In contrast to the Potosky study, no difference in the use of breast conserving surgery was found among women with HMO versus FFS insurance in a recent study conducted in Massachusetts and Minnesota (Guadagnoli et al., 1998). Guadagnoli and colleagues examined the medical records of women diagnosed with breast cancer from 1993 to 1995 cared for in a random sample of hospitals in Massachusetts and a convenience sample of hospitals in Minnesota. Among 2,135 women eligible for breast conserving surgery, 74 percent of women in Massachusetts and 48 percent of women in Minnesota underwent BCS. Investigators examined correlates of BCS and mastectomy use including sociodemographic characteristics of women (age, education, household income, urban residence), insurance status (HMO or non-HMO), characteristics of the surgeon (gender, board certification, years since graduation), and hospital characteristics (teaching status, bed size, presence of American College of Surgeons-approved cancer program, presence of a radiation facility). According to multivariate analyses, women in Massachusetts cared for in a teaching hospital were twice as likely as other women to undergo BCS (odds ratio [OR] = 2.4; C.I. 1.3-4.6). In Minnesota, younger women and residents of urban areas were more likely than others to undergo BCS. The absence of an HMO effect in Massachusetts and Minnesota in this study, in contrast to the Potosky findings, could be due to a number of factors, including the use of more recent data (1993-1995 versus 1985-1992) or the difference in managed care providers in Massachusetts and Minnesota relative to California and Washington. Unadjusted HMO versus non-HMO BCS rates were not reported for Massachusetts and Minnesota, so one cannot tell if an HMO advantage is apparent when provider and hospital characteristics are left out of the model. The Potosky finding of an HMO advantage could hypothetically be related to hospital teaching status or to other hospital or provider characteristics that were not considered in their analyses.

TABLE 5.13

Outcome and Process Odds Ratios for HMO versus FFS Care for Elderly Women with Breast Cancer (in situ, Stages I and II), by Location

End Point

San Francisco-Oakland

Seattle-Puget Sound

Outcome

10-year overall survivala

0.70 (0.62-0.79)b

0.86 (0.72-1.03)

10-year breast cancer survivala

0.71 (0.59-0.87)

1.01 (0.77-1.33)

Process

BCS

1.55 (1.35-1.77)c

3.39 (2.76-4.17)

XRT post-BCSd

2.49 (1.95-3.19)

4.62 (3.20-6.66)

NOTE: Reference group is FFS care. Outcome odds ratios less than 1 indicate greater survival, and process odds ratios greater than 1 indicate more frequent desired care.

a Adjusted for age, race, census tract education and income, comorbidity, and stage.

b Odds ratio of <l.0 means that women in HMOs were less likely to die than women in FFS.

c Odds ratio of >l.0 means that women in HMOs were more likely to receive the treatment than women in FFS.

d XRT post-BCS: x-ray therapy after breast conserving surgery.

SOURCE: Potosky et al. (1997).



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