Table 3 Cox proportional hazard model for second cancer with age, T-, N- and M-category and treatment as independent covariates

 Age [yrs]

<0.0001

   < 60

1

  60–<65

1.278

1.124

1.453

  65–<70

1.618

1.434

1.826

  70–<75

2.136

1.881

2.425

   > =75

2.177

1.836

2.581

 T-category

0.0023

  T1

1.089

0.964

1.231

  T2

1

  T3

1.204

1.095

1.324

  T4

1.086

0.786

1.501

  Missing

1.221

0.985

1.514

 N-category

0.0120

  N0

1

  N+

1.095

0.863

1.388

  NX

0.965

0.885

1.052

  Missing

1.373

1.117

1.688

 M-category

0.6458

  M0

1

  M1

0.913

0.619

1.346

 Treatment

<0.0001

  RPE only

1

  RT only

1.404

1.268

1.553

  RT after RPE

1.314

1.127

1.531