What is the fine-grained topic of the following text: Since the Centre Charlebourg-La Defense joined in 2015 Amethyst Radiotherapy group, it had benefited from a major investment plan: 2 additional bunkers are build and a new accelerator will be installed current 2017 year. Only return the topic.
Investment and developments in the Centre Charlebourg-La Defense under the Amethyst Radiotherapy group