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Journal of the National Cancer Institute Advance Access published online on October 28, 2008
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djn340
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© The Author 2008. Published by Oxford University Press.

ARTICLES

Refinement and Psychometric Evaluation of the Impact of Cancer Scale

Catherine M. Crespi, Patricia A. Ganz, Laura Petersen, Adrienne Castillo, Bette Caan

Affiliations of authors: School of Public Health and Jonsson Comprehensive Cancer Center, University of California at Los Angeles, CA (CMC, PAG, LP); Division of Research, Kaiser Permanente Medical Program, Oakland, CA (AC, BC)

Correspondence to: Catherine M. Crespi, PhD, Division of Cancer Prevention and Control Research, UCLA School of Public Health and Jonsson Comprehensive Cancer Center, 650 Charles Young Drive South, A2-125 CHS, Box 956900, Los Angeles, CA 90095-6900 (e-mail: ccrespi{at}ucla.edu).

Background: Instruments are needed to measure the influence of cancer on quality of life in the expanding population of long-term cancer survivors. We conducted refinement and psychometric evaluation of the Impact of Cancer (IOC) scale by use of data from a large sample of long-term breast cancer survivors and developed an instrument, the Impact of Cancer version 2 (IOCv2), to measure quality of life outcomes.

Methods: Questionnaires including 81 potential IOC scale items, the Center for Epidemiologic Studies-Depression (CES-D) scale, and the Breast Cancer Prevention Trial (BCPT) symptom scales, as well as demographic, treatment, and medical information, were completed by 1188 disease-free breast cancer survivors 5–10 years after diagnosis. We used exploratory factor analysis to identify scales and assessed reproducibility by split-sample cross-validation. Higher-order scales were extracted and all scales were evaluated for internal consistency and construct and concurrent validity.

Results: The analysis yielded a factor structure relating IOC items to psychosocial impact domains that exhibited high factor loadings (factor–item correlations of 0.59–0.94), high internal consistency (Cronbach’s {alpha} statistics of 0.76–0.89), and a total congruence of 0.98 across the split samples. The Impact of Cancer version 2 (IOCv2) scales consist of a Positive Impact Summary scale with four subscales (Altruism and Empathy, Health Awareness, Meaning of Cancer, and Positive Self-Evaluation), a Negative Impact Summary scale with four subscales (Appearance Concerns, Body Change Concerns, Life Interferences, and Worry), and subscales for Employment and Relationship Concerns. Patterns of association between IOCv2 scale scores and CES-D and BCPT scores indicated good concurrent validity. Patterns of associations between IOCv2 scale scores and demographic, medical, and treatment characteristics indicated good construct validity.

Conclusion: The IOCv2 scales provide a validated tool for measuring the impact of cancer on quality of life in long-term cancer survivors.


CONTEXT AND CAVEATS

Prior knowledge

Cancer diagnosis, treatment, and survival can engender lingering quality of life concerns.

Study design

Data from 1188 breast cancer survivors 5–10 years after diagnosis were used to develop and validate a questionnaire, the Impact of Cancer version 2 (IOCv2).

Contribution

Patterns of association between IOCv2 scale scores and demographic, medical, and treatment characteristics of the breast cancer survivors indicated good construct validity.

Implications

The IOCv2 is a validated tool for measuring the impact of cancer on the quality of life of long-term cancer survivors.

Limitations

Only data from breast cancer survivors were used and so IOCv2 has not been validated for survivors of other types of cancer. Most of the 1188 breast cancer survivors were white and none were more than 10 years away from their breast cancer diagnosis and so the data may not be fully representative of the population of all breast cancer survivors.

From the Editors

 
Manuscript received May 9, 2008; revised August 20, 2008; accepted August 25, 2008.


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J Natl Cancer Inst 2008 100: 1485. [Extract] [Full Text] [PDF]





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