In reply to Henry Chung You need a CBCT to determine the external extent of the lesion and whether it's surgically manageable. However, the location of the lesion is very bad and the prognosis is poor if you get in to do a root repair. Frankly, if no symptoms, I would recommend monitoring until the tooth become symptomatic. You can then do the endo and place a composite in the access in order to buy more time. When it breaks down periodontally then remove and replace with an implant. If the patient is adamant in trying to save then do the RCT and attempt to repair the lesion with the Putty or MTA but as I said, it would be unpredictable given the size and location of the lesion and it may expedite tooth loss. I would explain to the patient that this tooth requires palliative treatment until it's time for it to be replaced. 
Extraction is the most predictable outcome when the tooth becomes symptomatic. Good luck!