How is breast tumor size determined following preoperative (neoadjuvant) chemotherapy?

Updated: Mar 20, 2019
  • Author: Oudai Hassan, MD; Chief Editor: Chandandeep Nagi, MD  more...
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Multiple tumor foci are measured separately. A comment about their relative location and the intervening breast tissue is needed. The size of the largest focus is used for staging. [2]

In patients who have undergone preoperative chemotherapy, the presence of residual invasive and in situ disease in the tumor bed and lymph nodes provides important information. However, at this time, the only validated pathologic measure is pathologic complete response (ie, lack of invasive disease at surgery), in addition to the size of the residual tumor. Cellularity of the residual tumor is also an important prognostic indicator. Classification of the response either by Miller-Payne scoring or residual cancer burden (RCB) scoring appears to predict clinical outcome. [3]  Although the latter scoring systems require additional validation for widespread use in clinical practice, they may provide useful information for the oncologist.

After neoadjuvant chemotherapy, tumors with a partial response often present as scattered foci of the tumor with variable cellularity and with a residual tumor bed that can be identified as reactive changes, including fibrosis, histiocytes, and fat necrosis, but is sometimes microscopically indistinguishable from normal breast tissue. Tumor stage after neoadjuvant therapy should be decided based on the size of the largest residual foci with the M descriptor added if there is more than one residual foci within the tumor bed. [4] The Miller-Payne score divides the reduction in overall cellularity in five grades, with grade 1 as no significant reduction in overall cellularity and grade 5 as a complete pathologic response at the site of the primary tumor. RCB scoring [4] combines the size of the primary tumor bed in two dimensions, the cellularity of the invasive cancer, and the amount of residual disease in the lymph nodes (size of the tumor bed, tumor cellularity, and lymph node status are needed to calculate the score) into a single score.

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