Table 1.
Characteristics of women surviving ≥5 years after breast cancer diagnosis who subsequently developed esophageal cancer (cases, n = 252), and matched controls (n = 488)a
| Characteristic | Cases, n (%) | Controlsa, n (%) |
|---|---|---|
| Registrya | ||
| Denmark | 26 (10.3) | 38 (7.8) |
| Finland | 40 (15.9) | 79 (16.2) |
| Iowa | 16 (6.3) | 32 (6.6) |
| Ontario | 90 (35.7) | 179 (36.7) |
| Sweden | 80 (31.7) | 160 (32.8) |
| Age at breast cancer diagnosis (years)* | ||
| 28–49 | 68 (27.0) | 126 (25.8) |
| 50–59 | 60 (23.8) | 122 (25.0) |
| 60–69 | 69 (27.4) | 138 (28.3) |
| 70–88 | 55 (21.8) | 102 (20.9) |
| Calendar year of breast cancer diagnosisa | ||
| 1946–1964 | 22 (8.7) | 40 (8.2) |
| 1965–1974 | 90 (35.7) | 178 (36.5) |
| 1975–1984 | 85 (33.7) | 164 (33.6) |
| 1985–1996 | 55 (21.8) | 106 (21.7) |
| Breast cancer histology | ||
| DCIS | 3 (1.2) | 10 (2.0) |
| Invasive ductal carcinoma | 188 (74.6) | 379 (77.7) |
| Invasive lobular carcinoma | 12 (4.8) | 23 (4.7) |
| Other specified invasive histologyb | 23 (9.1) | 37 (7.6) |
| Unspecified | 26 (10.3) | 39 (8.0) |
| Breast cancer stage | ||
| DCIS | 3 (1.2) | 10 (2.0) |
| I | 98 (38.9) | 193 (39.5) |
| II | 99 (39.3) | 202 (41.4) |
| III/IV | 9 (3.6) | 13 (2.7) |
| Localized/regionalc | 43 (17.1) | 70 (14.3) |
| Initial surgery for breast cancer | ||
| Modified/radical mastectomy | 195 (77.4) | 362 (74.2) |
| Partial mastectomy (breast-conserving surgery) | 34 (13.5) | 78 (16.0) |
| Mastectomy, not otherwise specified | 21 (8.3) | 42 (8.6) |
| Other | 2 (0.8) | 6 (1.2) |
| Non-surgical breast cancer treatment categoryd | ||
| No chemotherapy or radiotherapy | 77 (30.6) | 173 (35.5) |
| Radiotherapy only | 152 (60.3) | 265 (54.3) |
| Chemotherapy and radiotherapy | 15 (6.0) | 20 (4.1) |
| Chemotherapy only | 4 (1.6) | 20 (4.1) |
| Unknown | 4 (1.6) | 10 (2.0) |
| Hormonal agentse | ||
| No | 198 (78.6) | 364 (74.6) |
| Yes | 49 (19.4) | 113 (23.2) |
| Unknown | 5 (2.0) | 11 (2.3) |
| Cigarette smoking statusf | ||
| Non-smoker | 47 (44.8) | 125 (58.4) |
| Former smoker | 12 (11.4) | 25 (11.7) |
| Current smoker <1 pack/day | 23 (21.9) | 46 (21.5) |
| Current smoker ≥1 pack/day | 23 (21.9) | 18 (8.4) |
| Unknown | 147 (—) | 274 (—) |
| Alcohol consumptionf,g | ||
| Non-drinker | 16 (27.6) | 61 (45.9) |
| Light drinker | 16 (27.6) | 50 (37.6) |
| Moderate drinker | 12 (20.7) | 16 (12.0) |
| Heavy drinker | 14 (24.1) | 6 (4.5) |
| Unknown | 194 (—) | 355 (—) |
| First-degree relative with cancerf | ||
| No | 75 (48.4) | 163 (62.5) |
| Yes | 80 (51.6) | 98 (37.5) |
| Unknown | 97 (—) | 227 (—) |
| BMI (kg/m2)f | ||
| 13.8–18.4 | 7 (5.9) | 11 (5.4) |
| 18.5–24.9 | 68 (57.1) | 107 (52.5) |
| 25.0–29.9 | 30 (25.2) | 57 (27.9) |
| 30.0–48.4 | 14 (11.8) | 29 (14.2) |
| Unknown | 133 (—) | 284 (—) |
| Interval from breast cancer to esophageal cancer diagnosis or comparable date for controls (years)a | ||
| 5–9 | 87 (34.5) | 169 (34.6) |
| 10–14 | 55 (21.8) | 107 (21.9) |
| 15–24 | 79 (31.3) | 155 (31.8) |
| 25–37 | 31 (12.3) | 57 (11.7) |
| Esophageal cancer locationh | ||
