Abstract P4-02-09: Can MRI be used to determine pathological complete response following neo-adjuvant chemotherapy for breast cancer?

Abstract

Abstract Intro Neo-adjuvant chemotherapy (NACT) is increasingly offered to patients with breast cancer, and it understood that patients with pathological complete response (PCR) have improved survival. It has been suggested that patients with radiological complete response may be spared surgery. We aimed to determine whether MRI findings can predict PCR following NACT. Methods This was a retrospective analysis of a prospectively maintained database. Most patients had NACT with 6 cycles of EC/DC+/-Traztuzumab and response was monitored using MRI. For univariate analysis χ2 and Fisher's exact test was used for categorical data. Log rank test by Kaplan Meier method was used for survival analysis. Results 310 patients had NACT from December 2007 to December 2014. Baseline MRI prior to embarking on NACT was achieved in 251 patients. MRI concorded with size on mammography/USS in the majority of cases (83%) and upgraded the overall size of the lesion in 16% (50% of unifocal lesions on USS upgraded to multifocal). In the 247 patients who had baseline MRI, a radiological response seen on the 2nd MRI (early responders, n=138), was predictive of eventual PCR (p=0.000, sensitivity = 77%). Patients with Her2+ve non-luminal (65%), triple negative (TNBC) (64%) and Luminal B Her2-ve (65%) tumours were more likely to be early responders on MRI. The non-early responders with Her2+ve tumours all had late radiological response, however, the TNBC tumours had low rates of late radiological response. Complete radiological response on the final MRI correlated strongly with PCR; p=0.000, specificity=98%. Tumour vascularity correlated positively and significantly with PCR. There was no difference in survival between those with early and late radiological response (median survival 66.2 months and 66.9 months), but those with no radiological response had significantly poorer survival 53.2 months, p=0.012). Conclusion Response on MRI is predictive of PCR, particularly within the non-luminal Her2+ve and TNBC molecular subtypes. Early response has high sensitivity, and complete response on final MRI has high specificity. Further work on larger data-sets is required before we confidently spare patient from surgery in the event of complete response on MRI. Citation Format: Sharma N, Dave R, Millican-slater R, Dodwell D, Horgan K. Can MRI be used to determine pathological complete response following neo-adjuvant chemotherapy for 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 P4-02-09.