Infection Incidence and Survival in Patients With Multiple Myeloma and Chronic Lymphocytic Leukaemia: A Growing Concern in the Era of Modern Therapies

ABSTRACT Introduction Patients with multiple myeloma (MM) and chronic lymphocytic leukaemia (CLL) are burdened by immunodeficiency due to treatment and underlying disease. Infection‐related mortality remains a significant concern for patients' overall survival (OS). Methods This Swedish, population‐based study examined incidence of infections and OS in patients with MM or CLL between January 2010 and December 2021, using Swedish Cancer Registry data. Results Overall, 15,766 patients were included (MM: 8532; CLL: 7234); the majority were male (MM: 57%; CLL: 62%); median age was 71 years (range: 19–100 [MM]; 23–102 [CLL]). The proportion with a Charlson Comorbidity Index ≥ 5 was 37% (MM) and 25% (CLL). At least one infection was reported in 66% (MM; n = 5618) and 50% (CLL; n = 3618), with a median follow‐up of 3.3 and 4.8 years, respectively. Pneumonia was the most common bacterial infection (21% for both), while herpes zoster was the most common specified viral infection (MM: 2.6%; CLL: 3.5%). Median OS (95% confidence interval) among these patients was 4.7 (4.6–4.9) and 9.7 (9.3–10.2) years, respectively. Infection (any) was the underlying/contributing cause of death for 1251/4822 (26%) deceased patients (MM) and 835/2571 (33%) (CLL). Higher comorbidity, prior infection and prophylaxis were associated with increased infection risk, while age, female sex and more recent diagnosis were associated with reduced risk. Conclusions This study demonstrates high mortality rates among patients with MM and CLL, due to underlying malignancy and high infection burden. This emphasises the need for optimised anticancer treatments and infection control strategies. Trial Registration The authors have confirmed clinical trial registration is not needed for this submission.