemic: Patients older than 50, including the 60-69 age group, are more likely to be affected by breast cancer compared to younger age groups; additionally, older women are more likely to be screened with mammograms and therefore may have been more susceptible to screening delays that occurred during the pandemic.
• Hispanic women experienced the sharpest decline from 2019 to 2020 among all races and ethnicities, with an 18.4% decrease. This is consistent with other disparities that Hispanic individuals faced during the pandemic, as research has shown that Hispanic people had higher rates of COVID-19 infection as well as mortality related to COVID-19, the authors noted.
• Women receiving care in the Western U.S. and mid-Atlantic regions experienced the largest declines in 2020, which may reflect the large COVID-19 outbreaks in New York and other mid-Atlantic states, the state of Washington and California during the study period.
• Though representing less than 1% of breast cancer cases in 2020, the number of breast cancer diagnoses in men declined sharply—by 20%—in 2020 compared to 2019.

The reasons behind these decreases are likely multifactorial, reflecting screening restrictions that occurred in the early months of the pandemic when stay-at-home orders were implemented in several states, as well as the fear of exposure that may have caused some patients to delay care for breast cancer symptoms, the authors noted. Other factors, such as unemployment, may have kept some people away from receiving care even after pandemic restrictions were lifted.

Future implications for breast cancer care

"There are so many unknowns. For example, in the next 5 to 10 years, are we going to see worse survival rates or higher recurrence rates because patients weren't getting their screening mammograms or coming in to be evaluated?" said Dr. Yao, a breast surgeon who also serves as vice chair of research within the department of surgery at NorthShore University in Evanston, Illinois. "We just don't know."

Future research is needed to determine when case numbers will return to baseline levels and the consequences of delayed diagnosis and care, particularly among patients and geographic areas that were most severely affected by the pandemic.

"I think it's important to have this data as a baseline so that we can look at future data and compare it to what happened in the past," Dr. Yao said. "To know that, we need to know where we started. And that's what this study really presents—a starting point. Looking at years after 2020, we'll gain a more complete picture and can start to see where the trends lie."