Radiation and hormonal therapy may replace chemotherapy for prostate cancer

Radiotherapy can be used alongside hormone therapy, delaying the need for chemotherapy and significantly improving the quality of life for some patients with advanced prostate cancer, according to a study led by researchers from The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research, London.

Results from the TRAP (Targeting Hormone Refractory Metastases with Radiotherapy) trial were presented at the annual congress of the European Society of Radiotherapy and Oncology (ESTRO).

Treatment of advanced cancer

Phase II of this study is the first prospective study examining the use of stereotactic body radiotherapy (SBRT) in patients with hormone-refractory oligoprogressive prostate cancer. Oligoprogressive cancer occurs when cells from the original tumor move to fewer than three sites in the body, forming new tumors or lesions.

At the moment, progression of the disease after hormonal therapy is considered a sign that the cancer has become resistant to treatment. However, the study results showed that only some tumors may be resistant, and if these tumors are treated with radiotherapy, the rest of the cancer will continue to respond to hormonal therapy.

The study demonstrated that patients were cancer-free for an average of six months (6.4), and 40.1% of patients were progression-free at 12 months.

SBRT and Hormone Therapy Study

In a national study conducted at cancer centers across the UK, researchers examined whether giving SBRT along with androgen receptor-targeted agents to patients with oligoprogressive prostate cancer could delay the progression of their disease.

SBRT, which can be performed on CyberKnife machines or standard radiotherapy machines, allows doctors to precisely target tumors with submillimeter precision. This approach uses advanced imaging and treatment planning techniques to deliver radiation with precision while minimizing damage to surrounding healthy tissue.

40% of men had no signs of cancer growth at 12 months

Patients in the study had advanced prostate cancer that was no longer responding to conventional treatment. They had no more than two new cancers appearing during the two types of hormone therapy after an initially good response to treatment. All patients received five or six SBRT sessions, which were painless and took approximately 20–30 minutes each.

A total of 81 men received SBRT, and the majority (67%) had a single oligoprogressive tumor. Treatment areas included bone (59%), lung (1%), lymph nodes (32%) and prostate (8%).

After an average of 19.2 months, 53 (65%) patients experienced disease progression; 32 (40%) progressed within six months of SBRT treatment. Median progression-free survival after SBRT was 6.4 months, and 40% of men had no evidence of cancer growth 12 months after treatment.

PSA levels may indicate the effectiveness of SBRT

PSA levels, in the context of prostate cancer, refer to the level of prostate specific antigen in the blood, a marker that is secreted by the prostate and increases in cancer. Among 43 men whose PSA results were available three months after SBRT and whose cancer had not progressed at six months, 84% had a significant decrease in PSA levels. This compares with 45% for those who progressed or died within six months. Thus, PSA seems to be a good indicator for the long-term effectiveness of SBRT.

Further research

The treatment is now being studied in the STAR-TRAP trial, led by Dr Julia Murray at The Royal Marsden NHS Foundation Trust, with the hope that the findings will help change the standard of care for patients with advanced prostate cancer.

Hope for delaying the need for chemotherapy

Dr Alison Tree, consultant clinical oncologist at The Royal Marsden NHS Foundation Trust, honorary reader at The Institute of Cancer Research and principal investigator of the TRAP trial, said: “These initial results may be great news for patients with advanced prostate cancer. We are committed to developing smarter, kinder and more effective treatments for patients in the UK and around the world.

"Currently, treatment options for men with advanced prostate cancer are limited, however I am hopeful that once larger studies are conducted to confirm our findings, we will see changes and be able to treat these patients differently, using radiotherapy as the standard to target drug-resistant parts cancer.

"Radiotherapy is well tolerated and significant side effects are rare, so we are hopeful that this treatment will delay the need for chemotherapy in the future, prolonging quality of life."

Simon Grieveson, assistant director of research at Prostate Cancer UK, said: "Radiotherapy can be an extremely effective treatment for men with early stage, localized prostate cancer, but we funded the TRAP trial to explore the use of radiotherapy in men whose cancer has spread to other parts of the body.

"These results are very promising and suggest that targeting radiotherapy to areas where cancer has spread may delay further progression of the disease and the need for subsequent treatments such as chemotherapy.

"While these results offer great promise for men with advanced prostate cancer who are beginning to exhaust treatment options, this now needs to be tested in a larger randomized trial, and Prostate Cancer UK is funding the STAR-TRAP trial to achieve this." p>