Purpose: Diagnostic laparotomy and splenectomy (DLS) were introduced for Hodgkin lymphoma (HL) patients in Sweden in the late 1960s/early-70s. It was soon established that splenectomised and functional hyposplenic (following irradiation) HL patients carried an increased risk of overwhelming infections, Streptococcus pneumoniae being the major causative agent. Despite this, DLS remained as a staging procedure for more than two decades. The purpose of this study was to compare incidence and outcome of pneumococcal infections between splenectomised (spl+) and non-splenectomised (spl-) HL patients.
Material and Methods: HL patients diagnosed 1973-1995 were identified in the Swedish Cancer Register. Information on splenectomies and severe pneumococcal infections was retrieved from the National Inpatient Register. Follow-up started a diagnosis and ended on date of infection, emigration, death, or December 31, 2010, whichever came first. Splenectomy was analysed as a time-varying covariate, i.e., patients were considered unexposed before the date of splenectomy and exposed after the date of splenectomy. Cox proportional hazard models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) comparing infection rates between spl+/spl- patients.
Results: A total of 4,237 HL patients were included, among whom 735 (17%) underwent a splenectomy, with a median time from splenectomy to infection of 6.8 years (range 0.1-30.8 years). The number of patients experiencing a severe pneumococcal infection was 39 (3.2 per 1,000 person-years) among spl+ and 60 (1.7 per 1,000 person-years) among spl- patients. The relative rate of severe pneumococcal infection comparing spl+/spl- HL patients was 2.43 (95% CI: 1.55-3.81), adjusted for diagnosis year, diagnosis age, and sex. The 30-day post-infection mortality proportion was 9/39 (23%) among the spl+ and 18% (11/60) among the spl- patients. Broken down by calendar period of infection, the 30-day post-infection mortality proportion among splenectomised patients was 44% (1973-1985), 23% (1986-1998), and 0% (1999-2010).
Conclusion: Severe pneumococcal disease is a serious event that is more likely to appear in splenectomised HL patients compared to non-splenectomised, possibly many years after diagnosis. However, the low proportion of deaths in later decades is reassuring, and likely a result of adequate pneumococcal vaccination together with patient and doctor education about the infection risk.
Magnus Björkholm, Caroline E. Weibull, Paul Dickman