Resistance to antibiotics risks blunting power of chemotherapy against cancer

Cancer patients are vulnerable to infections and at risk from rising antimicrobial resistance

Researchers into antibiotic resistance at work at the Eliava Institute of Bacteriophages in Tbilisi, Georgia. AFP

Chemotherapy drugs could be rendered useless in the fight against cancer as the effectiveness of antibiotics continues to decline, leaving patients even more vulnerable to infection and early death, doctors have warned.

The World Health Organisation has declared antimicrobial resistance (AMR) as one of the most significant global threats to public health, requiring urgent action to prevent existing antibiotics becoming useless against even the most common infections.

Cancer patients are particularly vulnerable, as intense treatments such as chemotherapy and radiation also destroy infection-battling white blood cells, the invisible warriors that keep bacteria and viruses at bay.

Speaking at the World Cancer Congress in Geneva, experts said around half of cancer deaths were related to some kind of infection, and that figure was likely to rise as existing drugs become ineffective.

“Over recent years, the importance of antimicrobial-resistant infections has been overlooked,” said Prof Jeff Dunn, president of Union for International Cancer Control (UICC).

“But there's been some momentum building, with a greater awareness, some understanding and there's been some collateral developed.

Prof Jeff Dunn, president of the Union for International Cancer Control, speaking at the World Cancer Congress in Geneva. Photo: UICC

“And of course, the timing is important because there is a growing rate of AMR threat in cancer control. If you think about cancer itself, the second leading cause of death is infection.”

According to UICC figures, almost 27 per cent of infections in patients with blood cancer undergoing chemotherapy are resistant to antibiotics, leading to more complications, longer hospital stays and higher treatment costs.

Antimicrobial drugs work against different microorganisms; with antibacterials or antibiotics taking on bacteria, while antivirals fight viruses, and anti-fungals work against fungi.

As these microorganisms change and mutate over time, they no longer respond to existing drugs, making infections harder to overcome. The effects are wider spread of disease, more severe illness and deaths.

Drug misuse

A rise in drug-resistant pathogens has been triggered largely by misuse and overprescription of antimicrobial drugs, as well as dirty water and poor sanitation that promotes the spread of disease-carrying microbes.

“It would be nice if we had a bacteria that's sensitive to many different antimicrobials,” said Dr Scott Howard, from the University of Tennessee Health Science Centre. “But sometimes there's other bacteria that are resistant to some things and sensitive to others.

“So if you happen to be in a place where you have the sensitive things, you can use it and cure your patient, but there's some bacteria that are so resistant there can be nothing we have currently that will treat them in any country.”

The challenge for science now is how to make new antimicrobials to overcome resistant infections, that are effective, affordable and accessible for all.

During the conference, Dr Howard referred to a case of AMR in a baby in Honduras who had a severe infection.

A course of tetracycline, a common antibiotic often used to treat malaria, cholera and a range of respiratory infections, would usually have been prescribed.

The drug costs around $100 for a 10-day course, but was unavailable in the country at the time, forcing medics to search for other suitable treatments.

“The patient had a moderately resistant organism, but it was sensitive to something that was widely used in the world, just not in Honduras,” said Dr Howard.

“In these cases we have to really think not just about the resistance pattern but the access pattern. It is very important to think about both resistance, overcoming resistance and overcoming lack of access.

“The newest antimicrobial that overcomes resistance can't be used in everybody because then you get resistance to that. Our goal is to get uniform efficacy and universal access, they both have to go together.”

Pandemic

It is thought the misuse of antibiotics soared during the Covid-19 pandemic, and may have accelerated antimicrobial resistance. When antibiotics are used incorrectly to treat viral infections, rather than bacteria, they become ineffective and increase the threat of resistance.

Although just 8 per cent of patients hospitalised with Covid-19 also had a bacterial infection requiring antibiotics, almost 75 per cent of those patients around the world were given the drugs as a precaution, the World Health Organisation reported.

The biggest misuse of the drugs during the pandemic was seen in the Eastern Mediterranean and African regions, where 83 per cent of patients were given antibiotics, many unnecessarily.

Antonella Cardone, director of Cancer Patients Europe, said vulnerable people receiving intense treatments were likely to become more exposed in the future.

“When dealing with cancer, we know patients are three times more likely to develop an infection than non-cancer patients,” she said. “This gives us a sense of how important it is to associate and trace AMR together with the diagnosis of cancer.

“The other striking data is that 50 per cent of cancer deaths are associated one way or the other with an infection. The problem is that the cancer death associated with an infection is often registered in the hospital as a death because of cancer, not because of the infection – this is undermining the dramatic impact of AMR on cancer patients.

“In a recent UK survey, 46 per cent of oncologists were concerned that soon chemotherapy will not be viable any more because of AMR. We cannot ignore the importance of continuing research and raising awareness, not only among cancer patients, but also among the general population and oncologists.”