Symptom burden and systemic inflammation as predictors of quality of life in women with breast cancer receiving chemotherapy.

417 Background: The interplay between chronic inflammation and cancer progression is well established. Inflammatory markers—Neutrophil-to-Lymphocyte Ratio (NLR), Platelet-to-Lymphocyte Ratio (PLR), Monocyte-to-Lymphocyte Ratio (MLR), and C-reactive protein (CRP)—are associated with prognosis and poorer quality of life (QoL). Cancer symptom clusters (CSCs) also reflect symptom burden and impact patient well-being. This study examined the longitudinal association between inflammatory biomarkers, CSCs, and QoL in Brazilian women undergoing chemotherapy (CT) for breast cancer (BC). Methods: A prospective cohort study (2022–2024) was conducted at a cancer center in southeastern Brazil. Women ≥18 years with newly diagnosed stage I–III BC receiving outpatient CT were included. Exclusion criteria: palliative care and multiple primary tumors. Data were collected at six 21-day CT cycles, including inflammatory markers (blood tests), CSCs (Memorial Symptom Assessment Scale), and QoL (EQ-5D-3L). Analyses involved descriptive statistics, bivariate tests, and multivariate models. Results: Fifty participants (mean age 53.3±11.4) were equally diagnosed with ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC), in stages I (16%), II (62%), and III (22%). Regimens included neoadjuvant (42%) or adjuvant (58%) CT with Doxorubicin, Cyclophosphamide, and Docetaxel. Inflammatory markers rose across cycles: NLR (Glass’ delta = 0.83; p=0.013), PLR (0.92; p<0.001), MLR (0.59; p=0.001). Significant differences were observed for PLR (CT3, CT4; p=0.042) and NLR (CT5; p=0.050) between DCIS and IDC. Mean QoL was 79.36 (p=0.219). MLR correlated with anxiety/depression (EQ-5D D5, CT3; p=0.028) and decreased usual activities (D3, CT6; p=0.019). CSCs identified included: i) Cluster 1 (emotional): concentration issues, nervousness, insomnia, sadness, worry, irritability (affecting D2, D3, D5; all p<0.001); ii) Cluster 2 (somatic): pain, fatigue, dry mouth (impacting D4, D5; p<0.001); iii) Cluster 4 (gastrointestinal): nausea, appetite loss, taste changes, bloating, weight loss, diarrhea—emerging at CT6—worsened all QoL domains (p<0.001). Conclusions: Progressive inflammation and persistent emotional, somatic, and gastrointestinal CSCs significantly compromised QoL during CT. Monitoring biomarkers and symptom clusters may enable earlier, targeted interventions to improve patient outcomes. Further research is needed to confirm findings and inform supportive care strategies.