Abstract P4-02-10: Response to neoadjuvant chemotherapy assessed by magnetic resonance imaging (MRI) texture analysis compared with residual cancer burden (RCB) and tumor subtype in primary breast cancer
Authors: Waugh SA , Purdie CA , Evans AJ , Lerski RA , McGhee H , Vinnicombe SJ , Thompson AM 
Published: May 2016

Purpose

MRI has great potential in the imaging of response to neoadjuvant chemotherapy in primary breast cancer. The aim of this study was to ascertain whether changes in lesion heterogeneity, as measured using texture analysis (TA),are linked with pathological response to treatment in primary breast cancer, according to lesion immunophenotype.

Materials & Methods

Sixty-one consecutive patients with biopsy-proven primary breast cancer underwent anthracycline-based NAC with baseline (pre-NAC) and interim (post 3-cycles NAC) MRI examinations performed on a 32-channel 3.0T MRI scanner (Siemens Trio; Erlangen) using a 7-channel breast biopsy coil. T2-weighted images (voxel size: 1.1x1.1x1.1mm3) were used for texture analysis, which was executed using MaZda software (University of Lodz; Poland). Slices were matched between imaging time-points and regions of interest manually placed to encompass the lesion. Where multiple lesions were present, only the index lesion was used. Lesion heterogeneity was assessed using the entropy feature, as derived from the co-occurrence matrix, and percentage changes between baseline and interim examinations calculated.

Final pathologic response of the surgical resections was assessed using the Residual Cancer Burden (RCB) index, as calculated from tumor bed dimensions, residual cellularity and axillary node burden. Good responders (GR) were classified as those attaining a pCR or RCB-I score, while RCB-II and RCB-III lesions were considered poor responders (PR).

Cancers were subdivided into estrogen-receptor positive (ER+), HER2 amplified (HER2+) and triple negative (TN) groups.

Changes in lesion heterogeneity in relation to RCB response category and tumor subtype were compared using Mann Whitney U tests with significance at p ≤0.05 level.

Results

Patients who ultimately achieved a good pathological response demonstrated significantly greater reduction in lesion heterogeneity at TA between baseline and interim (pCR: 20.0%, RCB-I: 10.6%) than those who had a poor response (RCB-II: 6.8%, RCB-III: 3.4%) (p&lt;0.001; Mann Whitney U).

RCB response categories in each tumor subtype was as follows: ER+: GR- 4 patients, PR- 13; HER2+: GR- 7, PR- 13; TNBC: GR- 7, PR- 17. There were statistically significant differences in the degree of reduction of lesion heterogeneity between good responders and poor responders for the ER+ (p=0.010; Mann-Whitney U) and TNBC patients (p&lt;0.001; Mann Whitney U), but not for the HER2+ cancers (p=0.097; Mann Whitney U).

Conclusion

Changes in lesion heterogeneity between baseline and interim MRI examinations, as measured using TA on T2-weighted images, correlate with pathologic response to NAC treatment in primary breast cancer using the RCB score. Larger reductions in lesion heterogeneity between baseline and interim examinations predict for a good response to treatment especially in ER+ and TNBC. Further evaluation of TA as a predictor of RCB score, with increased numbers in tumor subgroups, is required in a clinical trial setting.

Citation Format: Waugh SA, Purdie CA, Evans AJ, Lerski RA, McGhee H, Vinnicombe SJ, Thompson AM. Response to neoadjuvant chemotherapy assessed by magnetic resonance imaging (MRI) texture analysis compared with residual cancer burden (RCB) and tumor subtype in primary breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-02-10.