Abstract PS13-29: Four cycles of docetaxel-cyclophosphamide versus anthracycline-taxane adjuvant chemotherapy in node negative, HER2-negative breast cancer: A real-world comparison

Abstract Background: It is unknown whether four cycles of docetaxel-cyclophosphamide (DC) is an appropriate adjuvant chemotherapy option in patients with lymph node negative (LNN) and human epidermal growth factor receptor-2 (HER2) negative breast cancer in place of widely adopted anthracycline-taxane (AT) regimens. In the Canadian province of Alberta, four cycles of DC has been used preferably in the last decade as a standard adjuvant chemotherapy regimen in LNN, HER2-negative disease. We aimed to retrospectively compare the survival outcomes of patients diagnosed with LNN, HER2-negative breast cancer in Alberta who were treated with four cycles of DC as compared to those treated with an AT regimens. Methods: We identified all patients who were diagnosed with LNN, HER2-negative breast cancer treated with adjuvant chemotherapy following surgical resection in Alberta from 2008 through 2012. We used propensity score methods to match each patient treated with an AT regimen to up to 4 patients treated with four cycles of DC on all known/potential clinicopathologic and treatment variables (Table).We compared the 10-year invasive disease free survival (iDFS), breast cancer specific-survival (BCSS) and overall survival (OS) between the two patient groups and assessed effect of type of adjuvant chemotherapy on iDFS, BCSS and OS using Cox regression analyses.Results: Of the 726 eligible patients, 657 (90.5%) were treated with four cycles of DC and 69 (9.5%) were treated with an AT regimen. Prior to matching, women who received four cycles of DC compared to those treated with an AT regimen, were more likely to be older, have higher Charlson co-morbidity score and mastectomy for definitive surgery, and in terms of disease: earlier stage, lower grade, and HR-positive status. Matching created a group of 202 women treated with four cycles of DC and eliminated differences in clinicopathologic and treatment features between the two patient groups (Table). Four cycles of DC compared to an AT regimen was not associated with reduced iDFS (HR = 0.91, 95% CI = 0.52 to 1.6, P = 0.75), BCSS (HR = 1.10, 95% CI = 0.51 to 2.37, P = 0.8), or OS (HR = 1.01, 95% CI = 0.48 to 2.17, P = 0.96).Conclusion: In this real-life comparison, four cycles of DC as compared with an AT regimen, yielded similar survival outcomes amongst patients with LNN, HER2-negative breast cancer. Table Baseline patient and tumour characteristics of 726 patients diagnosed with LNN, HER2-negative breast cancer by type of adjuvant chemotherapy. CharacteristicAT (n=69)DC (n=657)p value*Matched DC (n=202)†p value‡Age (years) Median465347 Mean (SD; range)45.8 (9.7; 25 - 69)52.6 (9.8; 23 - 78)<0.000146 (9.4; 23 - 69)0.8BMI Median25.327.526 Mean (SD; range)27.1 (6.7;17.5 - 62)28.5 (6.6;15.6 - 64)0.127.1 (5.8;17.3- 49.4)0.9Year of diagnosis [n (%)] 2007 - 200811 (15.9%)78 (11.9%)0.2426 (13%)0.8 2009 - 201022 (31.9%)275 (41.9%)68 (33.5%) 2011 - 201236 (52.2%)304 (46.3%)108 (53%)Charlson co-morbidity score [n (%)] Mean (SD, range)0.04 (0.26; 0 - 2)0.33 (0.67; 0 - 4)<0.00010.04 (0.27; 0-2)0.9 Score > 0 - no. of patients (%)2 (2.9%)151(23%)0.00057 (3.4%)0.8 067 (97.1%)506 (77%)195 (96.6%) 11 (1.45%)97 (14.8%)4 (2%) 21 (1.45%)44 (6.7%)3 (1.4%) 309 (1.4%) 401 (0.15%)Histology [n (%)] Ductal58 (84%)479 (72.9%)0.12165 (82%)0.8 Mixed Ductal-Lobular5 (7.25%)96 (14.6%)20 (9.9%) Others6 (8.7%)82 (12.5%)17 (8.4%)T-stage [n (%)] Stage I12 (17.4%)253 (38.5%)0.000537 (18.3%)0.9 Stage II57 (82.6%)404 (61.5%)165 (81.6%)Grade differentiation [n (%)] Well differentiated026 (4%)<0.00700.9 Moderately differentiated6 (8.7%)139 (21.2%)20 (9.9%) Poorly differentiated63 (91.3%)492 (74.9%)182 (90.1%)Hormone receptor status [n (%)] Positive33 (47.8%)468 (71.2%)<0.000195 (47%)0.9 Negative36 (52.2%)189 (28.8%)107 (52.9%)Definitive breast surgery [n (%)] Breast-conserving surgery30 (43.5%)390 (59.4%)<0.0190 (44.5%)0.9 Mastectomy39 (56.5%)267 (40.6%)112 (55.5%)Radiotherapy [n (%)]36 (52.2%)397 (60.4%)0.18103 (51%)0.9Time interval to first cycle of chemotherapy (months) Median2.732.82.71 Mean (SD; range)2.86 (0.77; 1.2- 4.8)3.25 (1.38; 0 - 15)0.52.82 (0.8; 0– 5.9)0.7 No. of patients (%) 0 months ≥ – < 3 months39 (56%)404 (61.5%)0.42122 (60%)0.6 3 months ≥ – < 6 months30 (43.4%)245 (37.2%)80 (40%) ≥ 6 months08 (1.2%)0Type of adjuvant chemotherapy [n (%)] DC×4657 (100%)202 (100%) FEC×3→D×363 (91.3%) AC×4→T×43 (4.35%)TAC×63 (4.35%) Citation Format: Malek Bassam Hannouf, Atul Batra, Sasha Lupichuka. Four cycles of docetaxel-cyclophosphamide versus anthracycline-taxane adjuvant chemotherapy in node negative, HER2-negative breast cancer: A real-world comparison [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS13-29.

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