Background Senescent cells, which express p16 ^INK4a, accumulate with aging and contribute to age-related pathology. To understand whether cytotoxic agents promote molecular aging, we measured expression of p16 ^INK4a and other senescence markers in breast cancer patients treated with adjuvant chemotherapy. Methods Blood and clinical information were prospectively obtained from 33 women with stage I to III breast cancer at four time points: before anthracycline-based chemotherapy, immediately after anthracycline-based chemotherapy, 3 months after anthracycline-based chemotherapy, and 12 months after anthracycline-based chemotherapy. Expression of senescence markers p16 ^INK4a and ARF mRNA was determined using TaqMan quantitative reverse-transcription polymerase chain reaction in CD3⁺ T lymphocytes, telomere length was determined by Southern analysis, and senescence-associated cytokines were determined by enzyme-linked immunosorbent assay. Findings were independently assessed in a cross-sectional cohort of 176 breast cancer survivors enrolled a median of 3.4 years after treatment; 39% previously received chemotherapy. All statistical tests were two-sided. Results In prospectively analyzed patients, expression of p16 ^INK4a and ARF increased immediately after chemotherapy and remained elevated 12 months after treatment. Median increase in log₂ p16 ^INK4a was 0.81 (interquartile range = 0.28–1.62; Wilcoxon signed-rank P < .001), or a 75% absolute increase in expression, equivalent to the increase observed over 14.7 years of chronological aging. ARF expression was comparably increased (P < .001). Increased expression of p16 ^INK4a and ARF was associated with dose-dense therapy and hematological toxicity. Expression of two senescence-associated cytokines (VEGFA and MCP1) was durably increased by adjuvant chemotherapy. Telomere length was not affected by chemotherapy. In a cross-sectional cohort, prior chemotherapy exposure was independently associated with a log₂-increase in p16 ^INK4a expression of 0.57 (repeated measures model, P < .001), comparable with 10.4 years of chronological aging. Conclusions Adjuvant chemotherapy for breast cancer is gerontogenic, inducing cellular senescence in vivo, thereby accelerating molecular aging of hematopoietic tissues.

Purpose.: Breast cancer (BC) is a disease of aging and the number of older BC patients in the U.S. is rising. Immunohistochemical data show that with increasing age, the incidence of hormone receptor-positive tumors increases, whereas the incidence of triple-negative tumors decreases. Few data exist on the frequency of molecular subtypes in older women. Here, we characterize the incidence and outcomes of BC patients by molecular subtypes and age. Patients and Methods.: Data from 3,947 patients were pooled from publicly available clinical and gene expression microarray data sets. The PAM50 algorithm was used to classify tumors into five BC intrinsic subtypes: luminal A, luminal B, HER2-enriched, basal-like, and normal-like. The association of age and subtype with recurrence-free survival (RFS), overall survival, and disease-specific survival (DSS) was assessed. Results.: The incidence of luminal (A, B, and A+B) tumors increased with age (p < .01, p < .0001, and p < .0001, respectively), whereas the percentage of basal-like tumors decreased (p < .0001). Among patients 70 years and older, luminal B, HER2-enriched, and basal-like tumors were found at a frequency of 32%, 11%, and 9%, respectively. In older women, luminal subtypes had better outcomes than basal-like and HER2-enriched subtypes. After controlling for subtype, treatment, tumor size, nodal status, and grade, increasing age had no impact on RFS or DSS. Conclusion.: More favorable BC subtypes increase with age, but older patients still have a substantial percentage of high-risk tumor subtypes. After accounting for tumor subtypes, age at diagnosis is not an independent prognostic factor for outcome.

PURPOSE: Limited tools exist to predict the risk of chemotherapy toxicity in older adults with early-stage breast cancer. METHODS: Patients of age ≥ 65 years with stage I-III breast cancer from 16 institutions treated with neoadjuvant or adjuvant chemotherapy were prospectively evaluated for geriatric and clinical features predictive of grade 3-5 chemotherapy toxicity. Logistic regression with best-subsets selection was used to identify and incorporate independent predictors of toxicity into a model with weighted variable scoring. Model performance was evaluated using area under the ROC curve (AUC) and goodness-of-fit statistics. The model was internally and externally validated. RESULTS: In 473 patients (283 in development and 190 in validation cohort), 46% developed grade 3-5 chemotherapy toxicities. Eight independent predictors were identified (each assigned weighted points): anthracycline use (1 point), stage II or III (3 points), planned treatment duration > 3 months (4 points), abnormal liver function (3 points), low hemoglobin (3 points), falls (4 points), limited walking (3 points), and lack of social support (3 points). We calculated risk scores for each patient and defined three risk groups: low (0-5 points), intermediate (6-11 points), or high (≥ 12 points). In the development cohort, the rates of grade 3-5 chemotherapy toxicity for these three groups were 19%, 54%, and 87%, respectively ( P < .01). In the validation cohort, the corresponding toxicity rates were 27%, 45%, and 76%. The AUC was 0.75 (95% CI, 0.70 to 0.81) in the development cohort and 0.69 (95% CI, 0.62 to 0.77) in the validation cohort. Risk groups were also associated with hospitalizations and reduced dose intensity ( P < .01). CONCLUSION: The Cancer and Aging Research Group-Breast Cancer (CARG-BC) score was developed and validated to predict grade 3-5 chemotherapy toxicity in older adults with early-stage breast cancer.

Breast cancer is the most common cancer in women, with an incidence that rises dramatically with age. The average age at diagnosis of breast cancer is 61 years, and the majority of woman who die of breast cancer are age 65 years and older. Major improvements in public health and medical care have resulted in dramatic increases in longevity. The oldest old (those age 80 years and older) are a rapidly expanding group and now comprise 9 million members of the US population. The treatment of individuals who are age 80 years and older is complex and involves clearly defining the goals and value of treatment while also weighing risks, such as the potential effects of treatment on functional loss and quality of life. Limited evidence-based treatment guidelines exist for the caring of this older cohort of patients with breast cancer. Data from clinical trials that enroll primarily younger patients lack the information needed to estimate the likelihood of toxicities that can be life changing in older adults. Clinicians who make treatment recommendations should place the available evidence in the context of the patient’s life expectancy and geriatric assessment results that include an evaluation of a patient’s functional status, comorbidities, cognition, social support, nutritional status, and psychological state. Furthermore, these decisions should be placed in the context of the patient’s goals for treatment, preferences, and values. This review summarizes the current literature and focuses on the role of geriatric assessment in treatment recommendations for patients age 80 years and older with early and metastatic breast cancer.