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

Twenty-four patients (nine with squamous cell carcinoma, 14 with adenocarcinoma, and one with large cell carcinoma) underwent neoadjuvant therapy followed by surgical resection. The authors studied changes in tumor size, shape, and contrast enhancement on computed tomography (CT), and compared them with results of pathologic examination of surgical specimens. The size of tumors on CT was evaluated according to the criteria of the World Health Organization. Surgical specimens were evaluated histologically on the basis of the area of viable cancer cells. Of 14 patients considered to have a partial response on the basis of World Health Organization criteria, five had pathologic changes of complete response. After therapy, the residual tumors in these five patients showed irregular shapes with concave tumor margins on CT images and no enhancement. The authors found that CT size criteria tended to underestimate the therapeutic effect demonstrated by pathologic examination. On the basis of these results, the authors propose three CT criteria for complete response: 1) more than 50% size reduction, 2) a change in tumor morphologic features from round or oval to irregular after neoadjuvant therapy, and 3) disappearance of contrast enhancement.