The likelihood of multiple chronic health conditions, referred to as multimorbidity, increases with age [7]. Comorbidity burden affects life expectancy, risk of functional decline, and hospitalization risk [8–11]. Increasing multimorbidity impacts survival and treatment tolerance in older adults with cancer [12–14]. The Charlson Comorbidity Index (CCI) is widely used in geriatric oncology research to characterize comorbidity burden. The CCI weights 19 diseases from one to six points based on relative risk of death at 1 year [15]. Higher overall mortality is associated with CCI score of 3 or more in patients with lung, colorectal, and prostate cancer who are 70 years and older [16].

There are also potential interactions between existing chronic diseases, a new diagnosis of cancer, and treatment. For example, the risk of falls with chemotherapy such as taxanes is higher in patients with pre-existing diabetes or peripheral neuropathy [17]. With a diagnosis of cancer, older patients are at higher risk for drug–drug interactions as the number of medication increases to treat the disease and manage symptoms [18]. Potential complications and side effects of treatment should be anticipated to make appropriate adjustment to current medications. For example, blood pressure medications, especially diuretics, may need to be reduced or held during periods of poor nutrition and dehydration due to nausea and vomiting. A careful review of medications for all patients at the beginning of treatment and periodic medication reconciliation is a practical approach to polypharmacy in the oncology setting [18]. The Beers Criteria lists potentially inappropriate medications for older adults . Other screening tools that are increasingly used in geriatric oncology to appraise medications for older patients are the STOPP (Screening Tool of Older Persons’ Prescriptions) and START (Screening Tool to Alert doctors to Right Treatment) . (Chapter 5 provides details on the Beers Criteria and STOPP/START).

Functional impairment (limitations in ADL and IADL), frailty, and geriatric syndromes are common in older adults with cancer [19]. Impairments in IADL predict survival in older patients with cancer [20]. Patients with impairment in IADLs should be further assessed for impairments in cognition, physical performance, and activities of daily living (ADL) . Weight loss and malnutrition are associated with chemotherapy toxicity and decreased survival [21–23]. Treatment side effects such as nausea, vomiting, and mucositis can lead to dehydration and further weight loss. Fatigue can impair the ability to shop, prepare, and enjoy food. One third of patients 65 years and older fall at least once a year and up to half of those who fall have recurrent falls [24]. Treatment side effects such as neuropathy and advanced cancer stage increases the risk of falls in older patients with cancer [25]. Patients should be asked about falls or near falls in the last 6 months. (Further assessment for falls is described in the Assessment Chap. 8).

Geriatric syndromes are common health conditions in older adults. The etiology is characteristically multifactorial, with shared risk factors including older age, comorbidity burden, cognitive decline, functional impairment, and impaired mobility [26]. In geriatric oncology, the most relevant syndromes are frailty, falls, dementia, depression, and delirium [27]. (Chapter 1 provides a full description of frailty and validated assessment tools.)

Cancer treatment decisions are complex, especially for older patients. The treatment program typically involves multiple office visits and complex medication regimens. The assessment of cognition informs the provider of a patient’s decisional capacity, reliability of history, ability to understand and manage complex treatment plans and the insight to report toxicities [28]. Patients with cognitive impairment need close monitoring for toxicities, such as febrile neutropenia. The prevalence of depression in older cancer patients ranges from 17 to 25 % [29]. Depression is under-recognized and under-treated, in part due to the overlap of symptoms of cancer and cancer treatment (fatigue and anorexia) and the signs and symptoms of depression. Delirium is also common in patients with cancer, with risk factors including polypharmacy, fevers, anemia, fatigue, pain, and electrolyte disturbances. (Chapter 2 provides a full description of this syndrome and the Chap. 8 Tools for Assessment provides details on assessment using the Confusion Assessment Method.)

There is heterogeneity in physiological reserve, comorbidities, functional abilities, and presence of geriatric syndromes among older individuals, adding complexity to estimation of life expectancy and treatment management decisions. Geriatric assessment (GA) is a multidimensional assessment of an older patient’s health, fitness, and capabilities using validated tools. Potential components of GA include the following health domains: (1) medical: evaluation of comorbidity, polypharmacy, and nutritional status; (2) mental health: evaluation of cognition, depression, and delirium; (3) functional status: assessment of activities of daily living (ADL), instrumental activities of daily living (IADL), mobility (physical performance), and falls; (4) social: evaluation of environment, resources, and social support/network. There is a growing body of evidence on the utility of GA in oncology practice [30]. Many studies in geriatric oncology propose the use of GA in patients older than 70 years with cancer [30]. The ultimate goal of GA is to guide treatment management decisions and the design of a treatment plan that balances benefits and remaining life expectancy, anticipates complications and care needs, and implements targeted interventions to optimize outcomes and improve quality of life.

GA can be applied to help with clinical decision-making in various clinical scenarios including: (1) prior to cancer surgery to assess for risks and potential post-operative complications such as functional impairment, (2) to estimate life expectancy in the context of competing comorbidities and functional status, particularly in the setting of adjuvant chemotherapy, (3) to evaluate the risks and benefits of treatment options, (4) and to monitor for development of deficits as a result of cancer treatment during and post treatment [31]. Chapter 8, Tools for Assessment, describes validated tools to assess geriatric domains. Table 26.2 summarizes the assessment tools of value in older patients with cancer.

To be effective, GA must be followed by appropriate interventions to address deficits. Unfortunately, data on the impact of GA-driven interventions in older patients with cancer is limited. However, studies in community-dwelling older patients without cancer have demonstrated effectiveness in improving outcomes [44]. Table 26.3 outlines potential interventions to address deficits identified during GA.

Three screening tools have been proposed to identify patients most likely to benefit from GA. The data supporting the use of screening tools have primarily focused on predicting deficits during Comprehensive GA (CGA) which is considered the “gold standard” for detecting problems in vulnerable older people. The Vulnerable Elders Survey-13 (VES-13) is a 13-item survey including age, self-rated health, and functional status, and is scored from 0 to 13, with 13 being the worst. A score of greater than 3 identified vulnerable older adults at risk for mortality, morbidity, and hospitalization. Higher VES-13 scores predict death and functional decline in vulnerable community-dwelling older adults [45, 46]. VES-13 demonstrates high predictive value for having greater than two deficits on CGA in older patients with prostate cancer [47]. Another tool, the Geriatric-8 (G8) screening tool, includes age, self-rated health, nutrition, cognition, mobility, and polypharmacy, and is scored from 0 to 17, with 17 indicating better function. A score of 14 or less predicts at least one deficit on CGA domains in adults 70 years and older [48]. Finally, the National Cancer Network Guideline recommends using the Fried Frailty score to identify older patients in need of further assessment. See Chap. 1, for further discussion of this syndrome in older patients.