Should a postmenopausal woman with T1N1 (Tumor size 1, Node involvement 1) breast cancer receive ribociclib (Ribociclib)?

From the Guidelines

Ribociclib is recommended for postmenopausal women with hormone receptor-positive (HR+), HER2-negative T1N1 breast cancer, as it has been shown to improve progression-free survival when combined with an aromatase inhibitor. The standard regimen includes ribociclib 600 mg daily for 21 days followed by 7 days off, combined with an aromatase inhibitor (such as letrozole 2.5 mg daily) 1. Treatment typically continues for at least 2 years or until disease progression or unacceptable toxicity. Before starting treatment, baseline assessments including ECG, liver function tests, and complete blood count are necessary, with regular monitoring throughout therapy. Ribociclib works by inhibiting cyclin-dependent kinases 4 and 6 (CDK4/6), which prevents cancer cell proliferation by blocking cell cycle progression. Clinical trials have demonstrated that adding ribociclib to endocrine therapy significantly improves progression-free survival and overall survival in this patient population 1. Common side effects include neutropenia, fatigue, nausea, and potential QT interval prolongation, which necessitates the regular monitoring schedule.

Some key points to consider when prescribing ribociclib include:

• The importance of combining ribociclib with an aromatase inhibitor, as this has been shown to improve progression-free survival in clinical trials 1
• The need for regular monitoring of side effects, including neutropenia, fatigue, and QT interval prolongation 1
• The potential for ribociclib to improve overall survival in postmenopausal women with HR+, HER2-negative breast cancer, as suggested by clinical trial data 1

It is also worth noting that ribociclib has been approved for use in combination with an aromatase inhibitor as initial therapy in postmenopausal women with HR+, HER2-negative breast cancer 1. Overall, the evidence suggests that ribociclib is a valuable treatment option for postmenopausal women with HR+, HER2-negative T1N1 breast cancer, and should be considered as part of a comprehensive treatment plan.

From the FDA Drug Label

MONALEESA-3 (NCT06129786) was a randomized (2:1) double-blind, placebo-controlled study of ribociclib in combination with fulvestrant for the treatment of postmenopausal women (N=726) with hormone receptor positive, HER2-negative, advanced breast cancer who have received no or only one line of prior endocrine treatment

The patient in question has T1N1 breast cancer, which is not explicitly mentioned in the provided drug label as an indication for ribociclib. However, based on the information from the MONALEESA-3 study, ribociclib in combination with fulvestrant is used for the treatment of postmenopausal women with HR-positive, HER2-negative advanced or metastatic breast cancer.

• Key points:
  • The patient is postmenopausal.
  • The cancer is HR-positive and HER2-negative.
• Since the patient has T1N1 breast cancer, which is an early-stage breast cancer, and not advanced or metastatic breast cancer, the use of ribociclib is not directly supported by the provided drug label. Therefore, ribociclib should not be used for this patient based on the provided information. 2

From the Research

Patient Eligibility for Ribociclib

• The patient in question is a postmenopausal woman with T1N1 breast cancer, which is hormone receptor-positive (HR+) and HER2-negative.
• Studies have shown that ribociclib, a CDK 4/6 inhibitor, in combination with an aromatase inhibitor (AI) or fulvestrant, is effective in improving progression-free survival (PFS) and overall survival (OS) in postmenopausal women with HR+, HER2-negative advanced or metastatic breast cancer 3, 4.

Efficacy of Ribociclib in Early Breast Cancer

• The use of CDK 4/6 inhibitors, such as ribociclib, in the adjuvant and neoadjuvant settings may be beneficial in high-risk patients with HR+ breast cancer 3.
• A phase 2 trial (CORALLEEN) investigated the use of ribociclib plus letrozole in postmenopausal women with HR+, HER2-negative, luminal B breast cancer, and found that it was effective in achieving molecular downstaging of the disease 5.

Comparison with Chemotherapy

• A systematic review and network meta-analysis compared endocrine treatment with chemotherapy in postmenopausal women with HR+, HER2-negative metastatic breast cancer, and found that CDK 4/6 inhibitors plus hormone therapies were better than standard hormone therapies in terms of PFS 6.
• Real-world outcomes of ribociclib and AI use in first-line HR+, HER2-negative metastatic breast cancer have shown that the combination is well-tolerated and effective in achieving superior PFS 7.

Considerations for Treatment

• The decision to use ribociclib in a postmenopausal woman with T1N1 breast cancer should be based on individual patient characteristics, such as tumor size, nodal involvement, and menopausal status.
• The potential benefits and risks of ribociclib, including its efficacy in improving PFS and OS, as well as its potential side effects, such as neutropenia and liver function test abnormalities, should be carefully considered 3, 4, 7.