Antibiotics date back nearly 100 years, to the discovery of penicillin in 1928 by Alexander Fleming. With their ability to destroy or slow the growth of bacteria, antibiotics’ arrival launched the so-called antibiotic era—and revolutionized the treatment of infectious diseases around the world.
Antibiotics may be especially game-changing for cancer patients whose immune systems are weakened both by the disease itself and by the treatments designed to fight it, like surgery, radiation therapy and chemotherapy.
Each year, tens of thousands of cancer patients are hospitalized after developing an infection. Doctors depend on being able to use antibiotics to treat those infections—or to prevent one from developing during treatment. Patient outcomes may be impacted when antibiotics don’t work—which most often occurs when the bacteria they’re designed to kill has developed a response called antibiotic resistance.
In his Nobel Prize acceptance speech in 1945, Fleming warned the scientific community about the risk of antibiotic resistance. Today, organizations like the World Health Organization and the U.S. Centers for Disease Control and Prevention recognize it as a global threat, attributing its rise, in large part, to the misuse and overuse of antibiotics—linked to patients taking them when they aren’t needed or not taking them as directed.
“The more bacteria see antibiotics, the more likely they are to develop resistance to them,” says Suji Mathew, MD, Infectious Disease Physician and Chief of Medicine at City of Hope® Cancer Center Atlanta. “And that means more chances of worse outcomes for patients because the infection isn’t being treated adequately.”
Antibiotics are commonly prescribed in the fall and winter months, when cold and flu illnesses are widespread. But it’s critical to use them only when they’re needed and only as directed—especially for people with cancer.
In this article, we’ll explore:
- Antibiotics and cancer: When are they helpful?
- When are antibiotics harmful for cancer patients?
- Can antibiotics increase cancer risk or worsen cancer outcomes?
If you’ve been diagnosed with cancer and are interested in a second opinion on your diagnosis and treatment plan, call us or chat online with a member of our team.
Antibiotics and cancer: When are they helpful?
Antibiotics aren’t just helpful to cancer patients. In many cases, they’re vital.
“If someone with cancer develops an infection that is bacterial, then absolutely, antibiotics have a place,” Dr. Mathew says. “They’ll treat the infection. And that’s why we want to catch it early, especially in our immunosuppressed patients.”
Sometimes, antibiotics are also given to cancer patients to prevent infections. “Their immunity is low because of the chemotherapy they need,” Dr. Mathew says, “so they’re at a higher risk of infection.”
Indeed, a common side effect of chemotherapy is neutropenia, or a reduced white blood cell count. White blood cells help the body fight off infections and viruses.
When are antibiotics harmful for cancer patients?
Antibiotics aren’t effective against infections that are viral in nature, or that are caused by other non-bacterial sources, like a fungus. That’s why it’s important that antibiotics are given as the “right drug for the right bug at the right dose and for the right duration,” Dr. Mathew says, because otherwise, resistance can develop.
One way antibiotic resistance develops is when people don’t take the medicine as prescribed. By stopping it too soon, before completing the full dose, a partially treated infection can end up mutating and emerging as a tougher “superbug” the next time the immune system is suppressed—say, when the patient gets the next dose of chemotherapy.
“Undertreating a bacterial infection is bad because you can end up generating a real mastermind criminal in the bug,” Dr. Mathew says. “Overtreating it can cause a whole host of complications, too.”
A common concern for patients on antibiotics is developing clostridioides difficile or C. diff, a bacterium that causes diarrhea and colitis, or inflammation of the colon. Most cases of C. diff develop after taking an antibiotic, or not long after finishing a round of antibiotics. One bout of C. diff can make you more prone to developing it again.
Can antibiotics increase cancer risk or worsen cancer outcomes?
If an antibiotic doesn’t work against a bacterial infection, the patient may end up being hospitalized, disrupting the treatment schedule and leading to a potentially worse outcome. But that isn’t the only danger.
Although you should never hesitate to take an antibiotic when it’s prescribed by a doctor, taking antibiotics when you don’t need them may prevent certain cancer therapies from working well. That’s because they can interfere with the gut microbiome, which normally helps people with certain types of cancer respond better to treatments like immunotherapy.
The gut microbiome is the ecosystem of microorganisms in the gastrointestinal tract that usually works in harmony to help maintain digestive function. When the gut microbiome is thrown out of balance, though, health complications like inflammatory bowel diseases, diabetes, obesity or cancer may develop.
Recently, studies have suggested that antibiotic use may change the gut microbiome’s makeup by killing the good bacteria along with the bad. This disrupted environment can lead to infections like C. diff—and make immunotherapy drugs like immune checkpoint inhibitors work less effectively because the drugs interfere with the interaction between the immune system and the microbiome.
Antibiotics may also inhibit immune response and promote inflammation, which may impact cancer treatment, especially when taken during chemotherapy.
That’s why it’s a good idea to take probiotics to restore the gut flora in the microbiome, especially when you’re on antibiotics, Dr. Mathew says. She adds that studies are emerging that link past use of antibiotics to a higher risk of developing cancer in the colon. “While more research is needed in this area—this may be an association or a coincidence, we’re not sure yet—we know we need the good bacteria in our gut,” she says, “and by being mindful of how we use antibiotics, we can benefit our health overall.”
The bottom line?
“These bugs are getting harder and harder to treat,” Dr. Mathew says. “People should understand the pitfalls of prescribing antibiotics unnecessarily. Infections can be caused by bacteria, viruses, fungi, protozoa, all sorts of things. Not all infections are caused by bacteria, and not all infections need antibiotics.”
If you’ve been diagnosed with cancer and are interested in a second opinion on your diagnosis and treatment plan, call us or chat online with a member of our team.
