Thanks for the reading. Hopefully it can shed some light on how a VOC moon might play out in your grandmother's horary chart.
Just to be clear: I was never diagnosed with colon cancer. However, my brother died of it, and because it tends to run in families I requested a colonoscopy.
I understand cazimi to mean a planet within 17 minutes of the sun. My significator Mercury is a bit past that, so I viewed it as combust, not cazimi.
I tend to use J. Lee Lehman, The Martial Art of Horary Astrology, as my guide. Accordingly:
1st house: my health and vitality. Mercury is not well placed in the 8th, and (by my reckoning) is combust. However, it is in its own terms.
The 6th house shows the disease. Venus rules the 6th house of health. It is in its own triplicity but has no other dignity and is retrograde. Saturn is in the 6th house and has no essential dignity, which does not seem promising. However, Venus retrograde will perfect a sextile with Saturn, as will the sun and Mercury. However, before they get there, Mercury (me) perfects a square to Mars (not good. Probably a prohibition.)
Just to follow the sequence of events:
1. question asked at the end of 2013, procedure scheduled for early 2014. I'm Mercury.
2. Mercury's first aspect is a square to Mars. Prohibition?
3. Mercury opposes Jupiter.
4. Mercury sextiles Saturn.
5. Mercury conjuncts Venus.
7th house: doctor. Here the moon is VOC. Interestingly, he was an older man who was retiring right after he did my scope. Apparently my colon is twisted so he couldn't get the scope all the way up. What he found was fine, and the subsequent colonography to check the last bit was fine.
8th house: Possibility of death. My significator there was not so wonderful, notably if you use Pluto; but the 8th house also symbolizes the colon so that rulership was probably the right one to consider.
10th: outcome or cure. (4th from the 6th) Loops back to Saturn.
I note that Jupiter is retrograde, so it does not apply to a trine with Saturn.
OK, so if I look at your grandmother's horary:
First house: I would have turned the houses differently, but Rex E. Bills, The Rulership Book gives the first house for the grandmother of a man. Ruled by Venus. The house itself looks OK, but Venus is in detriment. But it's not entirely helpless: in its own face and angular.
6th house of health: ruled by Jupiter. Venus applies to a nice trine with a domiciled Jupiter. Jupiter, appropriately is in the 3rd house which rules the lungs.
Doctor, 7th house, ruled by Mars. After leaving Jupiter, Venus applies to a sextile with Mars.
Outcome, 10th house Ruled by the VOC moon.
So within reason, and allowing for her health condition going into her crisis as well as her age, to me a lot of the chart looks good, but I wouldn't expect much change in your grandmother's condition.
Probably I've missed a lot, and as I said, I don't want to be in the business of giving false hope, so please let us know what happens.