Pathophysiology/Cancer Question

Question

Explain the mechanisms whereby chemotherapy and irradiation are able to destroy cancer cells, while having less or no effect on normal cells. 

Any help with this question would be greatly appreciated. Thanks in advance!

Answer 1

Chemo and radiation target uncontrolled growth, replication and spread to cells. Chemo drugs kill or shrink cancer cells. Radiation kills cells with high energy beams.radiation slows growth by damaging DNA. RADIATION also had a negative effect on normal cells and genetically age normal cells faster. There is no free lunch with either chemo or radiation.

Answer 2

Fantastic question! So many traditional chemotherapy agents only target rapidly dividing cells. They often interfere in parts of DNA synthesis, which is really only happening in dividing cells. Since most "normal" cells are not dividing that means that the drug will largely target cancer cells. Some normal cells that are often impacted by chemo drugs are blood, skin, and hair producing cells. That is why cancer patients opn traditional chemotherapy drugs lose their hair and bleed easily - those cells are killed as well as the cancer cells.

Radiation is a different story. Radiation is usually targeted to tumor tissue only. Radiation can be delivered with very high precision (depending on the method). Being creative about how you delivery that dose of radiation means you can give the tumor a high dose, but only give other cells a low dose. Radiation used to treat cancer causes a lot of mutations in the DNA, and even though cancer exists because of lots of mutations, it can still be killed if you really mess up its DNA. But if the dose is kept low enough on regular cells then you can avoid killing them.

There are newer chemotherapy drugs that use very different mechanisms to kill cancers. Some of these include tyrosine kinase inhibitors and immunotherapy. These types of drugs target certain pathways that allow them to only impact the cancer cells but not regular cells as much.