Key words
cervix - cancer - prognosis - grading - histopathology - treatment - squamous cell
- survival
Schlüsselwörter
Zervix - Krebs - Prognose - Grading - Histopathologie - Therapie - Plattenepithelzelle
- Überleben
Introduction
There are several reports in the literature on survival and disease-free intervals
and on their relationship to surgical-pathological factors in cervical carcinoma of
the uterus [1], [2], [3], [4]. Among these factors, pelvic lymph node involvement and tumor stage are well-established
prognostic parameters. The histopathological grading of cervical cancer, however,
is one of the more controversial factors, especially in squamous cell carcinomas (SCC)
[2], [5], [6]. Historically, grading of cervical SCCs was performed using Broderʼs system or modifications
thereof based on the degree of keratinization, cytological atypia and mitotic activity
[7], [8]. This grading system has been adopted by the WHO classification and is still valid,
but it tends to be vague and unprecise [6], [9]. Therefore, the present study was designed to evaluate the prognostic impact of
the conventional grading based on the degree of keratinization within a large cohort
of SCCs. A potential correlation of the conventional tumor grade with the recurrence-free
and overall survival as well as pelvic lymph node metastases was used to determine
the prognostic significance of grading in squamous cell cervical carcinomas. This
may help to better define the role of tumor grade in cervical SCC and its possible
consequences on clinical treatment decisions.
Material and Methods
Patients
Data from 467 consecutive squamous cell cervical cancer patients, clinically staged
FIGO IB1 to IIB, who underwent upfront surgery were obtained from the files of the
Institute of Pathology, University Hospital of Leipzig, Germany. Patients who received
neoadjuvant therapy, those with incomplete local tumor resection and non-squamous
cell histology were excluded from the study. Prior to the introduction of the TMMR-technique
[10] at our institution, all women were treated by a radical abdominal hysterectomy Piver
type III [11]. All patients with parametrial involvement and/or lymph node metastases underwent
adjuvant intracavitary radiotherapy (ICRT) and external beam chemoradiation.
Pathological examination
The pathological examination of the radical hysterectomy specimen was performed in
a standardized manner [12]. All tumors were staged and classified according to the WHO and TNM-classifications
[6], [13].
As a detailed description of the different grades is not included in the current WHO
classification [6], tumors were graded in accordance to previous studies [14], [15], [16], [17]. In well-differentiated tumors (G1), the tumor cell nests were composed of keratinocyte-like
cells with easily visible keratinization features (layered or cytoplasmic keratin).
In the poorly differentiated tumors (G3), the squamous morphology was only noticeable
in a small area of the tumor, not exceeding 1% of the whole tumor. The moderately
differentiated tumors (G2) showed an intermediate degree of squamous differentiation
between the well- and poorly differentiated ones ([Fig. 1 a] to [c]).
Fig. 1 Histologic images of different grades of squamous cell carcinoma of the uterine cervix.
a G1: well-differentiated SCC: tumor cell nests with easily visible keratinization
features (layered or cytoplasmic keratin). b G2: moderately differentiated SCC with focal keratinization within the tumor cells.
c G3: tumor cell nests with squamous features without keratinization.
The original H & E-stained slides were re-examined on low power magnification (× 25).
If necessary, the infiltrating tumor cell nests were screened at intermediate power
fields (× 100) for single cell keratinization and intercellular bridges. Two to six
slides per case were investigated (mean 2.7 per case).
Follow-up data
Follow-up data were retrieved from the medical records. Written informed consent was
obtained from all patients. Additionally, the study was approved by the Institutional
Review Board.
Recurrence-free survival (RFS) was calculated from the day of diagnosis until tumor
recurrence or end of follow-up. Overall survival (OS) was calculated from the day
of diagnosis until death or end of follow-up. Kaplan-Meier survival curves and Log
rank tests were used to analyze the survival data. Cox regression analyses were fitted
to estimate the impact of grading. All statistical analyses were performed with IBM
SPSS Statistics version 24.0.
Results
Grading and prognosis
A total of 467 cases were available for review. The patient characteristics are summarized
in [Table 1].
Table 1 Patient characteristics (n = 467).
|
Follow-up (months)
|
|
|
69 (2 – 182)
|
|
Age (years)
|
|
|
41 (23 – 74)
|
|
|
42 ± 11
|
|
Post-surgical stage distribution
|
|
|
233 (49.9%)
|
|
|
55 (11.8%)
|
|
|
49 (10.5%)
|
|
|
130 (27.8%)
|
|
Pelvic lymph node involvement
|
|
|
314 (67.2%)
|
|
|
153 (32.8%)
|
|
Tumor grade
|
|
|
215 (46.0%)
|
|
|
143 (30.6%)
|
|
|
109 (23.3%)
|
|
Lymphovascular space involvement
|
|
|
169 (36.2%)
|
|
|
298 (63.8%)
|
|
Recurrent disease
|
|
|
346 (74.1%)
|
|
|
121 (25.9%)
|
46.0% (n = 215) presented with well-differentiated tumors (G1), 30.6% (n = 143) showed
moderate differentiation (G2) and 23.3% (n = 109) were poorly differentiated (G3).
