Can biological markers act as non-invasive, sensitive indicators of radiation-induced effects in the gastrointestinal mucosa?

Background Reliable, non-invasive biological markers of the severity of radiotherapy-induced damage to the gastrointestinal tract are not available. Clinicians continue to use symptom scores as surrogate indicators of toxicity. Aim To determine whether levels of potential biochemical markers of mucosal toxicity change during pelvic radiotherapy. Methods Fifty-nine patients (30:29 males:females) with mixed pelvic malignancies, receiving 45-70 Gy were recruited. At baseline and weeks 4 or 5 of radiotherapy, blood samples for citrulline, C-reactive protein, eosinophil cationic protein and stool samples for faecal calprotectin were obtained. Symptoms were measured using the Inflammatory Bowel Disease Questionnaire - Bowel Subset, Radiation Therapy Oncology Group and Vaizey Incontinence Questionnaires. Paired t-tests of change in marker values were calculated. Results Citrulline (P = 0.02) and faecal calprotectin (P = 0.01) values changed significantly between baseline and 4/5 weeks. Inflammatory Bowel Disease Questionnaire - Bowel Subset fell significantly (mean fall = 10 points, s.d.: 8.9). Changes in markers did not correlate with symptoms. Conclusions Some biochemical markers of mucosal toxicity change significantly during treatment. Further studies must investigate the timing of changes of these biochemical markers, their relationship to gastrointestinal physiological change and the radiotherapy dose delivered to the gastrointestinal tract and whether changes in markers acutely can predict the degree of long-term gastrointestinal dysfunction.