Minimal preparation computed tomography instead of barium enema/colonoscopy for suspected colon cancer in frail elderly patients: an outcome analysis study

AIM: To evaluate the efficacy of minimal preparation computed tomography (MPCT) in diagnosing clinically significant colonic tumours in frail, elderly patients. MATERIALS AND METHODS: A prospective study was performed in a group of consecutively referred, frail, elderly patients with symptoms or signs of anaemia, pain, rectal bleeding or weight loss. The MPCT protocol consisted of 1.51 Gastrografin 1% diluted with sterile water administered during the 48 h before the procedure with no bowel preparation or administration of-intravenous contrast medium. Eight millimetre contiguous scans through the abdomen and pelvis were performed. The scans were double-reported by two gastrointestinal radiologists as showing definite (> 90% certain), probable (50-90% certain), possible (< 50% certain) neoplasm or normal. Where observers disagreed the more pessimistic of the two reports was accepted. The gold standard was clinical outcome at 1 year with positive end-points defined as (1) histological confirmation of CRC, (2) clinical presentation consistent with CRC without histological confirmation if the patient was too unwell for biopsy/surgery, and (3) death directly attributable to colorectal carcinoma (CRC) with/without post-mortern confirmation. Negative endpoints were defined as patients with no clinical, radiological or post-mortern findings of CRC. Patients were followed for 1 year or until one of the above end-points were met. RESULTS: Seventy-two patients were included (mean age 81; range 62-93). One-year follow-up was completed in 94.4% (n = 68). Mortality from all causes was 33% (n = 24). Five histologically proven tumours were diagnosed with CT and there were two probable false-negatives. Results were analysed twice: assuming all CT lesions test positive and considering "possible" lesions test negative [brackets] (95% confidence intervals): sensitivity 0.88 (0.47-1.0) [0.75 (0.35-0.97)], specificity 0.47 (0.34-0.6) [0.87 (0.750. 94)], positive predictive value 0.18 [0.43], negative predictive value 0.97 [0.96], positive likelihood ratio result 1.6 [5.63], negative likelihood ratio result 0.27 [0.29], kappa 0.31 [0.43]. Tumour prevalence was 12%. A graph of conditional probabilities was generated and analysed. A variety of unsuspected pathology was also found in this series of patients. CONCLUSIONS: MPCT should be double-reported, at least initially. "Possible" lesions should beignored. Analysis of the graph of conditional probability applied to a group of rail, elderly patients with a high mortality from all causes (33% in our study) suggests: (1) if MPCT suggests definite or probable carcinoma, regardless of the pre-test probability, the post-test probability is high enough to warrant further action, (2) frail, elderly patients with a lowpre-test probability for CRC anda negative MPCT should not have further investigation, (3)frail, elderly patients with a higher pre-test probability of CRC (such as those presenting with rectal bleeding) and a negative MPCT should have either double contrast barium enema (DCBE) or cotonoscopy as further investigations or be followed clinically for 3-6 months. MPCT was acceptable to patients and clinicians and may reveal significant extra-colonic pathology. (C) 2004 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.