Researchers have created a set of statistical models that are more than 70 percent accurate for predicting the five-year risk of developing lymphedema after lymph node removal during breast cancer surgery. While the models continue to be refined, they could eventually become a useful decision-making tool for physicians.

This is the largest-ever prospective study of lymphedema occurrence, and these findings have important implications because it is currently very difficult to predict which patients with breast cancer will develop this surgical side effect.

In breast cancer patients, lymphedema is a swelling under the arm characterized by localized fluid retention and tissue swelling that can occur following axillary (underarm) lymph node surgery, which is often necessary if the cancer has spread to the lymph nodes.

It can be a chronic, disabling condition and affects about one-third of patients who have axillary lymph node surgery – approximately 4 million patients worldwide.

Investigators led by Jose Bevilacqua, MD, PhD, a surgical oncologist at Hospital Sirio Libanes in Sao Paulo, Brazil, prospectively studied 1,054 women with breast cancer undergoing axillary dissection between 2001 and 2002.

The overall five-year incidence of lymphedema in the group was 30.3 percent.Using a variety of clinical factors, including age, body mass index, ipsilateral (on the same side of the body) arm chemotherapy infusions, level of axillary dissection, location of radiotherapy field, development of postoperative seroma (fluid build-up), infection and early edema (swelling), the researchers developed three models and corresponding nomograms (graphic representation of a mathematical model) to predict the risk of developing lymphedema at different points in time following surgery:

In model 1, the goal was to predict lymphedema risk in advance of the surgery. It considered factors such as age, body mass index and number of cycles of chemotherapy prior to surgery.

For model 2, within six months of having surgery, these same predictors were used along with the extent of axillary dissection and the location of the radiotherapy field.

Model 3 aimed to predict lymphedema risk six months or later after surgery. It considered the same risk factors as model 2, plus the development of fluid buildup and swelling.

The researchers compared the models' predictions to the actual occurrence of lymphedema in this group of women, and found "concordance indexes" of .706, .729 and .736, respectively, for models 1, 2 and 3, meaning that the models correctly predicted a patient would develop lymphedema more than 7 out of 10 times.

"These models performed well," Dr. Bevilacqua said. "The statistical models and the corresponding nomograms use readily available clinical factors and allow for quick and easy estimation of individual risks of developing lymphedema after axillary lymph node surgery in women with breast cancer.

For the sake of comparison, these modeling tools are as accurate for predicting a woman's risk of developing lymphedema as mammography is for the detection of breast cancer.

"Dr. Bevilacqua suggested that the models may become useful decision-making tools in some cases to help physicians choose whether or not to recommend axillary dissection. "Knowing the risk of lymphedema can be important information to have when we speak to our patients about axillary dissection.

"The researchers believe that theirs is the first model to predict the risk of lymphedema, and they plan to continue to develop future models that they hope can be even more accurate.

These models are available online for free. To date, one tool to calculate arm volume is already available, while the other, the models to estimate the risk of lymphedema, will be available after journal publication, though it will be accessible during the 2011 Breast Cancer Symposium.

Source: ASCO