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Radiation changes do not interfere with postchemoradiation restaging of patients with rectal cancer by FDG PET/CT before curative surgical therapy

PURPOSE

Changes in F-18 fluorodeoxyglucose (FDG) uptake in normal tissues after chemoradiation therapy (CRT) potentially limit the ability of positron emission tomography (PET) to provide early assessment of therapeutic response. This study evaluated whether such changes negatively impact interpretation of posttherapy PET performed within 6 weeks of CRT completion and before definitive surgery in patients with locally advanced rectal cancer. The positive predictive value (PPV) and specificity of post-CRT PET, read clinically, was determined in 63 consecutive rectal cancer patients who had undergone preoperative CRT.

METHODS AND MATERIALS

A schema for identifying and scoring postradiation effects on PET was prospectively defined and applied in a blinded manner. This was compared with initial clinical reporting of response. Histologic assessment of the operative specimens was used as the reference standard. Correlation between clinical proctitis during CRT and radiation changes on subsequent PET was also assessed.

RESULTS

Clinical reporting of post-CRT PET yielded a high PPV (94%; 95% confidence interval, 89--100%) but may have been exaggerated by the low prevalence of complete tumor clearance (16%). The specificity was 80% with only two false-positive results. On blinded reading, significant post-CRT effects on PET were recorded in 4 of 63 patients (6% 95% confidence interval, 0-13%), but pattern recognition converted both false-positive PET results to a complete metabolic response. Clinical CRT proctitis was not correlated with PET findings.

CONCLUSION

Postradiation effects do not appear to significantly compromise the interpretation of PET for therapeutic response assessment. The proposed PET pattern of response may further improve the specificity of PET.

Total mesorectal excision and pelvic node dissection for rectal cancer: an appraisal

Total mesorectal excision has revolutionized the surgical treatment of rectal cancer since its introduction in the 1980s. The rationale, technique, and outcomes of total mesorectal excision in rectal cancer are explored. Lateral pelvic lymph node dissection is used by the Japanese in selected patients and has remained a controversial approach in the management of rectal cancer. The technique, controversies, and outcomes are summarized.