28. Ockham’s Razor – or putting it as simply as necessary and no more!

William_of_Ockham

(William of Ockham (1287-1347)) Accessed from https://en.wikipedia.org/wiki/William_of_Ockham#/media/File:William_of_Ockham.png on 3 January 2016).

So what is going on?

Perhaps I can start by reviewing my last Pre chemo meeting at Ninewells Hospital. This was taken by Dr L one of Dr P’s registrars.   She was helpful but could only answer one out of my nine questions, but promised to refer the rest to Dr P. I met with Dr P on Chemo day (7 December 2105).

I first asked about the possibility of abdominal lavage for cancers that had spread from the original site in the stomach to more distant tissues such as lymph nodes. Dr P reassured me that this issue had been reviewed on multiple occasions and whilst strong advocates occasionally emerged following some success, on balance, results were no better than via intravenous chemotherapy. One –nil.

Dr P agreed to look into the use of the new drug treatment for Malignant Melanoma using Almycin. One – all.

Dr P agreed to undertake CT scans to determine my progress by the beginning of my fourth round of Chemo. Two – one.

I mentioned that my iron tablets had been counter-indicated with two of my other medicines but he reassured me the risks were minor. Three – one.

One of my fellow brothers in arms, N had mentioned his own research into the merits of consuming high calorie diets. Dr P dismissed these concerns as it is more important that the patient be fit and has as much energy as possible for fighting the cancer. Five- two.

I then mentioned the possibility that when I had had my episode with the curry that I may have dislodged part of the tumour as food passed through the narrowed gastric canal. He didn’t dismiss this as fanciful since he’d had another patient that had a similar disease who thought she might have coughed up some of her cancer following a sneeze. She had the foresight to bring along a piece to the meeting and Dr P had the openness to have the tissue sample processed and then examined by an histo-pathologist. It turns out the patient was correct! Six – two.

Then came my killer question. Could it be that my progress was sufficient for me to be re-designated to a programme of curative rather than palliative care? Dr P was clear – NO! I’m not sure I understood this but decided to ‘park’ this issue for a while. Seven – two!

So why is there reluctance to recognise my progress as a positive outcome and to give me more encouragement? Dr P suggested that the progress could be temporary and that it might be more disappointing to discover this especially if this is confirmed by Scan data. And so, on balance, he favoured a conservative view. I still don’t buy this but leave it. However, I am determined to pursue the PET-CT scan route to uncover further information that might make my own case more persuasively.

So can I find an answer from a consideration of Ockham’s Razor.

(Accessed from Wikipedia at https://en.wikipedia.org/wiki/Occam’s_razor on 3 January 2016)

[Occam’s razor (also written as Ockham’s razor and in Latin lex parsimoniae, which means ‘law of parsimony’) is a problem-solving principle attributed to William of Ockham (c. 1287–1347), who was an English Franciscan friar and scholastic philosopher and theologian.]

The principle can be interpreted as

Among competing hypotheses, the one with the fewest assumptions should be selected.

[The application of the principle can be used to shift the burden of proof in a discussion. However, Alan Baker, who suggests this in the online Stanford Encyclopedia of Philosophy, is careful to point out that his suggestion should not be taken generally, but only as it applies in a particular context, that is: philosophers who argue in opposition to metaphysical theories that involve an allegedly “superfluous ontological apparatus.”

Baker then notes that principles, including Occam’s razor, are often expressed in a way that is unclear regarding which facet of “simplicity”—parsimony or elegance—the principle refers to, and that in a hypothetical formulation the facets of simplicity may work in different directions: a simpler description may refer to a more complex hypothesis, and a more complex description may refer to a simpler hypothesis.]

In other words, sometimes simple things are said in a complicated fashion (like much of my blogging) and others say more elegantly what appears to be a complicated idea in very simple, understandable language (how I’d like to write my blog!).

Would a shift to a curative regime mean that I would have to have further scans and that DR P was trying to protect me from my own enthusiasm? So what do other Scans help reveal about cancer?

