Clinical indications and biological mechanisms of splenic irradiation in chronic leukaemia and myeloproliferative disorders

Splenic irradiation (SI) was the first efficient treatment for chronic leuk aemia, but with the emergence of effective drugs its use has been more and more restricted to advanced cases presenting with splenomegaly. But in sele cted patients who are not responsive or not suitable to drug treatment, SI may offer still an effective, low toxic and cost-effective palliative modal ity. Eight studies of SI in chronic lymphatic leukaemia (CLL) including 198 patients, six reports about SI in prolymphocytic leukaemia (PLL), includin g 18 patients, one study and six case reports about SI in hairy cell leukae mia (HCL) and nine studies about SI in myeloproliferative disorders has bee n analyzed. In CLL, symptoms of splenomegaly have been improved in 50-87% o f all patients with overall doses between 4 and 10 Gy in mostly 1-Gy fracti ons. PLL seems to be more resistant to SI with a median response rate of 66 %. Casuistic reports described also efficacy of SI in HCL patients using si milar radiation schedules. Symptomatic relief is also provided by SI in mye loproliferative disorders using lower overall doses between 1 and 9 Gy with small single fractions of 0.25 Gy (median). Acute toxicity was low in lymp hoid disorders, but higher in myeloproliferative disorders with severe cyto penia in 10-30% of all cases, indicating the need for a cautious fractionat ion schedule. Interestingly, even complete systemic remissions after SI in all types of lymphoproliferative disorders have been described. Different m echanisms underlying SI such as direct cell kill, immune modulation via cha nges in lymphocyte subsets or cytokine induction or 'radiotherapeutic' sple nectomy with high doses are discussed. (C) 2001 Elsevier Science Ireland Lt d. All rights reserved.