Clinical benefit of post-trastuzumab deruxtecan treatment in patients with HER 2-positive unresectable or metastatic breast cancer: A single-institution retrospective observational study.

PURPOSE: Trastuzumab deruxtecan (T-DXd) can improve the prognosis of patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC). However, data on treatment recommendations after T-DXd are lacking. Thus, this study aimed to evaluate the treatment options after T-DXd and their effectiveness. METHODS: Patients with HER2-positive MBC were included in this study. Data from clinical records were retrospectively analyzed. The primary outcome was time to treatment failure (TTF). Secondary endpoints were TTF of each treatment and first-line treatment after interstitial lung disease (ILD) and overall survival (OS). RESULTS: A total of 29 patients were included. Among them, 18 (62%) were hormone receptor-positive. All patients had a median TTF (mTTF) of 3.5 months (95% confidence interval (CI) 2.1-10.03). The mTTF of each treatment, including HER2 tyrosine kinase inhibitor (HER2 TKI), other anti-HER2 treatments, and other treatments, was 2.6, 8.8, and 3.8 months, respectively. No significant differences were observed between treatments, but regimens that include trastuzumab showed a longer TTF than TKI. However, the mTTF among patients who developed T-DXd-related ILD was 2.33 months (95% CI 0.7-not reached), which was shorter than that among those who did not develop ILD (3.83 months, 95% CI 2.1-10.03, hazard ratio: 2.046, 95% CI 0.760-5.507, p = 0.258). The median OS was 14.9 months (95% CI 11.07-29.17). CONCLUSION: Treatments after T-DXd showed a shorter mTTF. Regimens that include trastuzumab may be more effective post-T-DXd treatment than HER2 TKI. Further data are needed to establish the best sequential treatment after T-DXd.

The Absence of Cancer in the Location of a Breast Tissue Marker After Neoadjuvant Chemotherapy may Predict Pathological Complete Response with High Accuracy: Results from a Phase II Trial.

BACKGROUND: It is difficult to determine pathological complete response (pCR) before surgery in clinical complete response (cCR) cases by imaging alone. We designed a prospective study to evaluate whether a breast tissue marker placed in a tumor before neoadjuvant chemotherapy (NAC) can predict a pCR, possibly removing the need for surgery. METHODS: We recruited patients with primary invasive breast cancer assigned to undergo curative surgery and possible NAC. A breast marker (UltraClip®) was placed in the primary tumor before standard NAC. We evaluated the probability of no cancer in the marker but cancer in removed specimens from a cCR group. RESULTS: A total of 102 patients were enrolled. Patients were categorized by cancer stage and subtypes. Seventy-two patients (70.6%) received standard NAC; 23 (34.3%) attained cCR, of whom pCR was obtained in 12 (52.2%). The probability of no cancer in the marker's location but cancer in the removed specimens was 4.3% (95% confidence interval, 0.1-21.9). The false-negative rate was 9.1% (1/11), and the negative predictive value was 92.3% (12/13). In only one case, no cancer was found in the marker's location, but cancer cells were present in the removed specimen. CONCLUSIONS: The absence of cancer in the location of a breast tissue marker after NAC predicted pCR with high accuracy. Therefore, the rebiopsy of a marker's location might mean surgery is unnecessary.

Satisfaction survey on a preoperative explanation method using three-dimensional breast imaging for breast cancer patients considering breast-conserving surgery.

PURPOSE: Although one of the essential factors in surgical shared decision-making is the body image, the breast morphology after breast-conserving surgery is particularly difficult to explain in a uniform manner due to large individual differences. METHODS: Patients with breast cancer eligible for breast-conserving surgery (BCS) were recruited between June 2020 and October 2021. We surveyed the patients' satisfaction with our method of explaining the likely breast morphology after BCS using three-dimensional (3D) breast imaging in the form of a questionnaire. RESULTS: A total of 162 patients were enrolled, and 137 (84.6%) answered the questionnaire. One hundred and sixteen patients (84.6%) answered that they were very satisfied or satisfied with our explanation method, and 100 (73.0%) patients were very satisfied or satisfied with the 3D breast imaging. Some patients answered that 3D breast imaging helped them prepare for BCS, or on the contrary, made them choose mastectomy with breast reconstruction because the deformation likely with BCS was considered unacceptable. Only a few patients who underwent BCS felt that their postoperative morphology was more deformed than the preoperatively imagined one. CONCLUSION: Our results suggest that our preoperative explanation method using 3D breast imaging was useful for shared decision-making.

