Table 1.
Characteristics of patients undergoing chemotherapy, N=236,304 who have 307,744 episodes; cared for by physicians in 2329 oncology practices
| Characteristic | N (%) patient episodes* | Proportion or mean (SD) Among patients not using bevacizumab | Proportion or mean (SD) among patients using bevacizumab | Adjusted Odds Ratio (95% CI) of Bevacizumab Use from Hierarchical Model | P value |
|---|---|---|---|---|---|
| Patient characteristics | |||||
|
| |||||
| Age in years, mean (SD) | 74.1 (6.1) | 74.2 (6.1) | 72.9 (5.7) | 0.98 (0.97–0.98) | <.001 |
| Sex, N (%) | |||||
| Male | 146,092 (47) | 133,601 (47) | 12,491 (48) | – | – |
| Female | 161,652 (53) | 147,990 (53) | 13,662 (52) | 0.98 (0.95–1.01) | 0.27 |
| Race/ethnicity, N (%) | |||||
| Non-Hispanic white | 277,427 (90) | 254,229 (90) | 23,198 (89) | – | – |
| Non-Hispanic black | 20,236 (7) | 18,250 (6) | 1,986 (8) | 1.10 (1.03–1.16) | 0.003 |
| Hispanic | 2,796 (1) | 2,550 (1) | 246 (1) | 1.03 (0.87–1.22) | 0.77 |
| Other/Unknown | 7,285 (2) | 6,562 (2) | 723 (3) | 1.02 (0.91–1.13) | 0.77 |
| Cancer type, N (%) | |||||
| Colorectal | 37,429 (12) | 24,032 (9) | 13,397 (51) | Reference | – |
| Lung | 69,318 (23) | 62,295 (22) | 7,023 (27) | 0.19 (0.18–0.20) | <.001 |
| Breast | 34,716 (11) | 32,466 (12) | 2,250 (9) | 0.11 (0.10–0.12) | <.001 |
| Kidney | 4,207 (1) | 3,754 (1) | 453 (2) | 0.19 (0.17–0.21) | <.001 |
| Brain | 910 (<1) | 347 (<1) | 563 (2) | 3.32 (2.78–3.98) | <.001 |
| Ovary | 14,522 (5) | 13,245 (5) | 1,277 (5) | 0.15 (0.14–0.17) | <.001 |
| Other | 146,642 (48) | 145,452 (52) | 1,190 (5) | 0.01 (0.01–0.02) | <.001 |
| Charlson comorbidity score, N (%) | |||||
| 0 | 142,558 (46) | 129,316 (46) | 13,242 (51) | Reference | – |
| 1 | 87,584 (28) | 80,122 (28) | 7,462 (29) | 0.83 (0.80–0.86) | <.001 |
| 2 | 41,574 (14) | 38,391(14) | 3,183 (12) | 0.77 (0.73–0.81) | <.001 |
| 3 | 19,154 (6) | 17,831(6) | 1,323 (5) | 0.69 (0.65–0.75) | <.001 |
| 4+ | 16,874 (5) | 15,931 (6) | 943 (4) | 0.56 (0.52–0.60) | <.001 |
| Census division, N (%) | |||||
| New England | 16,575 (5) | 15,378 (5) | 1,197 (5) | 0.74 (0.65–0.85) | <.001 |
| Mid Atlantic | 40,921 (13) | 37,645 (13) | 3,276 (13) | 0.77 (0.70–0.86) | <.001 |
| East North Central | 54,865 (18) | 50,200 (18) | 4,665 (18) | 0.84 (0.76–0.93) | <.001 |
| West North Central | 23,747 (8) | 21,817 (8) | 1,930 (7) | 0.85 (0.75–0.96) | 0.009 |
| South Atlantic | 66,650 (22) | 60,918 (22) | 5,732 (22) | 0.86 (0.78–0.95) | 0.003 |
| East South Central | 21,509 (7) | 19,627 (7) | 1,882 (7) | 0.80 (0.70–0.91) | <.001 |
| West South Central | 34,568 (11) | 31,484 (11) | 3,084 (12) | 0.91 (0.81–1.03) | 0.13 |
| Mountain | 16,485 (5) | 15,013 (5) | 1,472 (6) | 0.87 (0.75–0.99) | 0.041 |
| Pacific | 31,867 (10) | 29,010 (10) | 2,857 (11) | Reference | – |
| Median household income of zip code of residence, mean (SD) | $56,943 ($22,898) | $56,969 ($22,918) | $56,673 ($22,681) | 1.002 (1.0004–1.003)‡ | 0.007 |
| Proportion of residents in zip code living in poverty, mean (SD) | 10.1 (7.3) | 10.1 (7.3) | 10.3 (7.4) | 1.000 (0.997–1.004)¶ | 0.89 |
| Proportion of residents in zip code who graduated from high school, mean (SD) | 87.0 (8.3) | 87.1 (8.3) | 86.9 (8.5) | 1.002 (0.999–1.005)¶ | 0.28 |
| “Episodes” of chemotherapy during study period, N (%)* | |||||
| 1 | 186,245 (61) | 170,106 (60) | 16,139 (62) | – | – |
| >1 | 121,499 (39) | 111,485 (40) | 10,014 (38) | 1.07 (1.04–1.11) | <.001 |
| Metastatic cancer, N (%) | |||||
| No | 234,484 (76) | 218,492 (78) | 15,992 (61) | – | – |
| Yes | 73,260 (24) | 63,099 (22) | 10,161 (39) | 2.05 (1.98–2.12) | <.001 |
| Year of first chemotherapy episode, median (25th, 75th) | 2008 (2006, 2011) | 2009 (2006, 2011) | 2008 (2006, 2010) | 1.003 (0.995–1.012) | 0.45 |
|
| |||||
| Practice characteristics | |||||
|
| |||||
| Practice type, N (%) | |||||
| Independent | 239,001 (78) | 217,911 (77) | 21,090 (81) | Reference | – |
| Hospital-owned (non-academic) | 31,114 (10) | 28,686 (10) | 2,428 (9) | 0.82 (0.75–0.90) | <.001 |
| Academic | 37,629 (12) | 34,994 (12) | 2,635(10) | 0.84 (0.75–0.95) | 0.006 |
| Number of physicians in practice, median (25th/75th) | 17 (5,89) | 17 (5, 92) | 15 (5, 67) | Not included† | – |
| Number of oncologists in practice, median (25th/75th) | 7 (3,17) | 7 (3, 17) | 6 (3, 15) | 1.001 (0.999–1.003) | 0.54 |
| Ratio of oncologists to all physicians, median (25th/75th) | 0.77 (0.10,1.00) | 0.77 (0.10,1.00) | 0.80 (0.16, 1.00) | 1.009 (1.001–1.017) | 0.027 |
| Proportion of individuals treated in practice living in area with proportion living in poverty above the median, mean (SD) | 9.5 (12.4) | 9.5 (12.4) | 9.6 (12.4) | 0.999 (0.997–1.001)¶ | 0.30 |
*
An episode is defined as a new initiation of chemotherapy after 3 months without any chemotherapy.
†
Omitted from model because collinear with number of oncologists and ratio of oncologists to all physicians, which were both included.
‡
Reflects change per each $1000 increase above the mean.
¶
Reflects change per 10% increase above the mean.
All continuous variables are centered at the mean, so differences reflect increases per unit above the mean.