Feasibility Study of Transarterial Chemotherapy Followed by Chemoembolization for Recurrent Breast Cancer.

PURPOSE: To assess the treatment response to transarterial chemotherapy followed by chemoembolization for locally recurrent breast cancer. MATERIALS AND METHODS: Thirty-nine women with locally recurrent breast cancer after standard therapy underwent selective intra-arterial chemotherapy followed by embolization using drug-eluting microspheres for locally recurrent tumors and axillary lymph node metastases. Tumor response and toxicity were assessed by the Response Evaluation Criteria in Solid Tumors (RECIST) and Common Terminology Criteria for Adverse Events (CTCAE), and survival was evaluated by the Kaplan‒Meier method. RESULTS: The local responses of breast tumors at 3 and 6 months were as follows: complete response, 5.1% and 7.2%; partial response, 35.9% and 67.8%; stable disease, 59.0% and 21.4%; and progressive disease, 0.0% and 3.6%, respectively. All adverse events were mild and did not require treatment. The median overall survival (OS) was 46.5 months, and the OS rates for 1 and 2 years were 81.4% and 69.2%, respectively. The size of recurrent tumors and axillary lymph node metastases did not impact prognosis, but both liver and bone metastases adversely affected survival. CONCLUSION: Transarterial chemotherapy followed by chemoembolization may provide a favorable tumor response in patients with locally recurrent breast cancer in whom conventional therapy has failed.

Eribulin induces micronuclei and enhances the nuclear localization of cGAS in triple-negative breast cancer cells.

Eribulin (ERI), clinically utilized for locally advanced or metastatic breast tumors, has shown potential links to the immune system. Notably, the cGAS-STING pathway, a key component of innate immunity, has gained prominence. Yet, limited reports explore ERI's effects on the cGAS-STING pathway. Additionally, the nuclear presence of cGAS remains poorly understood. This study uniquely delves into ERI's impact on both the cytosolic cGAS-STING pathway and nuclear cGAS. ERI enhances nuclear localization of cGAS, resulting in hyper-activation of the cGAS-STING pathway in triple-negative breast cancer cells. Reduction of cGAS heightened both cell proliferation and ERI sensitivity. In clinical data using ERI in a neo-adjuvant setting, patients with low cGAS cases exhibited reduced likelihood of achieving pathological complete response after ERI treatment. These findings illuminate the potential of cGAS and IFNß as predictive biomarkers for ERI sensitivity, providing valuable insights for personalized breast cancer treatment strategies.

Survival advantage of locoregional and systemic therapy in oligometastatic breast cancer: an international retrospective cohort study (OLIGO-BC1).

BACKGROUND: An international retrospective cohort study was conducted to clarify the survival advantage of combination therapy with locoregional and systemic therapy (ST) in oligometastatic breast cancer (BC). METHODS: Patients with oligometastatic BC diagnosed from 2007 to 2012 were enrolled in center hospitals in China, Korea and Japan. It was defined as a low-volume metastatic disease at up to five sites and not necessarily in the same organ. Cases with brain, pleural, peritoneal and pericardial metastases were excluded. The primary endpoint was overall survival (OS) from the initial diagnosis of oligometastases. OS was summarized using the Kaplan-Meier method. A multivariable Cox regression model was used to estimate the hazard ratio (HR) for clinicopathological factors. RESULTS: Among 1,295 cases registered from February 2018 to May 2019, 932 remained for analysis after the exclusion of unavailable cases and locoregional recurrence. One metastatic site was found in 400 cases, 2 in 243, 3 in 130, 4 in 86 and 5 in 73. At the median follow-up of 4.5 years, 5-year OS was 54.7% and 39.7% for 321 cases in the combination therapy group and 611 cases in the ST group, respectively. An adjusted HR was 0.66 (95% confidence interval: 0.55, 0.79). Some types of ST without chemotherapy alone, younger age, ECOG performance status 0, early-stage BC, non-triple negative subtype, fewer metastatic sites and longer duration of surgery to relapse were significantly favorable prognostic factors. CONCLUSION: Combination therapy may be considered for longer survival under some conditions in oligometastatic BC.

Health-related quality of life and estimation of the minimally important difference in the Functional Assessment of Cancer Therapy-Endocrine Symptom score in postmenopausal ER+/HER2- metastatic breast cancer with low sensitivity to endocrine therapy.