Functions of Breast Cancer Predisposition Genes: Implications for Clinical Management.

Approximately 5-10% of all breast cancer (BC) cases are caused by germline pathogenic variants (GPVs) in various cancer predisposition genes (CPGs). The most common contributors to hereditary BC are BRCA1 and BRCA2, which are associated with hereditary breast and ovarian cancer (HBOC). ATM, BARD1, CHEK2, PALB2, RAD51C, and RAD51D have also been recognized as CPGs with a high to moderate risk of BC. Primary and secondary cancer prevention strategies have been established for HBOC patients; however, optimal preventive strategies for most hereditary BCs have not yet been established. Most BC-associated CPGs participate in DNA damage repair pathways and cell cycle checkpoint mechanisms, and function jointly in such cascades; therefore, a fundamental understanding of the disease drivers in such cascades can facilitate the accurate estimation of the genetic risk of developing BC and the selection of appropriate preventive and therapeutic strategies to manage hereditary BCs. Herein, we review the functions of key BC-associated CPGs and strategies for the clinical management in individuals harboring the GPVs of such genes.

Incidence of contralateral and ipsilateral breast cancers and prognosis in BRCA1/2 pathogenic variant carriers based on the Japanese HBOC Consortium registration.

This study aimed to clarify the breast cancer prognosis in Japanese patients with BRCA1/2 pathogenic variant. We analyzed 2235 women with breast cancer who underwent BRCA1/2 genetic testing between 1996 and 2018 using data from the Japanese hereditary breast and ovarian cancer syndrome registry. The cumulative risk for contralateral and ipsilateral breast cancers and time to death since the first breast cancer were stratified based on the BRCA1/2 variant status. The median follow-up was 3.0 years (0.1-34.1 years) after the first breast cancer. The annual average risks of contralateral breast cancer in BRCA1 and BRCA2 and non-BRCA1/2 pathogenic variant carriers were 4.0%, 2.9%, and 1.9%, respectively (P = 0.001). The annual average risks of ipsilateral breast cancer in the three groups were 2.7%, 1.4%, and 1.1%, respectively (P = 0.06). BRCA1 pathogenic variant carriers had significantly higher risks of contralateral (hazard ratio 1.91, P < 0.001) and ipsilateral (hazard ratio 2.00, P = 0.02) breast cancers than non-BRCA1/2 pathogenic variant carriers. The time to death by the BRCA1/2 variant status was not significantly difference (P = 0.28). The prognosis of breast cancer patients who received standard treatment was comparable regardless of the BRCA1/2 variant status.

Compression therapy using surgical gloves does not prevent paclitaxel-induced peripheral neuropathy: results from a double-blind phase 2 trial.

BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a common adverse effect of paclitaxel (PTX). There is no known prophylactic measure, although there are some reports of prevention with compression therapy using surgical gloves. On account of its predominantly subjective symptoms, it is difficult to exclude bias when assessing for CIPN. In this study, we assessed the effectiveness of the same procedure for the prevention of paclitaxel-induced PN based on a double-blind study design. METHODS: The patients with early and recurrent breast cancer (with no prior PTX exposure) initiating weekly chemotherapy with PTX 80 mg/m2 were enrolled. Each patient donned two gloves on each hand at every PTX infusion. Two one-size-smaller gloves were donned on one hand (study side) and two normal-size gloves were donned on the other hand (control side) during 90 min from 30 min before the infusion to 30 min after the end of the infusion. Study side are blind for both patients and assessing physicians according to determination of the study side by research nurses in the chemotherapy unit. The primary outcome was the difference in the frequency of CIPN (motor/sensory) determined by the physician using the common terminology criteria for adverse events (CTCAE v4.0), with an evaluation at each cycle of PTX infusion. McNemar test was used to assess the primary outcome. RESULTS: Between July 2017 and November 2018, 56 patients were enrolled and 49 patients were evaluated. Overall, Grade ≥ 2 PN (sensory) was observed in 30.6 and 36.7% in the study and control sides, respectively (McNemar p = 0.25). PN (motor) was observed in 4.1 and 6.1% in the study and control sides, respectively (McNemar p = 1.0). CONCLUSION: Surgical glove compression therapy showed no statistically significant effect on the incidence of PTX-induced PN. TRIAL REGISTRATIONS: This study was registered with the University Hospital Medical Information Network (UMIN) Clinical Trials Registry managed by the National University Hospital Council of Japan ( UMIN000027944 ). Registered 26 June 2017.

Differences in baseline risk estimated by physicians and patients with early breast cancer.

