Curcumin is a constituent of the turmeric plant. Forum member "Zoe's Life" talks about taking curcumin in
this forum thread. Turmeric was also mentioned in
this forum thread.
According to
Medline Plus, curcumin has shown some anti-cancer properties but there are no definitive human studies yet. The evidence is from animal and laboratory studies. Further research is apparently in progress.
Those animal/lab studies show that curcumin may increase the risk of bleeding, which is a concern for an MDS patient. You said your dad is diabetic and curcumin may lower blood sugar, so that's a consideration too.
If your dad is thinking of using curcumin he should definitely speak to his doctor about it.