Secondary malignancies more common after brachytherapy than after surgery

    

    

Doctors newspaper online, 10.08.2019

    

        
        
        

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prostate cancer

MONTREAL. Based on studies in USA and Europe with only a small number of patients, no definitive statement on the long-term risk of developing a bladder or rectal carcinoma after brachytherapy in comparison to radical prostatectomy was available.

That's why urologists and oncologists around Dr. Elio Mazzone from the University of Montreal Health Center evaluated in their study information from the US database SEER (Surveillance, Epidemiology, and End Results), which had been documented there between 1988 and 2015. These were the findings of more than 318,000 men who had localized, histologically confirmed prostate cancer as the sole primary tumor and had undergone brachytherapy or radical prostatectomy ( BJU Int 2019; online May 30 ).

Medianes follow-up of 102 months

The physicians hypothesized that brachytherapy in these patients is associated with a higher risk of secondary malignancy – primary bladder or rectal cancer – than radical prostatectomy. In addition, they postulated a trend towards less common bladder and rectal cancers following brachytherapy due to the recent improvement in radioactive prostate seed transplantation.

The median follow-up of the study was 102 months. During the study period, of the more than 318,000 men, nearly 55,600 (18.4%) underwent brachytherapy. Of all study participants, 4625 men (1.4%) developed bladder or rectal carcinoma for the first time.

Among patients with brachytherapy, the proportion of those who developed bladder cancer (2% versus 1%) or rectal cancer (0.4% versus 0.3%) was significantly higher than those with a prostatectomy , After 20 years, the incidence of bladder cancer was 6% in the radiation group and 2.4% in the Op group. For rectal cancer, the incidence at this time was 1.1% versus 0.5%.

According to multivariate analysis, brachytherapy was associated with significantly higher risk of bladder cancer than surgery (hazard ratio [HR]1.58) and was 58% higher. The risk of rectal cancer was similarly higher (HR: 1.59).

Less and less secondary malignancies after brachytherapy

Finally, the physicians – according to their statements for the first time ever – stated that, since 1988, secondary malignancies have become increasingly rare in patients with prostate cancer after brachytherapy. Thus, the cumulative 5-year incidence of secondary bladder cancer 1988/1989 was still at 1.7%, 2010/2011, there were only 0.6%. The rectal carcinoma after such a seed irradiation had become increasingly rare and almost never occurred in younger years (1.4% versus 0.1%).

The results of the current study contradict the results of previous European and North American studies, which showed no difference in the incidence of secondary cancers.

The doctors suspect that this is due to the significantly lower number of study participants, especially in the brachytherapy group and the shorter follow-up. A minimum of ten years of follow-up is therefore necessary for meaningful results.

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