Plasma citrulline levels predict intestinal toxicity in patients treated with pelvic radiotherapy.

BACKGROUND: Radiotherapy (RT) for abdominal and pelvic malignancies often causes severe small bowel toxicity. Citrulline concentrations are known to decrease with intestinal failure. We thus evaluated the feasibility of plasma citrulline levels in predicting radiation-induced intestinal toxicity. MATERIAL AND METHODS: Fifty-three patients (36 prostate cancer, 17 endometrial cancer) who received 45 Gy pelvic RT using conventional fractionation were prospectively evaluated. Patients with prostate cancer received an additional 25-30.6 Gy conformal boost. Plasma citrulline levels were assessed on day 0, mid- (week 3) and post-RT (week 8), and four months post-RT. Dose-volume histogram, citrulline concentration changes, and weekly intestinal toxicity scores were analyzed. RESULTS: Mean age was 63 years (range: 43-81 years) and mean baseline citrulline concentration was 38.0 ± 10.1 µmol/l. Citrulline concentrations were significantly reduced at week 3 (27.4 ± 5.9 µmol/l; p < 0.0001), treatment end (29.9 ± 8.8 µmol/l; p < 0.0001), and four months post-treatment (34.3 ± 12.1; p = 0.01). The following factor pairs were significantly positively correlated: Citrulline concentration/mean bowel dose during, end of treatment, and four months post-RT; dose-volume parameters/citrulline change groups; cumulative mean radiation dose/intestinal toxicity at end and four months post-RT; citrulline changes/intestinal toxicity during and end of RT. Citrulline concentration changes significantly differed during treatment according to RTOG intestinal toxicity grades (p < 0.0001). Although the citrulline changes differed significantly within RTOG intestinal toxicity grades (p = 0.003), the difference between Grade 0 and Grade 1 did not differ significantly at the end of the treatment. At four months after RT, no significant differences were apparent. CONCLUSION: Citrulline-based assessment scores are objective and should be considered in measuring radiation-induced intestinal toxicity.

Macroprolactinemia, like hyperprolactinemia, may promote platelet activation.

Insulin resistance, which provides a convenient milieu for platelet activation, has been closely associated with atherosclerotic disorders. Although it often accompanies hyperprolactinemia, findings conflict concerning its clinical impact in macroprolactinemia. In order to investigate the relationship between hyperprolactinemia and platelet activation evidenced by ADP-stimulated P-selectin expression on flow cytometry, we studied hyperprolactinemic, macroprolactinemic, and normoprolactinemic subjects. Thirty-four hyperprolactinemic and 44 age- and body mass index-matched euprolactinemic premenopausal women were included. They were matched regarding insulin sensitivity status, waist circumference, blood pressures, and plasma lipids. In order to detect macroprolactinemia among hyperprolactinemic cases, prolactin was measured before and after polyethylene glycol (PEG) precipitation in patients' sera. P-selectin expression was significantly higher in the hyperprolactinemic group (P =0.001), and 41.2% of them exhibited macroprolactinemia. Expression of P-selectin was comparable between the macroprolactin-negative (monomeric hyperprolactinemia; n = 20) and -positive (n = 14) subgroups (P = 0.90). Both subgroups showed greater expression compared with normoprolactinemic controls (P = 0.014 and 0.005, respectively). Platelet activation accompanies the atherosclerotic disorders closely associated with insulin resistance. Among groups matched with regard to insulin-sensitivity markers, both monomeric hyperprolactinemia and macroprolactinemia appeared to promote platelet activation.