Table 1.
Patient and treatment characteristics
| Parameters | Euthyroid (n = 82) | Hypothyroidism (n = 96) | P-value | |
|---|---|---|---|---|
| Age (years) | mean (SD) | 51.7 (10.2) | 47.9 (10.7) | 0.017a |
| Gender | ||||
| Male | N (%) | 71 (86.6) | 70 (72.9) | 0.025a |
| Female | N (%) | 11 (13.4) | 26 (27.1) | |
| T-classification | ||||
| T1–2 | N (%) | 48 (58.5) | 63 (65.6) | 0.331 |
| T3–4 | N (%) | 34 (41.5) | 33 (34.4) | |
| N-classification | ||||
| N0–1 | N (%) | 25 (30.5) | 22 (22.9) | 0.253 |
| N2–3 | N (%) | 57 (69.5) | 74 (77.1) | |
| WHO type | ||||
| Nonkeratinizing CA | N (%) | 20 (24.4) | 15 (15.6) | 0.142 |
| Undifferentiated CA | N (%) | 62 (75.6) | 81 (84.4) | |
| Stage | ||||
| I–II | N (%) | 12 (14.6) | 15 (15.6) | 0.395 |
| III | N (%) | 41 (50.0) | 56 (58.3) | |
| IVA–IVB | N (%) | 29 (35.4) | 25 (26.0) | |
| IMRT technique | ||||
| SIB | N (%) | 40 (48.8) | 52 (54.2) | 0.474 |
| SEQ | N (%) | 42 (51.2) | 44 (45.8) | |
| Pretreatment | ||||
| FT4 (ng/dl) | mean (SD) | 1.3 (0.3) | 1.3 (0.2) | 0.780 |
| TSH (μU/ml) | mean (SD) | 1.4 (0.8) | 2.0 (0.9) | <0.001a |
| Thyroid gland | ||||
| Volume (cm3) | mean (SD) | 17.2 (12.1) | 13.9 (6.9) | 0.025a |
| median (IQR) | 13.9 (11.7–18.8) | 12.1 (9.5–16.6) | 0.005a | |
| Dmean (Gy) | median (IQR) | 52.7 (49.1–55.0) | 53.6 (50.0–56.8) | 0.205 |
| Dmin (Gy) | median (IQR) | 34.5 (30.6–37.9) | 34.7 (31.1–38.8) | 0.417 |
| Dmax (Gy) | median (IQR) | 64.0 (61.3–70.2) | 68.2 (62.9–73.9) | 0.021a |
| V40 (%) | median (IQR) | 96.0 (87.0–100.0) | 96.0 (90.0–100.0) | 0.596 |
| V45 (%) | median (IQR) | 88.2 (78.7–94.3) | 87.7 (75.0–95.8) | 0.770 |
| V50 (%) | median (IQR) | 70.0 (57.3–79.9) | 73.8 (53.7–85.2) | 0.215 |
| VS45 (cm3) | median (IQR) | 1.8 (0.8–3.7) | 1.5 (0.5–3.2) | 0.543 |
| VS50 (cm3) | median (IQR) | 4.2 (2.7–6.8) | 3.7 (1.5–7.0) | 0.084 |
| VS60 (cm3) | median (IQR) | 12.5 (9.1–15.5) | 9.7 (6.9–13.9) | 0.006a |
| Concurrent chemotherapy | mean (SD) | 5.6 (1.4) | 5.7 (1.0) | 0.375 |
| <5 cycles | N (%) | 30 (36.6) | 39 (40.6) | 0.581 |
| ≥6 cycles | N (%) | 52 (63.4) | 57 (59.4) | |
| Adjuvant chemotherapy | mean (SD) | 2.4 (1.0) | 2.7 (0.7) | 0.059 |
| 0–2 cycles | N (%) | 25 (30.5) | 19 (19.8) | 0.099 |
| 3 cycles | N (%) | 57 (69.5) | 77 (80.2) |
WHO = World Health Organization, CA = carcinoma, IMRT = intensity-modulated radiotherapy, IQR = interquartile range, SIB = simultaneous-integrated boost, SEQ = sequential, FT4 = free levothyroxine, TSH = thyroid-stimulating hormone, Dmean = mean dose, Dmin = minimal dose, Dmax = maximal dose, Vx = volume receiving dose x Gy, VSx = volume-sparing dose x Gy, SD = standard deviation.
aP-value of <0.05 was considered statistically significant.