I think I found that article about stem cell transplants - from American Society of Hematology 's page called "Hematology, the education program",and the article was called Management of prolymphocytic leukemia by author Claire Dearden .
"In B-PLL, there are a number of case reports of successful transplants, although inevitably case reports are misleading because they fail to highlight the number of unsuccessful cases. Kalaycio et al report on 11 cases of B-PLL with a median follow-up of 13 months. At 1 year, Progression Free Survival was 33% and Transplant Related Mortality was 28%,..." (they don't say what happened with the other 39% of transplants so i assume they continued struggling with B-Pll and other treatments).