The type or amount of asbestos a victim is exposed to may have little effect on the sub-type of mesothelioma that they eventually develop, according to recent analysis of patient records spanning fifty years. However, the victim’s survival is known to be linked to the cancer sub-type diagnosed, which may also be vital as supporting evidence when pursuing a mesothelioma claim for asbestos exposure in the workplace.

There are three mesothelioma sub-types. Epithelioid mesothelioma – the most common sub-type – is formed from long shaped cells that tend to lump together with other epithelioid cells and accounts for as many as 7 in 10 of all diagnosed mesothelioma cases. Patients diagnosed with this mesothelioma type generally have the best life expectancy as the cancer tends to be most responsive to treatment.

The most difficult mesothelioma sub-type to treat

The least common sub-type, diagnosed in around 1 in 10 patients, is known as Sarcomatoid. The spindle-shaped cells tend to grow and spread the fastest and, as a result, are the most difficult to treat. Biphasic mesothelioma – containing both Epithelioid and Sarcomatoid cells – is the second-most common sub-type making up around 2 in 10 of all mesothelioma cases.

Identifying the mesothelioma sub-type is important to developing an effective asbestosis treatment for individual patients as the response from each type is different.

Patient’s history analysed

In the recent study, carried out at the University of Western Australia, researchers analysed malignant mesothelioma cases between 1962 and 2012. Each patient’s history was analysed to determine:

  • Total number of days each mesothelioma patient was exposed to asbestos
  • Number of years since first exposure
  • Source of the exposure, i.e. occupational or environmental
  • Form of asbestos, i.e. raw or processed
  • Type of asbestos.

The results were then compared to all the other patient’s mesothelioma sub-types.

Indicator of malignant mesothelioma cell sub-type

It was found that there was “no strong evidence” for the type or amount of asbestos, to which the patient was exposed, as an indicator of the resulting malignant mesothelioma cell sub-type. However, the study did find that patients with Biphasic mesothelioma were slightly more likely than other sub-types to have been exposed to asbestos at work (rather than their environment), and to have primarily encountered raw asbestos fibres.

Evidence of the resulting mesothelioma sub-type can be vital in securing mesothelioma compensation in a difficult case and will also help to determine a patient’s prognosis. Life expectancy for pleural mesothelioma victims is, on average, between two to 12 months from a confirmed diagnosis. If the tumour cells have spread to an advanced stage, there may be little more than two weeks remaining.

While all three mesothelioma sub-types carry a poor survival rate, a patient diagnosed with Sarcomatoid cell cancer is unlikely to survive beyond six months from diagnosis. Clinical research suggests that there are important ‘cellular differences’ between the sub-types, which appear to also have a crucial affect upon a patient’s survival rate.

Sub-type can present an equally poor prognosis

While the Epithelioid sub-type can be more responsive to treatment, a recent 10-year study of biopsy specimens plus accompanying survival data indicate that a further variation of the Epithelioid sub-type can present an equally poor prognosis as the Sarcomatoid and Biphasic types.

Analyses of the tissue sample types revealed the following median or “middle” value of the data set for overall survival:

  • Epithelioid – 10.5 months
  • Biphasic – 6.5 months
  • Sarcomatoid – 4 months

It was also discovered that patients with a specific sub-type of Epithelioid mesothelioma called ‘Pleomorphic’, the median survival was just 3 months, which places the survival rate below the Sarcomatoid type.

Ability to change shape or size as conditions change

In microbiology, a Pleomorphic cell possesses the ability to change shape or size as their conditions change. A well-known characteristic of a mesothelioma cell is the ability to grow in a wide variety of cell tissue patterns. The researchers concluded that the Pleomorphic sub-type of Epithelioid should be classified as Sarcomatoid, rather than as a subtype of Epithelioid mesothelioma.

Previously, the existence of the Pleomorphic sub type of Epithelioid mesothelioma had been identified in ten male patients aged 61 – 74 years in the US from a review of 640 mesothelioma cases. While they all received varying combinations of chemotherapy, surgery and chemotherapy at different times, six of the seven patients died of recurrent disease 3 to 7 months after diagnosis.

More than 2,500 people now lose their lives to mesothelioma every year – up by more than 10 per cent since 2011 – according to the latest available figures from Health & Safety Executive, Annual Report, 2014.