Prostate cancer: does radiation therapy raise the risk for second cancers?

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Takeaway
  • Radiation therapy (RT) was not associated with overall increased risk for second cancer (SC).
  • SC risk was increased with RT-only, but not with RT after radical prostatectomy (RP+RT).

Why this matters

  • Previous reports have provided conflicting results.

Key results

  • 10-y SC incidence was 15.9%, 13.2%, and 10.5% for RT-only, RP+RT, and RP-only (P<.0001). 
  • Incidence of colon cancer was 1.7%, 2.0%, and 1.1%, respectively. 
  • Rectal cancer occurred in 1.1%, 0.3%, and 0.6%. 
  • Bladder cancer occurred in 2.7%, 1.5%, and 1.1%. 
  • Nonmelanoma skin cancer (NMSC) occurred in 2.1%, 1.6%, and 1.2%. 
  • Incidence of lung cancer was 2.2% with RT-only and 1.2% with RP regardless of postoperative RT.
  • Age, T- and N-category and treatment were predictors for SC development. 
  • RP+RT and RT-only patients were at higher risk for colon cancer (HR, 1.903 and 1.326; P=.0035). 
  • Risk for rectal cancer increased with RT-only (HR, 1.751; P=.0077), and decreased with RP+RT (HR, 0.638; P=.0077). 
  • RT-only patients were at high risk for lung cancer (HR, 1.733; P=.0011). 
  • RT-only and RP+RT were associated with increased risk for bladder cancer (HR, 2.098 and 1.601; P<.001) and NMSC (HR, 1.658 and 1.305; P<.0020).

Study design

  • Retrospective study (N=19,538).
  • Funding: None.

Limitations

  • Small number of events in some subgroups.