Hello,
Welcome to Healthcaremagic.
I had gone through your query and understand your concern.
One thing you must agree is
Radiation is a form of energy.
The energy is in two forms photons and charged particles.
In radiation therapy, this radiation is focused on the area where the cancer cells to be killed.
The above said particles in the beam destroys the DNA in the tumour cells of that area.
As the tumour cells are immature cells, they are mostly not able to replicate faster.
Because main thing in cancer is uncontrolled and rapid multiplication and growth.
It does not the kill the red blood cells in blood because they do not contain DNa.
But immature and tumourous blood cells contain DNA and nucleus, thus they are prone for destruction by Radiation.
HOpe this Helps.
Take care.
If you have additional questions or follow up queries then please do not hesitate in writing to us. I will be happy to answer your queries.
Wishing you good health.
Regards,
Dr.Manjeth.