A Primer on Radiation

Emmett receives proton radiation at the Francis H. Burr Proton Therapy Center at Massachusetts General Hospital.  Radiation is another therapy doctors use to treat cancer.  Like chemotherapy, radiation targets rapidly dividing cells.  Cancerous cells are particularly vulnerable to attacks on DNA because of their high rate of division and their reduced abilities to repair DNA damage.

A normal, healthy cell must go through two mutations in order to become cancerous.  First, a cell must undergo a mutation that prevents it from being able to repair damage to its DNA.  Normal cells have the ability to fix themselves if they're damaged such that if something breaks within the cell which causes it to go crazy, the cell is able to fix its internal programming so that it begins to function normally again.  This is essentially like an antivirus program on your computer - if it detects a virus, it quickly removes it and your computer continues operating normally.

The second mutation a cell must undergo to become cancer is one which makes it grow (divide) uncontrollably.  A cell that is unable to repair itself which then undergoes a mutation that makes it divide without limit is a cancer by definition.  Without outside intervention, the cancerous cells will continue to divide and spread (metastasize) until the host dies.

Radiation therapy is one way to target rapidly dividing cells.  It works by using ionizing radiation to damage cell DNA.  Healthy cells are able to repair damaged DNA and in theory should be unaffected by controlled doses of ionizing radiation.  Cancerous cells, on the other hand, are unable to repair DNA damage and eventually die after prolonged exposure to radiation.  Because cell death is not immediate, tumors susceptible to radiation continue to shrink for months after the end of radiation therapy.

Proton radiation has several benefits over traditional photon radiation.  First, proton radiation is much more focused than photon radiation.  This allows the radiation beam to be shaped and targeted to the tumor while sparing most of the surrounding tissues.  Another benefit of proton radiation is that there is only an entrance dose and no exit dose.  This is because the proton beam essentially stops at the tumor.  Photon radiation, on the other hand, has both an entrance dose and an exit dose on either side of the tumor.  Because Emmett is receiving proton radiation, his incidental radiation exposure is essentially cut in half.  We consider ourselves very blessed that one of six pediatric proton radiation facilities in the United States is located here in Boston and that they accepted Emmett as a patient.

Emmett started proton therapy on May 21, 2012.  He receives radiation every morning M-F, excluding holidays.  His radiation therapy plan calls for six weeks of radiation, so we're just over halfway through.  Because positioning is critical in ensuring radiation is directed to the right locations in Emmett's body, he is sedated every time he's irradiated to make sure he holds completely still.  He also has a mask that secures his head to ensure it never receives any radiation.  In addition, they take a chest x-ray everyday to verify correct positioning.  All in all, this means that Emmett is receiving a TON of radiation and sedation.  We expect him to transform into a superhero any day now :)

Because children requiring sedation have to fast prior to receiving anesthetic, they always schedule the young kids like Emmett in the early morning.  With Boston traffic this means we're leaving home around 6:30 a.m.  When we arrive we head to the pediatric holding room where Emmett can play with toys while they take vitals and prep him for radiation.  After a half hour or so the phone rings signaling the room is ready and then one of us carries him down to the beam room where they sedate him with propofol and lay him on the table.  At that point they send us out and we head upstairs to the eighth floor where we visit the Healing Garden overlooking Boston and pray that angels watch over and protect him (and especially his spinal cord) during treatment.  After about an hour we head back down to the Proton Therapy Center waiting room in anticipation of the phone call signaling he's waking from sedation and that we can go get him in the pediatric holding room.  Emmett then insists on getting a "pop" (Dum Dum sucker) from the nurses before we head upstairs to ride the escalators for five minutes before getting him an Orange Fanta from the cafe.  We then head for home, typically arriving between 11 and noon.

So that's the low down on radiation.  The first two weeks Emmett did really well; he had lots of energy and seemed relatively unaffected by treatment.  The third week he started slowing down a little.  This week he's been much more tired and he's getting what looks like a dark sunburn on his left shoulder.  This is also the period in his chemo cycle where counts drop to zero so that's probably a contributing factor to his tiredness.

We found out this week we can take pictures of the proton beam room, just not video.  So we'll update this post in the future with some photos.