Confused about doc asking for a PET instead of a CT - 1273233

Hi all,

Let me give you a brief history of my mother's LC ordeal. Diagnosed with LC 10/1/14. Lobectomy on 10/15/14. A 7.5cm tumor was removed. Diagnosed as stage IIb NSCLC. No positive lymph nodes. Received 4 rounds of carboplatin and taxol. In November 2015, she started coughing up some blood, though not nearly as much as she was before she was diagnosed. It was such a small amount that it was thought that it could've been due to dryness of the air (cold weather, heat, etc). However, it did increase, so she had a CT scan in January of this year where four spots were seen. They were very, very small.

PET scan was ordered, and there was uptake in all 4 spots. I should note that these areas were TINY (as in millimeters). She had a wedge resection on the largest of the tiny spots a little over two weeks ago. Got results yesterday. It was organized pneumonia, but within that OP was a 4 millimeter (tiny) area of cancer, same kind as before (NSCLC).

So, her oncologist wants to do another PET in a month. I don't understand why she wouldn't want a CT instead, just to see if the areas are growing or shrinking. Additionally, it's my understanding that OP is treated with steroids, but my mother has been given nothing. So my question is, what is another PET scan going to show? This next one will be 2 months out from the last one. It's funny because someone on another forum said that PETs don't show growth, and I had actually asked my mother's doc about that when we got the last PET results. I asked if it had grown (I"m new to all this). And she said that PET doesn't show growth, just uptake. So that's the point in another one? Wouldn't a CT be more beneficial?