Diagnoses of six common cancer types dropped in the early months of the coronavirus pandemic, as routine screenings were postponed by health systems and patients avoided going to the doctor for fear of contracting the virus, a new study suggests.

The study, an analysis of Quest Diagnostics data published online in the Journal of the American Medical Association Network Open, found that new diagnoses of breast, colorectal, lung, pancreatic, gastric and esophageal cancers were down 46% between March 1 and April 18 compared with the average diagnosis rates from previous years.

New findings offer grim evidence of the consequences of delayed care: A rise in undetected cancers that, when diagnosed, may be more advanced and difficult to treat.

“No one is saying coronavirus prevents cancer. It just prevents getting care in a timely fashion,” said David S. Weinberg, a gastroenterologist and chair of Fox Chase Cancer Center’s department of medicine.

“As much as we focused on cancer, it applies to almost everything in health care. … To the extent we are all deferring health services, there’s a certain amount of risk that some of these conditions will advance and do more damage to our bodies than they would have otherwise,” said Harvey Kaufman, the study’s lead author and medical director at Quest Diagnostics.

Kaufman and his co-authors analyzed data from nearly 278,800 Quest Diagnostic patients between January 2018 and April 2020. They compared how often patients referred for testing had a new cancer diagnosis during a baseline period in 2018 and 2019 vs. during the early months of 2020.

The data do not offer insight into whether a delay in diagnosis necessarily resulted in worse outcomes. Still, the trend is one that worries cancer doctors. “We have certainly been worried that cancers that could have been conceivably prevented — and there are some cancers you can pretty easily prevent — will not necessarily be intercepted at a time they can be prevented,” Weinberg said.