A new drug treatment reduces the risk of breast cancer recurrence in women who have had their initial tumor removed, according to results of a clinical trial presented at the American Society of Clinical Oncology (ASCO) meeting ) held in Chicago.
The treatment has proven effective in the most common type of breast cancer, called HR /HER2-, which accounts for 70% of all cases of the disease. This type of cancer is characterized by tumor cells having many hormone receptors (HR) but few receptors for the HER2 protein.
The arrival of this new type of drugs represents the greatest advance in 25 years for the treatment of this type of tumor in cases diagnosed when there are no metastases, which are the majority. At that time the advance consisted of the introduction of aromatase inhibitors, an innovative hormonal treatment.
“These are early but impressive data showing a significant reduction in the risk of recurrence in high-risk patients. They will change clinical practice, ”Rita Nanda, from the University of Chicago, declared at a press conference on Wednesday that she did not participate in the study.
Approximately 30% of ER /HER2- breast cancer cases are considered high risk. Based on this estimate, around 20% of women diagnosed with breast cancer could benefit from the new treatment, which represents some 7,000 new patients a year in Spain.
According to the results presented at the Chicago congress, which with more than 40,000 participants is the largest cancer congress in the world, the drug ribociclib compared to regular hormone therapy has reduced breast cancer recurrences by 25.6% in the first three years from the start of treatment.
The drug inhibits the enzymes CDK4 and CDK6, which promote cell proliferation. The first three CDK4/6 inhibitors were approved in Europe between 2016 and 2018 for the treatment of patients with ER /HER2- metastatic breast cancer after demonstrating that they increase survival in this group. Since then, all three drugs have also been tested in patients without diagnosed metastases.
The results presented in Chicago correspond to ribociclib from the Novartis company. In the clinical trial, which began in January 2019 and has not yet ended, 5,101 patients considered at high risk due to the size of the initial tumor and/or the number of lymph nodes affected by tumor cells participate.
Spain is, after the US, the second country with the most participants in the study, with 761 patients from 47 hospitals.
After a median follow-up of three years, 12.9% of patients who received only standard hormone therapy after surgery had a recurrence of breast cancer. Among those who also received ribociclib, the figure dropped to 9.6%. The difference between the two figures equates to a risk reduction of 25.6%.
The most important side effect reported among patients treated with ribociclib was neutropenia, a reduction in a type of white blood cell in the blood, which increases the risk of infections. But in general the drug is well tolerated, said Dennis Slamon, an oncologist at the University of California in Los Angeles who led the study, at the press conference.
Ribociclib thus joins Lilly company's abemaciclib, another CDK4/6 inhibitor that has been shown to improve the prognosis of patients with ER/HER2- non-metastatic breast cancer. Lilly's drug has shown efficacy in a higher-risk group of patients, while Novartis's has shown efficacy in a broader group, which also includes women who do not have any lymph nodes affected by tumor cells.
The third CDK4/6 inhibitor, Pfizer's palbociclib, has not been shown to be effective in preventing recurrences.
Abemaciclib has been approved since last year in Europe, and is already available in Spain, for patients in whom it has shown efficacy. Ribociclib is currently only for patients with metastases. Both drugs are taken orally.
“These drugs will represent an important change in the treatment of patients with hormone-sensitive breast cancer,” says Aleix Prat, head of the oncology service at Hospital Clínic de Barcelona, who has participated in the clinical development of ribociclib. Prat points out that "they are the first therapeutic innovation for this group of patients since the approval of letrozole", a hormonal treatment that was authorized in 1996. But he warns that "longer-term patient follow-up data is lacking to verify that the reduction of recurrences translates into an improvement in survival”.
“There is a significant unmet need to reduce the risk of recurrence and provide a tolerable treatment option that keeps patients cancer-free without disrupting their daily lives. The Natalee study was specifically designed to address this unmet need,” says Dennis Slamon, who announced the results of the clinical trial at a press conference and will present them today at the congress.
The Natalee study will continue until 2026, when the full results will be available. The data presented in Chicago correspond to an interim analysis that was already provided for in the initial study design.
"Our options for curing patients are expanding, which is our great objective," says Cristina Saura, a breast cancer specialist at the Vall d'Hebron hospital in Barcelona. "With chemotherapy the risk of recurrence is reduced, with hormonal therapies it is further reduced and now with CDK4/6 inhibitors it is going to be reduced even more."
Transparency statement: La Vanguardia attends the American Society of Clinical Oncology congress in Chicago invited by Novartis
