A form of radiotherapy targeting the pelvis is safe for men with advanced localised prostate cancer, according to a new study.

In a trial part-funded by Cancer Research UK, patients who received the smallest dose of intensity modulated radiotherapy (IMRT) targeting lymph nodes in the pelvis were less likely to see their disease come back compared to patients who had the highest doses, although they experienced more side effects.

IMRT bends the radiotherapy beam to fit the tumour or target tissue, allowing cancer cells to receive a higher dose while reducing the dose to surrounding tissue.

The trial’s leader, Professor David Dearnaley, an expert in prostate cancer at the Institute of Cancer Research, London (ICR) and consultant clinical oncologist at The Royal Marsden NHS Foundation Trust, said the trial was one of the first to test the safety of this type of IMRT at different doses for prostate cancer.

“These long-term results demonstrate that using IMRT to target the pelvic lymph nodes is safe and effective for men with prostate cancer,” he said. “This technique has already proven to be a game changer for men with prostate cancer.”

The trial, published in the International Journal of Radiation Oncology Biology Physics, included 447 men who were split into 5 groups. All received standard hormone therapy, plus IMRT treatment:

• Groups 1-3 received 50-60 Gy in 35-37 doses to the lymph nodes, and 70-74 Gy to the prostate over 7 weeks;
• Groups 4-5 received 47 Gy in 20 doses to the lymph nodes, and 60 Gy to the prostate over 4 or 5 weeks.

Giving radiotherapy to the area around a prostate tumour is risky due to the damage that can be done to the bowel.

Patients in group 1 fewest side effects – around 8 in 100 had bowel complications and around 4 in 100 had bladder complications.

But survival was worst among that group: 38 in 100 patients were alive without a relapse after 5 years, compared to an average of 71 in 100 across the whole study.

Around 80 in 100 patients in groups 4 and 5, who received the least radiation overall, were alive without a relapse after 5 years - the best across the trial.

But these patients had most bowel and bladder complications.

“Between treating the first ever patients on this trial, and those we treat today, there has been a complete revolution in using this technique,” said Dearnaley.

“When we first started it took 45 minutes to provide treatment; today it only takes two or three minutes. It's been a giant leap forward for radiotherapy treatment.”

As a result of the latest findings and previous work using IMRT to target the prostate directly, IMRT is becoming the standard of care at major cancer centres in the UK, although it is not available everywhere.

The researchers said that results from ongoing and planned late stage clinical trials will be needed to see if combining the higher doses of IMRT to the pelvis and prostate yields survival benefits that outweigh the extra side effects.

Professor Paul Workman, chief executive of the ICR, said: “Radiotherapy is often seen as perhaps old-fashioned and crude compared with other cancer treatments – but nothing could be further from the truth. Radiotherapy today has been enhanced far beyond recognition since its first use over a century ago, and is now a highly precise, incredibly sophisticated treatment.

“It’s great to see this long-term evidence of the degree to which precision radiotherapy has transformed outcomes for men with prostate cancer."

The article is titled, "Phase 1/2 Dose-Escalation Study of the Use of Intensity Modulated Radiation Therapy to Treat the Prostate and Pelvic Nodes in Patients With Prostate Cancer."