Factors influencing Anti-SARS-CoV-2 IgG levels after vaccination in breast cancer patients

Breast cancer patients may exhibit impaired vaccine-induced immunity due to disease progression and treatment-related immunosuppression. This study examined clinical factors associated with anti-SARS-CoV-2 IgG responses post-COVID-19 vaccination, with a focus on disease stage and treatment timing. We analyzed 63 breast cancer patients vaccinated between 2021 and 2022. Clinical data—including tumor size, stage, lymph node involvement, estrogen receptor (ER) status, and treatments (chemotherapy, radiation)—were collected. Serum anti-SARS-CoV-2 IgG levels were assessed after each vaccine dose. After the first dose, lower IgG titers were observed in patients receiving chemotherapy, with lymph node involvement, or left-sided tumors. Higher titers were associated with larger tumors (≥ 2 cm), Stage > 2 A, ER positivity, and radiation therapy, possibly due to Th2-skewed responses. Longer diagnosis-to-vaccination intervals enhanced responses. No stage-related differences were found after the second dose, likely due to a ceiling effect. mRNA vaccines tended to elicited higher titers than adenoviral vector vaccines. Reported adverse effects were mild. Tumor stage, ER status, radiation, and vaccination timing influence humoral responses in breast cancer patients. These findings highlight the need for tailored vaccine strategies, including the timing of mRNA vaccines, to optimize protection in this population.