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Risk for secondary cancers after first-line radiation therapy for prostate cancer

Posted Nov 09 2010 12:00am


There is a recognized risk for development of secondary primary cancers (SPCs) after first-line treatment with radiation therapy for localized prostate cancer. However, a new article suggests that newer forms of radiation therapy may have noticeably reduced that risk.

Huang et al. reviewed data from a cohort of 2,120 patients treated with various types of radiation therapy for their localized prostate cancer. The types of radiation included:

  • Conventional, two-dimensional external beam radiation therapy (2D-EBRT), used in 36 percent of patients
  • Three-dimensional, conformal EBRT (3D-EBRT) and intensity-modulated radiation therapy (IMRT), used in 29 percent of patients
  • Brachytherapy alone (BT), used in 16 percent of patients
  • 2D-EBRT with a brachytherapy boost (2D-EBRT + BT), used in 19 percent of the patients

The researchers also matched data on SPCs from these 2,120 patients on a 1:1 basis with a series of surgical patients based on the patients’ ages and length of follow-up.

The results of this analysis are as follows:

  • Overall risk for SPCs regardless of follow-up time was not significantly higher in the radiation therapy patients than in the surgery patients (hazard ratio [HR] = 1.14).
  • At > 5 years of follow-up there was a significant risk for SPCs in the radiation therapy patients compared to the surgery patients (HR = 1.86).
  • At >10 years of follow-up, the risk for SPCs in the radiation therapy patients compared to the surgery patients was further increased (HR = 4.94).
  • When broken down by type of radiation, the overall relative risk for SPCs compared to surgery was
  •  The types of SPC occurring most commonly among the patients receiving primary radiation therapy were bladder cancers, lymphoproliferative cancers (e.g., non-Hodgkin’s disease), and sarcomas.

It appears from these data that the only type of primary radiation therapy that increased overall risk for SPCs in this patient population (compared to surgery) was 2D-EBRT classical radiation therapy that is rarely used today as first-line therapy for localized disease. However, the abstract to the paper does not provide a breakdown of either year of initial therapy or length of follow-up by type of radiation, so if (for example) 10-year follow-up data was only available for the 2D-EBRT patients, the results could be skewed in a manner that would perhaps be misleading. However, the authors clearly conclude that, “Radiation-related SPC risk varies depending on the [radiation therapy] technique and may be reduced by using BT, [BT + 2D-EBRT], or 3DCRT/IMRT.

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