BACKGROUND: Physicians recommend adjuvant therapy to patients based on baseline risk. A common recognition for baseline risk between patients and physicians is critical for successful adjuvant therapy. We prospectively investigated the differences in estimated baseline risk between physicians and patients with early breast cancer. METHODS: This analysis was performed at a single institution in Japan. Early breast cancer patients over 18 years old were enrolled after surgery. After explaining the pathological results, physicians asked each patient about an estimated baseline risk. Differences in estimated baseline risk were defined as the baseline risk estimated by patients minus the baseline risk estimated by physicians. The primary endpoint was that the number of patients who estimate baseline risk higher than physicians was higher than those who estimate a lower baseline risk. The secondary endpoints were differences in estimated baseline risk by stage, subtype and the influence of patient factors to differences in estimated baseline risk. RESULTS: From July 2017 to December 2018, 262 patients were enrolled. Among the 262 patients, 190 estimated a higher baseline risk than physicians, 53 estimated a lower baseline risk and 19 estimated the same. Overall, patients estimated a significantly higher baseline risk than physicians (P < 0.001). Differences in estimated baseline risk was significantly smaller in patients who knew the term 'baseline risk' than patients who did not (P = 0.0037). Differences in estimated baseline risk were also significantly smaller in patients with stage II breast cancer than patients with stage I (P = 0.0239). However, there were no statistically significant differences of differences in estimated baseline risk according to other factors. CONCLUSIONS: Patients with early breast cancer estimated a significantly higher baseline risk than physicians. Physicians should accurately explain baseline risk to patients for shared decision making.

The significance of biopsy scar excision at the time of skin- or nipple-sparing mastectomy with immediate breast reconstruction.

BACKGROUND: Neoplastic seeding (NS) can occur after tissue biopsy, which is a clinical issue especially in mastectomy with immediate reconstruction. This is because postoperative radiation is not usually given and local recurrence of preserved skin flap may increase. The purpose of this study is to investigate the importance of preoperative evaluation of NS and the validity of biopsy scar excision. PATIENTS AND METHODS: We retrospectively analysed 174 cases of mastectomy with immediate breast reconstruction. The primary endpoint is the frequency of clinical and pathological NS and the secondary endpoint is the problem of excision of needle biopsy site. RESULTS: Three cases (1.7%) had preoperative clinical findings of NS. Pathological examination revealed NS in all three cases. Biopsy scars could be excised in 115 cases among 171 cases without clinical NS. Pathological NS was found in 1 of 66 (1.5%) cases of which pathological examination was performed. Biopsy scars could not be excised in the remaining 56 cases: the biopsy scar could not be identified in 41 cases, and there was concern about a decrease in flap blood flow after excision in 15 cases. In 12 of these 15 cases, the scars were close to the skin incision; excision of these scars might have triggered skin necrosis between the incision and the biopsy scar excision site. No postoperative complications were observed. CONCLUSIONS: It is important to preoperatively evaluate clinical NS, and biopsy scars should be excised in clinical NS cases. Even in cases without clinical NS, biopsy scar excision should be considered. It is also important to perform a biopsy in consideration of the incision design for reconstructive surgery.

Patient-reported outcomes and objective assessments with arm measurement and bioimpedance analysis for lymphedema among breast cancer survivors.

PURPOSE: Lymphedema (LE) decreases the quality of life of breast cancer patients. Objective quantification of PRO may improve the discordance between patient-reported outcomes (PROs) and objective assessments of LE by establishing a standard follow-up for LE. This study determined the prevalence of subjective and objective LE and evaluated the correlation between objective assessment and PRO of LE in primary breast cancer patients undergoing breast and axilla surgery. METHODS: Breast cancer patients who underwent sentinel lymph node biopsy (SN) or axillary lymph node dissection (ALND) more than 1 year after surgery were enrolled. We prospectively evaluated LE using the Patient-Reported Outcomes version of the Common Terminology Criteria for Adverse Events (PRO-CTCAE) and two objective assessments (arm circumference and bioimpedance) and analyzed their correlations. RESULTS: Between November 2018 and January 2019, 631 patients (SN; n = 415, ALND; n = 216) were enrolled. The median age, body mass index, and duration from surgery was 56 years, 21.9 kg/m2, and 3.8 years, respectively. The prevalences of subjective and objective LE were 4.1% and 1.4% in the SN group and 51.8% and 24.1% in the ALND group, respectively. The objective assessments were weakly positively correlated with PRO-CTCAE. Arm circumference measurement correlated better than bioimpedance overall and was most strongly correlated with "frequency" (r = 0.485, p < 0.01). CONCLUSIONS: LE occurred in few SN patients. The prevalence of subjective LE was higher than that of objective LE. Arm circumference measurements better reflected PRO than did bioimpedance. These results underscore the limitation of LE detection by subjective or objective methods alone.

