Keytruda Plus Chemo Shows Superior Response to Chemo Alone in GI Cancer

The addition of immunotherapy to chemotherapy trended toward improved GI cancer outcomes, though not all outcomes had a statistically significant difference.

The treatment combination of Keytruda (pembrolizumab) and chemotherapy trended toward superior results when compared with placebo plus chemotherapy in patients with gastric or gastro-esophageal adenocarcinoma, according to a recent study.

A study published in The Lancet Oncology evaluated 804 patients with locally advanced, resectable (removable via surgery) gastric or gastro-esophageal adenocarcinoma in the KEYNOTE-585 trial. Patients were randomly assigned between two groups: 402 patients in the Keytruda-chemotherapy group and 402 patients in the placebo-chemotherapy group.

Keytruda is a type of monoclonal antibody and immune checkpoint inhibitor, which binds to a protein called PD-1 to help immune cells destroy cancer cells, as defined by the National Cancer Institute.

“Immunotherapies are immune checkpoint inhibitors such as (Keytruda) or (Opdivo [nivolumab]) —another common medication in the same category — that work by stimulating the patient’s own immune system to attack the cancer cells,” Dr. Samuel Cytryn, a GI medical oncologist at Memorial Sloan Kettering Cancer Center, said during an interview with CURE®. “This is different from chemotherapies, which work by indiscriminately killing rapidly dividing cells, which is why they work against cancer cells.”

The researchers from the study determined that the median event-free survival (time after treatment when cancer does not worsen or come back) was longer when patients received Keytruda plus chemotherapy, versus placebo plus chemotherapy. However, the researchers noted that the difference between the two treatment combinations was not statistically different, meaning that the researchers could not say, for sure that one regimen was superior than the other.

Still, Cytryn recognized how a combination of an immune checkpoint inhibitor and chemotherapy could be a beneficial treatment for this patient population.

He noted that in other large phase 3 trials, “the addition of immunotherapy to chemotherapy improved survival, meaning patients lived longer compared to just chemotherapy alone.”

In terms of median overall survival (OS; length of time from diagnosis or the start of treatment when a patient is still alive), the patients in the Keytruda group had a median OS of 60.7 months, whereas patients in the placebo group had a median OS of 58.0 months, the study’s researchers found. However, these findings also were not statistically significant.

The researchers also determined that 312 of 399 patients (78%) experienced grade 3 or worse side effects of any cause in the Keytruda group and 297 of 400 patients (74%) in the placebo group. Grade 3 side effects are considered serious and may require medical intervention. The most common side effects that patients experienced included nausea, anemia and decreased appetite.

According to the study, there were 102 serious treatment-related side effects in the Keytruda group, with 97 in the placebo group.

“What we do know and what has been continued across a number of different studies looking at immunotherapy plus chemotherapy is that this is a very safe combination,” Cytryn said. “Patients who were in the (Keytruda) and chemotherapy arm did not experience any unexpected or untoward toxicities that would limit giving these drugs in combination.”

Regarding the Keytruda plus chemotherapy combination, Cytryn also noted that the function of both chemotherapy and immunotherapy in the body should be considered.

“As I mentioned, chemotherapy indiscriminately kills rapidly dividing cells, which is why a lot of the toxicities and side effects that we think about with chemotherapy —especially with this intense regimen — lead to those sorts of side effects, meaning sometimes loss of hair, (it) can affect your blood counts (and) can cause a lot of GI distress,” he said.

“The side effects of immunotherapy follow the way the drug works, it stimulates your body’s immune system to attack the cancer,” Cytryn added. “If (a patient’s) immune system becomes overzealous, then (they) can develop side effects that are somewhat similar to autoimmune diseases because the immune system is attacking normal cells. It can be anywhere from the spectrum a very mild and very tolerable just a little bit of a skin rash that you just put some creams on, versus in rare circumstances, a little bit more severe, where we need to give patients immunosuppressive medications such as steroids to sort of calm down the immune system.”

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