BACKGROUND: The HORSE-BC study previously demonstrated that second-line endocrine therapy (ET) for patients with acquired endocrine-resistant metastatic breast cancer (MBC) still provided a clinically meaningful benefit. Herein, we investigated the health-related quality of life (HRQOL) in the HORSE-BC study. METHODS: Patients with acquired endocrine-resistant MBC who were scheduled for second-line ET were recruited. The HRQOL was assessed at baseline, and 1 and 3 months after second-line ET initiation. To investigate the minimally important difference (MID) in the Functional Assessment of Cancer Therapy-Endocrine Symptoms (FACT-ES), we evaluated the means and standard deviations for the distribution-based method, and differences in the change in HRQOL for the anchor-based method. We also investigated the association between FACT-ES total scores and clinical benefit. RESULTS: Overall, 56 patients were enrolled. Of these, 47 were analyzed. When defined as 1/3 standard deviation estimates based on the distribution method, the calculated MID was 5.9. The MIDs of the FACT-ES total scores based on the anchor method were 7.7 for decline and 4.1 for improvement. The MID decline proportions were 6.1% and 14.7% lower in patients who experienced clinical benefits than in those who did not at 1 and 3 months, respectively. The ratios of MID improvement in patients who experienced clinical benefits were 18.3% and 3.2% higher, respectively; the mean change in the FACT-ES total score from baseline improved in patients who experienced clinical benefits. CONCLUSIONS: Maintaining the HRQOL as determined by FACT-ES may be associated with clinical benefits in patients with acquired endocrine-resistant MBC treated with ET.

Strontium-89 plus zoledronic acid versus zoledronic acid for patients with painful bone metastatic breast cancer.

INTRODUCTION: ß-ray strontium-89 (Sr-89) intra-irradiation therapy has been approved and clinically used to reduce bone metastasis pain not alleviated by bone-modifying agents, external radiation, and analgesic agents. We examined the efficacy of zoledronic acid (ZOL) and Sr-89 combination therapy compared with ZOL alone in breast cancer patients with bone metastases. MATERIALS AND METHODS: A randomized controlled trial was conducted on breast cancer patients with bone metastasis to compare the efficacy between ZOL monotherapy and ZOL plus Sr-89 combination therapy. The primary endpoints were changes in urinary NTX levels at 13 weeks and brief pain inventory scores. The secondary endpoints were analgesic drug usages, response rates, changes in bone metabolism markers, quality of life, and adverse event rates. RESULTS: Thirty of the planned 60 cases were randomly assigned to ZOL alone or ZOL + Sr-89. There were no significant differences in the changes in urinary NTX levels between the 2 groups (P = 0.365). There was no consistent difference in the pain score changes between the 2 groups. Sr-89 addition to ZOL slightly reduced the white blood cell and platelet counts. However, all adverse events were Grade 1. Safety and analgesic drug dose reduction were more evident in ZOL + Sr-89. CONCLUSION: This trial showed the lack of benefits from Sr-89 addition to ZOL for breast cancer patients with painful bone metastases. However, safety and analgesic drug dose reduction were more evident in ZOL + Sr-89, indicating its potential for pain control. Sr-89 therapy is safe, thus more effective radiopharmaceuticals are anticipated.

Hippo-TAZ signaling is the master regulator of the onset of triple-negative basal-like breast cancers.

Breast cancer is the most frequent malignancy in women worldwide. Basal-like breast cancer (BLBC) is the most aggressive form of this disease, and patients have a poor prognosis. Here, we present data suggesting that the Hippo-transcriptional coactivator with PDZ-binding motif (TAZ) pathway is a key driver of BLBC onset and progression. Deletion of Mob1a/b in mouse mammary luminal epithelium induced rapid and highly reproducible mammary tumorigenesis that was dependent on TAZ but not yes-associated protein 1 (YAP1). In situ early-stage BLBC-like malignancies developed in mutant animals by 2 wk of age, and invasive BLBC appeared by 4 wk. In a human estrogen receptor+ luminal breast cancer cell line, TAZ hyperactivation skewed the features of these luminal cells to the basal phenotype, consistent with the aberrant TAZ activation frequently observed in human precancerous BLBC lesions. TP53 mutation is rare in human precancerous BLBC but frequent in invasive BLBC. Addition of Trp53 deficiency to our Mob1a/b-deficient mouse model enhanced tumor grade and accelerated cancer progression. Our work justifies targeting the Hippo-TAZ pathway as a therapy for human BLBC, and our mouse model represents a powerful tool for evaluating candidate agents.

