Discussant of the abstract on antibiotic exposure, Jarushka Naidoo, MBBCh, Assistant Professor of Oncology and Attending Physician at the Sidney Kimmel Cancer Center at Johns Hopkins University, said that Mr. Chu and colleagues have added to the recent literature examining concurrent use of antibiotics and immunotherapy by looking at the effect in stage III disease as well as melanoma-specific mortality. “The association between antibiotic exposure and high-grade colitis in the stage III population is also a new finding, and the authors are to be congratulated on this,” said Dr. Naidoo, who noted, however, that a number of important questions remain.

Jarushka Naidoo, MBBCh

“Is the association between colitis and the gut microbiota different depending upon the immunotherapy regimen in question, and does the timing of antibiotics matter for prognosis and colitis risk?” asked Dr. Naidoo. “We need to assess whether giving antibiotics through treatment, starting earlier, or starting later matters. Right now, all of our published data are in the pretreatment setting. Does the choice of antibiotic and antibiotic duration matter?”

Although the latter question is unlikely to be suitable for a prospective randomized trial, admitted Dr. Naidoo, a rigorous prospective study of real-world data may provide an answer. Most important, Dr. Naidoo emphasized the need for informed decision-making.

“I think it’s very important that this should not be a reason not to give antibiotics to those patients who need it,” Dr. Naidoo concluded. “In addition, the rationale for giving probiotics as a supplement may not be valid, as we don’t know which microbes are being depleted by the antibiotics and which need to be supplemented.” 

DISCLOSURE: Dr. Naidoo disclosed financial relationships with AstraZeneca/MedImmune, Bristol-Myers Squibb, and Roche/Genentech.