Colorectal Cancer: Intrinsic Characteristics Modulate Cancer Energy Expenditure and the Risk of Cachexia

Purpose: To conduct a prospective longitudinal study in colorectal cancer (CRC) patients: 1) to evaluate resting energy expenditure (REE), weight/dietary intake changes, and response to treatment, taking into consideration cancer stage and histology; 2) to determine their potential interrelations; and 3) to quantify the relative contributions to REE of cancer/nutrition/treatment. Patients and Methods: 101 CRC patients proposed for neoadjuvant radiotherapy (RT) were evaluated before and after RT: REE (indirect calorimetry measurements), percentage of weight loss, usual diet (diet history), current diet (24 hour recall), and treatment response. Results: REE was higher in Stages III/IV versus I/II, at the RT onset (p < 0.002) and end (p = 0.02), and in moderately/poorly/undifferentiated cancers vs well differentiated (onset, p < 0.001) and (RT end, p = 0.01); weight/intake reductions were also greater in Stages III/IV versus I/II (p < 0.01) and in moderately/poorly/undifferentiated cancers versus well differentiated (p < 0.02). According to patients' response to treatment, REE was increased in Stage III/IV (p < 0.005) and Grade 2/3 histology (p < 0.003). In nonresponders, REE increased 7.2 ± 1.3 kcal/kg/day and decreased 2.8 ± 0.4 kcal/kg/day in responders. REE changes were not-significantly influenced by weight/intake. Relative contributions to baseline REE were determined in 25 percent by stage, in 25 percent by histology, in 3 percent by intake and in 4 percent by weight loss. At the end of RT, higher REE was attributed in 26 percent to stage, in 27 percent to histology, in 30 percent to nontreatment response, in 9 percent to intake, and in 8 percent to weight loss. Conclusions: In this CRC patient population, higher metabolic rates were mainly determined by the tumor burden and aggressiveness in association with response to treatment clearly disclaiming the effect of weight loss and/or dietary intake reductions.