MADRID, 8 Oct. (EUROPA PRESS) –
The ‘PARSIFAL’ study, designed and coordinated by MEDSIR, an independent research company in oncology, is the first clinical trial that has directly compared the therapeutic efficacy of fulvestrant or letrozole in combination with palbociclib, as first-line treatment in patients with advanced luminal breast cancer (CM) (tumors that overexpress the hormone receptor (HR +), but not the HER2, HR + / HER2- receptor). Palbociclib is a drug from the group called CDK4 / 6 inhibitors.
The ‘PARSIFAL’ study evaluated whether fulvestrant in combination with palbociclib was more effective than the combination of letrozole with palbociclib.
“The results of ‘PARSIFAL’ have been awaited with great interest by the medical community, since it defines the best endocrine agent to combine with palbociclib in this tumor type,” says Dr. Javier Cortés, Director of the International Breast Cancer Center (IBCC ) and scientific co-leader of this study.
Researchers from 47 centers in Spain, France, Italy, the United Kingdom, Germany, Russia and the Czech Republic collaborated in the study. A total of 486 patients were randomly assigned to two cohorts receiving palbociclib in combination with fulvestrant (group A, 243 patients) or with letrozole (group B, 243 patients) until disease progression.
The ‘PARSIFAL’ study shows that the use of fulvestrant in combination with palbociclib is no more effective than the combination with letrozole. Also, it is important to note that the side effects of both combinations are similar and acceptable.
“‘PARSIFAL’ supports the combination of non-steroidal aromatase inhibitors (NSAIs) with CDK4 / 6 inhibitors as the preferred first-line therapy for patients with advanced-stage CM HR + / HER2-. Add fulvestrant to CDK4 / 6 inhibitors it is also a valid option as a first-line treatment in sensitive endocrine patients intolerant to NSAIs or in patients with tumors without a mutation in the PIK3CA molecule “, says Dr. Llombart, Head of the Medical Oncology Service at the Arnau de Vilanova Hospital in Valencia and scientific co-leader of the study.
HR + / HER2- subtype breast cancer represents the largest subgroup of patients with metastatic disease, approximately 65 percent of cases. The standard treatment for this type of tumor has been letrozole and other drugs from the same therapeutic group called NSAIs (non-steroidal aromatase inhibitors). Furthermore, fulvestrant has been the treatment of choice for endocrine-resistant tumors.
The introduction of CDK4 / 6 inhibitors such as palbociclib revolutionized the treatment of this type of tumor. Clinical studies investigating the effect of palbociclib showed that the combination of palbociclib and letrozole doubled the time after treatment without signs of disease (disease-free survival, PFS). Thus, the combination of palbociclib and letrozole became the standard treatment for this type of tumor.
However, different studies also showed that fulvestrant treatment provided higher PFS than NSAIs or that the combination of fulvestrant with CDK4 / 6 inhibitors also induced long responses, and in general a greater survival benefit. Thus, the results of the ‘PARSIFAL’ study resolve the open debate so far about the optimal endocrine therapy to be used in combination with palbociclib.
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