Lymph node status was resolved by stratification for the unknown category only. The results reported reflect surgeon volume for longer than 10 months of follow-up; for earlier follow-up times, the volume-outcome relationship was in the same direction but larger in magnitude. Patients treated by high-volume surgeons were slightly younger, were more likely to be white, and resided in more affluent areas than those treated by low-volume surgeons. The patients of high-volume surgeons had lower levels of comorbid illness, had tumors that were on average 1 to 2 mm smaller, and were more likely to be treated in high-volume hospitals.
The relationship of surgeon and hospital volume was moderate, with a Spearman rank correlation coefficient of 0. The point was raised previously that if the extent-of-disease information is missing differentially across volume groups, then inclusion of extent-of-disease factors in the model could bias the results. During the month median follow-up, women For 99 women, no cause of death was available. In unadjusted analyses Table 2 , the difference in mortality rates between patients of high- and low-volume surgeons was The survival curve for the patients of medium-volume surgeons was within the boundaries of the high- and low-volume curves throughout the period of observation Figure.
In the Cox proportional hazards models, adjusting for patient demographic factors, extent of disease, comorbidity, and hospital volume, the relationship of surgeon volume to overall mortality was significant, with a hazard ratio of 0. However, surgeon volume was not significantly related to breast cancer mortality Table 3. The extent-of-disease factors were much more strongly related to breast cancer—specific mortality than to non—breast cancer mortality Table 3.
The level of comorbid illness had a stronger association with non—breast cancer mortality than with breast cancer mortality. The most common cause of non—breast cancer mortality was cardiovascular diseases, which accounted for the deaths of women 7. The relationship of surgeon volume of breast cancer cases to death from cardiovascular disease was quite significant, with a hazard ratio of 0.
The purpose of the propensity score analysis was to control as much as possible for selection bias inherent in observational data. As a sensitivity analysis, the models were run separately within each of the propensity groupings. The relationship of surgeon volume to breast cancer mortality was small and statistically insignificant within each stratum. The relationship of surgeon volume to other-cause mortality was consistent within each grouping, achieving statistical significance for the medium- and high-volume propensity strata.
- Relationship between surgeon volume and outcomes: a systematic review of systematic reviews.
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This finding is similar to that reported by other investigators. However, our disease-specific mortality results call that interpretation into question.
The patients of high-volume surgeons were not less likely to die of breast cancer. Rather, they were significantly less likely to die of other causes. This finding is consistent with the possibility of a nonspecific effect, perhaps selection bias, in the types of patients cared for by high-volume surgeons as an explanation for at least some of the observed surgeon volume—mortality relationship.
We observed clear differences among the patients cared for by high-, medium-, and low-volume surgeons, particularly in terms of sociodemographic characteristics and level of comorbidity. These factors, and other unmeasured factors, could be confounding the surgeon volume—outcome relationship.
The Effect of Hospital Volume on Breast Cancer Mortality
With respect to possible selection by socioeconomic status, the socioeconomic factors were available for this study only at the zip code level. Even with individual-level information, it is difficult, perhaps impossible, to control fully for socioeconomic status. In addition, 1 recent study 31 found low socioeconomic status to be associated with impaired functional capacity and worse all-cause mortality, which could explain the relationship we observed between breast cancer surgeon volume and cardiovascular mortality.
Other explanations might also exist for these findings. High-volume high-quality surgeons may refer to other high-quality physicians, accounting for the reduction in non—breast cancer mortality. Even if so, however, one would expect the surgeon volume to breast cancer mortality relationship to be at least as strong as the relationship of surgeon volume to other mortality. Another possible explanation is that the breast cancer mortality model has several specific extent-of-disease predictors, while the non—breast cancer mortality model has only a general comorbidity measure.
However, although better specification of overall mortality predictors ie, general comorbidity might reduce or eliminate the relationship of surgeon volume to other mortality, such specification would be unlikely to strengthen the surgeon volume—breast cancer mortality relationship given that the available comorbidity information shows that the low-volume surgeons care for sicker patients Table 1. Therefore, if selection bias based on comorbid illness accounts for our findings, better controlling for the factor would likely reduce the association of surgeon volume to overall mortality.
