ABSTRACT
Shared decision making(SDM)plays a crucial role in treatment discussions for pregnant patients with breast cancer. A woman in her 30s was diagnosed with Stageâ breast cancer during the 20th week of her pregnancy. In SDM sessions, we proposed a total mastectomy and axillary sentinel lymph node biopsy with a radioisotope tracer. However, the patient opted for a conservative breast surgery and lymph node evaluation without tracer use. Following a comprehensive risk explanation, we performed a partial mastectomy and axillary lymph node sampling during her 22nd week of pregnancy. Post-delivery, further SDM sessions were held to discuss adjuvant therapy. Although we recommended the prompt initiation of radiotherapy, the patient chose to postpone it to continue breastfeeding. After she stopped breastfeeding, radiotherapy commenced 6 weeks post-delivery(24 weeks after surgery). After the SDM sessions, the chosen course may not align with optimal health practices. Nevertheless, SDM remains crucial, particularly for pregnancy-related breast cancer, given the limited high- grade evidence for treatment approaches in such cases.