UK Medical Research Council randomised, multicentre trial of interferon-αn1 for chronic myeloid leukaemia: improved survival irrespective of cytogenetic response

Interferon-&agr; may be better than cytotoxic drugs in the longterm management of patients with chronic myeloid leukaemia (CML) in chronic phase. To test this possibility 587 patients with CML in chronic phase were randomly allocated to receive lymphoblastoid cell-line interferon-&agr;n1 (IFN-&agr;, n=293) or chemotherapy with busulphan or hydroxyurea (no IFN-&agr;, n=294) as maintenance after initial induction treatment with cytotoxic drugs. There was a significant survival benefit for patients in the IFN-&agr; arm when analysed on the basis of intention to treat (2p=0·0009). The median survival for those allocated IFN-&agr; was 61 months and no IFN-&agr; was 41 months. Out of 269 patients with Philadelphia-positive CML in the IFN-&agr; arm with at least 6 months follow-up, 211 were evaluable for haematological response: 145 (68%) achieved good responses (A+ or A type), 37 (18%) had partial responses (B type) and 29 (14%) had poor responses (C type). Patients with types A and B responses had a better survival than those in the no IFN-&agr; arm; patients with type C responses had survival equivalent to the no IFN-&agr; arm. Of these 269 patients, 26 of whom had not started IFN-&agr;, 59 (22%) achieved a significant degree of cytogenetic response but 210 (78%) did not have a response. Cytogenetic responders survived significantly longer than non-responders and even non-responders survived longer than patients in the no IFN-&agr; arm. Since cytogenetic nonresponders had worse than average prognostic features, they may also benefit from IFN-&agr; therapy. We conclude that treatment with IFN-&agr; prolongs the survival of patients with CML; benefits of IFN-&agr; are not confined to cytogenetic responders but may extend to most, if not all patients receiving IFN-&agr; treatment; and cytogenetic response to IFN-&agr; treatment identifies patients with a relatively good prognosis.