Dramatic response of metaplastic breast cancer to chemo-immunotherapy

Abstract

Frequent overexpression of programmed death-ligand 1 has recently been demonstrated in metaplastic breast cancer, which is a rare breast cancer subtype with limited treatment options. This report describes the clinical course of a patient with metastatic metaplastic breast cancer who had a remarkable response to anti-programmed death-1 therapy with pembrolizumab in combination with nab-paclitaxel. Tissue correlates are presented including tumor-infiltrating lymphocytes and high-programmed death-ligand 1 expression in the tumor.

Fig. 1

Clinical response of a large chest wall recurrence of metaplastic breast cancer to Pembrolizumab/nab-paclitaxel after progression on single agent nab-paclitaxel. Photograph at a baseline, b after 1st treatment cycle (nab-paclitaxel alone), c after two cycles (nab-paclitaxel and pembrolizumab), d after three cycles and e after six cycles

Fig. 2

Radiographic response of recurrent metaplastic breast cancer with a bulky chest wall mass and pulmonary metastases to pembrolizumab/nab-paclitaxel. PET CT images a at baseline depicting the large and destructive chest wall mass (SUV 11.0, 10.1 × 3.6 cm, blue arrow), invading ribs, sternum, and pleura, b at 9 weeks (s/p three cycles) demonstrating a significant metabolic and anatomic response on the chest wall mass (SUV 5.6, 6.5 × 4.7 cm, blue arrow), c at baseline depicting bilateral lung parenchymal (red arrow) and nodal metastases (green arrow), d at 9 weeks demonstrating a decreased number, size, and metabolic activity of pulmonary metastases and worsening cavitation (red arrow) as sign of favorable response to therapy. Additionally, the protruding mass (seen on the clinical photographs) is shown with necrotic debris. Complete response to the previously identified intensely FDG avid necrotic right internal mammary chain lymph node (green arrow). e Coronal image at baseline depicting the bulky right chest wall recurrence, extensive bilateral lung parenchymal and pleural metastases as well as nodal metastases. f Coronal image at 9 weeks demonstrating marked interval improvement in the right chest wall mass consistent with a partial treatment response, as well as interval decrease of multiple FDG avid nodal, pulmonary, and pleural metastases

Fig. 3

Histopathologic features of the MPBC obtained by punch biopsy from peripheral chest wall lesion (inferolateral margin). a Baseline PD-L1 IHC stain at 20×. One-hundred percent of tumor cells stain positive for PD-L1 (95% at 3 + intensity, 5% at 2 + intensity), b Tumor H and E stain at 40× at baseline and c after treatment with pembrolizumab (biopsy cycle 3, day 1) with increase in TIL from baseline (10 to 30%)