I think it might be worth trying l-carnitine supplementation., there are a number of published studies (as well as on-going NCI-sponsored clinical trials) which suggest that a majority of cancer patinets are deficient in l-carnitine and benefit both in energy and mood after modest supplementation.

L-carnitine is an amino acid which is involved in the metabolism of long-chain fatty acids. Many cancer patients, esp. those receiving cisplatin, show depleted levels in their blood.
L-carntine supplements (the easiest to take is the liquid form from GNC) are widely available as many athletes use them to enhance performance. While evidence of the latter is weak (as these people have normal blood levels), the case with cancer fatigue is more compelling.

For example:
L-carnitine supplementation in cancer patients with fatigue and carnitine deficiency
R. A. Cruciani, et al. Beth Israel Medical Center, New York, NY;
(Presented at 2004 ASCO meeting)

Background: Fatigue is highly prevalent in the cancer population and nutritional factors are among the postulated causes. Deficiency of the micronutrient L-carnitine could play a role by reducing energy production through fatty acid oxidation. We are presenting preliminary data of an open-label, dose-finding study to determine safety of one week L-carnitine supplementation in cancer patients with fatigue and carnitine deficiency. The beginning dose was 250 mg/day; doses were increased by 500 mg up to 3000 mg/day. Three patients were enrolled at each dose level. Fatigue (BFI), depressed mood (CES-D), quality of sleep (ESS), and performance status (Karnofsky Performance Status), were assessed at baseline and after one week of L-carnitine supplementation. Results: 18 patients that fulfilled predictors for carnitine deficiency (decreased caloric intake and muscle mass) were accrued to date. 14 (age range=34