Adding radiotherapy can benefit some patients whose prostate cancer has spread

08 Jun 2022

Adding radiotherapy to standard hormone therapy helps patients with prostate cancer with limited spread of the disease, to live longer. This result from the STAMPEDE trial was published, in open access format, in PLOS Medicine journal yesterday.

These findings report the long-term follow-up of patients recruited to the “M1 | RT comparison” of the STAMPEDE trial. This study assessed the effects of adding radiotherapy to standard hormone treatment to treat patients with metastatic prostate cancer. In these patients, their prostate cancer had already spread beyond the prostate.

Radiotherapy is widely used to treat prostate cancer that has not spread outside the prostate to other sites in the body. It works by delivering high energy X-rays to the site of the tumour to damage the DNA of the cancer cells, which then stop dividing and die.

To evaluate whether adding radiotherapy to the prostate improves the survival of patients with metastatic prostate cancer, 2,061 patients with this condition were randomly assigned between two groups. Each group received either:

  • Standard hormone treatment alone
  • Standard hormone treatment plus Radiotherapy to the prostate

                            

The study took place in the UK and Switzerland and included patients with newly diagnosed metastatic prostate cancer. Consenting participants were followed-up for an average of five years after they were randomly allocated to one of the two treatment groups.

To determine the extent of the disease outside the prostate, patients had scans to detect the number of metastases. They were classified into two groups: those with a low volume of disease (“low metastatic burden”), and those with high volume (“high metastatic burden”).

The first findings of this study were reported in 2018, and the follow-up data confirms the benefit of radiotherapy in the longer term. The results show that adding radiotherapy did not improve the overall survival of all patients with metastatic prostate cancer.

However, patients whose disease had spread less (referred as “low metastatic burden”) did benefit from radiotherapy combined with standard hormonal treatment. These patients lived longer than those who received only the standard hormonal treatment. After five years, 65% of patients with low metastatic burden in the radiotherapy group were still alive, compared to 53% of patients receiving standard hormone treatment alone. Therefore, adding radiotherapy meant that an extra 12 out of every hundred patients treated would be alive after five years.

In contrast, patients whose disease had spread further (referred as “high metastatic burden”) did not benefit from receiving radiotherapy. Thus, additional treatment using radiotherapy can be avoided in this patient group.

                          

 

When the prostate cancer progresses, it can cause bladder symptoms, and it may affect the bowel. These symptoms are known as symptomatic local events (that is, within the pelvis) and they may need local intervention, such as insertion of a urinary catheter or surgery to relieve a blockage of the bladder. Both the number of symptomatic local events and the need for surgical intervention in the pelvic region was reduced when adding radiotherapy in the low metastatic burden group.  

The side-effects that patients experienced following radiotherapy were also similar between the two treatment groups. In addition, patient responses to questionnaires showed that radiotherapy had no long-term impact on the quality of life of patients with metastatic prostate cancer treated in this way.

                         

These findings from STAMPEDE confirm that radiotherapy to the prostate combined with standard hormone treatment improves survival for patients with low metastatic burden disease. However, adding radiotherapy did not help patients with high metastatic burden disease to live longer, and they should be treated using other therapies without adding radiotherapy to the prostate.

The study was funded by Cancer Research UK (CRUK), the Medical Research Council (MRC), and the Swiss Group for Cancer Clinical Research (SAKK), with further support from industry collaborators including Janssen, Astellas, Prostate Cancer UK, Clovis Oncology, Novartis, Pfizer, and Sanofi-Aventis.  

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