Role and evaluation of pathologic response in early breast cancer specimens after neoadjuvant therapy: consensus statement

Abstract

Pathologic evaluation of early breast cancer after neoadjuvant therapy is essential to provide prognostic information based on tumor response to treatment (pathologic complete response [pCR] or non-pCR) and to inform therapy decisions after surgery. To harmonize the pathologist’s handling of surgical specimens after neoadjuvant therapy, a panel of experts in breast cancer convened to developed a consensus on six main topics: (1) definition of pCR, (2) required clinical information, (3) gross examination and sampling, (4) microscopic examination, (5) evaluation of lymph node status, and (6) staging of residual breast tumor. The resulting consensus statements reported in this document highlight the role of an accurate evaluation of tumor response and define the minimum requirements to standardize the assessment of breast cancer specimens after neoadjuvant therapy.

Pathological examination of breast cancer samples before and after neoadjuvant therapy: recommendations from the Italian Group for the Study of Breast Pathology - Italian Society of Pathology (GIPaM-SIAPeC)

“…It is important to precisely quantify this parameter because different tumor(s) may respond differently to the same treatment 13 , 14 . The pathological evaluation of pre-NAT biopsies and post-NAT surgical samples is the gold standard procedure to assess treatment response 15 , 16 . In this respect, pathological complete response is associated with an improved prognosis; on the other hand, the characteristics of residual tumor deposits have a significant impact on subsequent treatment and ultimately on disease-free survival.…”

“…With the steady increase in the number of patients eligible for NAT, it is more and more important to harmonize how tumor response is assessed by pathologists 15 , 16 . Macroscopic evaluation of surgical samples in the post-NAT setting, the extent of sampling for histology, and microscopic examination require a different approach compared to that after primary surgery.…”

Clinical N3 is an independent risk factor of recurrence for breast cancer patients achieving pathological complete response and near-pathological complete response after neoadjuvant chemotherapy

“…Clinical and pathological data of these patients were collected: age, menstruation, tumor size, regional lymph node, estrogen receptor (ER), progesterone receptor (PR), HER2, Ki67 index, chemotherapy, radiation, endocrine, and surgery regimens. ypTisN0 (13)(14)(15). Near-pCR was defined as the residual tumor size ≤1 cm in the breast and negative axillary lymph nodes, or no residual invasive carcinoma in the breast yet existing micrometastasis in lymph node, including ypT1mi/a/bN0 and ypT0/isN1mi (9,16).…”

“…The assessment of obtaining a real pCR is of great importance and has been gradually standardized nowadays. The generally accepted definition of pCR is that there is no residual invasive carcinoma in the breast and in all sampled lymph nodes (ypT0/isN0) ( 13 – 15 ). More recently, the concept of near-pCR was gradually being proposed and has attracted more and more attention.…”

“…More recently, the concept of near-pCR was gradually being proposed and has attracted more and more attention. Substantial research elucidated that patients who achieved near-pCR also had outstanding DFS and OS ( 13 , 14 ). A variety of definitions of near-pCR have been used in neoadjuvant clinical trials in breast cancer.…”