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Originally published October 22, 2025
Last updated October 22, 2025
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Confirmation bias exists everywhere, even within cancer treatment. It can be difficult to know when to change the course of an initial treatment plan.
In oncology, the two most important factors to look at to determine whether you should alter treatment are effectiveness and tolerability, says Christopher Foss, MD, a hematologist-oncologist with USC Norris Comprehensive Cancer Center, part of Keck Medicine of USC.
“Generally speaking, if a treatment is effective and tolerable, you should continue,” he says. “But if you’re not accomplishing one or both of those things, that’s when you should start to think about the next line of treatment and have a discussion with the patient and their family.”
While effectiveness and tolerability are the main factors to consider, you should also keep the patient’s preferences top of mind, Foss says. You want the treatment plan to align with the patient’s and family’s goals regarding how aggressive they want to be and what they want their quality of life to look like, he adds.
Cancer type and stage can give a general sense of the course of treatment for a patient, but there’s always a possibility you will need to switch strategies, Foss says. “We have clinical trial data to draw our expectations on that indicate the probability of needing another form of treatment, and in some circumstances we can expect a ‘cure’ or a long-term, durable response,” he says. “Other times, we do know that at some point the cancer will become resistant to the treatment, and then we’ll have to switch to another line of treatment.”
“When we talk about functional performance status of the patient, it’s really just a fancy way of saying how healthy the patient is, how strong they are and what functions they can normally perform,” Foss says. “A 25-year-old with no medical history is going to have a much higher functional performance status than an 85-year-old on 10 different medications, so there’s a difference in how well we would expect them to tolerate treatment.”
It can be very difficult, however, to measure functional performance status across varying patient groups, he adds. “There are metrics, tools and scores that can be calculated, but at the end of the day, it’s not an exact science,” he says. “But we try to tailor the intensity of the treatment regimen accordingly to the health of the patient.”
“I usually start off with the best treatment that I think is going to help the patient at the beginning, but oftentimes I have to make adjustments based on assessments of the patient via bloodwork, physical exams and patient self-assessments on how they are feeling.”
Chemotherapy depresses the immune system, so infections are always a risk, Foss says.
“We’re always very cautious about infections,” he explains. “And if a patient is experiencing signs of infection, such as high fever, we generally stop or alter our course of treatment to focus on getting rid of the infection, potentially even sending them into the hospital for antibiotics.”
Every patient is different, and each patient has their own preference regarding tolerability and aggression for pursuing treatment. Some patients prefer a more tolerable treatment, whereas others want to pursue the most aggressive treatment possible, regardless of whether they are tolerating it well or not.
“The best thing to do in this situation is to talk to your patient to determine what they want,” Foss says.
Next-Generation-Sequencing (NGS) is a new form of genetic testing that can help guide treatment, Foss says.
“Every cancer is different, and one of the ways we differentiate between different cancer types is genetic testing where we are looking at specific markers and sequences that differentiate types of cancer,” he says. “This is sometimes a useful tool for deciding which treatment will be most effective for a particular type of cancer.”
Sometimes a different type of genetic marker can qualify a patient for a more targeted type of cancer treatment, Foss explains.
“At the end of the day, you want to do what’s best for your patients,” Foss says. “So, if that means referring to a different center or provider that can offer more advanced care or a different line of treatment, then you should consider doing that.”
One big indicator can be if there is a clinical trial with an experimental treatment that might provide a promising outcome for your patient, Foss says.
“In oncology, if a patient has tried all standard therapies and there’s really nothing else left to offer from that standpoint, then that would be a scenario where it’s a good time to switch treatments to another provider or center that might have something different to offer,” Foss says. “The best thing to do in this situation is to stay updated on the medical literature and know what’s available in your area so that you can offer the best treatments possible to your patients.”
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