Biomarkers of Aging and Radiation Therapy Tailored to the Elderly: Future of the Field

Common methods of biological age estimation

At present, no single indicator could be used as a golden index to estimate aging process. The biological age (BA), which combines several important biomarkers with mathematical modeling, has been proposed for >50 years as an aging estimation method to replace chronological age (CA). The common methods used for BA estimation include the multiple linear regression (MLR), the principal component analysis (PCA), the Hochschild's method, and the Klemera and Doubal's method (KDM). The fundamental differences in these four methods are the roles of CA and the selection criteria of aging biomarkers. In MLR and PCA, CA is treated as the selection criterion and an independent index. The Hochschild's method and KDM share a similar concept, making CA an independent variable. Previous studies have either simply constructed the BA model by one or compared the four methods together. However, reviews have yet to illustrate and compare the four methods systematically. Since the BA model is a potential estimation of aging for clinical use, such as predicting onset and prognosis of diseases, improving the elderly's living qualities, and realizing successful aging, here we summarize previous BA studies, illustrate the basic statistical steps, and thoroughly discuss the comparisons among the four common BA estimation methods.

Patient-reported symptoms and performance status before palliative radiotherapy in geriatric cancer patients (octogenarians)

Purpose

To evaluate differences in baseline parameters including performance status and self-reported symptom burden between geriatric and non-geriatric cancer patients, and to assess the hypothesis that these factors might predispose older patients to incomplete radiotherapy and short survival.

Patients and methods

Retrospective comparison of geriatric and non-geriatric patients treated with palliative radiotherapy (age ⩾80 years and <80 years, respectively). Between 2013 and 2015, 26 geriatric and 76 non-geriatric patients were treated. The Edmonton symptom assessment system (ESAS) was employed to document baseline symptoms.

Results

Most patients received radiotherapy for bone metastases, commonly 5-10 fractions. Geriatric patients had significantly less pain at rest and depression. No strong trends towards higher symptom burden in older patients emerged for any of the items. Overall survival was similar in the two subgroups with different age and also in a separate age-stratified analysis of patients with performance status >2. Relatively few patients were irradiated in the terminal stage of disease, defined as final 30 days of life (8% in geriatric and 12% in other patients, p = 0.73). A higher number of geriatric patients failed to complete their prescribed course of radiotherapy (14 vs. 3%, p = 0.08), despite lower rates of prescription of more than 10 fractions in this group (15 vs. 23%, p > 0.2).

Conclusions

These data support utilization of palliative radiotherapy irrespective of age. However, care should be taken in assigning the right fractionation regimen in order to avoid lengthy treatment courses when survival is limited, such as in patients with performance status >2.

Order of aging of major human organs or systems and evaluation of health status based on aging

To determine the functional age of an individual, a quantitative system for the assessment of aging status was developed in the present study. A total of 1579 subjects were selected randomly from patients undergoing physical examination. The index of organic mild impairment (IOMI) and IOMI corrected for age (COMI) were calculated. By receiver operating characteristic (ROC) curve analysis of the IOMIs of younger and elderly subjects, a cutoff value for COMI of 30% was obtained. About 95% of <30-year-old subjects were healthy. These data suggest that organs and systems reflect the aging status of an individual and may be a useful tool for evaluating health status.