What tests are used to detect stomach cancer? A range of measures are used. These include physical examination (GP) plus other general health checks, Endoscopy (Gastroscopy) and CT scan.  A full account of this is presented in Appendix 1.  Of particular interest is the section on further tests for gastric cancer involving various scan types such as CT scan, PET scan, PET-CT scan and MRI scan.

 

Summary

It is clear that Scans don’t do the same thing.  A particular scan type, say PET-CT scan, may reveal useful and specific information about my cancer.   MRI scans may reveal soft tissue better than CT scans alone.  So, for example, PET-CT scanning may reveal how well the chemotherapy treatment is working and it may also show the difference between scar tissue and actively growing cancer.

These and other aspects of what PET-CT scanning can do may be important in determining whether I might be considered for further curative treatment such as surgery.  So, should this be used at my first opportunity (after cycle 4 of EOX) rather than CT scanning alone?

 

Appendix 1

(Accessed from http://www.cancerresearchuk.org/ on 3 January 2016)

[Endoscopy
This is the main test to diagnose stomach cancer. An endoscope is a long, thin, flexible tube with a light and camera inside. During the test you usually have a sedative to make you drowsy and less aware of what is going on. Once you are drowsy and relaxed, the doctor or nurse endoscopist will pass the endoscope tube down your throat into your stomach. This allows them to look at the inside of the foodpipe (oesophagus), stomach and the first part of the small bowel (the duodenum). They will take tissue samples (biopsies) of any abnormal looking areas.
There is detailed information about having an endoscopy in our cancer tests section. Sometimes the endoscopy tube has an ultrasound probe at the end. It takes an ultrasound scan of the stomach and surrounding area. This is called an endoscopic ultrasound.
You can have this test as an outpatient. But you should take someone with you to take you home. You won’t be able to eat or drink for about 8 hours before the test so that your stomach and duodenum are empty.
Once the test is over you will need to rest for a while. Because of the sedative, you may not remember anything about the test once it is over.]
A Further test is the PET-CT scan.
A PET-CT scan uses a CT scan combined with a PET scan. A PET scan shows up areas of active cancer cells using small amounts of radioactive glucose. It can sometimes help to show up areas of cancer in the upper part of the stomach. We have detailed information about PET-CT scans.
A PET scan uses a very small amount of radioactive drug to show how body tissues are working. PET-CT scanners tend to be in the major cancer hospitals. So you may have to travel to another hospital if you need to have one. Not everybody who has cancer will need one. Other types of tests and scans may be more suitable.

PET CT Scan 2

PET CT Scan

PET Scans
[How a PET-CT scan works
A PET-CT scan uses X-rays to take pictures of the structures of your body. At the same time, a mildly radioactive drug shows up areas of your body where the cells are more active than normal. The scanner combines both of these types of information. This allows your doctor to see any changes in the activity of cells and know exactly where the changes are happening.
What doctors use PET-CT for
PET-CT scans are used for many types of cancer and are generally thought to be more accurate in diagnosing cancer than PET scans alone. PET-CT scans can help to
  • Diagnose cancer
  • Stage a cancer
  • Make decisions about whether you can have surgery to remove your cancer
  • Make decisions about which is the best treatment for your cancer
  • Show how well the treatment is working
  • Find the place in the body where you cancer first started to grow (primary cancer)
  • Check whether your cancer has come back
  • Show the difference between scar tissue and active cancer tissue]
 These are key decision making reasons for using PET-CT scans and I think I need such information? Note to self: ask Dr P about PET scans?

(Accessed from http://www.cancerresearchuk.org/ on 3 January 2016).

