Is there ever a good time to worry about being screened or treated for cancer? Alas, not. But thanks to the covid-19 pandemic, this is an especially troubling one.

Last month, Norman E. Sharpless, director of the National Cancer Institute, issued a warning about the dangers of the pandemic to past, present and future cancer patients. The bottom line: expect a great many more deaths.

“Fear of contracting coronavirus in health care settings has dissuaded people from screening, diagnosis, and treatment,” Sharpless wrote in Science. “The consequences for cancer outcomes . . . would be substantial.”

How substantial? Sharpless pointed to an NCI model examining colon and breast cancer that forecasts an additional 10,000 deaths in the United States from those two cancers alone over the next 10 years because of the pandemic. Sharpless emphasized that this is a “conservative” number; it doesn’t take into account other cancer types, the impact of upstaging (being staged later due to delays in being seen, probably with more extensive disease), and assumes only a moderate disruption in care that will be completely resolved after six months (which is to say it is not taking into account a “second wave” of the pandemic that would probably result in even more deaths than in the forecast).

This is not crystal-ball forecasting or medical hand-wringing. Statistics from Epic, the electronic health records vendor, show cancer screenings going off a cliff at the beginning of the pandemic, down between 86 and 94 percent across the United States — a combination of hospitals deferring nonurgent procedures and patients fearing contracting the virus at a health-care facility. The number of Americans getting breast cancer screenings (mammograms) each week dropped from 9,000 or so to fewer than 600. Colon cancer screenings went from 3,000 a week to 400. Fewer screenings mean fewer diagnoses, and fewer diagnoses mean fewer opportunities for early treatment.

Lawrence Shulman, professor of medicine and deputy director for clinical services at the Abramson Cancer Center at the University of Pennsylvania, says the number of new cancer diagnoses over the past four months has fallen by more than 50 percent in some geographic areas. But, he emphasized, that does not mean fewer people actually have cancer.

Instead, Shulman says, “that must mean there are a lot of patients out there who have cancer but are not undergoing diagnosis and entry into the cancer care system.”

Hospitals nationwide have reported fewer visits for heart attacks and strokes, as well, which many experts attribute to a fear of contracting covid-19 at emergency rooms. One study reported that patient visits for heart attack fell by a third during the pandemic compared with the same period the year before. For stroke, the decline was more than half for the same year over year comparison.

Several people I know have postponed inpatient cancer treatment, usually with the agreement of their doctors. While others have put off breast and colon screenings (often making decisions unilaterally) in the past several months, and they continue to do so.

Jeanne Ketterer, 65 and a writer who lives in Chapel Hill, N.C., echoed many others when she told me, “I delayed my colonoscopy . . . because I [didn’t] feel secure enough in how well I’ll be protected against the virus.”

Putting fears aside, numerous experts say the risk of contracting covid-19 is greatly lessened in a hospital or clinic that follows the Centers for Disease Control and Prevention guidelines,

This is personal to me, too, as I’m due for a colonoscopy this month.

This is not a routine screening — it’s a follow-up after several suspicious polyps were discovered (and removed) three years ago. I’m concerned about covid-19 infection, especially since I’m considered high risk because of my age, and I live in a state with surging numbers of covid cases and hospitalizations. And, like all too many other Americans, there’s part of me that’s happy to use any excuse to delay the procedure, especially the dreaded “prep.”

Shulman says that even after hospital clinics started opening up again, “they’d call patients who had postponed screenings, telling them, ‘You should feel comfortable coming in . . . ’ [And many] patients said, ‘Listen, I’m still too nervous about the risk of infection. And I just don’t want to come in.” I understand.

Who gets screened or treated? Who should wait? How much does covid prevalence in a community matter? These are thorny questions, and at the outset of the pandemic many oncology departments and hospitals created cross-institutional guidelines that largely triaged cancer patients into three buckets or tiers: treat now; delay a little (six to eight weeks); delay a lot.

For instance, Brant Inman, co-director of Duke Prostate and Urologic Cancer Center, drafted a set of guidelines for urologic oncologists and surgeons that was quickly adopted by his colleagues at Duke and other institutions. The guidelines created a labor-intensive process, with, for example, Inman and his Duke colleagues discussing 20 to 40 cancer cases a week. When lacking consensus about whether to delay or go ahead on a case, Inman says, “We err[ed] on the side of higher prioritization, i.e. on the patient’s side.”

For an oncologist, sooner is better when it comes to treatment. But that may not always be the case when trying to balance covid-19 risk with delays in cancer treatment.

A team of oncologists and data scientists from the University of Michigan Rogel Cancer Center and the University of Michigan School of Public Health had the same concern.

In response, they created the OncCOVID app, which draws on national cancer data sets, factoring in a patient’s individual characteristics, but equally important the prevalence of covid-19 in someone’s local community, to assess an individual’s risk in terms of when to start treatment.

The app (not available directly to patients) allows oncologists to enter more than 45 characteristics about an individual — age, location, cancer type and stage, treatment plan, underlying medical conditions, and any proposed length of delay in treatment. Daniel Spratt, associate professor and vice chair of research in the department of radiation oncology at Michigan Medicine and a senior researcher on the project, told me this personalized risk assessment sometimes ran counter to the three-bucket approach.

Other institutions, he claims, “have largely adopted a crude three-tier system of how to personalize who and when to treat cancer. We went from viewing cancer as a complex and heterogeneous entity of over 10,000 types, to viewing it as three large buckets.” Spratt says they found, “over 25 percent of patients classified as tier 2 [delay six to eight weeks] should likely be delayed longer than many tier 3 patients [delay more than eight weeks], and similarly over 30 percent of tier 2 patients should be tier 1 and be prioritized for immediate treatment.”

Should those diagnosed with cancer seek treatment in places where covid infection is lower? “It depends on local prevalence of the virus and what measures are in place to restrict the spread of the virus,” Spratt says. “If during the peak of the pandemic or a second wave, like what is happening in Houston, it very well may be safer to receive immunosuppressive chemotherapy or surgery in a county with substantially lower prevalence of covid.”

But he also points to the quality of the hospital and its oncology expertise, not to mention that a patient might not have a support system in a distant city.

As for me, does this mean I should travel out of my state — where covid-19 cases have been rising — for my colonoscopy because of my concern about getting the disease during the procedure? Probably not, as long as the clinic follows CDC guidance, which I learned it does when I called to ask. I’ve now scheduled the procedure because I sure don’t want to become one of those additional colon cancer deaths Sharpless warned us all about.