title: Association between very small tumour size and increased cancer-specific mortality after radical prostatectomy in lymph node-positive prostate cancer.
abstract: OBJECTIVE
  To determine whether very small prostate cancers present in patients who also have lymph node (LN) metastases represent a particularly aggressive disease variant compared with larger LN-positive tumours.
  
  
  METHODS
  We identified 37 501 patients diagnosed with prostate cancer between 1988 and 2001 treated with radical prostatectomy within the Surveillance, Epidemiology, and End Results database. The primary study variables were tumour size by largest dimension (stratified into: (i) microscopic focus only or 1 mm; (ii) 2-15 mm; (iii) 16-30 mm; (iv) >30 mm), regional LN involvement, and the corresponding interaction term. We evaluated the risk of 10-year prostate cancer-specific mortality (PCSM) using the Fine and Gray model for competing risks after controlling for race, tumour grade, T stage, receipt of radiation, number of dissected LNs, number of positive LNs, year of diagnosis, and age at diagnosis.
  
  
  RESULTS
  The median follow-up was 11.8 years. There was a significant interaction between tumour size and LN involvement (P-interaction <0.001). In the absence of LN involvement (36 561 patients), the risk of 10-year PCSM increased monotonically with increasing tumour size. Among patients with LN involvement (940), those with the smallest tumours had increased 10-year PCSM compared with patients with tumours sized 2-15 mm (24.7% vs 11.8%; adjusted hazard ratio [AHR] 2.84, 95% confidence interval [CI] 1.21-6.71; P = 0.017) or 16-30 mm (24.7% vs 15.5%; AHR 3.12, 95% CI 1.51-6.49; P = 0.002), and similar 10-year PCSM as those with tumours >30 mm (24.7% vs 24.9%; P = 0.156).
  
  
  CONCLUSIONS
  In patients with prostate cancer with LN involvement, very small tumour size may predict for higher PCSM compared with some larger tumours, even after controlling for other prognostic variables. These tumours might be particularly aggressive, beyond what is captured by pathological assessment of tumour grade and stage.
authors.affiliation: Harvard-MIT Division of Health Sciences and Technology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Vinayak
authors.initials: V
authors.lastname: Muralidhar
authors.affiliation: Harvard Medical School, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Brandon A
authors.initials: BA
authors.lastname: Mahal
authors.affiliation: Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Nezolosky
authors.affiliation: Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Clair J
authors.initials: CJ
authors.lastname: Beard
authors.affiliation: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA.
authors.forename: Felix Y
authors.initials: FY
authors.lastname: Feng
authors.affiliation: Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Neil E
authors.initials: NE
authors.lastname: Martin
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Efstathiou
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Toni K
authors.initials: TK
authors.lastname: Choueiri
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Pomerantz
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Sweeney
authors.affiliation: Department of Urology, Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Quoc-Dien
authors.initials: QD
authors.lastname: Trinh
authors.affiliation: Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Vander Heiden
authors.affiliation: Department of Radiation Oncology, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Nguyen
mesh_terms: D000368:Aged; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D011468:Prostatectomy / Q000379:methods; D011471:Prostatic Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000601:surgery; D012189:Retrospective Studies; D047368:Tumor Burden
keywords: microscopic tumour; node-positive prostate cancer; prostate cancer; tumour size