Colorectal cancer (CRC) is the fourth most common cancer in the United States and has a high prevalence among the older population.1 In 2017, there were an estimated 135,430 new cases of CRC and 50,260 deaths due to CRC. It is the second leading cause of cancer death in the United States, and the death rate for patients with CRC increases with age (Figure).2
Although elderly persons are more frequently diagnosed with CRC, they are underrepresented in clinical trials. This may be due in part to stringent eligibility criteria in prospective randomized controlled trials that exclude older patients with certain comorbidities and decreased functional status. Hutchins and colleagues compared the proportion of persons aged 65 years and older enrolled in Southwest Oncology Group (SWOG) clinical trials and the proportion of persons in this age group in the US population with the same cancer diagnoses.5 They found that while 72% of the US population with CRC were aged ≥ 65 years, persons in this age group comprised only 40% of patients enrolled in SWOG trials. An update on this study performed after Medicare policy changed in 2000 to include coverage of costs incurred due to clinical trials showed an upward trend in the accrual of older patients in SWOG trials, from 25% during the period 1993–1996 to 38% during the period 2001–2003; however, the percentage of older patients with CRC on clinical trials overall remained stable from 1993 to 2003.6
The underrepresentation of older adults with CRC in clinical trials presents oncologists with a challenging task when practicing evidence-based medicine in this patient population. Analysis of a large claims database demonstrated that the use of multi-agent chemotherapy for the treatment of metastatic CRC in older adults increased over time, while the use of single-agent 5-fluorouracil (5-FU) decreased.7 However, the adoption of combination therapy with irinotecan or oxaliplatin in older adults lagged behind the initial adoption of these agents in younger patients. This data demonstrates that as the field of medical oncology evolves, providers are becoming more comfortable treating older patients with multiple medical problems using standard approved regimens.
Before treating older patients with cancer, it is necessary to define the patient’s physiological age, ideally through a multidisciplinary team evaluation. Comprehensive geriatric assessment (CGA) is a multidisciplinary approach recommended for evaluation of an elderly person’s functional status, medical comorbidities, psychosocial status, cognitive function, and nutritional state.8,9 CGA may uncover geriatric syndromes not otherwise detected by routine oncology evaluation. Functional status can vary greatly across geriatric patients in the same age group, with some older patients as robust as their younger counterparts and others more frail. The remainder of the population will likely fall along a continuum between the 2 extremes and may appear fit but have borderline reserve.10 Robust older adults have a better performance status and fewer comorbidities; identifying these fit older patients is important, as they are more likely to benefit from standard anticancer treatments.11 Frail patients are more likely to have multiple comorbidities or other geriatric syndromes, such as cognitive impairment, depression, or gait disturbance, and are less likely to benefit from standard treatments.