| Upper esophagus | 50 (19.8) | — |
| Overlapping upper/middle esophagus | 17 (6.7) | — |
| Middle esophagus | 69 (27.4) | — |
| Overlapping middle/lower esophagus | 50 (19.8) | — |
| Lower esophagus | 39 (15.5) | — |
| Gastroesophageal junction | 15 (6.0) | — |
| Unknown | 12 (4.8) | — |
| Esophageal cancer histologyi | ||
| Squamous cell carcinoma | 178 (70.6) | — |
| Adenocarcinoma | 34 (13.5) | — |
| Other | 30 (11.9) | — |
| Unknownj | 10 (4.0) | — |
| Esophageal cancer stage | ||
| I/II | 103 (40.9) | — |
| III/IV | 93 (36.9) | — |
| Unknown | 56 (22.2) | — |
DCIS, ductal carcinoma in situ.
aControls were individually matched (2:1) to case patients by registry, race (Iowa only), birth date (within 5 years), breast cancer diagnosis date (within 5 years), and survival without a subsequent cancer at least as long as the period from breast cancer to esophageal cancer for the matched case. Only one matched control could be found for 16 cases.
bOther specified invasive breast cancer histologies included medullary carcinoma (9 cases, 11 controls), mucinous carcinoma (4 cases, 11 controls), tubular carcinoma (1 case, 6 controls), and other rarer or mixed histologies (9 cases, 9 controls).
cPatients were categorized as having localized or regional breast cancer when AJCC stages I–IV could not be assigned due to insufficient information. The category included localized (32 cases, 51 controls), regional (7 cases, 13 controls), and unknown (4 cases, 6 controls).
dBreast cancer treatment category includes radiotherapy and chemotherapy received within the matched time interval, including the first course of therapy as well as treatments for recurrence and/or new primary breast cancer. Patients who received a single cycle of chemotherapy prior to radiotherapy (cyclophosphamide: four cases, eight controls; thiotepa: one control) were categorized as receiving no chemotherapy. Patients with radiotherapy but unknown chemotherapy were categorized as receiving radiotherapy only (two controls). Radiotherapy data included external beam therapy and brachytherapy (n = 1).
eMost patients who received hormonal agents received tamoxifen. Only one case and five controls received non-tamoxifen hormonal agents exclusively.
fData on cigarette smoking, alcohol consumption, and family history of cancer were ascertained up to 1 year prior to esophageal cancer diagnosis (or comparable date for controls). BMI was computed from height and weight data within 5 years of breast cancer diagnosis. Percentages exclude patients with unknown values.
gLight, moderate, and heavy alcohol consumption was defined as <7, 7–20, and ≥21 drinks per week, respectively.
hThe upper, middle, and lower esophagus regions were defined as C6-T4, T4/5-T7/8, and T8-T10/11, respectively.
iOf 252 cases, 224 (89%) were histologically confirmed, 13 (5%) had diagnoses highly consistent with esophageal cancer, and for 15 (6%) the possibility of metastatic cancer to the esophagus could not be excluded.
jUnknown esophageal cancer histology included unspecified (one case) and no histologic confirmation (nine cases).