How long does the nausea side effect from radiation treatment for lung cancer last? how do you tell if nausea is caused by radiation or tarceva (erlotinib)?

Average 2 - 4 wks: Varies from person to person, areas involved in radiation, total dose received. Nausea worse when food pipe (esophagus) is affected and mucositis develops. Nausea from radiation tend to get better as time goes by. There is no easy way to tell the cause of the nausea, sometimes both are contributing.

Not from radiation: Most lung cancer treated with radiation does not cause nausea unless the fields are large and on the left bottom part of the lung overlaps the stomach. Chemo is systemic and more likely the cause of the nausea. Lung cancer can easily go to the brain and the presenting sign can be nausea so make sure a brain scan was negative.

Nausea & XRT: I would not attribute nausea and vomiting to either. Discuss with your radiotherapy doctor.