Hi @etb2, When you are diagnosed with a cancer, it's normal to feel overwhelmed with information, and to feel like you don't know anything at all! Hang in there and learn what you can. Hopefully your oncologist can help explain the details of your cancer. There are many different drivers of lung cancer. That's good news, as in some cases the researchers have been able to develop treatments that are specific to the different types of cancers.
When the lung cancer community talks about EGFR they are referring to the DNA of your cells, with the EGFR driver going awry, mutating, and causing the cancer to grow. That has nothing to do with the kidney lab test that is also named eGFR. I know it's confusing!
When I was diagnosed, I had a tissue biopsy (from my liver), but also a liquid/blood biopsy. Those showed that I had lung cancer, and the blood showed what was driving the cancer (I have an abnormal ALK mutation). Knowing what is driving your cancer is a first step in determining what treatment will work, and it will allow you to focus on learning about your specific type of cancer.
Tagrisso is designed to treat EGRF lung cancer. I take a different inhibitor, alectinib, which is designed to treat ALK lung cancer.
When is your next appointment with an oncologist? Have you seen one yet?