While several clinical trials of nab-paclitaxel have been conducted, prospective data on real-world practice consistent with increased use of prior taxane-containing regimens in the neoadjuvant setting have been lacking. “We wondered if patients, in fact, were able to receive the recommended 260 mg/m2 dose or if it was too toxic,” Dr. Potthoff said in an interview at her poster.
In a pivotal phase 3 trial conducted by Gradishar et al., nab-paclitaxel demonstrated high efficacy (overall response rate, 33%; time to tumor progression, 23.0 weeks; overall survival, 60 weeks) with an acceptable toxicity profile. Peripheral sensory polyneuropathy (grade 3) in 10% of patients was the most critical safety issue.2
In order to test that idea, NABUCCO study investigators collected data from approximately 100 oncology outpatient centers across Germany on the routine treatment of 697 patients with metastatic breast cancer in whom anthracycline therapy was contraindicated. Data on treatment for a maximum of six months were captured with follow-up data for a median of 17.7 months, including details on disease progression, overall survival, and safety with a focus on neurotoxicity.
Neurotoxic adverse events at grades 3 and 4 were observed in a low number of patients (5.2% overall: peripheral sensory neuropathy in 4.3%; peripheral motor neuropathy in 1.1%; and paresthesia in 0.1%). Among grade 1 and 2 events, which were reported in 47.3% of patients, peripheral sensory neuropathy was most common (35%).
Median age in the overall trial was 62.3 years; 58.2% of the patients were younger than 65 years of age. Median time from primary diagnosis was 65.2 months. Among the entire cohort, 419 patients (60.1%) had received prior taxane therapy with treatment schemes ranging from 78–260 mg/m2 every three or four weeks. Nab-paclitaxel was received as first-, second-, third-, and fourth-or-greater-line therapy in 40%, 24%, 20%, and 15% of patients, respectively.
Over half of the patient population had hormone receptor-positive/HER2-negative (HR+/HER2−) disease (58.4%). The rest of the patients had HR+/HER2+ (9.9%), HR−/HER2+ (3.9%), and triple-negative (13.8%) breast cancer, and receptor status was unknown in 14.1%.
Overall response rates ranged from 29.0% in fourth-or-greater-line therapy to 46.1% in first-line therapy. Those with stable disease ranged from 30.5% patients in third-line therapy to 37.3% in second-line therapy. Response rates were highest among patients who were HR−/HER2+ (55.6%) and lowest in triple-negative breast cancer (32.7%). “That rate for triple-negative disease is still quite good,” Dr. Potthoff noted. The progressive disease rate was highest in patients with triple-negative breast cancer (27.1%) and lowest in those with HR−/HER2+ disease (11.1%).
While overall response rates were lower in patients older than 65 years compared with patients younger than 65 years (31.6% versus 41.1%, respectively), the progressive disease rate was not higher in older patients compared with younger patients (17.2% versus 20.0%). Patients receiving nab-paclitaxel doses lower than 260 mg/m2 did not have lower overall response rates. Median time to tumor progression was 5.9 months for the overall population and similar for those younger than age 65 years (5.7 months) and those age 65 years or older (6.5 months). It was shortest for those with triple-negative disease (4.9 months) and longest for those who were HR+/HER2+ (8.6 months).
“Our real-world data from NABUCCO confirm the earlier clinical trial findings. They confirm also that nab-paclitaxel is an effective and safe treatment option with a favorable benefit–risk profile in metastatic breast cancer patients not eligible for anthracycline therapy,” Dr. Potthoff concluded. She underscored that response rates were high in populations typically difficult to treat—patients who had received multiple lines of prior therapy, older patients, and patients with triple-negative disease.