The three grading groups were prognostically relevant for recurrence-free (p = 0.008;
[Fig. 2 a]) but not for overall survival (p = 0.089; [Fig. 2 b]).
Fig. 2 Kaplan-Meier curves for the prognostic impact of conventional tumor grading in squamous
cell carcinoma of the uterine cervix using a 3-tiered grading system (please see text).
a Recurrence-free survival. b Overall survival.
A separate analysis of well- and moderately differentiated tumors regarding recurrence-free
and overall survival was performed and revealed no significant difference (p = 0.002
for 5-year recurrence-free survival and p = 0.033 for 5-year overall survival, [Table 2]). This is illustrated in [Fig. 2 b] where the survival curves are merging. Therefore, the well- and moderately differentiated
carcinomas were merged into a low-grade group, whereas the poorly differentiated carcinomas
formed the high-grade group. 358/467 patients (76.6%) were found to have low-grade,
109/467 (23.3%) high-grade tumors.
Table 2 5-year-recurrence-free (RFS) and -overall survival (OS) of the different grading
groups using the conventional grading system for squamous cell carcinomas of the uterine
cervix (p-values [Log rank test]).
|
5-year recurrence-free survival
|
p-values
|
|
G1
|
80.4% (95% CI: 74.7 – 86.0%)
|
p = 0.089 (G1 vs. G2)
|
p = 0.002 (G1 vs. G3)
|
|
G2
|
74.2% (95% CI: 66.9 – 81.5%)
|
|
|
G3
|
64.4% (95% CI: 54.9 – 73.8%)
|
p = 0.162 (G2 vs. G3)
|
|
|
global: p = 0.008
|
|
5-year overall survival
|
p-values
|
|
G1
|
76.4% (95% CI: 70.0 – 82.8%)
|
p = 0.603 (G1 vs. G2)
|
p = 0.033 (G1 vs. G3)
|
|
G2
|
76.4% (95% CI: 69.3 – 83.5%)
|
|
|
G3
|
67.8% (95% CI: 58.6 – 77.0%)
|
p = 0.121 (G2 vs. G3)
|
|
|
global: p = 0.089
|
As illustrated in [Fig. 3], there was a significant difference between low- and high-grade tumors regarding
the recurrence-free and overall survival, respectively. The 5-year recurrence-free
survival for G1/G2 versus G3 tumors was 77.9% (95% CI 73.4 – 82.3%) versus 64.4% for
the G3 tumors (95% CI 54.9 – 73.8%; p = 0.008). G1/G2 tumors showed a 5-year overall
survival of 76.9% (95% CI 72.3 – 81.5%) versus 67.8% for the G3 tumors (95% CI 58.6 – 77.0%;
p = 0.031). The survival rates are shown in [Table 3].
Fig. 3 Kaplan-Meier curves for the prognostic impact of conventional tumor grading in squamous
cell carcinoma of the uterine cervix using a 2-tiered grading system (please see text).
a Recurrence-free survival. b Overall survival.
Table 3 5-year-recurrence-free (RFS) and -overall survival (OS) of the different grading
groups using the conventional grading system for squamous cell carcinomas of the uterine
cervix (p-values [Log rank test]).
|
5-year recurrence-free survival
|
p-values
|
|
G1/G2
|
77.9% (95% CI: 73.4 – 82.3%)
|
p = 0.008
|
|
G3
|
64.4% (95% CI: 54.9 – 73.8%)
|
|
5-year overall survival
|
p-values
|
|
G1/G2
|
76.9% (95% CI: 72.3 – 81.5%)
|
p = 0.031
|
|
G3
|
67.8% (95% CI: 58.6 – 77.0%)
|
Grading and lymph node involvement
The frequency of pelvic lymph node involvement for the different grading systems used
is presented in [Table 5].
Table 5 Pelvic lymph node involvement within different grading groups.
|
Conventional grading
|
|
three-tired grading system
|
binary grading system
|
|
G1
(n = 215)
|
G2
(n = 143)
|
G3
(n = 109)
|
low-grade
(n = 358)
|
high-grade
(n = 109)
|
|
pN0
|
67.4%
|
67.8%
|
66.1%
|
67.6%
|
66.1%
|
|
pN1
|
32.6%
|
32.2%
|
33.9%
|
32.4%
|
33.9%
|
|
p-value
|
p = 0.953
|
p = 0.764
|
The conventional three-tiered grading system failed to predict pelvic lymph node involvement.
The odds ratios for G1 versus G2 (0.98 [95% CI: 0.62 – 1.54]) and G2 versus G3 (1.08
[95% CI: 0.64 – 1.84]) were not statistically different. Also, the binary grading
was unable to predict pelvic lymph node involvement (OR 1.07 [95% CI: 0.68 – 1.7];
p = 0.76).
Discussion
Clinical and postsurgical tumor stage as well as lymph node status are the most powerful
predictors of outcome in cervical cancer [2], [3], [4]. The data regarding the prognostic impact of the tumor grade in squamous cell cancers
(SCC) of the uterine cervix are controversial, and several approaches using different
morphologic variables have been applied [15].
