Researchers found just 22 randomized controlled studies into prophylactic strategies, with several of them conducted prior to 2000. According to the report, published in Blood Advances, the studies together only evaluated a few thousand participants.
Reliable findings are so sparse that study coauthor Zoe McQuilten, MBBS, PhD, MD, a hematologist at Monash University, Melbourne, said “we simply don’t know” which preventive strategy is most effective. This is especially worrisome because more patients will survive their cancers and “be at risk of infection or have significant cytopenias and will experience impaired quality of life as a result,” she said in an interview.
The study authors launched the analysis to better understand the evidence regarding infection prevention and to guide the development of clinical trials, study coauthor Robert Weinkove, MBBS, PhD, a hematologist at Malaghan Institute of Medical Research, Wellington, New Zealand, said in an interview.
As he explained, targeted therapies have revolutionized the treatment of some B-cell cancers. They also have boosted the number of patients who survive the diseases yet still have profound hypogammaglobulinemia.
“Indeed, we may soon reach the point at which infection, and not tumor progression, is the leading cause of death for patients with certain B-cell cancers,” he said. “The evidence base for managing hypogammaglobulinemia is largely based on randomized trials of immunoglobulin replacement conducted in the 1980s and early 1990s, before the advent of B cell–targeted therapies. Immunoglobulin replacement is a costly intervention, and many countries are facing a shortage of immunoglobulin.”
The report authors identified 22 total randomized controlled trials, including one led by Dr. McQuilten: 8 studies into prophylactic immunoglobulin (n = 370; all but 1 study published prior to 2000), 5 into prophylactic antibiotics (n = 1,587), 7 into vaccination (n = 3,996), and 1 comparing immunoglobulin versus antibiotics (n = 60).
No evidence was found to support a lowering of risk by prophylactic antibiotics, although they caused adverse events.
Prophylactic immunoglobulin also caused adverse events, but a meta-analysis found that it reduced the risk of clinically documented infection by 28% (n = 2 trials; relative risk, 0.72; 95% confidence interval, 0.54-0.96). Three trials reported adverse events and found a higher risk overall (RR, 2.23; 95% CI, 1.67-2.99).
Varicella zoster virus vaccination reduced the risk of one or more infections by 63% (n = 5 trials, RR, 0.37; 95% CI, 0.30-0.45, n = 3,515). Prophylactic antibiotics did not reduce the risk.
No intervention reduced all-cause mortality.
“Our findings should be interpreted with caution, Dr. McQuilten said, “because of the low number of patients, high risk of bias in the included studies, and lack of contemporary data applicable to the current standard of care for such patients.”
The lack of useful data is surprising, she said, especially considering “how commonly these interventions are used in current clinical practice and the cost and supply constraints for immunoglobulin. Given the variation in international guidelines, rising global demand and cost of immunoglobulin, and concerns regarding antimicrobial resistance, more evidence is needed to inform infection prevention strategies for this patient population.”
More data is expected soon. One ongoing study is examining intravenous immunoglobulin versus placebo in patients with CLL. It’s expected to be completed in September 2023.
What should clinicians do for now? “Given the lack of a proven survival benefit in favor of prophylactic immunoglobulin replacement, one strategy is to maximize use of vaccination and to educate both patients and clinicians regarding the need for early treatment of infections,” Dr. Weinkove said. “For people who have recurrent or severe infections despite these measures, both immunoglobulin replacement and prophylactic antibiotics are clinical options. It would be reasonable to take account of patient preference, logistical considerations, and reimbursement and availability in deciding between these options.”
He added that, “for people with severe hypogammaglobulinemia who experience recurrent or severe infections despite prophylactic antibiotics, switching to immunoglobulin replacement would be appropriate. We advocate enrollment in clinical trials, if possible.”
In an interview, Juthaporn Cowan, MD, PhD, an infectious disease physician with the University of Ottawa, said many patients with B-cell lymphomas develop acquired hypogammaglobulinemia. “Patients tend to get prolonged colds, frequent sinusitis, bronchitis, or pneumonia. Some can end up with severe infection. Many patients told me that, even though their cancer is cured or in remission, quality of life is still quite poor due to these infections and fatigue.”
Dr. Cowan said the new report is somewhat useful, although “concluding that vaccination reduces infection is misleading. Vaccination reduces the infection that patients were vaccinated against. Patients who received Shingrix will have less shingles but will continue to have bronchitis and other infections.”
As for advice for clinicians, she said preventing acquired hypogammaglobulinemia is difficult since it can be caused by the malignancies, by treatment, or both. “The other item to consider is that we do not know how long we should continue [immunoglobulin] treatment in these patients. I have a patient post CAR [chimeric antigen receptor] T therapy who still does not have B-cell 5-6 years after CAR T, while I have lymphoma patients who could safely discontinue [immunoglobulin] treatment in a few years.”
Dr. Cowan added that patients on immunoglobulin treatment can still get opportunistic infections from cytomegalovirus or herpes simplex virus “because the mechanism of host defense against these infections is different. Antimicrobial prophylaxis should still be considered as vaccination is not available for every single potential opportunistic infection.”
Australia funded the research through the National Blood Authority. Dr. McQuilten and Dr. Weinkove reported no disclosures. Other report authors disclosed ties with Aegros, CSL Behring, Janssen, AbbVie, and BeiGene. Monash University has received funding for unrelated projects from CSL Behring. Dr. Cowan reports honoraria from Takeda, CSL Behring, Octapharma, GlaxoSmithKline, Merck, and AstraZeneca.