Table 4.
Association between acute grade ≥2 cutaneous toxicity and clinical and dosimetric characteristics
| N | Acute grade ≥2 cutaneous toxicity | Univariate analysis* | Multivariate analysis** | |||
|---|---|---|---|---|---|---|
| n | % | p-value | OR (95%CI) | p-value | ||
| Age (years) | — | — | — | 0.51 | NA | |
| BMI (kg/m²) | — | — | — | 0.003 | 1.14 (1.05–1.24) | 0.003 |
| Bra cup size (n = 113) | 0.020 | ND | ||||
| A-B | 53 | 12 | 22.6% | |||
| ≥C | 60 | 26 | 43.3% | |||
| Smoking | 0.44 | NA | ||||
| No | 86 | 28 | 32.6% | |||
| Yes | 35 | 14 | 40.0% | |||
| Diabetes (n = 119) | 0.52 | NA | ||||
| No | 108 | 37 | 34.3% | |||
| Yes | 11 | 5 | 45.5% | |||
| Chemotherapy | 0.017 | 0.49 (0.16–1.49)*** | 0.21 | |||
| No | 28 | 15 | 53.6% | |||
| Yes | 93 | 27 | 29.0% | |||
| Aesthetic aspect before RT (n = 66) | 0.70 | NA | ||||
| Moderate | 14 | 6 | 42.9% | |||
| Good | 33 | 10 | 30.3% | |||
| Excellent | 19 | 7 | 36.8% | |||
| Dosimetric parameters | ||||||
| Volume of breast CTV (cc) | — | — | — | 0.064 | ND | |
| Volume of breast PTV (cc) | — | — | — | 0.055 | ND | |
| Volume of subclavian CTV (cc) | — | — | — | 0.064 | 0.98 (0.969–1.001)*** | 0.051 |
| Volume of subclavian PTV (cc) | — | — | — | 0.070 | ND | |
| Dmean (Gy) for the skin (Gy) | — | — | — | 0.045 | ND | |
| D50% for the skin (Gy) | — | — | — | 0.014 | ND | |
| D95% for the skin (Gy) | — | — | — | 0.047 | 1.11 (1.01–1.22) | 0.033 |
| D95% for the susclavian skin (Gy) | — | — | — | 0.089 | ND | |
| D98% for the susclavian skin (Gy) | — | — | — | 0.047 | 1.04 (1.003–1.09) | 0.034 |
| V95% of CTV breast (cc) | — | — | — | 0.068 | 1.00 (0.992–1.014)*** | 0.56 |
| V95% of PTV breast (cc) | — | — | — | 0.072 | ND | |
CTV: clinical target volume; PTV: planning target volume; RT: radiotherapy; OR: odds ratio; CI: confidence interval.
Dx%: dose (Gy) received by x% of the volume; Vx%: volume (cc) of the breast target volume that received x% of the dose.
*Univariate analysis: Khi-2 test, Student t-test or Wilcoxon test.
**Multivariate analysis: logistic regression.
NA: not applicable because not included in multivariate regression model (p > 0.10 in univariate analysis).
ND (not done): variable not included in multivariate analysis for collinearity reasons (bra cup size, volume of breast CTV and PTV: highly correlated to BMI; subclavian PTV volume: highly correlated to subclavian CTV volume; Dmean and D50% to skin: highly correlated to D95% to skin; D95% to susclavian skin: highly correlated to D98% to susclavian skin; V95% of PTV: highly correlated to V95% of CTV).
***Variable included in multivariate analysis but removed from the model because of the stepwise procedure.