[A case of effective trastuzumab plus gemcitabine therapy for human epidermal growth factor receptor 2-positive breast cancer].
A 71-year-old postmenopausal woman was undergoing treatment for depression. She visited the hospital with a chief complaint of fibrosclerosis of the entire left breast 8 years previously. She was diagnosed as having stage IV( T3N1M1b) left breast cancer (papillotubular>scirrhous carcinoma, g+, f+, estrogen receptor [ER]-negative, progesterone receptor [PgR]-negative, and human epidermal growth factor receptor 2[ HER2/neu]-positive[ 3+]). Synchronous bone metastases were detected in the left tenth rib, the eleventh dorsal vertebra, and in the area spanning the lower lumbar to sacral vertebrae. First-line treatment was systemic therapy with 4 cycles of Adriamycin and cyclophosphamide (AC) followed by 4 cycles of trastuzumab and paclitaxel. The breast mass initially observed on clinical imaging disappeared and only calcifications were observed. Bone metastases were detected only in the left tenth rib. As an additional therapy, 3-dimensional radiotherapy( 50 Gy/25 fractions), which irradiated the left mammary gland, axilla, and supraclavicular fossa, was administered. The tumor was well controlled for approximately 3 years. However, a gradual increase in the level of carcinoembryonic antigen( CEA) was accompanied by an increase in the left breast mass and enlargement of left axillary lymph nodes. Modified radical mastectomy (Bt+Ax [level I]) was performed for this condition 3 years ago. Papillotubular-type invasive ductal carcinoma (INF β, ly3, v0, g+, f+, s+, nuclear grade 3 [atypia 3+mitosis 3]) was diagnosed histopathologically. Lymph node metastases were also detected. As histopathological examination of the bone metastatic lesion showed no progression, administration of lapatinib and capecitabine was initiated. After 15 cycles of treatment, enlarged right axillary lymph nodes were observed and local excision was performed. Histopathological examination revealed recurrence of the breast cancer. The patient was diagnosed as having grade 3( atypia 3, mitosis 2) breast cancer( ER-negative, PgR-negative, HER2/neu positive[ 3+], and MIB-1 index 50%). The response to treatment with lapatinib and capecitabine was progressive disease( PD), and therefore, trastuzumab and gemcitabine therapy was selected. Currently, the patient has undergone 30 cycles of this regimen and the tumor is well controlled. This regimen was considered effective for the treatment of patients with HER2-positive metastatic breast cancer.