Stage 2 triple-negative breast cancer: pathologic complete response to chemotherapy

What happened, in summary

A 40-year-old postmenopausal woman was diagnosed in 2022 after finding a palpable lump in her right breast. Mammography showed an 18 × 20 mm mass in the upper inner quadrant, and core biopsy showed grade 3 invasive ductal carcinoma that was ER 0%, PR 0%, HER2-negative, and highly proliferative, with Ki-67 70%-80%. CT of the chest and abdomen and bone scan showed no distant metastases. Breast MRI showed a 21 × 14 mm mass without axillary lymph-node involvement, staged cT2N0M0 / Stage IIA triple-negative breast cancer. Her history made treatment planning unusually complex. At age 25, she had B-cell acute lymphoblastic leukemia treated with chemotherapy including daunorubicin, then relapsed and received high-dose cytosine arabinoside and mitoxantrone, total body irradiation, and allogeneic stem-cell transplant. She later developed graft-versus-host disease, although it was not active when breast cancer was diagnosed. Because of this history, pembrolizumab was omitted, and anthracycline exposure was limited. She received 12 weekly treatments of paclitaxel plus carboplatin. After 4 weeks, the tumor was no longer palpable, and MRI after 7 weeks showed a complete radiologic response. She then received 3 dose-dense cycles of doxorubicin plus cyclophosphamide, not 4, to stay within cumulative dose limits; the last dose was reduced for symptomatic anemia. Genetic testing found a pathogenic PALB2 variant. She underwent bilateral skin-sparing mastectomy, right sentinel lymph node biopsy, immediate implant reconstruction, and preventive laparoscopic bilateral adnexectomy. Pathology showed a complete response. As of May 2024, more than 1 year after surgery, she was well and free of cancer. A consulting hematologist did not oppose G-CSF support during treatment.