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Background: CDK4/6 inhibitors (CDK4/6i) have shown promising results in the treatment of hormone receptor‐positive (HR+) metastatic breast cancer (MBC) when combined with endocrine therapy (ET). It is crucial to evaluate the actual effectiveness and safety of CDK4/6i in clinical practice, as well as to analyze the factors that can predict their outcomes. Methods: Patients with HR+ MBC who received CDK4/6i‐based therapy between May 2016 and May 2023 at Hunan Cancer Hospital were evaluated for progression‐free survival (PFS). Adverse reactions were assessed based on the National Cancer Institute Common Toxicity Criteria (version 5.0). Results: This study included 344 patients, with a median PFS (mPFS) of 12.8 months (range: 10.4–15.2 months). After adjustment, Cox multivariate regression analysis revealed that visceral metastasis (specifically liver and brain metastases), Eastern Cooperative Oncology Group Performance Status (ECOG PS) ≥ 1, estrogen receptor ≤ 80%, progesterone receptor ≤ 10%, Ki‐67 > 30%, and treatment in later stages were significant factors associated with reduced PFS. Based on this, we created a prognostic nomogram and validated its performance, obtaining a C‐index of 0.714 (95% confidence interval: 0.640–0.787) as well as reliable calibration and clinical impact. The mPFS of CDK4/6i rechallenge was 7.7 months; for patients who initially discontinued CDK4/6i for reasons other than disease progression, CDK4/6i rechallenge still provided a mPFS of 11.4 months. The tolerability and safety of combining CDK4/6is with ET were manageable. Adverse events led to treatment discontinuation in 3.8% of patients. Neutropenia (29.1%), leukopenia (13.7%), and anemia (4.1%) were the primary grade 3/4 adverse reactions. Conclusions: This real‐world study highlights the ample efficacy and reasonable safety of combined CDK4/6i and ET in patients with HR+ MBC. Individualized treatment decisions and ongoing safety monitoring are important to optimize the therapeutic benefit of CDK4/6i treatment. [ABSTRACT FROM AUTHOR]

Circulating tumor DNA (ctDNA) has good clinical guiding value for metastatic breast cancer (MBC) patients. This study aimed to apply a novel genetic analysis approach for therapeutic prediction based on ctDNA alterations. This nonrandomized, multicenter study recruited 223 MBC patients (NCT05079074). Plasma samples were collected for target-capture deep sequencing of ctDNA at baseline, after the 2nd cycle of treatment, and when progressive disease (PD) was evaluated. Samples were categorized into four levels according to the number of ctDNA alterations: level 1 (no alterations), level 2 (1–2 alterations), level 3 (3–4 alterations) and level 4 (≥5 alterations). According to ctDNA alteration level and variant allele frequency (VAF), a novel ctDNA-level Response Evaluation Criterion in Solid Tumors (ctle-RECIST) was established to assess treatment response and predict progression-free survival (PFS). The median PFS in level 1 (6.63 months) patients was significantly longer than that in level 2–4 patients (level 2: 5.70 months; level 3–4: 4.90 months, p < 0.05). After 2 cycles of treatment, based on ctle-RECIST, the median PFS of level-based disease control rate (lev-DCR) patients was significantly longer than that of level-based PD (lev-PD) patients [HR 2.42 (1.52–3.85), p < 0.001]. In addition, we found that ctDNA level assessment could be a good supplement to radiologic assessment. The median PFS in the dual-DCR group tended to be longer than that in the single-DCR group [HR 1.41 (0.93–2.13), p = 0.107]. The ctDNA alteration level and ctle-RECIST could be novel biomarkers of prognosis and could complement radiologic assessment in MBC. • Based on the number of ctDNA alterations, samples were categorized into four levels: level 1 to level 4. • ctDNA alterations differed in different alteration level groups. • Higher ctDNA alteration levels (levels 3–4) were associated with a higher probability of liver metastasis. • According to ctDNA alteration level and variant allele frequency, a novel ctDNA-level RECIST (ctle-RECIST) was established to assess treatment response. • ctle-RECIST can not only independently predict PFS, but also assist radiologic assessment and improve the clinical application value of prediction. [ABSTRACT FROM AUTHOR]

