To Örebro University

Objective:  To examine the relative risks of iatrogenic and non-iatrogenic injuries during the period shortly before and after a diagnosis of cancer.

Design:  Nationwide register based study.

Setting:  Swedish national population and health registers.

Participants:  720 901 patients with diagnosis of cancer, 1991-2009, in Sweden.

Main outcome measures:  All hospital admissions in patients with cancer with a main discharge diagnosis of iatrogenic (from medical complications) or non-iatrogenic injuries in 1990-2010 identified from the Swedish patient register. Conditional Poisson regression was used to compare the incidence rate of injuries during the "diagnostic period" (16 weeks before to 16 weeks after diagnosis) with the incidence rate during a "pre-diagnostic period" (the same 32 weeks one year before diagnosis) among the same patients.

Results:  During the diagnostic period, there were 7306 iatrogenic (incidence rate 0.60 per 1000 person months) and 8331 non-iatrogenic injuries (incidence rate 0.69 per 1000 person months). For iatrogenic injuries, the incidence rate ratio was 7.0 (95% confidence interval 6.6 to 7.4) during the diagnostic period compared with the pre-diagnostic period. The increase in risk started two weeks before cancer diagnosis and peaked during the two weeks after diagnosis (48.6, 37.3 to 63.5). For non-iatrogenic injuries, the incidence rate ratio was 1.9 (1.8 to 2.0) during the diagnostic period compared with the pre-diagnostic period. The increase in risk began four weeks before diagnosis and peaked during the two weeks before diagnosis (5.3, 4.6 to 6.1). There were increased risks of both types of injury during the diagnostic period for all common cancers, with the smallest risk increase noted for non-melanoma skin cancer.

Conclusions:  Patients with cancer have highly increased risks of both iatrogenic and non-iatrogenic injuries requiring inpatient care : shortly before and after their diagnosis. These findings shed further light on the total burden of medical complications and call for prevention of intentional and unintentional injuries during the diagnostic process of cancer.