Comorbidity in older adults with cancer
Introduction
Comorbidity, defined as a medical condition that exists along with an index condition, is an issue of growing importance due to changing demographics and the increasing number of adults over the age of 65 with cancer [1], [2]. In a study of Medicare beneficiaries, over two-thirds had two or more medical conditions and nearly 25% of participants had four or more conditions [3]. Fig. 1 shows the prevalence of 10 common co-occurring chronic conditions among Medicare beneficiaries 65 years of age or older with various cancer types. While the prevalence of multiple chronic illnesses in older adults is rapidly increasing in the United States, [3] older adults with cancer have an even higher prevalence of comorbidity than an age-matched control group without cancer [4]. More than half of all older adults with cancer have at least one comorbidity that may impact their cancer treatment [5]. The frequent practice of excluding patients with common comorbid illnesses and the lack of systematic measurement of comorbidities in cancer clinical trials limit the evidence base for making informed decisions regarding these patients. The best approach to the clinical management and decision-making in older adults with comorbid conditions remains unclear [6]. Most clinical practice guidelines, in cancer and elsewhere, are single disease focused, limiting their application in patients with multiple comorbid illnesses [7]. Recognizing and managing comorbidities in older adults with cancer will become an increasingly routine issue for oncologists and may in fact already be the rule rather than the exception.
Although the term multimorbidity is frequently used interchangeably with comorbidity, we define multimorbidity as the presence of several comorbid illnesses in which one single condition is not the predominant focus. As this article is specifically addressing comorbidities within the context of cancer, we will be using the term comorbidity regardless of the number of comorbid illnesses. At the recent U13 conference “Design and Implementation of Intervention Studies to Improve or Maintain Quality of Survivorship in Older and/or Frail Adults with Cancer”, a session was included on comorbidity measurement, interventions, and future research. Based on the discussion from the U13 conference, this article will:
- 1)
Discuss the relevance of comorbidities in cancer
- 2)
Examine the commonly used tools to measure comorbidity
- 3)
Discuss the future direction of comorbidity research and key methodological considerations
Section snippets
Relevance in Cancer
Over the last decade, the importance of comorbidity in oncology has become clearer. Comorbid illnesses impact cancer in various ways. They serve as confounders that complicate the diagnosis and treatment of cancer, they mediate cancer or cancer treatment effects, and pose competing risks for morbidity and mortality [2]. The influence of comorbid conditions on cancer can vary dramatically as the comorbid illnesses themselves encompass a heterogeneous group of conditions ranging in number and
Measuring Comorbidity
Given the overall impact of comorbidities in cancer care, there is a compelling need to measure comorbidities in research and clinical settings. Standardized comorbidity assessment should be considered as a common data element for every patient. Without the systematic incorporation of comorbid conditions in cancer decision-making, oncologists may overestimate cancer risk, overestimate the benefits of cancer treatment, and may be unable to distinguish toxicity from comorbidity. Over the last
Studying Comorbidity
Many significant research gaps exist in the cancer care of individuals with comorbid conditions. Incorporating and developing standardized comorbidity assessments in clinical trials, as described above, is an important first step. Reducing the common eligibility criteria that limit the participation of older adults with comorbid conditions is necessary to improve the evidence base for treating these patients. The use of innovative trial designs can help to better incorporate comorbidities into
Conclusions
As the population continues to age and the prevalence of comorbidity in oncology grows, developing a better understanding of the impact of comorbid illnesses on cancer care and management strategies will be vital. Although oncologists and patients are primarily focused on cancer and its treatment, the implications and management of comorbidities will become increasingly important. Incorporating standardized comorbidity measurement, relaxing clinical trial eligibility criteria, and utilizing
Disclosures and Conflict of Interest Statements
The authors have no conflicts of interest to disclose.
Author Contributions
Concept and design: All authors Manuscript preparation, editing, and review: All authors.
Acknowledgements
This work was funded by a U13 AG038151 from the National Institute on Aging. The work was also funded by the American Cancer Society and a Patient-Centered Outcomes Research Institute (PCORI) Program contract (4634). The work received support from the James Wilmot Cancer Institute (WCI), the Alliance for Clinical Trials in Oncology (National Cancer Institute of the National Institutes of Health under Award Numbers U10CA18082 and 1UG1CA189823), and UG1CA189961 from the National Cancer Institute.
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