. Author manuscript; available in PMC: 2014 Dec 1.

Published in final edited form as: Surg Endosc. 2013 Aug 16;27(12):4449–4456. doi: 10.1007/s00464-013-3127-9

Table I.

Meta-Analysis Study Characteristics

Study	Design	Population	Intervention	Control	Outcome
Adams et al (2007)¹⁹	Retrospective Mean follow-up 7.1 years.	N = 15850 USA (Utah)	N = 7925 Obese patients undergoing roux-en-y gastric bypass.	N = 7925 Obese controls obtained from state registry individually matched for age, sex, BMI.	Cancer mortality. HR = 0.40 [0.25–0.65] Cox models adjusted for matching factors of age, sex, and BMI.

Sjostrom et al (2007)²⁵	Prospective Mean follow-up 10.9 years.	N = 4047 Sweden (SOS cohort)	N = 2010 Obese patients undergoing gastric band, vertical banded gastroplasty, or gastric bypass.	N = 2037 Obese controls obtained from the general population, risk-set matched on multiple (18) variables.	Cancer mortality. HR = 0.71 (all) [0.54–0.92] Univariate analyses for cancer-related mortality.

Christou et al (2008)²¹	Retrospective Follow-up of 5 years.	N = 6781 Canada (Montreal)	N = 1035 Obese patients undergoing vertical banded gastroplasty or roux-en-y gastric bypass.	N = 5746 Obese controls obtained from provincial health insurance data matched for age, gender, and diagnosis of obesity.	Relative risk of all cancer diagnoses. RR = 0.22 [0.14–0.35] Univariate analyses for relative risk of cancer over 5 years.

McCawley et al (2009)²³	Retrospective Follow-up time up to 16 years.	N = 4977 USA (Virginia)	N = 1482 Obese female patients undergoing gastric band, vertical banded gastroplasty or roux-en-y gastric bypass.	N = 3495 Obese female controls obtained from university database with diagnosis of morbid obesity, not matched to intervention group.	Change in prevalence of any cancer diagnosis in women only. 3.6% in surgical group versus 5.8% (p =0.002) in controls over a 16-year period. Univariate analyses without any matching.

Adams et al (2009)²⁰	Retrospective Mean follow-up of 12.5 years.	N = 16038 USA (Utah)	N = 6596 Obese patients undergoing roux-en-y gastric bypass.	N = 9442 Obese controls obtained from state registry individually matched for age, sex, BMI.	Incidence of all cancer diagnoses. HR = 0.76 (all) [0.65–0.89] HR = 0.73 (F) [0.62–0.87] HR = 1.02 (M) [0.69–1.52] Cox models adjusted for matching factors of age, sex, and BMI.

Sjostrom et al (2009)²⁴	Prospective Mean follow-up 10.9 years.	N = 4047 Sweden (SOS cohort)	N = 2010 Obese patients undergoing gastric band, vertical banded gastroplasty, or gastric bypass.	N = 2037 Obese controls obtained from the general population, risk-set matched on multiple (18) variables.	Incidence of all first-time cancers. HR = 0.67 (all) [0·53–0·85] HR = 0·58 (F) [0·44–0·77] HR = 0·97 (M) [0·62–1·52] Cox model adjusted for statistically significant confounders by forward stepwise selection.