Validation of a nuclear grading system for resected stage I-IIIA, high-risk, node-negative invasive breast carcinoma in the N·SAS-BC 01 trial.

BACKGROUND: This retrospective observational study validated nuclear grading criteria developed to identify a high-risk group with recurrence rate ≥20-30% and local pathology diagnosis used in a previous multi-institutional randomized N·SAS-BC 01 trial, where the efficacy of adjuvant chemotherapy regimens was evaluated in 733 high-risk node-negative invasive breast cancer patients. METHODS: Of 545 patients with long-term follow-up data (median 12.1 years), pathology slides, and local pathology diagnosis, 530 eligible patients were subjected to central pathology review (CPR) for histological type and nuclear grade (NG). Concordance in NGs was compared with local diagnosis. The 10/15-year recurrence-free survival (RFS) and overall survival (OS) rates stratified by NG and histological type were calculated. RESULTS: Local diagnoses were invasive ductal carcinoma (IDC)-NG2, IDC-NG3, invasive lobular carcinoma (ILC), and metaplastic carcinoma (MC) in 158/327/38/7 patients, respectively. The 10/15-year RFS rates were 87.2/82.6% for IDC-NG2 and 81.8/75.0% for IDC-NG3 (p = 0.061), and OS rates were 95.0/92.8% for IDC-NG2 and 90.8/85.7% for IDC-NG3 (p = 0.042). CPR graded 485 locally diagnosed IDCs as IDC-NG1/NG2/NG3/unknown in 98/116/267/4 patients, respectively. No significant difference was found among survival curves for the three NG groups. Although the agreement level between local and CPR diagnoses was low (κ = 0.311), both diagnoses identified a patient group with a 15-year recurrence rate ≥ 20%. The 10/15-year RFS rates were 79.4/63.5% for ILC and 68.6%/unknown for MC. CONCLUSIONS: The N·SAS grading system identified a patient group with high-risk node-negative invasive breast cancer, suggesting that local diagnosis was performed efficiently in the N·SAS-BC 01 trial. TRIAL REGISTRATION NUMBER: UMIN000022571. Date of registration: June 1, 2016.

Adipsin-Dependent Secretion of Hepatocyte Growth Factor Regulates the Adipocyte-Cancer Stem Cell Interaction.

Adipose tissue is a component of the tumor microenvironment and is involved in tumor progression. We have previously shown that adipokine adipsin (CFD) functions as an enhancer of tumor proliferation and cancer stem cell (CSC) properties in breast cancers. We established the Cfd-knockout (KO) mice and the mammary adipose tissue-derived stem cells (mADSCs) from them. Cfd-KO in mADSCs significantly reduced their ability to enhance tumorsphere formation of breast cancer patient-derived xenograft (PDX) cells, which was restored by the addition of Cfd in the culture medium. Hepatocyte growth factor (HGF) was expressed and secreted from mADSCs in a Cfd-dependent manner. HGF rescued the reduced ability of Cfd-KO mADSCs to promote tumorsphere formation in vitro and tumor formation in vivo by breast cancer PDX cells. These results suggest that HGF is a downstream effector of Cfd in mADSCs that enhances the CSC properties in breast cancers.

Investigation of a Novel S-1 Administration Schedule for Treating Metastatic and Recurrent Breast Cancer (KBCOG13).

BACKGROUND/AIM: S-1, a 5-fluorouracil(5-FU) oral anti-cancer drug, has been traditionally used with a schedule of 4-week oral administration followed by 2-week rest for breast cancer treatment. We, herein, aimed to investigate the clinical efficacy and safety of a schedule of 2-week oral administration followed by 1-week rest for patients with metastatic breast cancer. PATIENTS AND METHODS: We enrolled patients with HER2-negative metastatic breast cancer who had not received prior chemotherapy. S-1 was administered consecutively for 2-weeks followed by a 1-week rest. RESULTS: Between September 1, 2013 and August 31, 2016, 32 patients were enrolled. The median follow-up time was 32.1 months. The median progression-free survival (PFS) was 9.4 months. Overall survival (OS) was 41.0 months, time to treatment failure (TTF) was 7.8 months, response rate (RR) was 31.3%, and disease control rate (DCR) was 78.1%. The incidence of grade 3 side-effects was not high. CONCLUSION: The 3-week schedule of S-1 can be considered useful as a treatment for patients with metastatic breast cancer, helping in maintaining a high quality of life.

