Stage IIIA HR-positive HER2-negative breast cancer with radiation-induced brachial plexopathy

What happened, in summary

A 50-year-old woman presented with AJCC 8th edition anatomic Stage IIIA invasive ductal carcinoma of the left breast, cT2N1M0, grade 2. The tumor was ER-positive, PR-positive, and HER2-negative. Genetic testing found pathogenic heterozygous ATM c.5290del and PALB2 c.1619dup variants, plus an ATM c.4396C>G variant of uncertain significance. She received neoadjuvant dose-dense Adriamycin/Cytoxan followed by ddAC-T. About 1 month after chemotherapy, she underwent left breast lumpectomy and sentinel lymph-node biopsy, which showed residual Stage IA disease, ypmT1cN0Mx. About 8 weeks after chemotherapy, she received adjuvant radiation: 5000 cGy in 25 fractions to the left breast and regional nodes, including axilla, supraclavicular, and internal mammary nodes, plus a 1000 cGy boost in 4 fractions to the tumor bed. Letrozole started 2 weeks after radiation. Survivorship became dominated by toxicity rather than recurrence. Four months after therapy, she developed supraclavicular fullness and breast shrinkage. Later symptoms included lymphedema, severe back and axillary burning pain, rib fractures related to radiation, premature atrial contractions, progressive telangiectasias, and radiation-induced brachial plexopathy confirmed by MRI signal along the left brachial plexus. Supportive care included lymphedema therapy, prednisone, pain medicines, cardiac medications, hyperbaric oxygen, pentoxifylline with vitamin E, THC edibles, and neuromuscular/muscular electrical stimulation. At 10 months, spine MRI, PET, and CT showed no recurrence, supporting treatment toxicity rather than active cancer. Approximately 3.5 years after radiation, she had no evidence of disease recurrence but continued considering prophylactic procedures related to inherited risk variants. The supportive-care course matters because her symptoms waxed and waned but progressively worsened before stabilizing by about 2 years. This separates her cancer outcome, which was NED, from the ongoing morbidity caused by radiation fibrosis, telangiectasias, lymphedema, and brachial plexopathy.