Usefulness of preoperative multidetector-row computed tomography in evaluating the extent of invasive lobular carcinoma in patients with or without neoadjuvant chemotherapy

Background: The present study was conducted to assess the clinical usefulness of multidetector-row CT (MDCT) in determining the extent of invasive lobular carcinoma (ILC) and especially the extent of residual tumor after neoadjuvant chemotherapy (NAC). Patients and methods: The subjects were 24 patients with primary ILC who underwent surgery without NAC and 17 patients with ILC who underwent surgery after NAC at National Cancer Center Hospital (NCCH) between April 1999 and December 2005. The extent of primary ILC was assessed by ultrasound, mammography, and MDCT before surgery, and the results obtained using each modality were compared with the results of pathological examination after surgery. In addition, the characteristic findings of ILC obtained by MDCT were assessed. Similarly, the extent of residual tumor after NAC was evaluated using ultrasound, mammography, and MDCT before surgery in the subjects who underwent NAC, and the results obtained by each modality were compared with the results of pathological examination after surgery. Results: The findings of primary ILC obtained by MDCT showed that the carcinoma was the non-localized type rather than the localized type in 63% of the subjects. In addition, with regard to the pattern of time-sequential contrast enhancement, the persistent pattern (in which tumor enhancement is strong in the late phase rather than in the early phase) was observed in 46% of the subjects, and the plateau pattern (in which contrast enhancement is weak in both the early phase and the late phase) was observed in 38% of the subjects. These trends were significant in the subjects who underwent NAC and in whom tumor enhancement could not be clearly observed by MDCT. Assessment of the extent of carcinoma showed that the diagnostic accuracy of MDCT was 79%, as compared with 71% for either ultrasound or mammography. Assessment of the extent of carcinoma after NAC also showed that the diagnostic accuracy of MDCT was 71%, as compared with 48% for ultrasound and 53% for mammography, indicating that MDCT provided the highest accuracy. It should be noted that for all modalities, the extent of ILC was not overestimated as compared with the tumor diameter measured during pathological examination. Conclusion: Assessment by MDCT showed that ILC tends to be diffuse, tumor enhancement tends to be very weak, and the rate of enhancement tends to be low. In addition, MDCT was found to be useful for determining the extent of carcinoma, and the diagnostic accuracy of MDCT, especially in determining the extent of carcinoma after NAC, was much higher than that of ultrasound or mammography.