If he had disclosed all his conflicts, the same research would have been published in the same places with the same people. Nothing would have changed. At conferences academic oncologists get up and flash a slide with many conflicts of interest at the start of their talk. Nobody really cares or pays much attention.
When it comes to clinical trials, there are many checks and balances that prevent a 'rogue' conflicted investigator from influencing the results. Not the least of these are the other investigators on the study which put their name on the paper, who are free thinking individuals. The data is also collected and analysed by an independent data monitoring committee, who will for example stop the study early if it is looking futile, whatever the drug company thinks should happen. Independent clinical trial staff will also send out teams to hospitals running the trial and inspect the data and talk to the staff. For trials going for regulatory approval of the drug, there is often a formal independent audit which goes even deeper, to the point of interviewing staff in a confidential setting and asking them if they have been coerced for example.