healthmedicinet

Patients

We analyzed the outcomes of 1764 consecutive patients with histologically confirmed
primary cutaneous melanoma in clinical stages I–II according to the AJCC 2010 classification
9], who underwent sentinel node biopsy at the Department of Soft Tissue/Bone Sarcoma
and Melanoma at the Maria Sklodowska-Curie Memorial Cancer Centre and Institute of
Oncology, Warsaw, Poland (CCIO), between 1998 and 2008 (cohort 1) (Table 1). In all patients, the triple technique was used consisting of preoperative lymphoscintigraphy,
blue-dye injection, and intraoperative lymphoscintigraphy with a hand-held gamma-detecting
probe. We have already presented the detailed technique of SNB and of the pathologic
examination of SLNs in our previous publications 1]. The false-negative cases were defined as a nodal recurrence after an initially negative
SLN biopsy in the biopsied basin without preceding local or in-transit recurrences.
In the case of positive SLN, all but three patients underwent completion lymph node
dissection (CLND). The margin of excision of all the primaries was ?1 cm. Each patient
provided written informed consent. The study was approved by the local Bio-Ethics
Committee according to Good Clinical Practice Guidelines.

Table 1. Patient characteristics of all patients undergoing SLN biopsy (cohort 1) and overall
survival (OS)

All patients undergoing SLN biopsy met the following criteria:

Primary focus cutaneous melanoma after excisional biopsy with Breslow thickness ?0.75 mm
or ulcerated or Clark level ?IV (all histological diagnoses were confirmed in the
Department of Pathology, CCIO)

Clinically non-palpable regional lymph nodes

Absence of distant metastases (confirmed routinely by physical examination, chest
X-ray, and ultrasonography of the abdominal cavity)

Feasibility for general anesthesia

The patients had not undergone any other preliminary selection. Only patients who
met with all the conditions listed above were enrolled in the study.

The clinico-pathological stage of the melanoma patients was determined by pathological
evaluation of the primary lesion and of the dissected lymph nodes, as well as by physical
examination and routine imaging examinations (chest X-ray, ultrasonography of the
abdominal cavity, and computed tomography imaging, if necessary).

Patient characteristics of the cohort 1 are summarized in Table 1. In an additional 805 cases, two pathologists reviewed mitotic index per mm
²
. All patients had confirmed primary melanoma. Radical lymph node dissections were
performed according to the technique described by Karakoussis 10]. For ilio-inguinal lymphadenectomy, we routinely excised the superficial and deep
levels below the inguinal ligament to the level of the aortic bifurcation combined
with obturatory lymph node dissection. Two hundred and one patients received interferon-?2b
as adjuvant treatment in accordance with the European Organisation for Research and
Treatment of Cancer (EORTC) 18952 trial (without significant influence on overall
survival data) 11], 12].

Additionally, we analyzed all consecutive patients (N?=?473) who underwent radical CLND at the Department of Soft Tissue/Bone Sarcoma and
Melanoma at the CCIO between May 1995 and December 2008 due to positive SLN biopsy
(cohort 2) independent of the SLN biopsy technique used (Table 2).

Table 2. Patient characteristics of patients undergoing completion lymph node dissection due
to positive SLN biopsy (cohort 2) and overall survival (OS) N?=?473

All patients were followed carefully with a median follow-up time of 4.9 years (range:
6–151 months; cohort 1) and 5.4 years (range: 6–174 months; cohort 2). Postoperative
follow-up consisted of physical examination and routine imaging investigations (chest
X-ray and ultrasound examination of the abdominal cavity; chest/abdominal computed
tomography examination was done for follow-up in SLN-positive or symptomatic patients).
Routinely, surveillance was recommended every 3 months for the first 2 years, every
4 months in year 3, every 6 months for years 4–5, and thereafter annually.

Pathological examination

The SLNs were evaluated by serial sectioning, and HE staining was performed first.
If this was negative, other slides were stained with immunohistochemical methods.
The amount of SLN tumor burden was measured according to the Rotterdam criteria 13], which consist of the measure of the maximum diameter (in any direction) of the largest
lesion on a slide (N?=?363). All positive slides were examined, and this process of measuring the largest
lesion was repeated. The largest value overall (which is the largest diameter measured
anywhere on one slide in one patient) has been defined as the amount of SLN tumor
burden (in mm). If a patient had multiple positive SLNs, the largest maximum diameter
of any of the SLNs was the largest overall and thus the amount of SN tumor burden
for this patient. Categories were made for SLN tumor burden as follows: 0.1 (sub-micrometastases),
0.1–1.0, and 1.0 mm. The location of the metastases was also recorded, according
to the Dewar criteria for the microanatomic location of the metastasis 14] (N?=?347). This was either subcapsular, parenchymal, combined, multifocal, or extensive.

Statistical analyses

The statistical analysis was done using R 3.0.1 statistical software (R Core Team
(2013). R: A language and environment for statistical computing. R Foundation for
Statistical Computing, Vienna, Austria. URL http://www.R-project.org/). Packages: survival (Therneau T (2013). “A Package for Survival Analysis in S”.
R package version 2.37-4, URL: http://CRAN.R-project.org/package=survival).

Logistic regression and survival analysis methods were used in the analysis. Potential
risk factors of positive SLN (cohort 1) and metastases to non-sentinel lymph nodes
(NSLN) (cohort 2) were investigated using univariate and multivariate logistic regression
model. Variables with p??0.10 were included in the initial stage of multivariate model building. Backward
variable selection was then used to construct the final model.

The Kaplan-Meier estimates and Cox regression model were used in survival analysis.
Patient’s survival was described using 5- and 8-year survival probability (with 95 %
confidence interval) and survival curve plots. Overall survival (OS) time for the
assessment of the prognostic value of clinical and pathological parameters was calculated
from the date of primary tumor excision to the date of the most recent follow-up (censored
data) or death. Clinical and pathological parameters are as follows: gender, primary
tumor Breslow thickness (?1.0 vs. 1.01–2.0 vs. 2.01–4.0 vs. 4.0 mm), presence of
ulceration of primary lesion, primary tumor level of invasion according to Clark (II,
III, IV, V), primary tumor pathological type (nodular melanoma [NM], superficial spreading
melanoma [SSM], acral lentiginous melanoma [ALM], lentigo malignant melanoma [LMM],
others), mitotic index of primary tumor (1/mm
²
, 1/mm
²
, 2–5/mm
²
, 5/mm
²
; cohort 1 only), and presence of metastases to SLN (cohort 1 only), and additionally
in cohort 2: localization of lymphadenectomy (inguinal vs. axillary), number of lymph
nodes with metastases (1 vs. 2–3 vs. ?4), presence of extracapsular invasion in involved
lymph nodes, presence of metastases to NSLN (assessed after CLND), size of metastases
to SLN according to the Rotterdam criteria, and microanatomic location of the metastasis
in SLN (subcapsular, combined, parenchymal, multifocal, extensive) were tested as
a factors affecting patients survival.

The multivariate Cox model was used to identify independent risk factors affecting
patients’ survival. Procedure of final model building was the same as in case logistic
regression model. The differences were considered statistically significant if the
p values were 0.05.