The durability of previous examinations for cancer: Danish nationwide cohort study

Abstract

Objective

Patients previously examined for cancer with a negative result may present in general practice with ongoing or new symptoms or signs suggestive of cancer. This paper explores the potential existence of a relatively safe period for cancer occurrence after receiving negative examination results for specific types of cancer, including lung (CT thorax), upper gastrointestinal (gastroscopy), colorectal (colonoscopy), bladder (cystoscopy), and breast (clinical mammography).

Design

Register-based time-to-event analyses.

Setting

Denmark.

Subjects

All 3.3 million citizens aged 30–85 years who on January first, 2017, had not previously been diagnosed with the specific type of cancer were categorized based on the time since their most recent examination.

Main outcome measures

Using 1-year follow-up, we calculated the age- and sex-adjusted hazard ratios of being diagnosed with the related cancer, with non-examined individuals as reference. Negative examination results were defined as the absence of a cancer diagnosis within 6 months following the examination.

Results

Previous negative examination results were common, also among those diagnosed with cancer during follow-up. For 10 years after a negative colonoscopy the risk of diagnosing a colorectal cancer was nearly halved. However, already 1 year after a clinical mammography and 2 years after a CT thorax the risk of diagnosing the related cancers was significantly higher among those with a previous negative result compared to non-examined individuals.

Conclusion

This study did not identify a post-examination period in which the cancer risk, compared to non-examined individuals, was sufficiently low to confidently rule out any of the investigated cancers.

KEY POINTS

What should one expect when considering re-examining a patient with a negative result of a previous examination for cancer? We found that previous negative examination results are common in the general population and among those subsequently diagnosed with cancer. We did not find a safe period after any of the examinations in which a negative result alone could safely rule out the presence of cancer.

Keywords:

• (MeSH): Early Detection of Cancer
• Diagnostic Imaging
• Endoscopy
• Epidemiology
• Reproducibility of results
• General practice

Authors contribution

JL, SW, and DEJ designed the study. JL, JKO, and SW conducted the analyses. JL wrote the main manuscript text. JL and JKO prepared the figures and tables. All authors interpreted the findings and reviewed the manuscript.

Ethical approval

The study was performed in accordance with the Declaration of Helsinki. According to Danish law, ethics committee approvals and informed consents are not required for solely register-based studies (laws No. 593 14/06/2011 and 502 23/05/2018). Data were anonymized to the authors making any identification of individuals impossible. The study was approved by the Danish Data Protection Agency (jf.nr 10.148).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data supporting the findings of this study was used under a license granted specifically for the current study and therefore is not publicly available according to the data protection regulations of Danish Data Protection Agency, Statistics Denmark and the Danish Health and Medicines Authority.

Additional information

Funding

The study was funded by a grant from the region of Southern Denmark, Grant number 18/18056.