Researchers have identified a number of factors in a patient’s presentation with mesothelioma that serve as important indicators of the disease’s treatability and overall prognosis. Two of the most significant indicators are the gender of the patient and the histological subtype of the disease. In terms of gender, studies have shown time and time again that men are more likely to be given a limited prognosis than are women. Regarding histology, other studies have shown that patients who are diagnosed with epitheloid mesothelioma have a better prognosis—in some cases, a much better prognosis—than do patients who are diagnosed with either biphasic mesothelioma or sarcomatoid mesothelioma, which are the other subtypes of the disease. This information is important to mesothelioma physicians as they develop individualized treatment plans because the particular forms these indicators take will dictate one particular therapy over another.

Even as researchers have confirmed the importance of these factors in numerous trials, they have also investigated if other presentational features can function in a similar manner. A feature of particular interest to physicians involves the relationship—if any—between overall asbestos burden and treatment outcomes. Researchers have known for almost one hundred years that asbestos is the only cause of mesothelioma and that longer exposures to its dust and particulate matter, especially in occupational settings, often correlate with a greater likelihood of developing the disease, but few quantitative studies have been completed that specifically addressed the relationship between asbestos burden and treatment outcome.

In response to this, a group of researchers from some of the finest hospitals and mesothelioma research programs in the United States conducted a study that addressed this question and have recently published their findings in the journal Environmental Health Perspectives.

This article is a summary of their findings.

Overview of the Study

To address the question of the relationship between asbestos burden and mesothelioma prognosis, the study looked at a population of 128 pleural mesothelioma patients that were treated in the International Mesothelioma Program at Brigham and Women’s hospital in Boston, MA. To analyze asbestos burden, the researchers used two sets of data: self-reported data from individual patients, or data given during interviews with a trained industrial hygienist, on their occupational histories and known asbestos exposures, as well as an analysis of actual lung and tumor tissue that was removed from the patients during surgery. Reported data was available for all 128 patients, while the tissue samples were available for 83 patients.

The researchers looked at a number of factors in relation to this data, including overall asbestos exposures, actual body burden of asbestos fibers, tumor characteristics and patient demographics. Each piece of information was analyzed singularly and in combination with the other factors.

Results

In the cohort of 128 patients, there were 98 males and 38 females, with a mean age of 62 years. There were 91 cases of epitheloid mesothelioma, 33 cases of biphasic mesothelioma and 4 sarcomatoid cases. When the researchers compared the relationships between histology and gender with survival time, they again confirmed the efficacy of these two factors as important indicators of survivability: epitheloid types were associated with significantly better survival times than the other histological types, and longer survival times were demonstrated, on average, by more women than men.

To compare asbestos burden levels between individuals, the researchers used the patient’s reported data as well as data from an analysis of actual tissues (when such tissues were available). They analyzed multiple samples from resected lung tissues to determine the number of asbestos bodies per gram of tissue (ABs/g lung). The median level for the entire cohort was 158 ABs/g lung. Three individuals demonstrated a radically higher ABs/g lung figure than all other patients, so their information was not included in any of the reported statistics. The researchers also created a three-tiered structure that identified different levels of exposure and categorized those levels using the following: low burden (0-99 ABs/g lung), moderate burden (100-1099 ABs/g lung) and high burden (> 1099 ABs/g lung).

The researchers did not find an overall relationship between self-reported asbestos exposures and survival times, but they did find a relationship between older age at diagnosis of mesothelioma and self-reported exposures. An analysis of asbestos body burden levels between genders showed that men had significantly-higher median fiber levels than did women (219 vs 20 ABs/g lung), which is not surprising given the greater number of men who worked in occupations with products containing asbestos.

When the researchers compared actual tissue burden levels to survival times, they were quite surprised to learn that burden level and survivability did not progress in a linear fashion. Instead, they found that those with moderate levels of exposure survived longer, on average, than those with low or high burdens. The researchers were not able to determine the reason why the low burden group demonstrated a greater risk of shorter survival than did the moderate burden group, but they suggest that if certain individuals have a natural susceptibility to the disease then they may be susceptible to a more aggressive form of it as well.

The researchers did find, however, a significant correlation between the high asbestos burden category and shorter survival times compared to the other two levels.

Conclusion

The researchers conclude that asbestos burden could be an important factor in mesothelioma prognosis, but they state that more research studies involving larger sample populations are necessary before a final determination can be established. Mesothelioma, especially its most common form of pleural mesothelioma,is a difficult disease to manage effectively and still remains an enigma in many ways. It is through the innovative research of dedicated physicians and scientists that we’ve learned all that we currently know about this terrible disease and it is through the continual renewal of this research that we’ll learn even more.

Labels: mesothelioma, pleuralmesothelioma