How does radiotherapy help brain tumors?

Killing cancer cells. Radiaiton therapy uses high energy x-rays to cause injury to cancer cells. It is used in many cases were surgery is either not possible or even despite surgery, there will be cancer cells left behind. Radiation in general works by either killing or injurying cancer cells so that they either die off directly or die off as they try and grow/divide. The normal body is able to recover by healing.
Circuits still work. Both the above are correct. The reality is that cancer cells anywhere can be kill by radiation. The brain offers a special problem in that very important areas are often right next to tumors, even completely surrouding them. Radiation can kill cancer while normal tissue can repair itself day to day. Technology, perhaps the best being protons, can stop the radiation even millimeters from a tumor.
Kills cancer cells. Radiation uses high-energy x-rays that are focused on the tumor. They kill cancer cells by damaging their dna. The treatment is generally delivered daily (5-days each week) for about 6 weeks.

Related Questions

How does radiotherapy help brain tumor? Is it only a temporary treatment?

Tumor treatment. Radiation has been used for decades to attempt to destroy abnormal cancer tissue throughout the body. More recently, this has been defined with the usage of a focal gamma "knife" which decreases the risk of damaging normal brain tissue. The theory involves shrinking or debulking the brain tumor mass. Although in some cases this may be long lasting, in others there may only be brief benefit.

How effective is imft compared to conventional radiotherapy for brain tumors?

The same. You mean imrt. The dose used would be the same and therefore the same effectiveness. We would use imrt if there are critical structures we are trying to avoid and couldn't do so by using conventional 3d radiotherapy. Imrt is 3 times more expensive and so sometimes used when not really necessary. Conventional radiation can get the same results as long as all dose constraints are met.

How beneficial is radiotherapy compared to conventional radiotherapy for brain tumors?

Very. I'm assuming you are talking about stereotactic radiotherapy. Think of each area of your brain being exposed to only one beam of radiation but the tumor getting the focused beam of radiation. It's very effective and tolerated well.

How long after a brain tumor radiotherapy will the side effects start? Are they disabling?

Shortly after start. Symptoms will begin pretty soon after your first treatment and will persist until after your treatment is over. They are not disabling although they are inconvenient. The worst symptoms are fatigue, weight loss, possible hair loss, nausea. Some people get none of these except the fatigue. Good luck.

How long after a brain tumor operation and radiotherapy will the side effects start?

Weeks. Side effects of radiation may start within 2 weeks of starting tx.
It varies. Side effects from radiotherapy can be classified as acute or delayed. Acute side effects (hair loss, fatigue) usually begin during the course of radiotherapy and gradually improve in the weeks after treatment (usually a few months for hair loss). Delayed side effects are far less common and can occur months or even years after radiotherapy.