Routine use of pelvic CT scans in Wilms tumor questioned

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Omitting pelvic computed tomography (CT) scans from the routine surveillance of off-therapy patients with Wilms tumor could reduce radiation exposure without compromising relapse detection rates, researchers report.

In a retrospective study of 110 patients with Wilms tumor, only three patients developed pelvic relapse when they were followed up for a maximum of 12.5 years. All three patients were symptomatic when diagnosed and were considered at high risk for recurrence.

The authors also estimated the potential saving in absorbed dose if pelvic CT scans are not performed. Using anthropomorphic phantoms, they showed that omitting pelvic scans could reduce the effective dose by 30% to 45% in patients aged 15 years and under.

The authors believe the findings could impact on the controversial use of routine, off-therapy pelvic CT surveillance despite a low risk for pelvic recurrence and little evidence of an effect on tumor detection using this strategy.

"In keeping with 'As Low As Reasonably Achievable Radiation'… principles, we recommend reconsidering surveillance methodologies by omitting imaging of the pelvis altogether," say Sue Kaste (St Jude Children's Research Hospital, Memphis, Tennessee, USA) and colleagues.

Overall, 94% of patients in the study were alive at a median follow up after diagnosis of 6.5 years. Sixteen of the patients relapsed, most within the first year of diagnosis. Of the three patients with pelvic relapse, all were alive and without evidence of disease at their last follow up: 9.0, 4.6, and 4.2 years after relapse.

As well as being symptomatic, all three children had at least one previously defined risk factor for abdominal relapse, such as age greater than 48 months (n=2) and higher disease stage (stage III, n=2). Other identified high-risk features include a specimen weight in excess of 1000 g, tumor spillage, and unfavorable histology.

The authors suggest in Cancer that prospective national clinical trials could investigate the role of pelvic CT in such high-risk patients. However, they propose ultrasound or magnetic resonance imaging should be explored as an alternative to routine CT surveillance, to help limit childhood exposure to ionizing radiation.

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