post ABVD treatment headeache

Hi all,
By brother have been found with hodgkin's lymphoma last year(july 2010), in january he 've finished 6 corses of abvd treatment but recently started heaving headeaches;(he did not have any of this while his treatment)_
I just want to know if he should contact his consultant asap to ask for an MRI, or to wait to see his consultant at the appointed day he has(after 2 weeks).I just want to mention that on the 4 of february he has a PET scan and he is waiting for the results(3 of March).
Can abvd cause post treatment headeache(are not normal headeaches, he is feeling some time the top of his head very hot and dizzy)