Historically, cervical SCCs were graded using Broderʼs system [7] or modifications thereof based on the degree of keratinization [8]. This particular grading system of cervical SCCs is currently mentioned in the last
two editions of the WHO classification [6], [9] and is referred to as the conventional grading in order to separate it from other
grading systems. In an earlier GOG-study, the three-year disease-free interval correlated
significantly with the conventional tumor grade (G1: 90.6%, G2: 86.0% and for G3:
76.1%; p = 0.001) [14]. In a small study of 97 patients, grading had an impact on overall survival [18]. Other studies including those with multivariate approaches showed no prognostic
significance of conventional grading [1], [16]. In the present study, the conventional grading failed to show a prognostic impact
on overall survival. There were no differences between well-differentiated (G1) and
moderately differentiated (G2) tumors in regards to recurrence-free and overall survival
([Fig. 2] and [Table 2]). After merging G1 and G2 tumors into low-grade tumors, the two-tiered conventional
grading of cervical SCCs showed a prognostic impact both on recurrence-free and overall
survival ([Fig. 3] and [Tables 2] and [3]).
In the present study, both the conventional three-tiered and the binary grading system
failed to predict pelvic lymph node involvement ([Table 5]).
In multivariate analyses including pelvic lymph node status, grading and the post-surgical
tumor stage, the binary grading system was prognostically significant for recurrence-free
as well as overall survival ([Table 4]).
Table 4 Cox-regression analyses for recurrence-free and overall survival.
|
HR
|
p-values
|
|
Recurrence-free survival
|
|
Pelvic lymph node involvement
|
|
|
|
|
ref
|
|
|
|
2.7 (95% CI: 1.8 – 3.9)
|
p < 0.001
|
|
Histological tumor grade
|
|
|
|
|
ref
|
|
|
|
1.8 (95% CI: 1.2 – 2.6)
|
p = 0.003
|
|
Post-surgical stage
|
|
|
|
|
ref
|
|
|
|
2.2 (95% CI: 1.2 – 3.5)
|
p = 0.013
|
|
|
1.4 (95% CI: 0.7 – 2.8)
|
p = 0.373
|
|
|
2.4 (95% CI: 1.5 – 3.7)
|
p < 0.001
|
|
Overall survival
|
|
Pelvic lymph node involvement
|
|
|
|
|
ref
|
|
|
|
2.8 (95% CI: 1.9 – 4.1)
|
p < 0.001
|
|
Histological tumor grade
|
|
|
|
|
ref
|
|
|
|
1.7 (95% CI: 1.1 – 2.4)
|
p = 0.011
|
|
Post-surgical stage
|
|
|
|
|
ref
|
|
|
|
1.6 (95% CI: 0.9 – 3.0)
|
p = 0.107
|
|
|
1.7 (95% CI: 0.9 – 3.3)
|
p = 0.102
|
|
|
2.7 (95% CI: 1.7 – 4.1)
|
p < 0.001
|
The advantage of the binary grading system may be the easier morphological categorization
using only two rather than three different categories as well as the better reproducibility.
While the conventional three-tiered grading system failed to predict prognosis, the
binary system was useful in predicting both a reduced recurrence-free and overall
survival. One limitation of the present study may be that it includes a variety of
different stages of cervical carcinoma which may impact the results. The inclusion
of different stages may also be responsible for the failure to predict pelvic lymph
node involvement within the different grading groups.
Many attempts regarding the definition of grading systems on SCCs of the cervix uteri
have been made [15]. Within that context, an invasive front grading was suggested [19]. This type of grading was first introduced in head and neck SCCs [20] and evaluates the degree of keratinization, nuclear pleomorphism, pattern of invasion
and peritumoral host response at the infiltrative edge of SCCs. In cervical cancer,
however, data on this grading system are very limited. Very recently, tumor cell budding
(evaluating tumor growth by cell nest size) was studied in cervical SCC [21]. The tumor budding as a variant of the grading of a malignancy was previously validated
in esophageal, lung and oral SCC.
Furthermore, studies that discuss tumor grade as a prognostic factor give no detailed
description of the grading system that was applied [22], [23]. At this point, there is no well-accepted and widely used grading system for cervical
SCCs [24], [25], nor has one been recommended by the current WHO classification [6]. Because of these limitations, tumor grading is not listed as a required but rather
a recommended feature in the most recent recommendations of the International Collaboration
on Cancer Reporting [5] for cervical cancer. The German national guidelines for the diagnosis and treatment
of cervical carcinoma point out that grading should not be used as a single factor
for adjuvant treatment decision [26].
Finally, additional studies are required to define standardized and reproducible criteria
for grading with stage-by-stage analyses and a multivariate approach.
Conclusions
A binary grading model for the conventional tumor grade (based on the degree of keratinization)
in SCC of the uterine cervix may be suitable for the prognostic survival evaluation
but failed to predict pelvic lymph node involvement.
