T1-weighted magnetic resonance imaging in breast cancer vertebral metastases: changes on treatment and correlation with response to therapy.

PURPOSE

To document the MR appearances of vertebral metastases in breast cancer on treatment and to determine whether a single T1-weighted (T1-W) sequence of the spine could provide a quick and effective method of response assessment.

PATIENTS AND METHODS

One-hundred and nine spinal magnetic resonance (MR) examinations in 41 metastatic breast cancer patients on treatment were reviewed. The changes in number, size and signal intensity of vertebral metastases during 68 intervals (mean length 6.9 months) were documented. T1-W signal intensity (SI) before and after treatment was assigned to three patterns: (A) low homogeneous SI; (B) low heterogeneous SI; and (C) high homogeneous SI. For each interval between MR examinations, an objective assessment of the overall response (disease regression, no change, disease progression) to treatment of metastases was made based on standard assessment criteria.

RESULTS

The number and size of treated vertebral metastases increased in 47% and 43% of cases and showed no change in 53% and 54% of cases, respectively. A reduction in size of lesions was seen in 3% of cases only and no reduction in the number of lesions was seen. T1-W [corrected] signal intensity changes occurred in approximately one-third of cases documented. The most commonly observed SI change in 25% of all intervals (17 of 68) was from type A to type B. There was no correlation between SI change and response to therapy. T1-W [corrected] MR response assessment, based on changes in size and number of vertebral metastases, accurately predicted progression of disease in 79% of cases and stable disease in 75% of cases. It did not predict regression of disease.

CONCLUSION

A T1-W MR spinal assessment is a simple and effective method of evaluation of therapeutic response of lytic and sclerotic vertebral metastases in breast cancer being able to distinguish patients with progressive disease from those with a favourable response (no change or disease regression) to therapy. These findings have important clinical implications.