How do I best manage the care of older patients with cancer with multimorbidity?

The typical older patient with cancer presents with several other chronic conditions. The coexistence of multiple chronic conditions in one patient is best termed multimorbidity, and it affects a growing percentage of the population each year. In cancer care, as in much sub-specialty care, "other diseases" have been approached from a research and clinical standpoint as "comorbidities"--other age-associated diseases that are of secondary importance to cancer care. This is not the same as the newer concept of "multimorbidity", a situation in which several overlapping chronic conditions are managed as equally-important to patient quality of life and outcomes. In the absence of a substantial evidence base or clinical practice guidelines that are tailored for multimorbid patients, clinicians need practical guidance for a rational approach to care for these complex patients. We adapt the American Geriatrics Society's Guiding Principles as an excellent starting point for clinical decision-making and management. These Guiding Principles include: 1) assessing patient preferences, 2) interpreting the available evidence, 3) estimating prognosis, 4) considering treatment feasibility, and 5) optimizing therapies and care plans. We apply them to older patients with cancer. As the population of older adults with cancer and multimorbidity grows, understanding the impact of multimorbidity on the care of patients with cancer and developing a management approach for these vulnerable patients will be vital for oncology care.