The exact reasons for the better outcomes are unclear, according to an article in the current issue of the British Journal of Surgery, but the correlation between high volume and better outcomes, especially in pancreatic, esophageal, gastric and rectal cancers, was consistent across most studies.
"All studies showed either an inverse relationship, of variable magnitude, between provider volume and mortality," according to authors S.D. Killeen and colleagues of the Cork University Hospital and University College in Ireland. "The majority of clinical studies revealed a statistically significant correlation between volume and outcome; no study demonstrated the opposite relationship."
The authors point out that the results make a good argument for centralizing cancer and possibly other treatments to high-volume medical centers. "Present findings support volume-based referral initiatives," they write. "Centralization of most, if not all, oncological procedures now seems appropriate."
The current review included 41 studies from 1984 to 2004. Because studies varied, no exact definition of low volume versus high volume for either providers or hospitals was established. Some studies measured hospital volume only, some provider volume only, and some both. Low-volume hospitals ranged from one case per year to fewer than 22 per year for a single procedure. Surgeons considered low-volume providers had rates varying from two, five, or 13 cases per year.
The measurement of success or failure was fairly was consistent across studies--thirty-day or inpatient mortality was the primary outcome used. However, authors note that the variability of criteria made interpreting the results difficult. "A note of caution is advisable before advocating policy changes based solely on currently
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