Aims: Neoadjuvant systemic therapy of large and locally advanced breast cancers may, through shrinkage, enable breast conservation surgery. Letrozole, an aromatase inhibitor, is used frequently in the treatment of oestrogen receptor-positive breast cancer. The aim was to examine the response patterns in a letrozole-treated group compared with a chemotherapy-treated group.
Materials and methods: Fifty patients with primary breast cancer were treated with 3 months of chemotherapy and 53 with 3 months of neoadjuvant letrozole. Excised tumours were compared with preoperative core biopsy specimens. Volume calculations before and after therapy were used to calculate clinical response in the letrozole group.
Results: Response patterns were significantly different between the two therapies (P < 0.0005). Chemotherapy produced more complete pathological responses (P = 0.008) and a scattered cell pattern was also seen more frequently (P = 0.035). Letrozole produced substantially more central scars – 31 cases as opposed to two cases in the chemotherapy group (P = 0.0001) – and there was a statistically significant correlation with central scarring and clinical tumour volume reduction (P = 0.034).
Conclusions: There are significantly different histological responses between cancers treated with chemotherapy and endocrine therapy, particularly central scarring. This has not been documented previously and may be an important factor in down-sizing tumours with letrozole, enabling subsequent conservation surgery.