In the past, tumor growth for patients on immunotherapy meant treatment should be stopped. But research now shows it may not mean a patient’s cancer has worsened.

As Ashish Sangal, MD, Medical Director of the Lung Cancer Center and Medical Oncologist at Cancer Treatment Centers of America, Phoenix explains, Immunotherapy drugs cause the tumor to flare up initially and get bigger, but that’s only temporary. So anything that looks bigger in the first three to six months after treatment doesn’t mean it’s a progression.”

Read more on why tumor growth may not always be a bad thing for some cancer patients.