EDINBURGH – Routine empiric prophylaxis against pneumocystis jiroveci pneumonia (PJP) may be unwarranted in chronic lymphocytic leukemia patients initiating Bruton tyrosine kinase (BTK) inhibitor therapy, a retrospective chart review suggests.
Among 212 patients with chronic lymphocytic leukemia (CLL) who were treated with ibrutinib or acalabrutinib either as monotherapy or as part of a combination regimen for at least 30 days between Jan. 1, 2010, and Feb. 1, 2019, at Dana-Farber Cancer Institute and Brigham and Women’s Hospital in Boston, 125 (59%) received PJP prophylaxis, including either trimethoprim-sulfamethoxazole (74%) or atovaquone (26%),, reported at the International Workshop on CLL.
Two PJP cases occurred in the 120 patients on single-agent ibrutinib, including one in a previously untreated patient and one in a patient with relapsed/refractory CLL. Neither patient had received PJP prophylaxis, said Dr. Ryan, a senior resident at Brigham and Women’s Hospital.
No PJP cases occurred in the 21 patients who received acalabrutinib monotherapy or in the 14 patients who received acalabrutinib combination therapy, and 1 occurred in a trial cohort of 57 patients receiving frontline ibrutinib plus fludarabine-based chemotherapy (FCR). The latter had been prescribed PJP prophylaxis, but “unfortunately self-discontinued the prophylaxis” 2 months prior to the infection, Dr. Ryan said.
“The overall prevalence of PJP in patients not on prophylaxis was 3.4%, there were no cases of PJP in patients on prophylaxis, and the incidence rate in patients not on prophylaxis was 1.9 per 100 person-years, with a number needed to treat to prevent 1 case of PJP calculated to be 42 patients,” she said.
In addition to PJP, three cases of proven or probable invasive fungal infections (IFI) occurred, including one case of pulmonary histoplasmosis in the ibrutinib plus FCR trial cohort and two cases of aspergillosis, including a pulmonary case and a brain abscess, in an ibrutinib plus umbralisib trial cohort.
“The overall prevalence of aspergillosis or histoplasmosis in our entire cohort was 1.4%, and notably there were no cases of IFI in the single-agent therapy cohort, but the prevalence in the ibrutinib-combination therapy patients was 4.2%,” Dr. Ryan said.
Patients included in the review were adults with a median age of 64.8 years, and 64% were men. The median duration of BTK inhibitor therapy was 23.2 months.
“We know that CLL patients treated with fludarabine have an increased risk of PJP,” she said. “As such, it is routinely recommended that patients receiving fludarabine-containing chemotherapy regimens are prescribed PJP prophylaxis.”
Additionally, the increasing use of oral BTK inhibitors has raised concerns about the potential risk of PJP or other IFIs in patients on those agents, Dr. Ryan explained, noting that existing case reports and case series looking at PJP have shown varying prevalence rates, and little is known about the effects of prophylaxis.
“At present, there are no international guidelines regarding the use of antimicrobial prophylaxis in CLL patients treated with BTK inhibitors, and prophylaxis practices vary widely across countries and institutions,” she said.
The findings of the current study demonstrate that such variation exists “even within our own institution,” Dr. Ryan added.
The findings also show an overall low PJP prevalence of 3.4% in patients not receiving prophylaxis, which falls below the “commonly accepted threshold of 5%, above which routine prophylaxis becomes recommended,” she said.
“Overall, our data suggest that routine PJP or IFI prophylaxis in patients receiving BTK inhibitors may not be needed, but this is definitely an area that requires further study, ideally with a prospective trial with a larger sample size and multiple institutions, to support the development of consensus guidelines on this issue,” she said.
Dr. Ryan reported having no financial disclosures.