Clinical-pathological characterization of patients with HER2 negative breast cancer submitted to adjuvant docetaxel/cyclophosphamide (TC), TC4 versus TC6.
Authors: Kraychete Mila Meyer Campos , de Almeida Guilherme , Santana Leonardo , Cesca Marcelle Goldner , Leite Luciana de Moura , Tavares Monique Celeste , Sanches Solange Moraes 
Published: June 2023

e12530 Background: The optimal number of cycles of adjuvant docetaxel and cyclophosphamide (TC) in patients with HER2 negative breast cancer is unknown. The serious long-term adverse events associated with anthracyclines led researchers to question the risk-benefit ratio of anthracycline-based regimens, especially in those without axillary lymph node involvement, leading to an increasing trend to omit anthracyclines in adjuvant treatment. Therefore, we do not know for sure which clinical-pathological characteristics would favor the use of TC4 versus TC6. Objective: To evaluate the clinical-pathological characteristics of patients who received adjuvant treatment for invasive breast cancer, her2 negative, stage I-III with TC4 or TC6 in a Brazilian service. Methods: This is a retrospective observational cohort study of patients diagnosed with invasive breast cancer, her2 negative, stage I-III, who received adjuvant treatment with TC4 or TC6, between January 2010 and December 2022 at AC Camargo Cancer Center, São Paulo, Brazil. Results: We analyzed 186 patients, 98% female, 52.3% pre-menopausal, 68.7% had at least one comorbidity, 10% mutation in the BRCA1/2 gene, 5% had a previous history of DCis or IDC. 62.2% underwent breast-conserving surgery and 80% underwent sentinel lymph node (SL). Regarding the pathological characteristics of the tumor 82.9% invasive ductal carcinoma (IDC), 42.7% histological grade (HG) III, 90% were hormone receptor positive (HR+) and only 10% triple negative (TN), staging 66% pT1, 71% pN0, being grouped into 63.7% stage I, 34.6% stage II; 1.7% stage III. Only 9% underwent oncotype, 5% of them had some contraindication to anthracycline. Regarding treatment groups 72.4% received TC4 versus 27.6% TC6. There were no treatment-related deaths. Regarding the TC4 / TC6 groups (%) and clinical-pathological characteristics: pre-menopausal 60.5 / 49% ( p= 0.225), comorbidity 3 / 6% ( p= 0.400), contraindication to anthracycline 4.7 / 6% ( p= 0.714). Conservative surgery 61.5 / 64% ( p= 0.894), SL 81 / 78% ( p= 0.504), GH III 39.8 / 50% (p = 0.334), pT2 staging 26.4 / 40 % (p = 0.087), pN1 11.7/ 22% (p = 0.050), stage I 65.9/58%, II 33.3 / 38%, III 0.8 /4 % (p = 0.212). RH- 8.7 / 14% (p = 0.444). Did not complete treatment 3.2 / 12% (p = 0.033), toxicities G3/4 9.7 / 12.5% (p = 0.791), FN G3/4 3.8 / 4% (p = 1.00) and neuropathies 8.9 / 28.6% (p = 0.002). Late toxicities 5.7 / 18.4% (p = 0.018). Extended hormone therapy 35/ 50% (p = 0.142). Systemic recurrences 12.5% / 2% (p = 0.566). Conclusions: TC6 was more indicated in patients with GH III, pT2 and/or pN1, stage II and III, RH-, therefore patients who received TC6 had a lower chance of completing the treatment, as well as greater toxicities, mainly late peripheral neuropathy, and more indications of extended hormone therapy, however those who performed the TC6 had less chance of systemic recurrences.