Welch is known for his research into
cancer screening. In 2012, Welch co-authored a study which found that
mammography was having little to no impact on breast cancer death rates. The study also concluded that substantial
overdiagnosis was associated with mammographic screening, "accounting for nearly a third of all newly diagnosed breast cancers." In 2014, Welch and two other researchers published a perspective piece in the
New England Journal of Medicine examining trends in
thyroid cancer incidence and mortality in
South Korea. The piece found that thyroid-cancer mortality has not changed appreciably there from 1993 to 2011, despite the rate of diagnoses for this type of cancer increasing by a factor of 15 during the same time period. In 2016, he led a study which concluded that women were more likely to be diagnosed with a small tumor that will never increase in size through mammography than they are to have a dangerous tumor detected through the practice. This 2016 study, which included two staff members of the
National Cancer Institute (Barnett Kramer and Philip Prorok), was found to have contained uncredited data from a colleague, Samir Soneji. In 2018, after a 20-month investigation, Dartmouth College determined that Welch had "engaged in research misconduct, namely, plagiarism, by knowingly, intentionally, or recklessly appropriating the ideas, processes, results or words of Complainants without giving them appropriate credit, and that these actions represented a significant departure from accepted practices of the relevant research community." Welch disputed the investigation's finding, telling
Retraction Watch that "the underlying data are publicly available — all the analyses, all the figures and all the writing in the article are my co-authors' and mine." Dartmouth College considered Welch's claims in a formal appeal process before concluding he engaged in research misconduct, specifically plagiarism. ==Views on early detection==