Clinical usefulness of eribulin as first- or second-line chemotherapy for recurrent HER2-negative breast cancer: a randomized phase II study (JBCRG-19).

BACKGROUND: Anthracycline (A) or taxane T-based regimens are the standard early-line chemotherapy for metastatic breast cancer (BC). A previous study has shown a survival benefit of eribulin in heavily pretreated advanced/recurrent BC patients. The present study aimed to compare the benefit of eribulin with treatment of physician's choice (TPC) as first- or second-line chemotherapy for recurrent HER2-negative BC. METHODS: Patients with recurrent HER2-negative BC previously receiving anthracycline and taxane AT-based chemotherapy in the adjuvant or first-line setting were eligible for this open-label, randomized, parallel-group study. Patients were randomized 1:1 by the minimization method to receive either eribulin (1.4 mg/m2 on day one and eight of each 21-day cycle) or TPC (paclitaxel, docetaxel, nab-paclitaxel or vinorelbine) until disease progression or unacceptable toxicity. The primary endpoint was progression-free survival (PFS). Secondary endpoints included time to treatment failure (TTF), overall response rate (ORR), duration of response, and safety (UMIN000009886). RESULTS: Between May 2013 and January 2017, 58 patients were randomized, 57 of whom (26 eribulin and 31 TPC) were analyzed for efficacy. The median PFS was 6.6 months with eribulin versus 4.2 months with TPC (hazard ratio: 0.72 [95% confidence interval (CI), 0.40-1.30], p = 0.276). Median TTF was 6.0 months with eribulin versus 3.6 months with TPC (hazard ratio: 0.66 [95% CI, 0.39-1.14], p = 0.136). Other endpoints were also similar between groups. The most common grade ≥ 3 adverse event was neutropenia (22.2% with eribulin versus 16.1% with TPC). CONCLUSIONS: Eribulin seemed to improve PFS or TTF compared with TPC without statistical significance. Further validation studies are needed.

Relationships between pathological factors and long-term outcomes in patients enrolled in two prospective randomized controlled trials comparing the efficacy of oral tegafur-uracil with CMF (N·SAS-BC 01 trial and CUBC trial).

PURPOSE: To evaluate the efficacies of cyclophosphamide, methotrexate, and fluorouracil (CMF) and tegafur-uracil (UFT) as adjuvant therapy in patients with resected stage I-IIIA breast cancer by immunohistochemistry (IHC)-based subtype and to determine the relationships between clinicopathological factors and long-term outcomes. METHODS: A pooled analysis of the randomized controlled N·SAS-BC 01 and CUBC studies was conducted. Expression of hormone receptors (HRs; estrogen and progesterone receptors), human epidermal growth factor receptor 2 (HER2), and Ki67were assessed by IHC. Tumor-infiltrating lymphocytes (TILs) and nuclear/histological grades were determined by hematoxylin and eosin staining. Relapse-free survival (RFS) and overall survival (OS) were estimated by Kaplan-Meier analysis and hazard ratios were determined by Cox model adjusted for baseline tumor size and nodal status. RESULTS: A total of 689 patients (342 CMF and 347 UFT) were included in the analyses with a median follow-up of 11.1 years. There was no significant difference in RFS or OS between the two cohorts (RFS: 0.96 [95% confidence interval: 0.71-1.30], log-rank test p = 0.80; OS: 0.93 [0.64-1.35], p = 0.70). There was no difference in RFS or OS between the two cohorts for HR+/HER2- and HR+/HER2+ subtypes. RFS was significantly longer in patients treated with UFT compared with CMF in patients with HR-/HER2+ subtype (0.30 [0.10-0.88], p = 0.03). A high TILs level was associated with a better OS compared with low TILs level (p = 0.02). CONCLUSIONS: This long-term follow-up study showed that RFS and OS were similar in patients with luminal-type breast cancer treated with CMF and UFT.

Upregulation of S100A10 in metastasized breast cancer stem cells.

