Prostate cancer trial finds no difference among treatments for 10-year mortality

By Jane Lewis
The much-anticipated results of the UK ProtecT trial, published in The New England Journal of Medicine, show no significant difference among treatment modalities for prostate cancer in terms of survival at 10 years.

Professor Phillip Stricker, Director of St Vincent’s Prostate Cancer Centre and Director of Australian Prostate Cancer Research Centre, told Medicine Today that although the study had its strengths, it had several serious problems, the most important being that most men (77%) participating in the trial had only a low-grade tumour (Gleason score of 6).

‘These are men who were not going to die of prostate cancer, who we simply wouldn’t treat these days,’ he said. ‘So the whole study is about how you treat people who don’t need to be treated. They really needed to include men with worse disease.’

The trial featured 1643 men (aged 50 to 69 years) diagnosed with localised prostate cancer by prostate specific antigen testing between 1999 and 2009, who were randomised to three treatment groups. At a median of 10 years, the rate of disease progression among men assigned to active monitoring was more than twice that of men assigned to surgery or radiotherapy (33 men monitored vs 13 assigned surgery and 16 assigned radiotherapy), as was the rate of metastatic disease (112 men vs 46 in each of the other groups). However, mortality was low irrespective of the treatment, with only 17 prostate cancer-specific deaths in total (about 1%).

According to Professor Stricker, any conclusion based on such a low mortality rate – which the researchers acknowledge was ‘considerably lower’ than anticipated – is ‘going to be questionable.’ Other problems included that the surgical standard was ‘very poor’, and the radiotherapy ‘grossly inadequate.’ However, the study did show that in low-risk patients, there is no need for active treatment, he said. 

A second paper reporting the trial’s results, focusing on patient-reported outcomes, concluded there were significant differences between the treatment groups in terms of urinary, bowel and sexual functions, and associated quality of life. Although prostatectomy had the greatest negative effect on sexual and urinary functions, bowel function was worse in the radiotherapy group. In the active monitoring group, sexual and urinary functions were affected much less, but worsened gradually over time.

‘These results echo what we already know about functional outcomes associated with treatment,’ commented Professor Stricker. ‘Unfortunately, the trial did not look at other outcomes, such as the incidence of secondary cancers in other organs, or repeated surgeries or hospitalisations required due to complications.’

GPs asked about the study should focus on ‘the critical message,’ which is that most participants ‘were low-risk patients who we wouldn’t treat these days,’ he advised.
N Engl J Med 2016; doi: 10.1056/NEJMoa1606220.
N Engl J Med 2016;doi: 10.1056/NEJMoa1606221.

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