Table 2 Univariable and multivariate Cox analysis of local control

Age

 <35

1.000

 ≥ 35

2.059(1.422–2.983)

< 0.001

Sex

 male

1.000

 female

0.460(0.323–0.654)

< 0.001

Causes of keloids

 piercing

1.000

 scar

3.442(1.980–5.983)

< 0.001

 acne

4.906(3.094–7.779)

< 0.001

 trauma

3.137(1.857-5.300)

< 0.001

 other

3.685(2.097–6.475)

< 0.001

Longest axis

 <5 cm

1.000

 ≥ 5 cm,<10 cm

3.021(1.926–4.739)

< 0.001

 ≥ 10 cm

3.539(2.389–5.242)

< 0.001

Number of keloids

 1

1.000

 ≥ 2

1.250(0.656–2.383)

0.498

Location

 ear

1.000

 head neck

3.443(1.981–5.985)

< 0.001

 chest

4.908(3.095–7.782)

< 0.001

 abdomen

3.830(2.090–7.019)

< 0.001

 perineum

3.686(2.098–6.476)

< 0.001

 limb and back

2.304(1.035–5.130)

0.041

Pain and/or pruritus

 no

1.000

1.000

 yes

37.829(24.385–58.686)

< 0.001

14.926(6.760-32.958)

< 0.001

Duration of pain or pruritus

 <6 month

1.000

 6-12month

2.029(0.338–12.167)

0.439

 ≥ 12month

3.647(1.130-11.766)

0.030

Treatment before RT

 surgery alone

1.000

 compression + surgery

1.582(0.637–3.930)

0.323

 corticosteroid + surgery

6.383(3.850-10.582)

< 0.001

 silicone + surgery

1.501(0.939–2.397)

0.089

 compression + corticosteroid + silicone + surgery

2.924(1.691–5.057)

< 0.001