[After you have had treatment for cancer, a scan may show that there are still some signs of the cancer left. But this may not be active cancer. It could be scar tissue left over from cancer killed off by your treatment. A PET-CT scan can sometimes show whether this tissue is active cancer or not.
What having a PET-CT scan involves
The scanning department will give you instructions on how to prepare for your scan. These are normally written in your appointment letter. Generally, you should not have anything to eat for about 6 hours beforehand. You can usually only drink water during this time. You may be told not to do any strenuous exercise for 24 hours before the scan. Unless you are told otherwise, you should carry on taking any medicines prescribed for you by your doctor. If you are diabetic, you should contact the department a couple of days before your appointment. You may need to adapt your diet and sugar control routine a little.
When you arrive, check in with the receptionist so the radiographers know you are there. Then you usually take a seat in the waiting room until someone calls you for your scan. You can take a friend or relative, but they will usually not be allowed to go into the scanning room with you. The radiographer may ask you to change into a hospital gown. You will need to take off all your jewellery and any other metallic objects. They may want you to take a dose of diazepam (Valium) to relax the muscles around your neck and shoulders. This can give clearer pictures on the scan.
You will have a small tube (cannula) put into one of the veins in the back of your hand or arm. Then you have the radioactive drug (tracer) as an injection through the tube. You need to rest for about an hour afterwards. This allows the drug to spread through your body and into your tissues. Before your scan begins, you will go to the toilet to empty your bladder.
In the scanning room, you lie on your back on the narrow bed. The radiographer will help you to get comfortable and make sure you are in the right position. The bed gently moves through the scanner. The scan takes between 30 to 60 minutes, depending on which parts of your body are scanned. The scan is not particularly noisy but the computers and air conditioning make a constant background noise. You need to stay as still as you can during the scan. You can talk to the scan operator through an intercom if you need to.
Some people feel a bit claustrophobic (‘closed in’) when they are having a scan. If you think you are likely to feel this way, tell the radiographers before the day of your appointment.
After the scan
Once the scan is over you will be able to go home straight away. You can eat and drink what you like and go back to normal activities. Although the amount of radiation from the radioactive drug is very small, it is best not to have long periods of close contact with pregnant women, babies and young children for the rest of the day.
If you have had diazepam (Valium) you must not drive for the rest of the day, as it makes you drowsy. You will need someone to take you home from the hospital.
If you are travelling abroad within a few days of your scan, it may be a good idea to take your appointment letter with you to show that you have had a scan. Most airports have sensitive radiation monitors which may pick up the trace of radiation following your test.
Possible risks of a PET-CT scan
During a PET-CT scan you are exposed to radiation from the X-rays and the radioactive drug. The radiation in the radioactive tracer is very small, and goes away (decays) very quickly. It does not make you feel unwell. Drinking plenty after the scan helps flush the drug out of your system. The radiation from the CT part of the scan is also kept to the minimum necessary. The risk of the radiation causing any problems in the future is very small. Doctors only do these scans if they are necessary. They make sure the benefit of having the scan outweighs any possible risks.
You should not usually have a PET-CT scan if you are pregnant, as there is a risk that the radiation could harm the baby. If your doctors think it is essential for you to have the scan, they will tell the staff in the scanning department and the dose of radiation will normally be reduced. You should not bring babies, young children or anyone who is pregnant to the scanning department.
If you are breast feeding, let the department know a few days before your appointment. They will let you know if you need to stop breast feeding for a length of time after having the radioactive drug. You may need to store enough expressed milk for at least one feed.
The results
It can take time for test results to come through. Usually, a specialist in radiology or nuclear medicine examines the scan and has a report typed up. The scanning department sends the report to your specialist, who gives you the results.
Understandably, waiting for results can make you anxious. It usually takes up to a couple of weeks. If your doctor needs the results urgently, they make a note of this on the scan request form and the results are ready sooner. Remember to ask how long you should expect to wait for the results when the doctor first asks you to go for the test. If it is not an emergency, and you have not heard a couple of weeks after your scan, ring your doctor’s secretary or specialist nurse to check if the results are back.]

(Accessed from http://www.cancerresearchuk.org/ on 3 January 2106).

 

MRI Scan

[This scan uses magnetism to build up a picture of the inside of the body. Your doctor may suggest an MRI because it sometimes shows up soft tissue more clearly than a CT scan. There is more about having an MRI scan in the about cancer tests section.]

 

 

 

 

 

 

 

 

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