Hi Sarah, My husband had oesphageal cancer.  With his first chemo treatment (weekly) he had an allergic reaction to the chemo (which is fairly common from what we were told) they stopped the treatment, treated his allergic reaction and once that had settled, continued the chemo.  Made it very long day.  His side-effects after that first treatment weren't too severe.  He did find though that subsequent rounds of chemo got progressively worse.  So severe in his case that the last (6th) round was cancelled altogether and he was hospitalized for nearly 3 weeks.  Sorry I can't remember to name of that chemo treatment.  Then months later he went through 4 rounds of Folfox (different to the first chemo) and the effect of this one was worse than the first chemo and he was hospitalized after each of the 4 treatments.  The 5th round he was supposed to have was cancelled.  He had vomitting, nausea, extreme exhaustion, numbness, sensitivity to cold, weakness, problems with his heart (not sure if this was from chemo or the previous radiation treatment). His side effects lasted for weeks after treatment finished.  It really does vary with the individual.  The Drs thought he would cope well with treatment as he was healthy and relatively fit prior to starting treatment. 
Wishing you and your relative all the best.
Sue