I don't know any hematologists personally, but you could either ask a doctor you already trust, who is the best in that field in Santo Domingo, or here are some of the listings in the Yellow Pages. There are only a few listed, and none with the same address as Dr Norman de Castro:
Dr Julio Castaños Guzman, Hematolgo - Oncologo, Instituto de Hemoterapia y Bioanalisis, A J Aybar No 19, tele" (809) 732-9898
Dr Luis Echeverria Yapor, Ave Nuñez de Caceres No 102, Santo Domingo, tele: (809) 482-8070
Dra Rosa Nieves Paulino, Pedro H. Ureña, Santo Domingo, tele: (809) 472-1509
OR, try Hospital General de La Plaza de La Salud, where they have probably the best onco- hematologia specialty department, on Ortega y Gasset, tele: 809-565-7477 , 24 Hours services. This is THE clinic people use when they are really sick, big shots included.
Good luck. Shout if you need more help.