One week of treatment is over.
This week has been all about radiation – 5 sessions in radiation treatment room number 3 of the Grand River Regional Cancer Centre. Each time, I get up on the couch, lie face down and listen to the radiation therapists compare numbers, sometimes positioning my body to match the specifications in the planning images. Then they usually say something like, “OK, Don, that’s perfect. Now don’t move. We’ll be back in a few minutes.”
After that, being face down, all I can hear is the sound of the Clinac 21 EX linear accelerator machine from Varian Medical Systems moving around my body into 3 different positions to cover the 2 sides and the back of the pelvis, generating the sound I have come to recognize as part of the shaped radiation beam penetrating the skin and organs of my body in an effort to target the tumour and possibly infected lymph nodes.
Thursday afternoon, since I was the last patient for the day, we had time for a demonstration of what actually happens. The machine, worth about $4 million and surrounded by highly insulated walls, ceiling and floor, employs a technology called intensity-modulated radiation therapy (IMRT) and something Varian calls SmartBeam, which refers to the way the company’s machinery shapes and modulates the treatment beams to maximize the dose delivered to the tumour while sparing, as much as possible, normal tissues. The photograph with today’s blog illustrates an example of how the beam is shaped with the plates being adjusted according to computer programs which reflect the design of the treatment planned by the radiation oncologist.
The technology, even for an information technology manager like me, is incredibly complex. I could never hope to get a detailed understanding of the technology during my treatment cycle. The best I can hope for is some appreciation for the principles involved.
Radiation oncologists are motivated by a desire to increase cancer cure rates and to reduce unnecessary toxicity from treatment. Improvements in radiation technology are currently geared towards modulating dosage. Varian’s Clinac machines, for example, come with up to 300 upgrade options. The machinery and its options provide the radiation oncologist with variables for maximizing doses for rapid patient treatment. They are also intended to stabilize and even lower cost per patient treatment.
Using IMRT techniques, there is growing evidence that local tumour control is improving. For prostate cancer, for instance, IMRT has doubled the rate of local tumour control over conventional radiation therapy and reduced complications for normal tissue from 10 to 2 percent.
I haven’t found studies specific to IMRT and rectal cancer yet (maybe I haven’t looked hard enough), but until Friday evening, I had no side-effects at all from 5 fractions of radiation therapy. Friday night, approximately 5 hours after treatment, I experienced a dramatic case of diarrhea which, fortunately, did not continue today.
Clearly, the effects of both low-dose 5-flurouracil and radiation treatment will do something to my body. The effects accumulate, so I expect further side-effects as the treatments continue. But, thus far, it has all been quite manageable.
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