Hi Geckoz,
I hope your Mom is doing well.
A CT scan can detect cancer when the cancer cells create a mass or something observable. I don't think they can see a small cancer cluster and definitely can't see small cells that migrate away from a tumor. Chemo and radiation are used to kill cells that haven't been removed by surgery. Some cells may remain around the surgical site or may have moved elsewhere (via the lymphatic system or circulatory system.) So, in a sense post-surgical chemo and radiation are precautionary.
On the other hand, with stomach cancer, if the mass has grown outside the stomach, or if cancer cells are dislodged during surgery into the lymph or blood system, there is a chance the cancer cells are still around somewhere. Chemo and radiation can kill these cells, preventing a new growth.
I was more than happy to get post-surgical chemo and radiation in an effort to kill any remaining micro-clusters of cancer cells.
It is tough to say whether chemo or radiation are more difficult to tolerate. It depends on the type of chemo and the location/size of the target for radiation. My chemo was not too bad. I had IV Carboplatin and oral Xeloda. I tolerated the chemo fairly well, all things considered.
For radiation I had 5 angle, IMRT, targeted from the top of my chest to the beginings of my intestinal tract (upper sternum to lower abdomen). Since my mass was at the gastric/esophageal junction, I had a section of esophagus surgically removed in addition to most of my stomach. This was a large target. They couldn't avoid hitting my bronchial tubes and lungs. I also took oral chemo (Xeloda) while I had radiation.
Even so, it wasn't too bad. When I finished chemo/radiation I was exhausted, weak, lost a lot of weight, had a bad cough from the damage to bronchial my tubes and lungs, and nauseated. It took a few weeks to recover. The side effects of radiation persist for a while after the treatments.
Since your Mom was stage 3. There is less chance that the cancer has spread. But there is still a chance. My cancer was stage 4, involving several lymph nodes outside the stomach in my abdomen, so there was good chance I had some cancer cells that had spread.
Best wishes,
Tom