Men da forudgående behandling med alkylerende midler er bredt anvendt inden behandling med Zevalin, er det derfor vanskeligt at vide, hvorvidt Zevalin bidrager til denne risiko for at udvikle en sekundær cancer, idet stråling muligvis også kan forårsage disse cancertyper.
However, as previous treatment with alkylating agents is widespread prior to Zevalin treatment, one does not know the exact role of Zevalin when these cancers occur after treatment with Zevalin, since radiation may potentially also cause these cancers.