Background: Recent data on first-line treatment patterns administered to hormone receptor-positive (HR+) advanced breast cancer (ABC) patients in the real-world setting are limited. This study aimed to report the first-line treatment patterns and outcomes of HR+ ABC patients in China. Methods: This was a multicenter, noninterventional study. Eligible patients were cytologically or histologically confirmed to have HR+ ABC with ≥2 complete medical records and received first-line therapies between January 2015 and June 2019. Treatment patterns and outcomes were extracted from structured or unstructured electronic medical records. Progression-free survival (PFS) was analyzed with the Kaplan-Meier method. Results: In total, 1072 patients with HR+ ABC were enrolled at 6 treatment sites: 327 human epidermal growth factor receptor 2-positive (HER2+) patients, 696 HER2-negative (HER2-) patients and 49 HER2-unknown patients. Overall, 62.41% of patients received first-line chemotherapy (CT), 21.08% received targeted therapy (TT) and 15.49% received endocrine therapy (ET). For HR+/HER2+ patients, 65.14% received TT, 28.44% received CT, and 5.81% received ET. Compared with patients who received TT, patients who received CT alone, had a significantly worse median PFS (adjusted hazard ratio [HR] =2.59, 95% confidence interval [CI], 1.64-4.10, p<0.001). For HR+/HER2- patients, 77.01% received CT, 20.69% received ET and 1.15% received TT. Compared with patients who received ET, patients who received CT with maintenance therapy had a significantly prolonged median PFS (adjusted HR =0.57, 95% CI, 0.44-0.76, p<0.001). Among HR+/HER2- patients who received CT with maintenance treatment, those with maintenance ET had a longer median PFS than those with maintenance CT, but the difference was not significant (adjusted HR=0.92, 95% CI, 0.64-1.33, p=0.66). Conclusions: This real-world study demonstrates that CT remains the mainstream first-line treatment option for HR+ patients in China. Among patients with HR+/HER2+ ABC, the majority received first-line TT and experienced a PFS benefit. A high percentage of HR+/HER2- patients received CT as first-line therapy in clinical practice. PFS benefit was significantly longer in patients who received CT with maintenance therapy. Moreover, there was no obvious difference in PFS between maintenance ET and CT. Maintenance ET may be a better choice considering its lower toxicity and better quality of life. [ABSTRACT FROM AUTHOR]

Inetetamab is a novel recombinant humanized anti-HER2 monoclonal antibody. This study aimed to evaluate the efficacy and safety of inetetamab and predictive factors for response in HER2-positive metastatic breast cancer (MBC) patients. A cohort of HER2-positive MBC patients who received inetetamab-based therapy between June 2020 and August 2021 was evaluated. The primary endpoint was progression-free survival (PFS), and the secondary endpoints included objective response rate (ORR) and disease control rate (DCR). Adverse events (AEs) were graded according to the National Cancer Institute Common Toxicity Criteria. A total of 141 patients were included in the final analysis. The median PFS of the entire cohort was 7.1 months. The median number of treatment lines administered was three. The ORR was 36.9 %, and the DCR was 80.9 %. The most frequently employed treatment strategy was inetetamab + chemotherapy (49/141, 34.8 %), followed by inetetamab + HER2-tyrosine kinase inhibitors (HER2-TKIs) + chemotherapy, inetetamab + pertuzumab + chemotherapy, inetetamab + endocrine treatment and inetetamab + HER2-TKIs. Cox multivariate analysis revealed that PFS was associated with liver metastasis (hazard ratio [HR] 2.112, 95 % confidence interval [CI] 1.334–3.343, p = 0.001), previous HER2-TKI treatment (HR 2.019, 95 % CI 1.133–3.597, p = 0.017) and estrogen receptor positivity (HR 0.587, 95 % CI 0.370–0.934, p = 0.024). The toxicity was tolerable, with neutropenia being the most common treatment-related grade 3/4 AE (14.9 %). Inetetamab demonstrates effectiveness with a manageable safety profile, offering a promising therapeutic option for HER2-positive breast cancer patients who have shown resistance to prior anti-HER2 treatments. • Inetetamab is a novel recombinant humanized anti-HER2 monoclonal antibody, used with other drugs to treat HER2-positive breast cancer. • In a cohort of 141 patients, we observed a median PFS of 7.1 months, an ORR of 36.9 %, and a DCR of 80.9 %. • Liver metastasis, previous HER2-TKI treatment, and estrogen receptor positivity identified as predictive factors for PFS. • Inetetamab demonstrated a manageable safety profile, with neutropenia being the most frequently observed grade 3/4 adverse event. • Inetetamab is a new treatment option for HER2-positive MBC patients, especially those who have received other anti-HER2 treatments.Inetetamab is a new treatment option for HER2-positive MBC patients, especially those who have received other anti-HER2 treatments. [ABSTRACT FROM AUTHOR]