On Sept. 13, the Food and Drug Administration (FDA) added new warnings to the patient package insert for commonly used breast cancer medications. Known as cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors, these drugs may cause rare but severe inflammation of the lungs. The forewarned products include Ibrance, Kisqali and Verzenio. 

All mentioned drugs are approved for use in patients with HR-positive, HER2-negative and advanced or metastatic breast cancer. 

According to the FDA safety announcement, patients should be monitored for pulmonary symptoms of interstitial lung disease (ILD) while on while on CDK 4/6 inhibitors. Symptoms include hypoxia, cough, dyspnea or interstitial infiltrates on radiologic exams in patients where infectious, neoplastic and other causes have been ruled out.

Professionals are advised to interrupt the administration of CDK 4/6 inhibitor treatment in patients who have new or worsening respiratory symptoms, and permanently discontinued in patients with severe ILD and/or pneumonitis. 

Patients are instructed to notify a healthcare professional right away if new or worsening symptoms involving the lungs occur. Symptoms to watch for include difficulty with breathing and shortness of breath during rest or low activity.

The FDA urges patients to avoid discontinuing treatment without talking to a healthcare professional first. People respond differently to medication depending on their health, disease status, genetic factors, other medications and many other considerations.

Specific risk factors to determine how likely it is that a patient will experience severe lung inflammation when taking Ibrance, Kisqali or Verzenio have not been identified.

CDK 4/6 inhibitors have been shown to improve patients' progression-free survival. The overall benefit of CDK 4/6 inhibitors in cancer patients still trumps the risks, according to the FDA.