title: Relative effectiveness of adjuvant chemotherapy for invasive lobular compared with invasive ductal carcinoma of the breast.
abstract: BACKGROUND
  Invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) have distinct clinical, pathologic, and genomic characteristics. The objective of the current study was to compare the relative impact of adjuvant chemotherapy on the survival of patients with ILC versus those with IDC.
  
  
  METHODS
  Women with estrogen receptor (ER)-positive, human epidermal growth factor receptor 1 (HER2) -negative, stage I/II IDC and ILC who received endocrine therapy were identified from the 2000 to 2014 California Cancer Registry. Patient, tumor, and treatment characteristics were collected. Ten-year overall survival (OS) was estimated using the Kaplan-Meier method and Cox proportional-hazards modeling.
  
  
  RESULTS
  In total, 32,997 women with IDC and 4638 with ILC were identified. The receipt of chemotherapy significantly decreased during the study for both subtypes. For patients with IDC, the 10-year OS rate was 95% among those who received endocrine therapy alone versus 93% (P < .01) among those who received endocrine therapy plus chemotherapy. For patients with ILC, the 10-year OS rate was 94% among those who received endocrine therapy alone versus 92% (P < .01) among those who received endocrine therapy plus chemotherapy. After adjusting for patient and treatment factors, adjuvant chemotherapy was significantly associated with a decreased 10-year hazard of death for patients with IDC (hazard ratio, 0.83; 95% confidence interval, 0.74-0.92). In contrast, adjuvant chemotherapy was not independently associated with the adjusted 10-year hazard of death for patients with ILC (hazard ratio, 1.14; 95% confidence interval, 0.90-1.46).
  
  
  CONCLUSIONS
  Adjuvant chemotherapy was not associated with improved OS for patients with ER-positive, HER2-negative, stage I/II ILC. Avoidance of ineffective chemotherapy will markedly reduce the adverse effects and economic burden of breast cancer treatment for a large proportion of patients with breast cancer. Cancer 2017;123:3015-21. © 2017 American Cancer Society.
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Schelomo
authors.identifier: http://orcid.org/0000-0003-0880-2721
authors.initials: S
authors.lastname: Marmor
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Jane Yuet Ching
authors.initials: JYC
authors.lastname: Hui
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Jing Li
authors.initials: JL
authors.lastname: Huang
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Scott
authors.identifier: http://orcid.org/0000-0001-5622-3594
authors.initials: S
authors.lastname: Kizy
authors.affiliation: Division of Hematology, Oncology, and Transplantation, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Heather
authors.initials: H
authors.lastname: Beckwith
authors.affiliation: Division of Hematology, Oncology, and Transplantation, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Anne H
authors.initials: AH
authors.lastname: Blaes
authors.affiliation: Department of Surgical Oncology, Abbot Northwestern Hospital, Minneapolis, Minnesota.
authors.forename: Natasha M
authors.initials: NM
authors.lastname: Rueth
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Tuttle
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D018275:Carcinoma, Lobular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017024:Chemotherapy, Adjuvant; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008408:Mastectomy; D015412:Mastectomy, Segmental; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D016016:Proportional Hazards Models; D018714:Radiotherapy, Adjuvant; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012042:Registries; D012189:Retrospective Studies; D012923:Social Class; D015996:Survival Rate; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000970:Antineoplastic Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C508053:ERBB2 protein, human
keywords: breast cancer; chemotherapy; endocrine therapy; invasive ductal carcinoma (IDC); invasive lobular carcinoma (ILC); survival