A new type of immunotherapy drug, Pembrolizumab (also known by its brand name Keytruda) has shown significant effectiveness in the treatment of malignant pleural mesothelioma.
The treatment is not currently available to mesothelioma sufferers through the NHS but funding for the treatment can pursued as part of a personal injury claim by those mesothelioma sufferers seeking compensation due to asbestos exposure.
What is Pembrolizumab and how does it work?
Pembrolizumab is an immune checkpoint inhibitor. It is designed to enhance the body’s natural defences against tumours. It achieves this by blocking a protein on the surface of the T-cells called PD-1. Blocking PD-1 allows the T-cells to recognise cancer cells as a threat and kill them.
The treatment, as will be seen in the summary of clinical trials below, is thought to be more effective in patients whose tumours are PD-L1 positive. PD-L1 is a protein found on the surface of cancer cells. However, on current evidence, negativity for PD-L1 should not preclude use of the treatment.
Clinical Trials of Pembrolizumab
A 2017 study published by Dr Evan Alley looked at the effect of Pembrolizumab treatment in 25 mesothelioma patients who had previously received chemotherapy and who were experiencing disease progression when they joined the trial.
The drug was administered to the patients every two weeks, in some cases for up to two years. 14 of the 25 patients experienced initial tumour reduction during treatment. Median progression free survival was 5.4 months. Median overall survival was 18 months. 4 patients lived for more than two years from the trial start date.
This initial study included only patients whose tumours were PD-L1 positive. A subsequent study in Australia (Rivalland et al) showed response in 2 of 9 patients who were PD-L1 negative and in 2 of 5 patients who were PD-L1 positive. An American study (Kindler et al) reported a numerically higher response rate in patients with PD-L1 positive tumours (27%) than PD-L1 negative tumours (12%). Based on the current evidence, patients whose tumours are PD-L1 negative are less likely to show a favourable response but negativity for this protein should not automatically preclude treatment.
How and when is Pembrolizumab administered?
Pembrolizumab is a second line treatment, to be administered once the patient shows signs of a progressive disease after chemotherapy treatment has been exhausted.
The treatment is administered intravenously every three weeks. Initially clinical assessments before treatment will be used to assess progress, with scans taking place usually after 4 treatments. Treatment continues if the patient’s clinical status is stable or improving and if scans show no progression of the disease.
CT scans are the usual method of radiological assessment in mesothelioma cases but PET scans are recommended as they may show additional information; serial PET scans can show increases or decreases of metabolic activity, providing further insight into the effectiveness of the treatment.
How can patients access the immunotherapy drug treatment?
Pembrolizumab treatment for mesothelioma patients is not available on the NHS and so it must be funded privately. Unfortunately, as can be seen from the funding outline below, the treatment is very expensive:
Estimated costs for 2 cycles of treatment: £61,500
Cycle 1
- Oncologist an clinic fees and blood tests & scans providing baseline measure of mesothelioma activity: £3,000
- Four doses of Pembrolizumab at approximately £7,000 per dose: £28,000
Cycle 2
- CT Scan or PET scan to assess treatment outcomes: £2,500
- Four further doses of Pembrolizumab: £28,000
The fact is very few mesothelioma patients will be able to afford the treatment. However, for those patients pursuing a personal injury claim due to asbestos exposure, it is possible to seek the costs of the treatment to be included in the amount of compensation payable. As part of the compensation process, expert medical evidence will be sought. If this supports eligibility for treatment then the costs can be claimed for as long as the treatment is shown to be effective.
Access to this breakthrough treatment is therefore, for the majority of mesothelioma sufferers, intrinsically linked to recovering compensation because otherwise the treatment cannot be paid for.