Abstract

Imatinib and recombinant interferon alpha (rIFN) can induce remission in polycythemia vera (PV) patients, but gauging the depth of responses has not been possible due to lack of a specific disease marker. We found that patients undergoing imatinib (n = 14) or rIFN (n = 7) therapy remained strongly positive for V617F JAK2, although there was a significant reduction in the median percentage of mutant alleles that correlated with hematologic response (P = .001). Furthermore, individuals who achieved complete hematologic remission had lower levels of V617F than those who did not (P = .001). Of 9 imatinib-treated cases for whom pretreatment samples were available, 7 with no or partial hematologic responses showed a marginal increase (median, 1.2-fold; range, 1.0-1.5) in the percentage of V617F alleles on treatment, whereas the 2 patients who achieved complete hematologic remission showed a 2- to 3-fold reduction. Our data indicate that, although PV patients may benefit from imatinib or rIFN, molecular responses are relatively modest.