Typically, we assess the benefit of a therapy in a cancer patient in one of two ways. Sometimes a specific patient will have something that you can see externally, for example, an enlarged lymph node or mass in the neck. More commonly though, we do scans, either a CAT scan or an MRI or a PET scan, before the treatment. Then we do some treatment and then we do a follow-up scan. And this follow-up scan is compared to the prior scan and we look and say: "Okay, things that we saw before, are they the same? Are they smaller? Are there new spots? Are there no new spots?" Depending on what we see on the follow-up scans, which are done on a periodic basis, we determine whether the patient is benefiting or not.
The unique thing about immunotherapies is that a relatively brief amount of therapy, say a year or even two years, can last many, many years. So, think about the polio vaccine that you got when you were growing up. It's effect remains throughout the lifetime. The current round of immunotherapies may not have a lifetime benefit, but they certainly have a prolonged benefit, as opposed to chemotherapy, where the benefit that you get at the end of a course of chemotherapy is all that you're going to get.
With early stage lung cancer, for example, the goal is to cure or eradicate the cancer. In patients with more advanced cancers, previously the goals were much more modest, trying to modestly extend survival. These days, our goal is to turn what previously had been a rapidly fatal condition into a more chronic disease, not unlike diabetes or high blood pressure or high cholesterol. All those conditions, diabetes, high blood pressure or high cholesterol, are usually things that we can't eradicate in somebody, but we can control and allow them to lead a more or less normal life.