Chemotherapy was not associated with cognitive decline in older adults with breast and colorectal cancer: findings from a prospective cohort study.
OBJECTIVE
This study tested 2 hypotheses: (1) chemotherapy increases the rate of cognitive decline in breast and colorectal cancer patients beyond what is typical of normal aging and (2) chemotherapy results in systematic cognitive declines when compared with breast and colorectal cancer patients who did not receive chemotherapy.


METHODS
Data came from personal interviews with a prospective cohort of patients with breast (n=141) or colorectal cancer (n=224) with incident disease drawn from the nationally representative Health and Retirement Study (1998-2006) with linked Medicare claims.


METHODS
The 27-point modified Telephone Interview for Cognitive Status was used to assess cognitive functioning, focusing on memory and attention. We defined the smallest clinically significant change as 0.4 points per year.


RESULTS
We used Bayesian hierarchical linear models to test the hypotheses, adjusting for multiple possible confounders. Eighty-eight patients were treated with chemotherapy; 277 were not. The mean age at diagnosis was 75.5. Patients were followed for a median of 3.1 years after diagnosis, with a range of 0 to 8.3 years. We found no differences in the rates of cognitive decline before and after diagnosis for patients who received chemotherapy in adjusted models (P=0.86, one-sided 95% posterior intervals lower bound: 0.09 worse after chemotherapy), where patients served as their own controls. Moreover, the rate of cognitive decline after diagnosis did not differ between patients who had chemotherapy and those who did not (P=0.84, one-sided 95% posterior intervals lower bound: 0.11 worse for chemotherapy group in adjusted model).


CONCLUSIONS
There was no evidence of cognitive decline associated with chemotherapy in this sample of older adults with breast and colorectal cancer.
Department of Health Sciences, School of Health Professions, University of Missouri, Columbia, MO 65221-4290, USA. shafferv@health.missouri.edu
Victoria A
VA
Shaffer
Edgar C
EC
Merkle
Angela
A
Fagerlin
Jennifer J
JJ
Griggs
Kenneth M
KM
Langa
Theodore J
TJ
Iwashyna
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D000970:Antineoplastic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D024221:Antineoplastic Protocols; D001499:Bayes Theorem; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000453:epidemiology; D003072:Cognition Disorders / Q000139:chemically induced* / Q000453:epidemiology; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000453:epidemiology; D005260:Female; D015438:Health Behavior; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D008568:Memory; D011446:Prospective Studies
D000970:Antineoplastic Agents