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
- HR =1.76 for 2D-EBRT
- HR =0.81 for 3D-EBRT/IMRT
- HR = 0.53 for BT
- HR = 0.83 for 2D-EBRT + BT
- 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.