Metastatic progression remains the major cause of death in human breast cancer. Cancer cells with cancer stem cell (CSC) properties drive initiation and growth of metastases at distant sites. We have previously established the breast cancer patient-derived tumor xenograft (PDX) mouse model in which CSC marker CD44+ cancer cells formed spontaneous microscopic metastases in the liver. In this PDX mouse, the expression levels of S100A10 and its family proteins were much higher in the CD44+ cancer cells metastasized to the liver than those at the primary site. Knockdown of S100A10 in breast cancer cells suppressed and overexpression of S100A10 in breast cancer PDX cells enhanced their invasion abilities and 3D organoid formation capacities in vitro. Mechanistically, S100A10 regulated the matrix metalloproteinase activity and the expression levels of stem cell-related genes. Finally, constitutive knockdown of S100A10 significantly reduced their metastatic ability to the liver in vivo. These findings suggest that S100A10 functions as a metastasis promoter of breast CSCs by conferring both invasion ability and CSC properties in breast cancers.

The efficacy of sequential second-line endocrine therapies (ETs) in postmenopausal estrogen receptor-positive and HER2-negative metastatic breast cancer patients with lower sensitivity to initial ETs.

PURPOSE: Second-line endocrine therapy (ET) for estrogen receptor (ER)-positive and human epidermal growth factor 2 (HER2)-negative metastatic breast cancer (MBC) is offered based on the response to first-line ET. However, no clinical trials have evaluated the efficacy and safety of secondary ETs in patients with poor responses to initial ET. This study evaluated the efficacy of second-line ET in ER-positive and HER2-negative postmenopausal MBC patients with low or very low sensitivity to initial ET. METHODS: This multicenter prospective observational cohort study evaluated the response of 49 patients to second-line ETs in postmenopausal MBC patients with low or very low sensitivity to initial ET. The primary endpoint was the clinical benefit rate (CBR) for 24 weeks. RESULTS: Of the 49 patients assessed, 40 (82%) received fulvestrant in the second line, 5 (10%) received selective estrogen receptor modulators, 3 (6%) received aromatase inhibitors (AIs) alone, and 1 received everolimus with a steroidal AI. The overall CBR was 44.9% [90% confidence interval (CI): 34.6-57.6, p = 0.009]; CBR demonstrated similar significance across the progesterone receptor-positive (n = 39, 51.3%, 90% CI: 39.6-65.2, p = 0.002), very low sensitivity (n = 17, 58.8%, 90% CI: 42.0-78.8, p = 0.003), and non-visceral metastases (n = 25, 48.0%, 90% CI: 34.1-65.9, p = 0.018) groups. The median progression-free survival was 7.1 months (95% CI: 5.6-10.6). CONCLUSION: Second-line ET might be a viable treatment option for postmenopausal patients with MBC with low and very low sensitivity to initial ET. Future studies based on larger and independent cohorts are needed to validate these findings.

Physical activity among patients with breast cancer receiving aromatase inhibitors is associated with bone health: a cross-sectional observational study.

PURPOSE: To examine the association of physical activity (PA) with bone health among patients with breast cancer receiving adjuvant aromatase inhibitor (AI) treatment. METHODS: In this single-center observational study, we enrolled postmenopausal women with primary hormone receptor-positive breast cancer who were receiving adjuvant AI treatment. We assessed patient bone health [bone mineral density (BMD) and biomarkers of bone turnover] as main outcomes. PA was assessed using Baecke physical activity questionnaires (BPAQ) and an accelerometer. Multiple regression analysis was performed after adjustment for age, body mass index, smoking history and duration of AI treatment. For missing data, multiple imputation analysis was adapted. RESULTS: The mean age of the 53 enrolled patients was 67.4 ± 8.4 years. The mean duration of AI administration was 25.7 ± 18.9 months. The most frequently administered AI was anastrozole (73.6%). Although not related to BMD, PA was related to bone turnover. Serum collagen type I amino-terminal propeptide, a bone formation marker, was associated with only light PA (t = - 2.55, p = 0.015), while tartrate-resistant acid phosphatase 5b, a bone absorption marker, was associated with work index in the BPAQ subscale and light PA (t = - 2.28, p = 0.028, t = - 2.26, p = 0.031, respectively). The results for all patients were similar to those observed in the multiple imputation analysis. CONCLUSION: PA was significantly associated with bone turnover among cancer patients receiving AI treatment. Light PA and PA in the work domain were the most important factors among various PA intensities and PA domains.

Real-World Outcomes of Treating Advanced Breast Cancer Patients With Palbociclib: A Multicenter Retrospective Cohort Study in Japan-The KBCOG-14 Study.

