Hi there my dad was diagnosed with this in August and the options for him were Radiotherapy (which he had for 3 days) and about 3 weeks after that he had his left lung removed so after he has recovered from this he will have to have some more radiotherapy and the chemotherapy due to a shadow on his heart but all i can say is that everyone is different, so as for the best treatment it will be chose by your grandfathers specialist.
Hope this helps!!

Treatments for mesothelioma are based on the stage of the disease and the patient’s age and general health.
The most common treatments are surgery, radiation, and chemotherapy. Multimodality therapy, the combination of surgery, radiation, and/or chemotherapy, is a common therapeutic approach for early stage mesothelioma. Trimodality therapy, in which all three of these modalities are used, is considered the most effective aggressive approach.

Get Mesothelioma Information here:
www.mesoaid.com

Hope this will help you.