Selecting patients for breast conserving therapy: The importance of lobular histology

May 8 2006

Invasive lobular carcinoma (ILC) of the breast can be treated with breast conserving surgery (BCT), as is invasive ductal carcinoma (IDC), without greater future risk of radical surgical treatment or additional surgeries, according to a new study.

Published in the June 15, 2006 issue of CANCER, a peer-reviewed journal of the American Cancer Society, the study reveals that when compared to ductal carcinoma, which is far more common, there is no difference in the success rate of BCT or the number of surgical procedures for patients with invasive lobular breast cancer. These findings challenge recent reports suggesting BCT may not be appropriate treatment for ILC.

IDC makes up over 85 percent of all breast cancers while ILC accounts for only 10 percent. Consequently, much of the data supporting mammography for breast screening and BCT for treatment was obtained from patients with IDC. While comparatively less data exists for ILC of the breast, what is known suggests that ILC may behave differently than IDC. For example, many ILCs are not detected by routine mammograms and breast exams and are therefore identified at later - and presumably poorer prognostic - stages. Also, recent data from ILC patients undergoing preoperative MRI suggest that up to 50 percent of ILC patients have more extensive, multifocal disease than initial examination suggested and therefore require more extensive surgical therapy, such as mastectomy. Therefore, ILC is perceived to be difficult to treat compared to IDC, though previous studies have suggested no significant difference in BCT success rates.

To reconcile the concern regarding the use of BCT, due to the observation of more extensive disease on MRI in ILC patients, Monica Morrow, M.D. of the Fox Chase Cancer Center in Philadelphia and colleagues compared the outcomes of 318 ILC patients and 634 matched IDC patients.

The researchers found that ILC patients were older, had larger tumors compared to IDC patients (2.6 cm versus 2.1 cm), and more occult tumors - that is, not detected on routine screening. However, among those patients who received BCT there was no difference in the success rate between the two histologic groups. Moreover, ILC patients treated with BCT had similar numbers of surgeries as IDC patients treated with BCT.

The authors conclude that "the findings of our study do not support the idea that infiltrating lobular carcinoma is more difficult to treat surgically than infiltrating ductal carcinoma." Additionally, the authors assert that the data does "not provide a justification for the routine use of MRI in the breast cancer patient newly diagnosed with infiltrating lobular carcinoma."