Table 3.
Proportional hazards regression: Predictors of adjusted subsequent mastectomy risk (N=35,947)
| HR | 95% CI | P value | |
|---|---|---|---|
| Treatment factors | |||
| For invasive cancers, type of radiation* | |||
| Lumpectomy alone | 1 | — | — |
| Brachytherapy | 0.61 | 0.40–0.94 | .02 |
| EBRT | 0.22 | 0.18–0.28 | <.001 |
| For DCIS, type of radiation* | |||
| Lumpectomy alone | 1 | — | — |
| Brachytherapy | 1.18 | 0.51–2.73 | .71 |
| EBRT | 0.40 | 0.28–0.55 | <.001 |
| Receipt of chemotherapy | |||
| No | 1 | — | — |
| Yes | 1.00 | 0.78–1.27 | .98 |
| Patient factors | |||
| Age | |||
| 66–69 y | 1 | — | — |
| 70–74 y | 0.82 | 0.66–1.03 | .08 |
| 75–79 y | 0.84 | 0.67–1.05 | .13 |
| ≥80 y | 0.68 | 0.54–0.85 | .001 |
| Race | |||
| White | 1 | — | — |
| Black | 1.37 | 1.03–1.82 | .03 |
| Other/unknown | 0.66 | 0.41–1.06 | .08 |
| Charlson Comorbidity score | |||
| 0 | 1 | — | — |
| 1 | 1.11 | 0.92–1.34 | .28 |
| ≥2 | 1.21 | 0.97–1.52 | .10 |
| Year of diagnosis | |||
| 2002 | 1 | — | — |
| 2003 | 0.95 | 0.75–1.20 | .66 |
| 2004 | 0.99 | 0.77–1.27 | .94 |
| 2005 | 1.08 | 0.83–1.40 | .57 |
| 2006 | 0.99 | 0.74–1.33 | .96 |
| 2007 | 1.19 | 0.86–1.66 | .30 |
| Tumor factors | |||
| Size | |||
| 0–2.0 cm | 1 | — | — |
| 2.1–5.0 cm | 1.30 | 1.06–1.59 | .01 |
| >5 cm | 2.14 | 1.28–3.56 | .004 |
| Unknown | 1.22 | 0.93–1.61 | .14 |
| T4 involvement | |||
| No | 1 | — | — |
| Yes | 1.65 | 1.10–2.48 | .02 |
| Nodal status | |||
| Pathologic N0 | 1 | — | — |
| Clinical N0 | 0.90 | 0.70–1.16 | .40 |
| Pathologic N+ | 1.26 | 0.98–1.61 | .08 |
| Unknown | 0.83 | 0.54–1.29 | .41 |
| Estrogen receptor status | |||
| Positive | 1 | — | — |
| Negative or borderline | 2.65 | 2.15–3.26 | <.001 |
| Unknown | 1.14 | 0.91–1.44 | .25 |
| Grade | |||
| Low/intermediate grade | 1 | — | — |
| High grade | 1.63 | 1.36–1.96 | <.001 |
| Missing | 1.15 | 0.88–1.51 | .31 |
| Tumor behavior in lumpectomy-alone patients | |||
| DCIS | 1 | — | — |
| Invasive cancer | 1.35 | 0.82–2.21 | .24 |
| Tumor behavior in brachytherapy patients | |||
| DCIS | 1 | — | — |
| Invasive cancer | 0.70 | 0.27–1.82 | .46 |
| Tumor behavior in EBRT patients | |||
| DCIS | 1 | — | — |
| Invasive cancer | 0.76 | 0.48–1.20 | .24 |
| Overlapping lesion | |||
| No | 1 | — | — |
| Yes | 1.10 | 0.88–1.37 | .42 |
| Laterality | |||
| Right | 1 | — | — |
| Left | 1.11 | 0.95–1.30 | .18 |
| Sociodemographic factors | |||
| SEER registry | |||
| Greater California | 1 | — | — |
| Connecticut | 0.98 | 0.63–1.53 | .93 |
| Detroit | 0.98 | 0.71–1.37 | .92 |
| Hawaii | 1.25 | 0.90–1.74 | .19 |
| Iowa | 0.98 | 0.44–2.22 | .97 |
| New Mexico | 0.97 | 0.64–1.48 | .89 |
| Seattle | 1.10 | 0.65–1.88 | .72 |
| Utah | 0.77 | 0.52–1.13 | .18 |
| Rural Georgia | 1.11 | 0.69–1.81 | .67 |
| Kentucky | 1.23 | 0.87–1.74 | .24 |
| Louisiana | 1.77 | 1.28–2.44 | <.001 |
| New Jersey | 0.93 | 0.71–1.20 | .57 |
| Percent of adults in census tract or ZIP code with at least some college education | |||
| 0–7.4 | 1 | — | — |
| 7.5–13.0 | 0.95 | 0.75–1.21 | .69 |
| 13.1–21.1 | 0.75 | 0.57–0.99 | .04 |
| 21.2–100 | 0.86 | 0.63–1.18 | .36 |
| Median income in census tract or ZIP code | |||
| $0–$37,413 | 1 | — | — |
| $37,414–$50,066 | 1.22 | 0.96–1.54 | .11 |
| $50,067–$66,720 | 1.04 | 0.77–1.39 | .81 |
| $66,721–$200,008 | 0.98 | 0.70–1.39 | .92 |
| Urban/rural status | |||
| Large metropolitan | 1 | — | — |
| Metropolitan | 1.11 | 0.89–1.37 | .35 |
| Urban | 1.28 | 0.90–1.84 | .17 |
| Less urban | 0.91 | 0.60–1.38 | .67 |
| Rural | 1.24 | 0.61–2.55 | .55 |
| Surgeon density in county of residence† | |||
| 0–8.3 | 1 | — | — |
| 8.4–11.6 | 0.79 | 0.63–0.99 | .04 |
| 11.7–15.4 | 0.93 | 0.74–1.17 | .54 |
| ≥15.5 | 0.86 | 0.67–1.09 | .21 |
Abbreviations: CI = confidence interval; DCIS = ductal carcinoma in situ; EBRT = external beam radiation therapy; HR = hazard ratio; SEER = Surveillance, Epidemiology, and End Results.
*
Interaction of type of treatment with tumor behavior was significant at P=.01.
†
Per 100,000 persons in county of residence.