Impact of BMI for clinical outcomes in Japanese breast cancer patients.

OBJECTIVE: The relationship between the body mass index (BMI) at the time of breast cancer diagnosis and the prognosis of breast cancer patients has not yet been clarified. We investigated the impact of obesity for clinical outcomes in Japanese breast cancer patients. METHODS: Women with primary breast cancer operated between 2002 and 2014 were identified. All patients are categorized into four groups according to BMI. The range of BMI is <18.5 kg/m2, from 18.5 to 24.9 kg/m2, 25 to 29.9 kg/m2, >30 kg/m2 in underweight, normal, overweight and obesity groups, respectively. The correlation between BMI and overall survival (OS), breast cancer-specific survival (BCSS) and disease-free survival (DFS) were statistically analyzed. RESULTS: From the database of our institution, we identified 3223 patients. The median follow-up period was 57 months (1-149). We categorized 2257 (70.0%), 318 (9.9%), 545 (16.9%) and 103 (3.2%) patients into normal, underweight, overweight obesity groups respectively. There were189 patients (5.9%) deaths due to breast cancer recurrence (137 patients) and other disease (52 patients). Obesity groups was significantly high compared with normal groups for OS (adjusted HR, 2.43; 95% CI, 1.38-4.28; P < 0.001), BCSS (adjusted HR, 2.73; 95% CI, 1.15-6.44; P = 0.02) and DFS (adjusted HR, 1.83; 95% CI, 1.11-3.02; P = 0.017) by multivariate analysis. Especially, OS (adjusted HR, 4.87; 95% CI, 2.15-11.04; P < 0.001), BCSS (adjusted HR, 4.51; 95% CI, 1.52-13.34; P < 0.001) and DFS (adjusted HR, 4.87; 95% CI, 1.02-4.89; P = 0.04) were statistically insignificant in postmenopausal ER-positive breast cancer patients. CONCLUSION: Obesity might be risk factor for OS, BCSS and DFS, especially postmenopausal ER-positive women.

A single-arm, phase 2 study of steroid-containing mouthwash for the prevention of everolimus-associated stomatitis in multiple tumor types.

BACKGROUND: Everolimus is a mammalian target of rapamycin inhibitor used in the treatment of multiple tumor types, and its most common toxicity, stomatitis, can affect patient quality of life. Recent studies in breast cancer have supported the efficacy of steroid mouthwash for the prevention of everolimus-associated stomatitis. However, a few studies have been reported to date, and none have examined this effect in other tumor types. METHODS: This single-arm phase 2 study was designed to evaluate the efficacy of steroid-containing mouthwash for the prevention of stomatitis in patients with multiple tumor types receiving everolimus. The primary outcome was incidence of grade ≥ 2 stomatitis at 8 weeks of everolimus with steroid-containing mouthwash prophylaxis. We also assessed the stability of steroid-containing mouthwash components. RESULTS: Twenty-nine patients were evaluated, of which 76% had breast cancer and 24% had neuroendocrine tumors originating in the lung, gastrointestinal tract, pancreas, or of unknown primary origin. Grade ≥ 2 stomatitis incidence at 8 weeks was 28.1% (90% CI 16.2-46.1); the higher confidence limit exceeded the prespecified threshold of 30%. No patients developed grade ≥ 3 stomatitis. Most stomatitis occurred behind the oral cavity, with no lesions observed on the lips or floor of the mouth. CONCLUSIONS: Our findings did not support a prophylactic effect of steroid-containing mouthwash on everolimus-associated stomatitis. Given the needs of prevention of everolimus-associated stomatitis in various tumor types, further studies in a larger population using a randomized controlled trial design are, therefore, required to confirm the efficacy of steroid-containing mouthwash.

Prediction of pathological margin status using preoperative contrast-enhanced MRI in patients with early breast cancer who underwent skin-sparing mastectomy.

