JACS study finds gaps in SEER registry data

A new Journal of the American College of Surgeons study is a reminder that “population-based” cancer data is only as complete as the records that make it into the registry. Researchers found that missing information in the National Cancer Institute’s SEER database was more common among patients treated outside American College of Surgeons Commission on Cancer-accredited centers, especially in settings such as community hospitals, safety-net hospitals and rural medical centers. (facs.org) The authors said that matters because many SEER-based studies exclude incomplete cases. When that happens, the patients most likely to drop out of the analysis are also those with worse outcomes, making survival results look better than they are. (facs.org) (seer.cancer.gov) ### What did the study actually examine? McKenzie J. White and co-authors examined SEER records for 328,030 patients with breast, pancreatic, colon or non-small cell lung cancer diagnosed from 2018 to 2020. They compared how often records were missing data based on whether treatment occurred at a Commission on Cancer-accredited center or a non-accredited center. (facs.org) SEER is one of the main U.S. cancer surveillance resources and covers about half of the U.S. population across 18 population-based registries in 22 geographic regions, according to the National Cancer Institute and the American College of Surgeons. ### Where were the biggest gaps? (facs.org) Across all four cancers, non-CoC centers had higher rates of missing data than CoC-accredited centers. The gap was 23% versus 9% for breast cancer, 36% versus 14% for pancreatic cancer, 30% versus 13% for colon cancer, and 42% versus 13% for non-small cell lung cancer. The American College of Surgeons said patients treated at non-CoC centers were more than two to three times more likely to have missing data in SEER than patients treated at accredited facilities. (facs.org) The group said those patients were more likely to be treated in community hospitals, safety-net hospitals and rural medical centers. (seer.cancer.gov) ### Why does missing data change the picture? Patients with missing data had worse three-year overall survival in every cancer type the researchers studied. The survival rates were 63% versus 81% for breast cancer, 5% versus 12% for pancreatic cancer, 43% versus 61% for colon cancer, and 17% versus 27% for non-small cell lung cancer, with p values below 0.001 for all comparisons. (facs.org) Schelomo Marmor, the study’s senior author and a professor at the University of Minnesota, said the missing cases create “blind spots” in the data. He said patients with missing data were “a high-risk, underserved population that effectively disappears from the scientific record every time a study excludes incomplete cases.” (facs.org) ### Does this mean SEER is unusable? The study did not say SEER should be abandoned. The National Cancer Institute describes SEER as a core source for incidence, survival and population-based cancer statistics, and the authors’ point was narrower: researchers need to be more careful about how they handle incomplete records. The American College of Surgeons said the authors suggested using multiple data sources, including SEER and the National Cancer Database, when possible. (facs.org) That recommendation is aimed at reducing the risk that analyses reflect registry completeness rather than the full population of patients with cancer. ### What happens next for researchers using SEER? The practical next step is methodological. (facs.org) Future SEER-based studies will need to state more clearly how missing records were handled and whether excluded cases were concentrated in non-accredited, rural or safety-net settings, based on the findings reported by White and colleagues. (seer.cancer.gov) The National Cancer Institute’s SEER program released updated research data on April 22, 2026, through its Data & Software portal, where researchers can access the incidence files and documentation used for population-based cancer analyses. (seer.cancer.gov) (facs.org 1) (facs.org 2)