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.