Eleven studies (n=18,031 patients, number taken from table one), including four prospective studies and six retrospective studies, met the inclusion criteria, but only 10 were included in the meta-analysis. All studies were judged to be representative of rectal cancer patients. The adequacy of follow-up was satisfactory in 10 studies. The ascertainment of surgeon case-load volume was satisfactory in seven studies. Comparability of volume groups was satisfactory in five studies. Four studies fulfilled five of the six assessment criteria.
Patients treated by the surgeons with high case-load volume had a significantly lower 30-day postoperative mortality rate (unadjusted OR 0.57, 95% CI 0.43 to 0.77; three studies; n=4809 patients) than those treated by surgeons with a lower case-load volume.
Patients had an increase in overall survival (unadjusted HR 0.75, 95% CI 0.65 to 0.86; two studies; n=2,917 patients) when treated by high case-load volume surgeons compared with lower case-load volume surgeons.
Patients treated by high case-load volume surgeons had a lower rate of permanent stoma formation (adjusted OR 0.75, 95% CI 0.64 to 0.88; two studies; n=9,685 patients) and a lower rate for abdominoperineal excision of the rectum (unadjusted OR 0.58, 95% CI 0.45 to 0.76; six studies; n=3,921 patients) compared with those treated by lower case-load volume surgeons.
The findings did not change when one study was removed as it included patients with rectosigmoid cancers. However, there was no significant difference between the two surgeon groups when only adjusted analyses were pooled for 30-day or post-operative survival (two studies).
There was no significant difference between high and low case-load volume surgeons groups for anastomotic leak rate. The level of heterogeneity was low in most cases, with the exception of two small studies which showed a large benefit for high case-load volume surgeons.
There was no evidence of publication bias.