Hospital procedure volume and survival of cancer patients in Osaka, Japan: A population-based study with latest cases

Background: Recent studies reported that hospital procedure volume (i.e. volume of patients per hospital receiving a particular treatment)was directly proportional to cancer survival; however the degree of association might be different according to the primary tumor site, extent of disease and year of diagnosis. We performed a systematical examination of survivals by hospital procedure volume according to the primary site with inclusion of latest cases in Osaka,Japan. Methods: Individual data on reported cancer cases with active follow-up information and diagnosis between 1994 and 1998 were retrieved from Osaka Cancer Registry's database. The analysed primary sites included oesophagus, stomach, large bowel, liver, gall bladder, pancreas, lung, breast, uterus, ovary, prostate, bladder and lymphoma. Hospitals were ranked as high-, medium-, low- and very low-volume hospitals for every primary site by dividing the number of cancer patients who received treatment in hospitals into four quartiles. Results: The primary sites could be classified into three categories based on the association between hospital procedure volume and cancer survival: In type 1, a better survival was associated with a higher procedure volume as for oesophagus, liver, lung, ovary, prostate, or lymphoma; in type 2, a better survival was associated with a higher procedure volume but there was no significant difference in survival between high- and medium-volume hospitals as for uterus; and in type 3, there was no significant difference in survival among high-, medium- and low-volume hospitals as for stomach, large bowel, gall bladder, pancreas, breast, or bladder sites. Conclusions: A higher procedure volume was generally associated with a better survival; however, this association could be classified into three types according to the primary site.