title: Implementation of the 7th edition AJCC staging system: Effects on staging and survival for pT1 melanoma. A Dutch population based study.
abstract: In the 7thedition of the AJCC staging system, the mitotic rate criterion replaced Clark level to increase correct classification of high-risk thin melanoma patients (pT1B). Additionally, sentinel node biopsy (SNB) was recommended for nodal staging of pT1B melanomas. The aim of this article was to evaluate the effects on pT1 substaging and clinical implications in the national pT1 melanoma population. All pT1 melanomas diagnosed in the Netherlands between 2003 and 2014 were selected from the Netherlands Cancer Registry (IKNL). Patients were stratified by cohort according to AJCC edition: (1) 2003-2009 (6th) and (2) 2010-2014 (7th). Relative survival was calculated to estimate melanoma-specific survival. A total of 29.546 pT1 melanoma patients were included. The pT1b proportion increased from 10.1% in Cohort 1 to 21.5% in Cohort 2. The proportion of performed SNBs per cohort increased: for pT1b melanomas alone from 4.5% to 13.0%. SNB positivity rate decreased from 10.5% to 8.8% for the entire pT1 population, and for pT1b melanomas from 11.3% to 8.6%. At 5 years, the relative survival rate was similar for pT1a and pT1b in both cohorts, namely, pT1a 100% vs pT1b 97% (Cohort 1), and pT1a 100% vs pT1b 98% (Cohort 2). The 7thedition of the AJCC staging system has caused an increased number of patients to undergo SNB, without an increase in SNB positivity rate. Survival between pT1 subgroups remains similar. The mitotic rate criterion for pT1b classification and the recommendation to perform SNB for pT1b melanomas should be reconsidered.
authors.affiliation: Department of Surgical Oncology, Erasmus MC Cancer Institute, Groene Hilledijk 301, 3075 EA, Rotterdam, The Netherlands.
authors.forename: Charlotte M C
authors.identifier: 0000-0003-3066-1240
authors.initials: CM
authors.lastname: Oude Ophuis
authors.affiliation: Department of Research, Netherlands Comprehensive Cancer Organization (IKNL), Postbus 19079, 3501 DB, Utrecht, The Netherlands.
authors.forename: Marieke W J
authors.initials: MW
authors.lastname: Louwman
authors.affiliation: Department of Surgical Oncology, Erasmus MC Cancer Institute, Groene Hilledijk 301, 3075 EA, Rotterdam, The Netherlands.
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Grünhagen
authors.affiliation: Department of Surgical Oncology, Erasmus MC Cancer Institute, Groene Hilledijk 301, 3075 EA, Rotterdam, The Netherlands.
authors.forename: Kees
authors.initials: K
authors.lastname: Verhoef
authors.affiliation: Department of Surgical Oncology, Netherlands Cancer Institute - Antoni van Leeuwenhoek, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands.
authors.forename: Alexander C J
authors.initials: AC
authors.lastname: van Akkooi
mesh_terms: D000328:Adult; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D008545:Melanoma / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology*; D008875:Middle Aged; D008938:Mitosis; D009367:Neoplasm Staging; D009426:Netherlands / Q000453:epidemiology; D011379:Prognosis; D021701:Sentinel Lymph Node Biopsy; D012878:Skin Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology*
keywords: AJCC staging; melanoma; pT1; pT1a; pT1b; population; prognosis; thin melanoma