Drug resistance is a problem when treating infections and cancer. Sometimes the solution is to contain instead of destroy infectious organisms and cancer cells.

When you have a serious infection or cancer, it’s natural to want it destroyed as quickly as possible.

Aggressive treatment, however, may not always be for the best.

Even when it initially works, antimicrobial medicines and chemotherapy can suddenly become ineffective.

Research suggests that in some cases where drug resistance can lead to treatment failure, containing an infection or a tumor at a tolerable level can improve patient outcomes.

In other cases, the traditional approach of elimination might be better.

The problem is in determining which option is likely to be successful.

Researchers at Penn State University and the University of Michigan developed a mathematical analysis to identify factors that can help in that determination.

Their paper was published in PLOS Biology.

Read more: Using ‘brute force’ to beat antibiotic resistance »

The researchers compared containment to eradication.

Their goal was to lengthen the amount of time until drug resistance developed.

You can have a certain amount of infection or tumor without being sick. It’s called an “acceptable burden.”

In their paper, the researchers wrote that the concept of an acceptable burden is their core premise.

They acknowledge this is likely to make clinicians uneasy.

They recognize situations, such as bacterial meningitis, where there’s no acceptable burden.

Identifying the maximum acceptable burden is a complex problem.

To determine if an infection or tumor would develop drug resistance, the researchers looked at two key things.

One was the rate at which cells become resistant.

The other was “competitive suppression.” In cells that are responding to treatment, there’s a competition for resources. More competition can slow the spread of resistant cells. However, there’s a risk that the sensitive cells will also develop resistance.

The infection or tumor was considered to be managed if it was maintained at or below the level of acceptable burden. The treatment was considered a failure if a pathogen rose above that level.

The researchers found that containment can sometimes double a patient’s survival time.

“There are situations where we can be relatively sure that treatment will completely eliminate the infection or tumor, so aggressive treatment is the obvious choice,” Elsa Hansen, a research associate at Penn State, and an author of the paper, said in a press release.

“On the opposite end of the spectrum, there are low-level situations like urinary tract or ear infections where a doctor may decide not to treat at all,” she continued.

“The majority of cases, however, are somewhere in between,” she added, “and require hard choices that balance the damage caused by the infection or tumor and the risk of mutation with the damage caused by the treatment itself and the risk of developing uncontrollable resistance. Our analysis provides guidance for making these decisions from a standpoint of maximizing patient well-being.”

How long treatment can continue before failing depends on the disease and the person. There won’t be a single solution that applies to everyone.

The researchers’ goal is to provide a basic outline so doctors and patients can make informed choices.

Read more: Treat cancer like an infectious disease, researchers say »

There’s no doubt that antimicrobial drugs have saved a lot of lives.

But the more we use them, the more resistant infectious organisms become.

According to the U.S. Centers for Disease Control and Prevention (CDC), 2 million people are infected with antibiotic-resistant organisms every year, causing 23,000 deaths.

“Drug resistance is a major problem in cancer and infection,” said Dr. Timothy Byun, medical oncologist at the Center for Cancer Prevention and Treatment at St. Joseph Hospital in California.

“Antimicrobial drug resistance is a major public health crisis. According to WHO [World Health Organization], it is a major global health threat,” Byun wrote in an email to Healthline. “Many cancers are incurable because chemotherapy may not completely eradicate cancer cells.”

Antibiotic resistance is a consequence of evolution, said Dr. Santosh Kesari. “We’ve had various stages of health crises over the years. Flesh-eating bacteria, for example, is very resistant.”

Kesari is a board-certified neurologist and neuro-oncologist, and current chair of the Department of Translational Neuro-Oncology and Neurotherapeutics at the John Wayne Cancer Institute at Providence Saint John’s Health Center in California.

In an interview with Healthline, Kesari said that antibiotic resistance is obvious right away when a patient doesn’t respond. Sometimes that’s the case with chemotherapy as well.

“But here we’re talking about getting an initial response to treatment. Then resistance develops. This can take weeks or months,” he said.

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There are several reasons cancer cells become resistant to treatment.

Cells mutate.

Sometimes the cancer is heterogeneous to begin with.

You might wipe out one type, but a different type of cell starts to grow. It takes over and creates a resistant tumor.

Kesari explained that sometimes killing a tumor with drugs can actually promote regrowth. It may be better to just keep it stable.

“The question is, can we do better in preventing resistance by understanding the tumor better in the beginning? Maybe giving multiple drugs rather than one could resolve this at the start,” said Kesari.

“What you’re doing in the short term may, in the long run, be bad because of the emergence of resistance. Rather than aggressive treatment up front, containment might have a better long-term effect,” he continued.

“For infection, we use multiple antibiotics right away. This is to prevent resistance from happening. In cancer, combination therapy rather than a single agent is more complicated. It takes time to study each drug and combine them safely.”

“It’s a significant problem,” said Kesari.

“We need to think about this more carefully. This paper describes an approach of containment rather than elimination. That’s interesting. But it needs to be proven in a clinical setting that this concept works using drugs that don’t necessarily kill 100 percent of cells, but contain the tumor, and with the same outcome. That includes different cancer types and types of infection. That’s what ultimately needs to be proven,” said Kesari.