On the 3rd of April 2019 we went to Melbourne for Isla’s 15th examination under general anesthetic (EUA). This trip we were not planning to attempt any intra-arterial chemo (after 3 failed attempts the previous 3 months) and we were back to just the overnight stay on the normal retinoblastoma clinic day. Everything went well during the EUA. The doctors came to speak to us afterwards and said everything looked stable. There were no new tumours and the main tumour had not grown since the successful round of intra-arterial chemo in December 2018. After that one infusion of intra arterial chemo the tumour did shrink and it has remained unchanged since then. Again, they don’t believe it is dead yet and we will have to keep a very close eye on it and administer some other form of treatment at some stage, but it is certainly not growing rapidly and we do have time on our side.
We had a bit of a chat with the doctors about the various treatment options available when the time comes. Due to the location of Isla’s tumour and the difficulty they have had with her intra-arterial chemo delivery, it’s possible we could try a different route for the chemo delivery.
One option would be to catheterise the carotid artery (main artery) and inflate a small balloon just beyond the ophthalmic artery to momentarily block the blood supply to the rest of the brain and infuse the chemo drug into the carotid artery. By blocking the blood flow just beyond the ophthalmic artery, the chemo will be directed mainly into the ophthalmic artery without having to catheterise the much smaller artery (see diagram below). Obviously blocking any blood supply to the brain is never ideal and this method certainly has its risks.
Option 1
Image reprinted courtesy of Dana-Farber/Boston Children's Cancer and Blood Disorders Center
Alternatively, they could attempt a different route and go up the vertebral artery instead of the carotid (see diagram below). The angle from the carotid artery to the ophthalmic artery can often be quite sharp. This angle varies among different people, but in Isla it is a very sharp angle. This makes navigation with a guidewire quite difficult and can lead to artery spasm. The French practice the alternate route, which enters the brain through the vertebral artery (back of the neck) and has a slightly straighter route to the ophthalmic artery. To me, this method made a lot of sense. I can certainly understand why you would want to avoid blocking off the blood supply with the balloon, but I couldn’t see any reason not to attempt the vertebral artery route. I queried this with the eye team and asked what are the risks of doing it this way, and basically why are we not doing that now? They said that was probably a question for the interventional radiologists and they would pass that question on to them.
Option 2
Carotid route marked in blue, vertebral route marked in green.
The other treatment options we spoke about were plaque radiotherapy, reservoir treatment and as always enucleation (removing the eye).
Plaque radiotherapy is a form of brachytherapy where radioactive seeds are placed inside a metal disc (usually gold), which is attached to the outside of the eye. The radioactive seeds emit radiation towards to tumour cells and the gold stops the radiation going the other way (and exposing any healthy tissues/other people too much). The plaque is then removed after a few days.
Plaque Radiotherapy
Image by The Eye Cancer Foundation via https://eyecancer.com/eye-cancer/treatments/eye-and-vision-sparing-radiation-therapy-for-intraocular-tumors/
Plaque Placement
Image by The Eye Cancer Foundation via https://eyecancer.com/eye-cancer/treatments/eye-and-vision-sparing-radiation-therapy-for-intraocular-tumors/
This form of therapy works best on tumours in the anterior half of the eye, up to the ora serrata (marked in red on image below). Isla’s tumour is much too posterior for this to be a favourable option and the rough location of her tumour is marked in green on the image below.
By Rhcastilhos. And Jmarchn.- Schematic_diagram_of_the_human_eye_with_English_annotations.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1597930
Reservoir treatment was only touched on briefly as the doctors are not really considering this as an option. It is still in the trial phase. I haven’t even been able to find any more information about this online, so I’m not entirely sure what this even is. An Ommaya Reservoir is used in trilateral retinoblastoma (tumour also in pineal gland in the brain) and I can only assume it may be something similar to this, whether it somehow directs chemo directly into the eye or into the ophthalmic artery, but I’m not 100% sure.
Ommaya Reservoir - used in trilateral retinoblastoma
Patrick L. Lynch, Public domain, via Wikimedia Commons
At this stage though, we are planning to attempt intra-arterial chemo again at some stage, probably using the vertebral artery route and if that doesn’t work we will probably be starting to think about removing Isla’s right eye and replacing it with a prosthetic.
Isla took a little while to wake up in recovery this time, but once she woke up she was back to her happy little self in no time.
© Alison Davey 2021
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