MRI and ¹⁸F-FDG PET/CT in monitoring the response to neoadjuvant chemotherapy: is it necessary to appropriately select the patients?

Excerpt

Neoadjuvant or preoperative chemotherapy (NAC) is considered the standard of care in the treatment of locally advanced breast cancer [1]. Its potential benefits include: (1) reduction in size of the primary tumour allowing conversion of mastectomy candidates to breast-conserving surgery candidates; (2) reduction in lymph node involvement allowing to conversion of patients requiring axillary dissection to candidates for sentinel node biopsy; (3) testing of tumour chemosensitivity to allow changes in therapy regimen, if needed; (4) correlation between achievement of a pathological complete response (pCR) on NAC completion and long-term prognosis; and (5) assessment of molecular changes during NAC as a means to assess response to specific chemotherapy and to discover of future possible drug targets [2]. Therefore, monitoring tumour response to NAC is useful from a clinical, diagnostic and prognostic point of view. It is usually evaluated by clinical and conventional imaging modalities, such as mammography and/or ultrasonography, although these are unreliable and inaccurate tools. There is evidence that contrast-enhanced MRI could be superior to standard clinical assessment methods in determining the prognostic response to NAC [3, 4]. Conversely, in recent years the role of PET/CT with ¹⁸F-FDG in this setting has been the main end-point of many studies [5‐7], but its utility should still be the subject of investigation. Moreover, breast cancer includes several molecular entities that differ in clinical behaviour, biological characteristics and outcome [8‐10]. It is typically differentiated into three groups (basal-like or triple-negative, HER2-enriched, and luminal A and B) that are widely correlated with different response rates to NAC. …