Urology>>>>>Basic Science and Molecular Oncology
Question 4#

Which of the following is NOT classically related to the effect of radiation therapy on tumour tissue?

a. Radiosensitivity
b. Repair of the cell
c. Hybridisation
d. Reoxygenation
e. Repopulation

Correct Answer is C


Answer C

The factors that influence the response of tumour and normal tissue to radiation are known as the 5 R’s: radiosensitivity, repair, repopulation, redistribution and reoxygenation. Tumours contain heterogenous cell populations, which vary in their response to radiation. The radiosensitivity, put simply, is the cell kill effect of radiation on a particular type of tissue. The cells ability to repair DNA damage caused by radiation will impact its ability to survive. After or during therapy surviving cells will have the ability to proliferate there by effecting response. A tumour with poor oxygen supply due to inadequate blood supply will be resistant to radiation. After a treatment the tumour blood supply may improve and hence reoxygenation occurs and this improves cell kill effect of further radiation doses. Radiation has differing cell kill effect depending on the cells position within the cell cycle. Radiation results in some synchrony of surviving cells, which then redistribute around the cell cycle. Hybridisation is the fusion of two somatic cells to form a single cell. It can also mean the binding of complimentary sequences of DNA or RNA. This is not classically involved in radiation effect on tumour tissues.