In treatment of cancer, radiation is given, but radiation can also be the cause of cancer. In the drugs of chemotherapy it is written that it is highly carcinogenic. Then why are such methods performed? Is there any recently discovered new method to cure cancer?
It is clearly a trade-off between benefit and harm. Often cancers which are irradiated are the ones, that cannot be removed surgically (or completely). Then the tumor is immediately dangerous for the patient. From the dose the patient gets, you can calculate how likely additional damage is. And then you need to make a decision.
The same is true for the "classic" chemotherapeutic drugs (like Paclitaxel or Carboplatin), which attack all dividing cells. They have a lot of side-effects, but again, there is a trade-off between the benefit this drug has and the harm it causes. See references 1 and 2 for some more details.
There are quite a few new therapy options besides the "classic" ones. These include oncolytic viruses aimed against the tumor (see reference 3), as well as targeted therapies (see reference 4) which only attack certain molecules or proteins important for the cancer. And last, but not least the probably most important new therapy option are immunotherapies to turn the immune system against the tumor. This gives (when the patient is susceptible), spectacular results and I think there will be a lot of development in this field in the future. See reference 5 for details.
An overview over the new therapy options can be found in reference 6.