Staging of cancer requires the following:
1. Status of the primary tumor
2. Status of the draining lymph
nodes (N stage)
3. Status of metastases to distant organs (M Stage).
Cancer cells usually utilise more glucose
than normal cells. In PET scan, the medicine used is FDG (Fluoro deoxy glucose) which is a glucose analogue. FDG behaves exactly like glucose and is trapped in the cancer cells. Normal cells also take up FDG but the amount of FDG in cancer cells is many time greater than normal cells. This is imaged using PET camera and are seen as hot spots.
PET scan is the most sensitive modality in identifying N stage and M stage. Hence, PET scan is very useful in accurate staging.