Effects of Total Parenteral Nutrition and Chemotherapy on the Metabolic Derangements in Small Cell Lung Cancer
Carcinoma, Small Cell
Parenteral Nutrition, Total
Changes in energy metabolism, substrate use, and hormone profiles were prospectively studied in 31 patients with small cell lung cancer receiving chemotherapy. Patients were randomized to receive either 4 weeks of total parenteral nutrition (n = 15) or to continue self-regulated p.o. diet (control group; n = 16). The initial actual resting energy expenditure measured by indirect calorimetry was 31% higher than the predicted resting energy expenditure determined by the Harris-Benedict formula. The p.o. calorie intake was inappropriately low for these hypermetabolic patients. Total parenteral nutrition resulted in a significant positive net energy balance, but in follow-up was associated with prolonged anorexia and a negative energy balance. Complete response to therapy reduced resting energy expenditure and increased calorie intake, whereas the contrary was true in nonresponders. Elevated plasma-free fatty acids (800 +/- 62 microM; S.E.) and a low respiratory quotient (0.74 +/- 0.02) indicate that the dominant energy source in patients with small cell lung cancer is fat, and that increased fat oxidation continues despite tumor response. Elevated fasting plasma catecholamines and insulin resistance may contribute to continued fat mobilization. Initially, there was a significant increase in blood lactate (1118 +/- 95 microM) suggesting either increased tumor or tumor-mediated glycolytic activity. Response to therapy was associated with a fall in blood lactate levels. The most effective way of improving the metabolic derangements in patients with small cell lung cancer was to achieve tumor response to therapy.