Histologic Analysis of the Lymphatic Vessels Used for Supermicrosurgical Lymphatico-venous Anastomoses in Lymphedema

Background:

Lymphedema is a chronic pathologic condition that causes significant functional impairment to the patient and has a great impact on his quality of life. It may be primary or secondary. Secondary lymphedema, that is the most common, is generally due to surgery and radiotherapy for cancer, particularly of the breast, uterus and prostate but can also occur after a trauma. Primary lymphedema can be congenital or begin at puberty, or more rarely after age 35, in this case, often following a trigger event such as trauma or infection.

There is no specific treatment for this highly disabling disease and patients must lifelong try to reduce edema and limit its progression by the use of elastic compression garments and with manual lymphatic drainage. Over the years several surgical approaches have been proposed, including more recently super microsurgical lymphatic-venous anastomosis (sLVA) to allow drainage of the lymph in the venous stream distal to the obstruction. sLVA is a minimally invasive procedure performed under local anesthesia with discharge the day after surgery. It requires an accurate visualization of the lymphatic vessels that are still functional. Lymphatic vessels are visualized with lymphography using a fluorescent dye, indocyanine green. In selected cases, magnetic resonance can also be useful. Small samples of the vessel selected to perform the LVA can easily be taken during surgery, formalin-fixed and paraffin-embedded for histologic and immunohistochemical studies without further discomfort or complications for the patient.

Knowledge on the histopathological aspects of lymphedema is extremely limited, this study must therefore be considered an exploratory one, possibly intended to generate more hypotheses than to solve them. A better understanding of the physio-pathological mechanisms of lymphedema can lead to a more effective surgical approach and, in selected cases, even prevent its development with considerable advantages in terms of the patient's quality of life and also in reducing national health care system costs (direct costs arising from the need to undergo continuous physiotherapy and indirect costs due to disability, serious intercurrent infections requiring hospitalization and loss of work days).

Primary purpose of the study is to evaluate the histopathologic features of the lymphatic vessels anastomosed with veins. The primary purpose will be divided in two phases: 1. on secondary lymphedema; 2. on primary lymphedema.

Secondary purpose of the study is the correlation of histopathologic parameters with other clinical data: type of lymphedema (primary versus secondary), age of the patient, years from the onset of the disease, anatomic site of the anastomosis, morphologic characteristics of the vessel as assessed pre-operatively by lymphography and or magnetic resonance imaging.

The acquired knowledge will be valuable to customize the approach to prevent and treat lymphedema. In particular, will help to:

1. Select patients who can better benefit from sLVA and within them prioritize intervention.

2. Select the lymphatic vessels that are more likely to give an efficient anastomosis with veins.

3. Based on the comparison between the morphological features of lymphatic vessels of various parts of the limb affected by lymphedema, select the anatomical sites where efficient anastomosis are more likely to be achieved.

Experimental design This is a single center, non commercial laboratory study to be performed on human biological material. Patients will be recruited with a consecutive participant sampling of all those who meet the eligibility criteria and are willing to provide informed consent. Samples of the lymphatic vessels to be anastomosed with veins will be taken at time of sLVA, this can be done without any inconvenience for the patient because the lymphatic vessels are often too long and a segment must be removed to perform the anastomosis. Usually during surgery 1-3 lymphatic vessels/patient are removed for technical reasons. These samples instead of being destroyed, will be transported to the laboratory of Prof. Elisabetta Weber where they will be formalin-fixed and paraffin embedded. Histologic and immunohistochemical studies will be performed on the obtained sections stained with appropriate markers and or/stains for the lymphatic endothelium (D2-40 and VEGFR-3) and of smooth muscle cells. Appropriate stains will be used to determine the relative proportions of smooth muscle cells and collagen fibers in the lymphatic wall. A morphometric analysis of data will be performed and data will be related with the clinical results obtained.

All data will be statistically evaluated. As there are no previous experiences that allow to estimate the variability of the parameters in the study, it is not possible to hazard a formal analysis of the statistical power of the study. However, a sample of 25 patients should be sufficient to provide a first estimate of the variability of the parameters and inform future efficacy studies based on the hypothesis testing model tests (Tukey, 1977). Since the sample comprises two different types of lymphedema, primary and secondary, a minimum of 25 patients is required to have a sufficient number of patients for each of these two groups. It will not be difficult to find cases of secondary lymphedema, since it is very common (especially in industrialized countries, as a consequence of surgery and radiotherapy for cancer treatment), while it will be more difficult to find cases of primary lymphedema since this type of lymphedema is rare and often undiagnosed or misdiagnosed. Should the individual variability be considerable, it would be necessary to increase the number of patients. Finally, it should be noted that, given the small size of the samples (maximum of 0.4mm diameter, 2-5mm in length), not all histological preparations will be successful. Therefore, the investigators believe it prudent to set a maximum number of samples of 200.

The statistical analysis will make use, as well as of descriptive methods, of methods of comparison and correlation of parametric (Student t, linear correlation) or non-parametric (logistics analysis, chi-square, Spearman's rank correlation), in agreement to the features of the data distribution that will be found. The correlation between the time from onset of lymphedema and primary and secondary outcomes will be investigated with Cox proportional hazard model. Differences in outcome measures between recent (<1 year) and long standing lymphedema will be investigated using Generalized Linear Models using gaussian family and identity link. When more than one sample from the same patient is present, the patient will be included in the model as a random effect variable. A p value of 0.05 or less for a two tails distribution will be considered statistically significant. Data is presented as M ± robust SE All the analyses will be performed using Stata vers. 12 (Stata Corp, College Station, TX).

Aim of the study:

The aim is to better understand the pathogenetic aspects and pathophysiology of lymphedema (of which very little is known) and evaluate the structure of lymphatic vessel in relation to the stage of lymphedema, to optimize the choice of the lymphatic vessels better suited to achieve functioning anastomoses. The obtained data will be correlated with clinical outcome which will be evaluated with the following objective parameters: reduction in limb circumference measured at several points (hand, wrist, -5 cm from the elbow, elbow and +5 cm from the elbow; for leg: foot, ankle, -10 cm from the knee, the knee, to +10 cm from the knee); reduction/absence of episodes of lymphangitis; decreasing compression class of elastic compression garments. Subjective parameters will also be evaluated as indexes of the patient's life quality: reduction of discomfort, reduced sense of heaviness, ability to wear clothes more easily, improved social life.

The study will be conducted in accordance with the ethical principles in the Declaration of Helsinki in its latest revision. Participation in the study will be subject to obtaining the free and informed consent.