Abstract P3-03-18: Invasive lobular carcinoma does not fit to axillary lymph node management according to NCCN guideline influenced by ACOSOG Z0011 criteria

[Introduction] Surgery for breast cancer (BC) became less invasion, from radical mastectomy to modified or breast conserving surgery (BCS). Axillary lymph node (ALN) management for cN0 also became less, from ALN dissection (ALND) to sentinel lymph node (SLN) biopsy. In some cases, management without ALND is allowed even if ALN macro-metastasis exist.

[Background] ALND for SLN metastasis positive case is useful for local control, staging and decision making for post-operative treatment. Since the ACOSOG Z0011 trial (Z11) result was reported, however, the necessity of ALND, even if SLN metastasis, became less. In the NCCN guideline (NCCN), strongly influenced by Z11, for cN0 BC with SLN metastasis, operations without ALND are allowed in cases of T1 or T2, the number of metastatic ALN 1 or 2, BCS with whole breast radiation and no-neoadjuvant therapy. This does not mean ALND was abolished but the position of ALND changed, from the perspective that over invasive procedure must be prohibited with appropriate pre-operative and intra-operative diagnosis. If there are some discordance between clinical and pathological diagnosis of tumor size or ALN metastasis, however, the criteria for axillary operation by NCCN will not be recommended. We have major two types of invasive carcinoma, ductal (IDC) and lobular (ILC). Z11 or NCCN did not describe about these two phenotypes. We compared these at the point of suitable axillary management.

[Subjects] Out of 1320 invasive BC (IDC; 1212, ILC; 108) cases in our hospital from January 2008 to January 2018, 1210 cases (IDC; 1113, ILC; 97) with T1/T2 and cN0 were reviewed in two points, the judgment of the competence for BCS was appropriate or not, and cN0 reflected the condition for the omission of ALND (ALN metastasis within 2) or not.

[Results] The difference of diameter between cT and pT; dT (=pT-cT) were measured significantly larger in ILC (0.68±1.97cm) than IDC (0.01±1.08cm)(p<0.01, t-test) with the wide scattering. We can make proper evaluation for the cT of IDC, but underestimate for ILC. The conversion rate from cN0 to pN1 was significantly higher in ILC (33/97; 34.0%) than IDC (238/1113; 21.4%)(p<0.01, χ2 test). In addition, the cases with 3 or more ALN metastasis, this means ALND is necessary, was observed with significantly higher frequent in ILC (13/97; 13.4%) than IDC (74/1113; 7.1%)(p=0.02, χ2 test). Clinical evaluation for ALN in ILC was difficult and inaccurate.

[Discussion] Commonly, ILC makes diffuse spread into the breast tissue. This feature will make it difficult to evaluate the clinical appropriate tumor size. Because of not only underestimation but wide scattering, the diagnosis for safety BCS may not be guaranteed in ILC. For ALN, cN0 did not reflect adequately the condition of omission for ALND in ILC compared with IDC. ILC patients with SLN metastasis have to be performed ALND at higher risk. These facts will mean that ILC does not fit to ALN management according to NCCN. Few guidelines separate ILC from IDC for the axillary management. The validation of clinical trials for ALND should be done in histological subtype as well as intrinsic again. Clinically, we must observe carefully in cases of ILC without ALND according to Z11.

Citation Format: Miyamoto T, Fujisawa T, Morishita A, Yanagita Y, Fujii T-A. Invasive lobular carcinoma does not fit to axillary lymph node management according to NCCN guideline influenced by ACOSOG Z0011 criteria [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-18.