In patients diagnosed with prostate cancer, the selection of treatment, including the type of therapy and its aggressiveness, is often based on a patient's age and life expectancy. Life expectancy estimates are too often calculated solely on the patient's chronological age, overlooking comorbid conditions and their severity, which can greatly affect life expectancy. If, in addition to chronological age, comorbid conditions are used to assess a patient's life expectancy, the most appropriate treatment options are more likely to be selected. Older, healthy patients might be able to tolerate more aggressive treatment than would be administered on the basis of their age alone, and younger patients with numerous comorbid conditions could avoid harsh therapy that might not be appropriate given their current state of health. The key idea to consider in treatment selection is what a patient's quality of life would be like with or without a particular treatment option. In an era of precision medicine, decisions regarding the provision of health care should be made rationally and on the basis of objective estimates of the threat of disease and the benefits and costs of intervention and within the context of the patient's characteristics and desires.