Stage IA ER/PR-positive breast cancer in SLE: arm-behind-back radiation after lumpectomy

What happened, in summary

This 43-year-old woman had lived with systemic lupus erythematosus for 10 years before a medical checkup found a localized lesion in her left breast. Her lupus had previously caused facial rash, oral ulcers, polyarthritis, alopecia, organizing pneumonia, neuropsychiatric symptoms, and later osteonecrosis related to treatment. At the time of breast cancer diagnosis, her lupus activity was stable, and staging CT and bone scans showed no lymph node or distant metastasis. Ultrasound showed a 20 mm mass in the left upper inner quadrant, and MRI showed a 17 mm mass in the same area. Core needle biopsy diagnosed invasive ductal carcinoma with ER >95%, PR >95%, and HER2 1+. No BRCA1/2 variants were found. She underwent breast-conserving surgery with sentinel lymph node biopsy. Final pathology showed Stage IA invasive ductal carcinoma, pT1cN0M0, grade I, with negative margins, no lymphatic or vascular invasion, ER >95%, PR >95%, HER2 1+, and Ki-67 of 23%. She started tamoxifen after surgery. Radiation required special planning because arthritis and steroid-related complications made it painful for her to hold the usual raised-arm position. Her team used an arm-behind-the-back setup for 3D conformal radiotherapy, delivering 42.56 Gy in 16 fractions while keeping lung and heart doses acceptable. Treatment took longer each day because setup was more complex, but scheduled irradiation was completed safely. She developed grade 2 radiation dermatitis, treated with ointments, and the redness resolved over 7 weeks. As of April 2025, 15 months after radiotherapy, she had no local recurrence, distant metastasis, or radiation pneumonitis.