Image having 35 million dental x-rays...
Updated: Feb 13, 2021
Not all surprises on your birthday turn out to be nice, and last year’s confirmation of having Head and Neck Cancer (HNC) on February 12th kind of put a damper on the fancy meal David and I had booked that evening for my birthday. More specifically, my diagnosis identified I had squamous cell carcinoma in my right tonsil, that had spread to lymph nodes in my neck. In the UK, HNCs are not common, accounting for c. 3% of all cancer cases, and of those, only 12% were found diagnosed in the tonsil as the primary site (most linked to the human papillomavirus virus, or HPV) (i.e. 0.36% of all cancers in the UK) – I like to be different
Treatment involved radical chemoradiation therapy (CRT), complemented by 4 weekly sessions of chemotherapy. I’ve blogged before about the early side-effects of CRT), which involved loss of saliva, fatigue, weight-loss and of course mental health and other wellbeing issues. For late side-effects, these are many, and not knowing when they will materialise, or worse, if they have they already started to occur, is always worrying. And this is what I’ve been researching this past wee while. In many senses, my recovery has been brilliant; I’ve had two follow-up face-to-face meetings with a wonderful ENT Registrar, which involved nasoendoscopies (ie a flexible camera on a tube up one’s nose) that showed no sign of cancer reoccurrence. Yay.
But I still have difficulty eating (thank god dinner parties are out of the question at the moment), and my tongue & mouth seem to be in a permanent state of inflammation. And just this week, some of my teeth are feeling ‘fragile’, so much so that I thought one of the front ones was about to fall out. And over the past month, the skin around my mouth, jaw and neck are starting to tighten. The ENT specialist referred to this as developing a “woody neck” 🥺.
So what’s going on here?
Major late side-effects from extensive radiation therapy to the head and neck include osteoradionecrosis (ORN), tooth decay, fibrosis and lymphodema. ORN, or bone death, can be serious, although thankfully rare, where tissue in the jaw bone dies. To help prevent tooth decay I'm prescribed a toothpaste (Duraphat) that contains 5000 pmm fluoride, and to stop my neck and jaw freezing up, I’m back to doing daily head and neck exercises. Increasing skin and muscle tightness is caused by a process called fibrosis (which affects soft tissues alongside lymphedema), and is one of the most common long-term effects of radiation therapy.
So this got me thinking, what does the amount of radiation I received actually mean? Can I express this in a way that I can get my head around, because to be honest, 70 grays (Gy) of radiation (measured in joules per kilogram (J/kg)) over 35 days in 7 weeks doesn't mean much. All I remember was at the time it was pretty brutal.
So I’ve tried to compare it to a common dental x-ray, that we’ve probably all had (especially if you’re Scottish!!), and holiday flights to Spain.
An effective radiation dose is the amount of radiation that a specific type of body tissue absorbs, and is measured in joules per kilogram (J/kg), i.e. grays (Gy), and any risk of tissue damage is based on the effective dose. An effective dose of x-ray radiation is measured in a special unit called the sievert (Sv), but in dentistry, this dose can be very small, so doses are commonly measured as thousandth of a sievert, or a milli sievert (mSv).
There are different types of dental x-rays, but on average an intraoral radiograph (i.e. ones the dentist will take when they ask you to bite down on a piece of film; a bitewing) are on average c. 0.002 mSv. This amount is ten times less than a single return flight to Spain!
So 1 mSv = 0.001 Gy
0.001 mSv = 0.000001 Gy
0.002 mSv = 0.000002 Gy
70 Gy = 70,000 mSv, and if 1 typical x-ray dose is 0.002 mSv, that means I’ve had the equivalent of 35,000,000 x-rays, or 3,500,000 holiday flights to Barcelona and back!**
So maybe it’s hardly surprising the late-side effects cause so much tissue and DNA damage that the results will be felt now and in decades to come.
And on that note, I’m now off to enjoy my 54th birthday. And that’s the best surprise of all.
**If I have this calculation wrong, I blame the treatment 😆