Mum has Stage IV

LDH is affected by many things including infections and abcesses.  "LDH" itself is the sum of five isoforms, tetramers built with 2 components, yielding  LDH1, LDH2,...LDH5. LDH2 is the most comon LDH for healthy people. Certain organ failures will increase LDH1.  A nasty, anaerobic cancer will be spewing out lots of LDH5, also.  All measured together in LDH. Assuming the 4000 is almost all the cancer, not other problems, this is very high and reflects both tumor load and CRC cell type.  A healthy person would be typically be 100-180, less healthy up to 250 but could be cancerous too.  4000 is really high (units?).   

There are several  blood work panels that are important clues to the initial condition, how urgent or critical the situation is, what you're mom and any doctors are really dealing with.  CBC (complete blood count) with differentials and platelets; ESR and CRP, the inflammation markers; CEA and CA199 cancer markers; albumin levels (from Total Protein); bilirubin, PT/INR; and the common liver panels SGPT, SGOT, ALP.  

Typically metastatic CRC is treated with chemo first in conventional medicine, non metastatic cases with radiation or surgery first.  Some of us have used nutritional and alternative methods too.  Our first two days, I was busy arranging large scale nutrients and cimetidine to restore and prepare my wife's depleted body for surgery and chemo.  

The more tumor dieoff that occurs, the more toxicity the liver has to neutralize and excrete. If patient's physical condition is poor, or liver is largely replaced by tumor, the trickier the situation is to bring an initial raging condition under control.   You've given us only one less common clue to compare profiles and our treatment histories on "back from the brink". But yes, sometimes there are amazing turnarounds and "luck" can be "helped" extra.