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Pretherapeutic MRI for decision-making regarding selective neoadjuvant radiochemotherapy for rectal carcinoma:
Henry Ptok1, Reinhard Ruppert, Joachim Stassburg
1Department of Surgery at Carl-Thiem-Klinik, Cottbus, Germany.
Purpose:
To study the accuracy of different cutoffs for an involved circumferential resection margin (CRM) compared with T and N categories measured by MRI as basis for selective application of neoadjuvant radiochemotherapy (nRCT) in rectal carcinoma.
Materials And Methods:
In a prospective multicenter observational study involving 153 primarily operated patients, the preoperative results of MRI with pathohistological findings of resected specimens were compared.
Results:
For a cutoff of ≤1 mm for involvement of the CRM, the accuracy of preoperative MRI was 90.9% (139/153). The negative predictive value was 98.5% (134/136). The four participating departments did not differ significantly. For a cutoff of >2 mm and >5 mm, the rates of false-positive findings increased significantly from 5% to 12% and 35% with a decrease in accuracy to 82% and 62%, respectively. In contrast, the accuracy in predicting T (69.3%) and N categories (61.4%) was much lower.
Conclusion:
The indication for nRCT should be based on the determination of the minimal distance of the tumor from mesorectal fascia with a cutoff point of >1 mm as measured by MRI.