Skin-sparing mastectomy (SSM) with immediate reconstruction is standard surgical treatment for early breast cancer with widespread ductal carcinoma in situ (DCIS). The local recurrence rate after SSM is up to 7.0%. We investigated prediction of the pathological margin using contrast-enhanced MRI, and evaluated the cut-off point to obtain the safety margin. We performed SSM with immediate reconstruction in 216 early breast cancer patients with widespread DCIS and/or invasive cancer from January 2014 to December 2015. Forty cases were retrospectively reviewed after excluding those with >15 mm between skin and tumor, determined by preoperative contrast-enhanced MRI, or involving reconstructive surgery for local recurrence, immeasurable lesion by preoperative contrast-enhanced MRI, or neoadjuvant chemotherapy. We defined a positive pathological margin as <1 mm from the cancer nest. We reviewed the distance between skin and tumor by MRI and pathological examination. To identify the cut-off for predicting a positive pathological margin, we performed sensitivity analysis using an ROC curve. The margin-positive rate by pathological examination was 27.5% (n = 11/40), with a moderate correlation of MRI margin and pathological margin (r = 0.44). The best cut-off point for margin positivity was 5 mm of MRI margin, with sensitivity and specificity of 54% and 86%, respectively (P = 0.009). This is the first prediction of pathological margin by preoperative contrast-enhanced MRI in early breast cancer patients with SSM. Care is required for SSM if the MRI margin is less than 5 mm due to pathological margin positivity.

The overall survival of breast cancer patients without adjuvant therapy.

PURPOSE: There are little data regarding the overall survival (OS) of patients without adjuvant systemic therapy, because most patients have been subject to standardized systemic therapies. We evaluated the baseline risk to facilitate making decisions about adjuvant therapy. PATIENTS AND METHODS: A total of 1835 breast cancer patients who did not receive adjuvant systemic therapy between 1964 and 1992 were retrospectively evaluated. We investigated the 10-year disease-free survival (DFS) and OS according to the number of metastatic lymph nodes, pathological T classification, stage, and estrogen receptor (ER) status. RESULTS: Survival curves showed that as the number of metastatic lymph nodes, pathological T classification, and staging increased, the 10-year OS and DFS decreased. In univariate and multivariable analyses, the number of metastatic lymph nodes was significantly associated with the DFS and OS, while in a univariate analysis, the pathological T classification and stage were significantly associated with the DFS and OS. ER positivity was a good prognostic factor for the 5-year DFS. However, between 6 and 7 years after surgery, ER negativity was a better prognostic factor than ER positivity. CONCLUSION: We showed survival rates of patients without adjuvant therapy according to TNM classification and ER status. This information can aid in treatment selection for doctors and patients through a shared decision-making approach.

Occult breast cancer may originate from ectopic breast tissue present in axillary lymph nodes.

PURPOSE: Occult breast cancer (OBC) is classified as a carcinoma of unknown primary, and involves axillary lymphadenopathy and is histologically consistent with metastatic breast cancer. OBC has been conventionally considered as a metastatic lymph node lesion, the origin of which is an undetectable breast tumor. Therefore, OBC patients would usually have undergone axillary lymph node dissection, and mastectomy or whole breast radiotherapy (WBRT). However, majority of OBC reports have been based on cases that were diagnosed during a period when diagnostics was still relatively primitive, and when magnetic resonance imaging was not yet a standard preoperative assessment. Therefore, there have been many false negatives in the breast based on preoperative assessment. METHODS: We herein hypothesize that the origin of OBC is ectopic breast tissue present in axillary lymph nodes (ALNs). If our hypothesis is true, mastectomy and WBRT may be unnecessary for OBC patients. RESULTS: Our hypothesis is supported by several findings. First, advances in radiological imaging have suggested that a primary breast tumor is absent in OBC patients. Second, proliferative breast lesions arising from ectopic breast present in ALNs have been reported. Lastly, cellular subtypes in OBC based on immunohistochemistry are of various types including ordinary breast cancer and the prognosis is not worse than stage II breast cancer. CONCLUSION: It is important to distinguish between "primary" OBC in ALNs and "metastatic" OBC from micro-primary breast tumor. Further studies are required to determine if omission of mastectomy and WBRT is acceptable.

The investigation study using a questionnaire about the employment of Japanese breast cancer patients.

