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Final safety results of our PARSIFAL study were presented at SABCS 2020

Updated: Dec 7, 2022

Last week, MEDSIR had the chance to participate in the San Antonio Breast Cancer Symposium (SABCS) 2020, one of the most relevant meetings in the field aiming to provide state-of-the-art information on the experimental biology, etiology, prevention, diagnosis and therapy of premalignant breast disease and breast cancer. In response to the novel coronavirus global pandemic, the symposium took place virtually to ensure that the sessions were available to the international audience of academic and private researchers and physicians from over 90 countries.

Results from the MEDSIR-sponsored PARSIFAL trial (NCT02491983) were communicated at the conference by Dr José-Manuel Pérez-García, from the International Breast Cancer Center (IBCC), Quiron Group (Barcelona, Spain). The PARSIFAL study is an international, open-label phase II trial that accrued a total of 486 patients with endocrine-sensitive, estrogen receptor positive (ER[+]) and human epidermal growth factor receptor 2 negative (HER2[-]) metastatic breast cancer (MBC). Patients were recruited in 48 hospitals from 7 different countries and randomized in a 1:1 ratio to receive palbociclib (P) in combination with either fulvestrant (F) or letrozole (L). The aim of this study was to investigate the optimal endocrine agent to combine with palbociclib as the frontline therapy for these patients.

The PARSIFAL study results presented during SABCS focused on the comprehensive assessment of the adverse events (AEs) of patients included in the PARSIFAL, with a particular emphasis given to AEs of special interest. The safety analysis showed that neutropenia, leukopenia, anemia, asthenia, arthralgia, fatigue, and diarrhea were the most frequent AEs in both treatment arms, with no significant differences in the total number of related AEs nor Grade 3-4 AEs between arms. However, the percentage of pulmonary embolism (PE) events was doubled in the F+P arm (5%) compared to the L+P arm (2.5%). Analysis of baseline characteristics in the whole population revealed that patients who developed PE were older than patients who did not develop PE (mean age of 69.5 vs. 62 years, respectively), which indicates that risk for developing PE significantly increased with age.

Altogether, the PARSIFAL study was able to confirm a favorable profile of both F+P and L+P regimens for the treatment of ER[+]/HER2[-] MBC, with neutropenia representing the most common AE. In addition, it showed incidence rates of AEs of special interest –including thromboembolic events and pneumonitis– were rare and consistent with those seen in the large, randomized, pivotal PALOMA trials.

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