It is true that EPO drugs have less effect if our serum-EPO already is high but they can be effective if the serum-EPO is less than 500. EPO drugs should be combined with Neupogen or a similar drug for better effect: http://www.ncbi.nlm.nih.gov/pubmed/12648074
Du you know how high your mother's serum EPO was initially?
As far as I understand your mother has low risk MDS. Her WBC are OK and her platelets are excellent. Then many doctors recommend watch and wait. If your mother will respond to EPO + Neupogen or a similar drug she will perhaps be transfusion independent.
The high ferritin level after only 18 unit is really quite high - your mother probably had a high ferritin level before transfusions due to hemolysis (the red blood cells burst too early). It takes years to develope toxic effects from iron overload but since your mother hopefully will have many years before her she could start iron chelation now.
73 yo, dx MDS Interm-1 2006, transfusion dependent from dx with HGB 7.0. Serum EPO more than 800 at dx so I never received EPO drugs. Only supportive treatment with txs, Neupogen and iron chelating drugs until 2010. Since then Thalidomide + Prednisone with positive results.