Comparison of computed tomography and pathologic examination for evaluation of response of primary lung cancer to neoadjuvant therapy

Twenty-four patients (nine with squamous cell carcinoma, 14 with adenocarci noma, and one with large cell carcinoma) underwent neoadjuvant therapy foll owed by surgical resection. The authors studied changes in tumor size, shap e, and contrast enhancement on computed tomography (CT), and compared them with results of pathologic examination of surgical specimens. The size of t umors on CT was evaluated according to the criteria of the World Health Org anization. Surgical specimens were evaluated histologically on the basis of the area of viable cancer cells. Of 14 patients considered to have a parti al response on the basis of World Health Organization criteria, five had pa thologic changes of complete response. After therapy, the residual tumors i n these five patients showed irregular shapes with concave tumor margins on CT images and no enhancement. The authors found that CT size criteria tend ed to underestimate the therapeutic effect demonstrated by pathologic exami nation. On the basis of these results, the authors propose three CT criteri a for complete response: 1) more than 50% size reduction, 2) a change in tu mor morphologic features from round or oval to irregular after neoadjuvant therapy, and 3) disappearance of contrast enhancement.