BACKGROUND: Clinical studies have shown that palbociclib improves progression-free survival in hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) patients with advanced breast cancer (ABC). However, there are insufficient data on its use in a real-world setting in Japan. The aim of this study was to investigate the effectiveness, predictive factors, and safety of palbociclib among Japanese patients in routine clinical practice. METHODS: Between December 1, 2017, and April 30, 2019, we recruited patients from 9 hospitals and retrospectively evaluated the data on HR+/HER2- patients with ABC who received palbociclib for at least 1 week. The correlation between time-to-treatment discontinuation (TTD) and clinical background was investigated via univariate and multivariate analyses using Cox hazards models. RESULTS: A total of 177 women were available for analysis. Of these patients, 58 (33%) patients were treated with palbociclib with an aromatase inhibitor and 117 (66%) patients were treated with palbociclib and a selective estrogen receptor degrader. Approximately three-fourths of the patients (n = 130, 73%) received palbociclib as third- or later-line therapy. One-third of the patients had 3 or more metastatic sites (n = 59, 33%), and one-third of the patients had liver metastasis (n = 59, 33%). The median follow-up duration at the time of data cutoff was 8.9 months, the median TTD was 6.3 months, and the median overall survival was not reached. Liver metastasis (hazard ratio [HR]: 1.54 [95% confidence interval {CI}: 1.03-2.27]), high serum lactate dehydrogenase (LDH) level (>300 U/L) (HR: 2.58 [95% CI: 1.49-4.26]), and high neutrophil-to-lymphocyte ratio (NLR) (⩾3.0) (HR: 1.76 [95% CI: 1.13-2.69]) were significantly associated with shorter TTD. The most common hematologic adverse event was neutropenia, which occurred in 93% of the patients. CONCLUSION: Based on the results of the pivotal phase 3 trials, the median TTD recorded in this study was shorter than expected. Our results suggest that liver metastasis, serum LDH level, and NLR may be predictive factors for HR+/HER2- ABC treatment outcomes.

Risk Analysis for Chemotherapy-induced Nausea and Vomiting (CINV) in Patients Receiving FEC100 Treatment.

BACKGROUND/AIM: Risk factors for chemotherapy-induced nausea and vomiting (CINV) with anthracycline-containing regimen for breast cancer patients remain unknown. The risk factors for CINV with FEC100 were investigated. PATIENTS AND METHODS: Data on CINV events and patient backgrounds of 180 patients were collected from the first cycle of FEC100 treatment. In this regimen, patients were administered various antiemetics (ADs). The combinations of ADs were classified into four categories, while body mass index (BMI) was stratified into three categories. Risk factors were selected based on patient characteristics and combination of ADs. Risks for CINV were analyzed by univariate and multivariate analyses. RESULTS: In the univariate analysis of nausea, BMI was a significant factor, while BMI and combination of ADs were significant in vomiting. In the multivariate analysis concerning nausea, BMI was a significant factor. In the analysis concerning vomiting, the combination of ADs and BMI were significant. CONCLUSION: BMI was the most important risk factor for nausea and vomiting, while the combination of ADs was for vomiting.

Safety and Relative Dose Intensity of Dose-dense Doxorubicin and Cyclophosphamide Followed by Dose-dense Paclitaxel.

BACKGROUND/AIM: Dose-dense doxorubicin and cyclophosphamide (ddAC) followed by dose-dense paclitaxel (ddP) (ddAC-P) has improved disease-free survival of patients with breast cancer. The aim of this study was to evaluate the safety and relative dose intensity (RDI) of ddAC-P administered together with pegfilgrastim. PATIENTS AND METHODS: Between May 2015 and Aug 2017, 44 patients were retrospectively reviewed; they were administered 4 cycles of ddAC, followed by 4 cycles of ddP. Pegfilgrastim (3.6 mg) was administered in every cycle. RESULTS: The mean RDIs for ddAC-P, ddAC, and ddP were 95.0%, 94.5%, and 93.3%, respectively. The prevalence of high RDIs (≥85%) for ddAC-P, ddAC, and ddP was 90.9%, 84.1%, and 88.6%, respectively. Seven of the 10 patients with low RDIs experienced grade 1 or 2 fever. CONCLUSION: DdAC-P administered together with pegfilgrastim (3.6 mg) appears to be feasible and maintains RDI in most of Japanese patients with breast cancer. Rapid evaluation and proper management of fever may prevent low RDI.