Introduction
It is unknown if gastric bypass surgery for obesity increases the risk and delays the diagnosis of adenocarcinoma in the excluded stomach. This study aimed to help clarify this question.
Aims & Methods
This multinational and population-based cohort study included patients who underwent bariatric surgery in Denmark (between 1996-2019), Finland (1997-2019), or Sweden (1980-2019). Data came from complete nationwide registers for diagnoses and surgery, cancer and death. The risk of developing gastric non-cardia adenocarcinoma was analyzed in two ways: (1) comparing gastric bypass with other bariatric procedures using Cox regression, providing hazard ratios (HR) with 95% confidence intervals (CI), adjusted for age, sex, comorbidity, smoking, alcohol abuse, country, and calendar year, and (2) comparing gastric bypass with the background population of the corresponding age, sex, calendar year, and country by calculating standardized incidence ratios (SIR) with 95% CI. Differences in gastrectomy rates among those who developed gastric non-cardia adenocarcinoma (indicating early and curable tumor stage) between gastric bypass and other bariatric procedures were analyzed using logistic regression, providing odds ratios (OR) with 95% CI, adjusted for confounders.
Results
Among 98,881 patients who underwent bariatric surgery (mean age 42 years, 76% women) 31 (0.03%) developed gastric non-cardia adenocarcinoma during up to 40 years of follow-up. Gastric bypass (n=76,446; 77.3%) was associated with an increased risk of gastric non-cardia adenocarcinoma between 10-40 years after surgery (HR 5.5, 95% CI 1.5-19.8; SIR 2.5, 95% CI 0.8-5.4), but not within the first 1-9 years (HR 0.8, 95% CI 0.1-4.2; SIR 0.9, 95% CI 0.5-1.6). The gastrectomy rate was seemingly decreased after gastric bypass (OR 0.2, 95% CI <0.1-1.0).
Bariatric procedure
| Cohort
| Observed cases
| Expected cases
| SIR* (95% CI)
| Adjusted HR** (95% CI)
|
|---|
Follow-up year 1-40
|
Other bariatric surgery
| 22,435
| 13 | 12.3 | 1.1 (0.6-1.8)
| 1.0 (reference)
|
Gastric bypass surgery
| 76,446
| 18 | 15.3 | 1.2 (0.7-1.9)
| 2.3 (0.6-9.7)
|
Follow-up year 1-9
|
Other bariatric surgery
| 22,435
| 6 | 4.6 | 1.3 (0.5-2.8)
| 1.0 (reference)
|
Gastric bypass surgery
| 76,446
| 12 | 12.9 | 0.9 (0.5-1.6)
| 0.8 (0.1-4.2)
|
Follow-up year 10-40
|
Other bariatric surgery
| 9,705
| 7 | 7.7 | 0.9 (0.4-1.9)
| 1.0 (reference)
|
Gastric bypass surgery
| 19,233
| 6 | 2.4 | 2.5 (0.9-5.4)
| 5.5 (1.5-19.8)
|
* Adjusted for age, sex, calendar year, and country.
** Adjusted for age, sex, comorbidity, tobacco-related diseases, alcohol-related diseases, country, and calendar year.
Conclusion
Gastric bypass may be associated with an increased risk and a delayed diagnosis of gastric non-cardia adenocarcinoma in the excluded stomach. Yet, this cancer is rare after bariatric surgery.