Other studies may indirectly support the possibility that selection bias could be an operative factor explaining at least some of the volume-outcome relationships described in the literature. This study raised a question of whether other differences exist in the patients served by high- vs low-volume hospitals. Another study 33 found mortality to be related not only to the volume of the same procedure but also to the hospital volume of many other procedures.
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While this finding could be because of shared process characteristics of large-volume hospitals, systematic differences in the types of patients admitted to high-volume hospitals could also account for it. With respect to breast cancer, 3 previous studies 13 - 15 have found a relationship between higher surgeon volume and better overall survival.
The survival of patients with breast cancer may be affected by other factors than surgeon quality, such as medical oncology care. In the 2 UK studies 13 , 14 that examined oncologic processes of care such as receipt of adjuvant therapy , these process measures did not explain the differential in overall survival by surgeon volume. This raises the question of what does account for the better survival of patients of high-volume surgeons.
Unmeasured improvements in the care provided by high-volume surgeons might mediate the relationship, but patient selection bias also could account for this finding. A limitation of this study is that the cause-of-death information, derived from death certificates, may be inaccurate. Problems with the accuracy of cause of death, as determined by death certificate, have been described, including poor sensitivity for some cancers.
However, the cancer extent-of-disease factors were much stronger predictors of breast cancer mortality than of other causes of death Table 3. Similarly, the comorbidity score was much more strongly predictive of overall and non—breast cancer mortality than breast cancer mortality was. These findings provide support for the validity of the coding of cause of death in this study. Also, a lack of sensitivity for breast cancer deaths would be unlikely to explain the association we observed between surgeon volume and non—breast cancer mortality.
Another limitation is that the study included only patients 65 years or older, and the surgeon volume was determined by measuring the number of operations performed on women in this age group. However, about half of all incident breast cancer cases occur in women 65 years or older, and there is no reason to believe case volume would be systematically biased by measuring it in this age group. A number of other investigators 3 , 8 have also used this approach to determining volume.
The study of Medicare patients permitted analysis of a large population-based cohort of patients and surgeons, an important strength. In summary, this study found a significant relationship between surgeon volume and non—breast cancer mortality, but not between surgeon volume and breast cancer mortality. This finding is evidence of possible selection bias, which could be based on socioeconomic status or general comorbidity. It is possible that the beneficial effect of high surgeon volume on breast cancer mortality has been overstated.
Future studies should further evaluate this possibility and rigorously consider whether selection bias could account for volume-outcome relationships for other health conditions. Author Contributions: Study concept and design : Nattinger and Laud. Acquisition of data : Nattinger.
Drafting of the manuscript : Nattinger and Laud. Critical revision of the manuscript for important intellectual content : Nattinger, Laud, Sparapani, Zhang, Neuner, and Gilligan. Statistical analysis : Laud, Sparapani, and Zhang. Obtained funding : Nattinger. Study supervision : Nattinger and Laud.
Role of the Sponsor: The funding bodies had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript. Additional Contributions: James S. All Rights Reserved. View Large Download.
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Table 1. Accessed November 17, Socioeconomic status in health research: one size does not fit all.
Association of hospital procedure volume and outcomes in patients with colon cancer at high risk for recurrence. PubMed Google Scholar Crossref. It assesses the status of professional education and training and applied clinical and health services research and proposes policies to improve the quality of care and quality of life for women with breast cancer and their families.
Because cancer of the breast is likely a good model for cancer at other sites, recommendations for this cancer should be applicable to the psychosocial care provided generally to individuals with cancer. For breast cancer, and indeed probably for any cancer, the report finds that psychosocial services can provide significant benefits in quality of life and success in coping with serious and life-threatening disease for patients and their families. Passar bra ihop. Bloggat om Meeting Psychosocial Needs of Women with
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