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Aloha Joyce,
Only during the time that the beam is on, does radiation kill cells. The radiation knocks out electrons from molecules that make up a cell. This destroys the molecules, hence, disrupting the cell nuclear balance and depending on the amount of damage, the cells fall apart.
My background is radiation physics. Spent most of my time helping to build Nuclear Power Plants.
Ionizing radiation when beamed at the body, kills all cells. Cancer cells seem to receive more damage than healthy cells and cancer cells do not appear to make a strong come back after being zapped by EBRT/IMRT. Healthy cells do seem to grow back, but it takes time.
The multiple beams are directed at a target, from different angles around the body. Where the beams cross, the killing zone is very intense. A single beam passing into the body (hopefully not out again)(the beam strength is calculated to be mostly adsorbed by the target)passes from the outer skin, down into the target. So, basically a lot of good cells between the skin and the target are getting hit with this one beam. If you have 5 to 7 beams per session, the target gets 5 to 7 times the energy that the good cells receive. So, theoretically the good cells are less damaged and can grow back.
Hope this was not too much.
From the Hamakua Coast,
Faith, Hope & Love,
Joe
I don't like to disagree with Joe, given his background, but the effects of radiation treatment continue well beyond the end of the treatment cycle.
For example it is commonly reported that radiation prostatitis commonly occurs somewhere between 18 and 24 months after radiation - and this is thought to be behind the so-called "PSA bump" that occurs about this time.
There are other studies showing effects appearing later in the day.
Aloha Terry,
What you say is true. My own rectum problems and weak anus occurred seven months after EBRT/IMRT. This start was sorta confusing as I had hemorrhoid surgery three months after EBRT/IMRT which did not really heal before the bleeding started in June 08.
Ok, what is happing here, the after effects, are due to uncontrolled growth of cells, initially damaged by the ionizing radiation. So, a rectum cell is not distroyed, but severely damaged.(story break)
Ok, about 3 to 4 weeks after hemorrhoidictomy + PPK staple job, one of the staples misfired and did not seat properly, it looked like a fish hook, 1/2 open, 1/2 closed. This started moving down from where the PPK was performed. I was using a cream and felt this staple move. So, I went to my PCP, 4 months after radiation, using an anus-scope, she said "that looks terribly irritated" and did not want to remove the staple. (end story)
So, this area of rectum damage, begins to uncontrolled growth of very small blood vessels, 100's per/sqcm.
So, back to what I was saying, the ionizing radiation, once stopped, does no more damage. However, some badly damaged cells grow uncontrollably, not always in the direction we would like, as in abnormal recovery. And which hopefully will eventually heal. Bad place to heal, takes a long...long...time. So, yes, the effects of radiation treatment continue well beyond the end of the treatment cycle, but damaging ionizing radiation has long since stopped.
Ok, did this confuse more or less?
Faith, Hope, & Love,
Joe
Per my oncologist, up to 4 months after the last treatment which we just discussed in December '08. The cells continue to die off hence, the 1st PSA check is done around that time after radiation stops.
I too hate to disagree with Joe given his background but I am under the impression that radiation continues even after treatment stops....My oncologist [a surgeon of course] disparaged radiation that I was considering by saying it is "The gift that keeps on giving" Needless to say I am glad I had good advice and avoided his knife. I did IMRT+ADT and have come out of it just fine.
Regarding R/T;( external beam), I was told that the radiation continues actively for about twelve to fourteen weeks after the last treatment.
Healthy cells can repair. Cancer cells cannot.
The effect of the radiation rather than the activity lasts longer; up to a couple of years. Then all cells should have settled down.
I am puzzled also. I have (as yet) no experience of radiation, but a friend of mine in his 70's had radiation treatment for PC 7 years ago. He had anus problems from early on which either stabilized or he learnt to live with. But his PSA was consistently zero and he was pronounced "cured".
Now , a few weeks ago, he had a complete urinary blockage. He was admitted to the ER and the doctors were unable to insert a catheter and their first attempt at a supra-pubic insertion failed. He was on morphine before they fixed it. He is now scheduled for surgery (probably a TURP?).
The thing is, the uro told him that what he has is radiation damage to the urethra. So to go back to what puzzles me, how did that happen when for seven years he has had no problem there? Does it mean that the radiation damage was done way back and the scar tissue has just hardened ? Or has the damage continued? (Of course it could all be due to something else entirely, but that is not what he is being told.)
