Drug company Hoffman-La Roche is telling doctors prescribing Tarceva to lung cancer patients to closely monitor the liver function of those who recently have taken or who are taking the drug.

The drug Tarceva (erlotinib) is used to treat patients with non-small-cell lung cancer at an advanced stage when chemotherapy has not helped to stop the disease.

The letter issued by Hoffman-La Roche says a study of patients with advanced cancer and moderate liver impairment found that a higher number of patients died during treatment or within 30 days of the last dose, compared to patients with normal liver function.

Patients on the drug need to consult their doctor immediately if they show signs or symptoms suggesting possible serious liver side-effects, the company said.

These include dark urine, yellowing of the skin, abdominal pain — especially on the right side — general itchiness, less appetite, nausea, vomiting, or fatigue.

Patients should also tell their doctor or pharmacist if they have any liver problems before beginning treatment with Tarceva, says the letter signed by Lorenzo Biondi, the drug company's vice-president of medical and regulatory affairs.

The company's letter has been posted on Health Canada's website, and any suspected adverse reactions can be reported to the marketed health products directorate at Health Canada.