Table 4.
Poisson regression models assessing characteristics associated with specialty physicians who refer or enroll a higher volume of patients in clinical trials (N = 857)*
| Characteristic | Medical and radiation oncologists (n = 582) |
Surgeons (n = 275) |
||
| Adjusted CR (95% CI) | P† | Adjusted CR (95% CI) | P† | |
| Physicians | ||||
| Specialty | ||||
| Medical oncology | 1.27 (1.16 to 1.38) | <.001 | — | .007 |
| Radiation oncology | 1.00 (referent) | — | ||
| General surgery | — | 1.00 (referent) | ||
| Colorectal surgery | — | 1.01 (0.83 to 1.24) | ||
| Thoracic surgery | — | 1.48 (1.25 to 1.76) | ||
| Surgical oncology | — | 1.74 (1.48 to 2.06) | ||
| Other surgical subspecialty | — | 1.60 (1.22 to 2.09) | ||
| Age, y | ||||
| <50 | 1.14 (1.04 to 1.26) | .066 | 0.82 (0.70 to 0.95) | .040 |
| 50–59 | 1.12 (1.01 to 1.23) | 0.75 (0.64 to 0.88) | ||
| ≥60 | 1.00 (referent) | 1.00 (referent) | ||
| Sex | ||||
| Male | 1.00 (referent) | .749 | 1.00 (referent) | .029 |
| Female | 0.99 (0.94 to 1.05) | 1.33 (1.10 to 1.61) | ||
| US or Canadian medical school graduate | ||||
| Yes | 1.00 (referent) | .019 | 1.00 (referent) | .502 |
| No | 0.91 (0.86 to 0.97) | 0.93 (0.74 to 1.16) | ||
| Practice setting | ||||
| Income increases as a result of enrolling patients on clinical trials | ||||
| Yes | 1.20 (1.12 to 1.30) | .001 | 1.38 (1.08 to 1.75) | .050 |
| No | 1.00 (referent) | 1.00 (referent) | ||
| Practice type | ||||
| Office based, solo | 0.91 (0.79 to 1.06) | .038 | 0.82 (0.63 to 1.08) | .162 |
| Office based, group‡ | 1.08 (1.01 to 1.16) | 1.12 (0.98 to 1.29) | ||
| Hospital based | 1.00 (referent) | 1.00 (referent) | ||
| Practice size, No. of physicians | ||||
| 1–5 | 1.00 (referent) | .035 | 1.00 (referent) | .112 |
| 6–10 | 0.98 (0.91 to 1.06) | 0.79 (0.67 to 0.92) | ||
| 11–20 | 1.13 (1.05 to 1.22) | 0.92 (0.78 to 1.07) | ||
| >20 | 1.03 (0.94 to 1.13) | 0.93 (0.81 to 1.07) | ||
| Study site | ||||
| Five large HMOs§ | 1.00 (referent) | .020 | 1.00 (referent) | .065 |
| Northern California Counties | 0.90 (0.82 to 0.99) | 1.14 (0.93 to 1.38) | ||
| Los Angeles County | 0.96 (0.86 to 1.08) | 1.00 (0.78 to 1.27) | ||
| State of Alabama | 1.15 (1.02 to 1.29) | 0.98 (0.80 to 1.19) | ||
| State of Iowa | 1.05 (0.94 to 1.18) | 1.64 (1.31 to 2.06) | ||
| State of North Carolina | 0.98 (0.87 to 1.09) | 1.26 (1.01 to 1.56) | ||
| Veteran’s Administration | 0.99 (0.88 to 1.11) | 1.02 (0.85 to 1.23) | ||
| Practice affiliated with a CCOP | ||||
| Yes | 0.96 (0.91 to 1.02) | .225 | 1.02 (0.92 to 1.13) | .732 |
| No | 1.00 (referent) | 1.00 (referent) | ||
| Practice affiliated with an NCI-designated cancer center | ||||
| Yes | 1.30 (1.21 to 1.39) | <.001 | 1.26 (1.11 to 1.42) | .013 |
| No | 1.00 (referent) | 1.00 (referent) | ||
| Physician practice style | ||||
| Percentage of patients in managed care, quartiles | ||||
| 0–20 | 1.04 (0.95 to 1.14) | .047 | 0.94 (0.74 to 1.19) | .140 |
| 21–49 | 1.13 (1.03 to 1.25) | 0.93 (0.74 to 1.16) | ||
| 50–78 | 1.03 (0.88 to 1.20) | 1.12 (0.94 to 1.34) | ||
| 79–100 | 1.00 (referent) | 1.00 (referent) | ||
| Teaches medical students and/or residents | ||||
| Yes | 1.12 (1.06 to 1.19) | .004 | 1.20 (1.05 to 1.36) | .040 |
| No | 1.00 (referent) | 1.00 (referent) | ||
| Attends tumor board meetings | ||||
| Weekly | 1.15 (1.01 to 1.31) | <.001 | 1.42 (0.82 to 2.44) | .012 |
| Monthly | 0.91 (0.79 to 1.06) | 1.07 (0.55 to 2.07) | ||
| Quarterly or less frequently | 1.00 (referent) | 1.00 (referent) | ||
| No. of colorectal or lung cancer patients seen per month | ||||
| <5 | 1.00 (referent) | <.001 | 1.00 (referent) | .035 |
| 5–9 | 0.93 (0.82 to 1.06) | 1.00 (0.84 to 1.19) | ||
| 10–19 | 0.91 (0.80 to 1.02) | 0.94 (0.83 to 1.07) | ||
| ≥20 | 1.22 (1.12 to 1.34) | 1.29 (1.12 to 1.49) | ||
| Time spent with a newly diagnosed cancer patient, min | ||||
| <60 | 1.00 (referent) | .031 | 1.00 | .099 |
| ≥60 | 1.08 (1.02 to 1.15) | .031 | 0.88 (0.78 to 1.00) | |
| Type of trial participation | ||||
| Pharmaceutical and cooperative groups | 1.00 (referent) | <.001 | 1.00 (referent) | <.001 |
| Pharmaceutical only or cooperative groups only | 0.57 (0.52 to 0.63) | 0.61 (0.55 to 0.67) | ||
| Unknown | 0.63 (0.50 to 0.78) | 0.67 (0.54 to 0.83) | ||
*
— = not applicable; CCOP = Community Clinical Oncology Program; CI = confidence interval; CR = count ratio (the expected number of patients referred or enrolled for the group of interest divided by the expected number for the reference group); HMO = health maintenance organization; NCI = National Cancer Institute.
†
Based on an overall Wald χ2 test for association obtained from the Poisson regression models.
‡
Includes office-based HMO, community health center, and other (a questionnaire item).
§
Group Health Cooperative of Puget Sound, Harvard Pilgrim Health Care, Henry Ford Health System, Kaiser Permanente Northwest, and Kaiser Permanente Hawaii.