For ovarian cancer, there was modest market concentration to the highest volume hospitals over the years of study. The percentage of patients who underwent surgery at the highest quartile by volume hospitals increased from 62.9% in 2000–2001, to 63.8% in 2002–2003, to 64.1% in 2004–2005, and to 69.0% in 2006–2007 (P=.01). The analysis was then limited to the highest decile by volume hospitals. In 2000–2001, 37.8% (n=467) of patients were treated at the 35 highest decile by volume hospitals compared with 41.4% (n=453) of women who underwent surgery at the 33 highest volume centers in 2006–2007 (P=.14).
The percentage of women treated at hospitals that performed one procedure per time period was 47.5% in 2000–2001, 48.0% in 2002–2003, 48.5% in 2004–2005, and 45.3% in 2006–2007 (P=.85). Among women with advanced-stage ovarian cancer, similar trends were noted, mean volume increased from 2.7 to 3.2 (P=.39), whereas median volume increased from one to two cases (P=.40).
Our findings suggest that, for women with ovarian and uterine cancer, public health initiatives to promote volume concentration have had a minimal effect in elderly women. Over the last decade, we noted modest market concentration with a small increase in the number of patients referred to high-volume hospitals. A large number of women with gynecologic cancers are still treated at very low-volume centers.
A number of reports have suggested that several high-risk or technically complex operations, particularly oncologic procedures, have been increasingly regionalized to high-volume centers.8,10,11,21–25 A study of Medicare beneficiaries who underwent cancer resections or cardiovascular surgery noted increases in hospital volume for all four of the oncologic procedures studied (esophagectomy, pancreatectomy, lung resection, and cystectomy). The median hospital volume for cystectomy increased from five procedures in 1999–2000 to 10 procedures in 2007–2008, whereas the median pancreatectomy volume more than tripled from five to 16 cases over the same time period. The underlying cause for the increased hospital volume was accounted for by both volume creep and market concentration. For example, for esophagectomy, the number of patients who underwent the procedure remained relatively constant but the number of hospitals that performed the procedure declined; in contrast, for pancreatectomy, not only did the number of hospitals performing the procedure decline, but the number of patients undergoing the procedure increased by more than 50%.8
Studies examining regionalization of care for gynecologic cancers have been limited.26–28 A report that analyzed referral patterns in Maryland found an increase in treatment at high-volume hospitals and by high-volume surgeons for women with ovarian cancer in 2001–2008 compared with those treated in the 1990s.27 Similar data were noted in a report from Norway.28 Our findings were clearly more modest; we found no change in the median number of ovarian cancer procedures and a small increase in hospital procedural volume for endometrial cancer.
The goal of regionalization of care is to reduce perioperative mortality and several reports have suggested that this is, in fact, feasible for some procedures.8,9,22,29 A study examining trends in operative mortality suggested that increased procedural volume for six cancer operations was associated with a reduction in inpatient mortality ranging from 0.1% to 2.3%.9 The report by Finks and colleagues8 of Medicare recipients described previously found that increased hospital volume was directly associated with a 32% reduction in mortality for esophagectomy, a 37% reduction in the risk of death for cystectomy, and a 67% reduction in death after pancreatectomy. A population-based analysis from Norway that examined centralization of the care of patients with ovarian cancer to a teaching hospital reported improved survival after centralization.29 A priori, the goal of our study was to assess whether changing referral patterns were associated with reductions in mortality for gynecologic cancer; however, the minimal change in hospital volume precluded examination of mortality.
Regionalization of care tends to be most pronounced for those procedures with the strongest correlation between volume and outcome. Compared with other cancer resections, the association between volume and outcome for gynecologic tumors has been weaker.12–17 A report of elderly women with ovarian cancer found that high hospital procedural volume was associated with a small decrease in 2-year mortality but had no effect on overall survival.13 Similarly, an analysis of women undergoing abdominal hysterectomy for endometrial cancer found that, although patients treated by high-volume physicians had decreased perioperative morbidity, hospital volume had no effect on complications; neither hospital nor surgeon volume was associated with perioperative mortality.12 The limited change in hospital referral patterns we noted may stem, at least in part, from the modest effect of volume on outcome for gynecologic cancer surgery.
Although the effect of procedural volume on outcome for gynecologic cancers is relatively small, the specialty of the surgeon appears to have an important influence on survival for both endometrial and ovarian cancer.30–34 A population-based analysis of women with ovarian cancer found higher rates of tumor cytoreduction for advanced-stage disease, a higher rate of receipt of chemotherapy, and improved survival for patients treated by gynecologic oncologists compared with general gynecologists or surgeons.30 Similarly, Chan and coworkers31 found that treatment by a gynecologic oncologist was an independent predictor of improved survival for women with endometrial cancer. Referral based on physician specialty and not hospital volume may, in part, underlie the minimal regionalization that we noted.
Although our study benefits from the inclusion of a large number of hospitals and patients, we recognize a number of important limitations. Foremost, our data represent relative and not absolute changes in volume. Our data set did not include patients younger than 65 years age, non–Medicare recipients, or patients treated outside of the SEER registries studied. Although our data are a proxy for overall hospital volume, prior work has shown a high correlation between volume calculated using SEER–Medicare data and the actual rank order of hospitals based on volume.35 We did not examine how physician volume and physician characteristics influence referral patterns. Given the importance of physician characteristics in the treatment of gynecologic cancer, this clearly warrants further investigation. We only analyzed data from 2000 to 2007 and cannot exclude the possibility that regionalization may have occurred before that time. Finally, within each cohort, patients often underwent ancillary procedures such as lymphadenectomy or extended cytoreductive procedures. To limit this bias, separate analyses were performed for early and advanced-stage patients for both primary tumor sites.
Should regionalization of care for gynecologic malignancies be encouraged? Although regionalization may be attractive, it is often difficult to implement.36–39 Referral to high-volume centers is often met with resistance by both patients and health care providers, leads to disparities in which minorities and the underinsured are less likely to receive referral to a high-volume center, and is problematic in many regions that lack high-volume facilities.36–39 Furthermore, for lower-risk patients undergoing high-risk surgery, the benefits of volume-based referral are questionable; it appears that the greatest benefits are derived in the highest risk patient population undergoing the highest risk surgeries.40 Given these difficulties, some authors have suggested that regionalization should primarily be encouraged for high morbidity procedures with strong volume–outcome relationships like pancreatectomy and esophagectomy.8 Given the modest association between volume and survival for gynecologic cancer, it is difficult to endorse volume-based referral, and our data suggest that, to date, there has been minimal regionalization. For gynecologic cancer, it would appear that initiatives to promote referral to gynecologic oncologists would offer the greatest benefit to patients.
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