2018-19 Section 7-Neoplastic and Inflammatory Diseases of the Head and Neck eBook

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CHERAGHLOU ET AL .

TABLE 1 (Continued)

No. of patients (%)

Early-stage without adverse features (n 5 1138)

Early-stage with adverse features (n 5 2966)

Late-stage without adverse features (n 5 118)

Late-stage with adverse features (n 5 4358) 722 (16.6) 236 (5.4) 581 (13.3) 526 (12.1) 239 (5.5) 2054 (47.1)

Total (n 5 8580)

Variables

Histologic type

Mucoepidermoid

2205 (25.7) 905 (10.6) 1207 (14.1)

586 (51.5) 308 (27.1)

856 (28.9) 337 (11.4) 626 (21.1) 216 (7.3) 127 (4.3) 804 (27.1)

41 (34.8) 24 (20.3)

Acinar

Adenoid cystic Adenocarcinoma Malignant mixed Other/unknown

. . .

. . .

775 (9.0) 391 (4.6)

29 (2.6) 22 (1.9)

4 (3.4) 3 (2.5)

3097 (36.1)

193 (17.0)

46 (39.0)

Grade Low

1806 (21.0) 1981 (23.1) 3213 (37.4) 1580 (18.4)

1138 (100.0)

295 (10.0) 1156 (39.0) 859 (29.0) 656 (22.1)

118 (100.0)

255 (5.8) 825 (28.9) 2354 (54.0) 924 (21.2)

Intermediate

. . . . . . . . .

. . . . . . . . .

High

Unknown

Surgical margins Negative

5277 (61.5) 2993 (34.9)

1138 (100.0)

1824 (61.5) 1076 (36.3)

118 (100.0)

2197 (50.4) 1917 (44.0)

Positive

. . . . . .

. . . . . .

Unknown

310 (3.6)

66 (2.2)

244 (5.6)

Treatment fac

Treatment combination Surgery only

3504 (40.8) 4152 (48.4) 924 (10.8)

944 (83.0) 193 (17.0)

1274 (43.0) 1605 (54.1)

69 (58.5) 47 (39.8)

1217 (27.9) 2307 (52.9) 834 (19.1)

Surgery 1 RT Surgery 1 CRT

1 (0.1)

87 (2.9)

2 (1.7)

Abbreviations: CRT, chemoradiotherapy; RT, radiotherapy. Adverse features include positive surgical margins, intermediate/high grade, adenoid cystic histology, and nodal metastases. Early-stage includes stages I/II disease, whereas late-stage includes stages III/IV disease.

factors associated with the administration of adjuvant therapy as well as with the addition of chemotherapy to adjuvant treatment. As for Cox survival regressions, stepwise removal was conducted for these logistic regressions. Statistical sig- nificance was determined at the P < .05 level. Data analysis was performed using SPSS version 23.0 (IBM, Armonk, NY) and STATA version 13 (StataCorp LP, College Station, TX).

neighbor match without replacement. In order to determine the caliper width for the matching algorithm, calipers between 0.0001 and 0.1 were tested in order to determine the number of matched patients and the standardized difference between groups. With this methodology, a caliper width of 0.005 was selected as it maintained sufficient patient num- bers and minimized the standardized difference between groups. This number is consistent with caliper widths used in previous analyses. 31,32 All patient, tumor, and treatment fac- tors were included in a multivariate Cox regression within each risk group. Factors were eliminated from this regression by stepwise removal in order to minimize the effects of mul- ticollinearity. A multivariate Cox regression was also con- ducted for patients with late-stage disease with adverse features who were treated with adjuvant therapy in order to evaluate the effect of addition of chemotherapy to adjuvant treatment. Landmark analysis was performed at 1, 2, and 3 months after surgery to account for immortal time bias. 33 Logistic regressions were conducted in order to identify

3 | RESULTS

The characteristics of the study population are described in Table 1. The majority had no comorbidities (82.5%) or nodal involvements (67.5%) and were treated at nonacademic facilities (61.8%). The most common identified histologic subtypes were mucoepidermoid (25.7%) and adenoid cystic (14.1%). All results were unchanged when landmark analy- ses of 1, 2, and 3 months were conducted.

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