Standardising an Approach for Analysis of Lymph Node Specimens From Radical Cystectomy With Pelvic Lymph Node Dissection Through the Use of an Organic Fat-emulsifying Agent
This research aims to compare the clinical significance of the use of a fat emulsifying
protocol versus the current standard in the processing of lymph node specimens following
radical cystectomy and pelvic lymph node dissection.
The investigators hypothesize that the use of a fat-emulsifying protocol in the processing
of lymph nodes harvested at the time of radical cystectomy will increase the proportion of
patients found to have lymph node metastases when compared to the current standard
The mainstay of management of muscle invasive bladder cancer is radical cystectomy with
pelvic lymph node dissection (PLND). Despite optimal multimodal therapy, approximately half
of patients with invasive bladder cancer die of their disease. Efforts to improve patient
outcome have focussed on two principle factors: the delivery of pre-operative chemotherapy
and the adequacy of PLND. While a PLND is ultimately defined by its anatomic extent, a
popular surrogate measure of extent is the number of lymph nodes removed. Beyond assessing
the adequacy of the PLND in the sense of quality of care, the accurate determination of
lymph node involvement is essential for the correct staging of the patient, which is used to
guide adjuvant therapy and determine patient prognosis. The processing and analysis of the
lymph node specimens is therefore critical in multiple ways.
The current convention at Vancouver General Hospital for specimen handling involves the
dissection of the nodal specimen by a laboratory technologist in the pathology lab. Only
palpable nodes are processed for sectioning and the remaining fat tissue is discarded. The
nodal count is determined by the pathologist when reviewing the slides based on a
combination of the macroscopic and microscopic examination. This process is highly
subjective, depends on the diligence of the technologist's dissection, and limits the final
examination to palpable nodes. In the fat emulsifying technique, all fat is dissolved so
that the pathologist can visualize and process all nodes. The investigators believe that
this may provide for a more standardized and reproducible method in processing lymph nodes.
A standardized and reproducible method for processing lymph nodes is a prerequisite to any
use of lymph node counts as a measure of the quality of the PLND. And, it is necessary to
allow the comparison of results between centers. Furthermore, standardized methodology is
essential to ensure adequate sampling of lymph nodes for clinical staging and
The investigators have designed a prospective trial to compare our current protocol for
processing pelvic lymph nodes from radical cystectomy with PLND to a fat-emulsifying
protocol. The investigators aim to answer three questions with this trial:
i. While the fat-emulsifying technique will almost certainly identify more nodes than the
current technique of manual dissection, and will likely identify more nodal metastases, the
aim of this study is to determine whether a more careful analysis will find a greater
proportion of patients to have lymph node metastases. This will translate into better
staging and prognostication.
ii. The current technique likely misses particularly small lymph nodes that are not easily
palpated. The investigators hypothesize that there is no threshold lymph node size below
which the risk of metastasis is negligible, and that identification of these smaller nodes
is therefore clinically meaningful.
iii. The investigators hypothesize that a fat-emulsifying protocol will remove much of the
variability due to human element of manual dissection by the prosector. While the
investigators will not test this hypothesis directly, the investigators believe the
methodology and photographic documentation of the results will reflect a degree of
objectivity in this methodology that is not seen with other techniques.
The ultimate goal of this research proposal is to develop a standardized and reproducible
technique that can be used everywhere in order to enhance the care of our patients with
invasive bladder cancer.
All patients who undergo radical cystectomy with pelvic lymph node dissection at Vancouver
General Hospital (VGH) will be invited to participate in this prospective study. Patients
with clinical stage T1-4,N0,M0 bladder cancer will be invited to participate in the study
and will be enrolled after informed consent is obtained.
The extent of lymph node dissection will be defined as either conventional (up to
bifurcation of common iliac artery) or extended (at least up to the aortic bifurcation) and
will be determined by the surgeon on a case-by-case basis. Dissection of the pre-sacral
lymph nodes is also up to the surgeon. Objective documentation of the extent of node
dissection will be assured by intra-operative photography in every case.
Pathologic processing of PLND specimen:
Each specimen will be analyzed by both conventional means and by a fat-emulsifying protocol.
The current convention at Vancouver General Hospital for specimen handling is described
above. In this study the pathologist will count the number of nodes dissected by the
prosector according to this current protocol. The tissue remaining after removal of the
grossly palpable lymph nodes will be submitted for processing by the fat-emulsifying
protocol, which is identical to the LNRS ("lymph node removing solution") protocol defined
by Koren et al. This consists of placement of the entire specimen in a specialized solution
for 12 hours. The solution is a mixture of 95% ethanol, diethyl ether, glacial acetic acid
and buffered formalin in a ratio by volume of 6.5:2:0.5:1 Specimens so treated will be
photographed for objective documentation of the nodal count. The additional nodes are then
embedded in paraffin, sectioned at 2 mm intervals, and stained with eosin and hematoxylin.
The total number of nodes, their size and presence of metastasis will be recorded.
Demographic, clinical and pathological information will be recorded prospectively.
Demographic variables analyzed will include: age, sex, weight, height and race. Clinical
variables will include: date of cancer diagnosis, clinical and pathologic stage at diagnosis
and at time of surgery (TNM staging), date of radical cystectomy, history of intravesical
chemotherapy, other medical co-morbidities and prior abdominal surgeries, extent of lymph
node dissection, and complications during the procedure. Pathological variables will be
recorded for the findings on both the conventional and fat-emulsifying protocols. The
number, size and presence of metastasis for each node found will be recorded.
The primary outcome will be the proportion of patients found to have lymph nodes metastases
on pathologic examination. Specifically, the difference in proportion of specimens found to
contain nodal metastases using the fat-emulsifying protocol compared to the conventional
lymph node processing will be analyzed. Secondary outcome measures will be: the total number
of lymph nodes and the total number of lymph node metastases counted by both techniques and
the relationship between the size of lymph node and the presence of metastatic carcinoma.
Sample size calculation:
An increase in the identification of nodal metastases by 15% (fat-emulsifying compared to
conventional processing) will be considered clinically significant. The current rate of node
positivity at the time of radical cystectomy with PLND at VGH is 28%, so that an increase to
43% would be deemed clinically relevant. To detect this difference with a power (1-β) of 80%
and an α error of 10%, 125 patients will need be enrolled in each arm of the study.
Analysis of Data:
Data will be analyzed using SPSS software. The independent samples t-test will be used to
compare the results from the lymph node analysis when processed by conventional means versus
the same nodes processed using the fat-emulsifying protocol (p<0.5). The relationship of
size to presence of metastatic disease will be done by linear regression model (p<0.5). A
significant difference between the groups will be defined as p<0.05. A biostatistician
(Robert Bell) at the Vancouver Prostate Centre will assist with data analysis.
The investigators have the opportunity with simple and inexpensive technical processing
measures to enhance an integral component of our clinical risk stratification in patients
with invasive bladder cancer. The investigators can establish a solid foundation in pelvic
lymph node counting upon which clinical concepts of lymph node yield and density can be
validated. The investigators expect to demonstrate that the fat-emulsifying protocol is easy
to adopt, reproducible and suitable for widespread use. It has the potential to impact every
patient undergoing radical cystectomy with PLND.
Time Perspective: Prospective
Proportion of patients with lymph node metastasis on pathologic examination
The primary outcome will be the proportion of patients found to have lymph nodes metastases on pathologic examination. Specifically, the difference in proportion of specimens found to contain nodal metastases using the fat-emulsifying protocol compared to the conventional lymph node processing will be analyzed.
Peter Black, MD
University of British Columbia
Canada: Canadian Institutes of Health Research