A recent study suggests that crizotinib (Xalkori) can reduce kidney function. Lung cancer patients treated with Xalkori saw their kidney function decrease by 23.9% on average. Kidney function recovered when Xalkori was discontinued. However, as patients usually have to take Xalkori for months or years, these findings still warrant caution, especially in patients taking other medications that affect kidney function or with preexisting kidney damage. In an earlier study, investigators had found that Xalkori decreased testosterone levels in 84% of male patients. Because cancer drugs like Xalkori increasingly receive accelerated approval, not all of their side effects are known by the time they are approved. Doctors therefore need to carefully monitor their patients for possible adverse effects.