BACKGROUND: Breast cancer is the most common cancer among women, and its survival rate has improved. As the number of cancer survivors increases, it is important to support their social comeback during and after treatment. METHODS: Questionnaires were distributed to breast cancer patients treated in Aichi Cancer Center Hospital between June and November 2014. Responders were categorized according to adjuvant therapy (Group A: none, Group B: endocrine therapy, Group C: chemotherapy), or if they had advanced or recurrent breast cancer (Group D). RESULTS: A total of 279 patients returned questionnaires (62, 79, 92 and 46 patients in Groups A, B, C and D, respectively). In adjuvant treatment groups, 43 patients (18.5%) quit their job during or after treatment. Most patients had quit their jobs at the time of diagnosis (7.5%), followed by those undergoing chemotherapy (5.6%) and those at the time of operation (4.9%). Quit rate from the workplace in which patients worked at the time of diagnosis was highest in Group C (30%), followed by Group B (20%) and Group A (13%). At the time of operation, 127 patients (57%) were absent from work. In Group D, 16 patients (35%) quit their job during treatment. Rates for patients currently working who had anxiety were 62, 30, 26 and 9% in Groups D, C, B and A, respectively. CONCLUSIONS: In adjuvant treatment groups, in which quit rate was highest at the time of diagnosis, consultation about working is necessary immediately after diagnosis. Patients treated most heavily had higher quit rates and experienced more anxiety about working.

Recent Improvement in the Long-term Survival of Breast Cancer Patients by Age and Stage in Japan.

BACKGROUND: Recent improvements in 5-year survival of breast cancer have been reported in Japan and other countries. Though the number of long-term breast cancer survivors has been increasing, recent improvements in 10-year survival have not been reported. Moreover, the degree of improvement according to age and disease stage remains unclear. METHODS: We calculated long-term survival using data on breast cancer diagnosed from 1993 through 2006 from six prefectural population-based cancer registries in Japan. The recent increase in 10-year relative survival was assessed by comparing the results of period analysis in 2002-2006 with the results of cohort analysis in 1993-1997. We also conducted stratified analyses by age group (15-34, 35-49, 50-69, and 70-99 years) and disease stage (localized, regional, and distant). RESULTS: A total of 63,348 patients were analysed. Ten-year relative survival improved by 2.4% (76.9% vs 79.3%) from 1993 through 2006. By age and stage, 10-year relative survival clearly improved in the age 35-49 years (+2.9%; 78.1% vs 81.0%), 50-69 years (+2.8%; 75.2% vs 78.0%) and regional disease (+3.4%; 64.9% vs 68.3%). In contrast, the degree of improvement was small in the age 15-34 years (+0.1%; 68.2% vs 68.3%), 70-99 years (+1.0%; 87.6% vs 88.6%), localized disease (+1.1%; 92.6% vs 93.7%) and distant metastasis (+0.9%; 13.8% vs 14.7%). CONCLUSIONS: These population-based cancer registry data show that 10-year relative survival improved 2.4% over this period in Japan. By age and stage, improvement in the age 15-34 years and distant metastasis was very small, which suggests the need for new therapeutic strategies in these patients.

Comparison of clinical outcomes between luminal invasive ductal carcinoma and luminal invasive lobular carcinoma.

BACKGROUND: The pathological and clinical features of invasive lobular carcinoma (ILC) differ from those of invasive ductal carcinoma (IDC). Several studies have indicated that patients with ILC have a better prognosis than those with ductal carcinoma. However, no previous study has considered the molecular subtypes and histological subtypes of ILC. We compared prognosis between IDC and classical, luminal type ILC and developed prognostic factors for early breast cancer patients with classical luminal ILC. METHODS: Four thousand one hundred ten breast cancer patients were treated at the Aichi Cancer Center Hospital from 2003 to 2012. We identified 1,661 cases with luminal IDC and 105 cases with luminal classical ILC. We examined baseline characteristics, clinical outcomes, and prognostic factors of luminal ILC. RESULTS: The prognosis of luminal ILC was significantly worse than that of luminal IDC. The rates of 5-year disease free survival (DFS) were 91.9% and 88.4% for patients with luminal IDC and luminal ILC, respectively (P = 0.008). The rates of 5-year overall survival (OS) were 97.6% and 93.1% for patients with luminal IDC and luminal ILC respectively (P = 0.030). Although we analyzed prognosis according to stratification by tumor size, luminal ILC tended to have worse DFS than luminal IDC in the large tumor group. In addition, although our analysis was performed according to matching lymph node status, luminal ILC had a significantly worse DFS and OS than luminal IDC in node-positive patients. Survival curves showed that the prognosis for ILC became worse than IDC over time. Multivariate analysis showed that ILC was an important factor related to higher risk of recurrence of luminal type breast cancer, even when tumor size, lymph node status and histological grade were considered. CONCLUSIONS: Luminal ILC had worse outcomes than luminal IDC. Consequently, different treatment approaches should be used for luminal ILC than for luminal IDC.