welcome to the forum and i'm sorry to hear about your brother's health problems.
your brother's msdx and symptoms (eyes, gut, numbness), in addition to the cancer dx, made me think of zinc, so i had a quick search and came up with this study:
Concentrations of antioxidative trace elements – selenium and zinc – in patients with sigmoid or rectal cancershttp://cornetis.pl/pliki/GP/2008/6/GP_2008_6_391.pdf
"Introduction: Colorectal cancer (CRC) is one of the most common neoplasms of alimentary tract in the world. Both its diagnosis and treatment outcomes are still far from satisfactory. Therefore, different studies focusing on determination of preventive measures of the drugs have been initiated. It was found that reactive oxygen species (ROS) are one of many carcinogens in the pathogenesis of CRC, and their pathogenic effect manifests when so called antioxidative protection barrier of the organism is weakened. Two important compounds of this barrier are, among others, selenium (Se) and zinc (Zn) – antioxidative trace elements providing prevention against carcinogenesis.
Aim of study: Determination of concentrations of selenium and zinc in blood plasma of patients with sigmoid and rectal cancers in comparison to the concentrations of these trace elements in healthy individuals.
Material and methods: One hundred sixty consecutive patients were included into the study. Patients were divided into four groups (n=40, each): the control group, patients with adenomatous polyps of sigmoid or rectum, patients with operative adenocarcinoma of sigmoid or rectum, and those with non-operable adenocarcinoma of sigmoid or rectum.
Results: Selenium and zinc concentrations determined in all groups of affected patients were significantly lower than in the control group which supports the involvement of these elements in the inhibition of carcinogenesis of CRC.
Conclusions: Implementation of controlled supplementation with Se and Zn preparations may seem to be beneficial in the prevention of CRC in high-risk patients."
the article is available in full and well worth reading. if you get into the data tables provided, you can see that on average, the zinc and selenium levels in patients are a fraction of the levels seen in healthy controls.
if your brother can request bloodwork, see if the docs will test SERUM zinc and selenium. if i recall correctly, plasma is supposed to be comparable to serum, in the case of zinc at least, but this study doesn't seem to be consistent with that idea.
if he does get some test results i can help you interpret. based on the literature out there, i have pretty solid target area within the 'normal' range for serum zinc. it's a little more variable for selenium, but still would be some useful pieces of info. if he decides to follow up i can help with diet and supplement options for both zinc and selenium. if you are interested in reading more about nutrition in health and disease, you might want to check out some of my 'signature' links below.
wishing all the best to your brother. he's fortunate to have you here for him.