Aims:  The Mini-Mental Adjustment to Cancer (Mini-MAC) Scale is a commonly used measure of psychological response to cancer diagnosis and treatment.  The aim of this study was to conduct confirmatory factor analysis comparing three published factor structures.

Method:  Relevant data from three pre-existing clinical studies were combined to produce a sample size sufficient for Structural Equation Modelling.  This resulted in a sample of 183 breast, prostate, lung and colorectal cancer patients with an almost even gender distribution.  Their mean age was 64.8 years (SD=12 yrs) and they were, on average, 163 days post diagnosis (range = 30-577 days).    There was good distribution of participants at each disease stage; approximately one quarter were were treated with palliative intent.  Quality of life, anxiety, depression, stress and benefit finding data were collected for analysis of concurrent validity.

Results:  The brief four-factor structure outperformed other models with respect to inter-item correlation, and overall statistical fit (RMSEA=.084, ECVI=.923, PNFI=.604, AGFI=.857).   Internal reliability was, however, slightly lower though this is likely a product of reduced items numbers than a true reflection of its psychometric reliability.  Test-retest reliability was comparable across all factor structures.  None of the sub-scales significantly correlated with all measures of concurrent validity, though the original five-factor model was certainly no better than comparison models.

Conclusion:  These results suggests that: (a) alternative scoring structures of the mini-MAC can be equally valid and reliable; and, (b) that a brief version consisting just 12 items performs superior to longer versions in many respects.   Given the improved feasibility of using shorter scales in clinical practice we recommend adoption of this shorter version for regular screening and assessment of adjustment.