When It Comes to RT for Prostate Cancer, More May Be Better

An intense higher-dose radiotherapy regimen may be a better treatment option for men with localized prostate cancer, according to the 10-year results of the international phase III RT01 trial. The results are published in the Lancet Oncology.

The RT01 trial shows that at a median of 10 years, more fractions of radiotherapy (37 fractions compared with 32) and at a higher dose (74 Gy compared with 64 Gy) resulted in a better biochemical progression-free survival. Prior to the start of radiotherapy, men in both treatment arms also received neoadjuvant androgen deprivation therapy for 3 to 6 months, which was continued until the end of the radiotherapy regimen. The measurable progression-free survival advantage, however, did not translate into improvement in overall survival.

“Our study has proven that treating men with localized prostate cancer using higher doses of radiotherapy is more effective than a less intensive regimen. The dose-escalated regimen is safe in the long term, and reduces the chances that a cancer will return and men will require further hormone deprivation treatment,” said lead study author David Dearnaley, MD, professor of uro-oncology at the Institute of Cancer Research in London, in a statement. “The side effects of hormone treatment do need to be balanced against those of the extra radiotherapy doses, but overall our study has shown men are better off after having the escalated regimen, as is now the norm in the UK,” he added.

The RT01 trial is an open-label, randomized trial that enrolled men with confirmed T1b (no tumor can actually be visualized) to T3a (the prostate tumor extends outside of the prostate but not to the seminal vesicles) prostate cancer, with no lymph node involvement and no metastasis. Men had prostate-specific antigen levels of less than 50 ng/mL. Patients were randomized 1:1 to either the standard-dose radiotherapy (64 Gy in 32 fractions) or the escalating-dose radiotherapy (74 Gy in 37 fractions). A total of 843 men were randomized between 1998 and 2001. The study was conducted in the United Kingdom, New Zealand, and Australia.

As of August 2011, 118 men from each treatment group had died.

The overall survival at a median of 10 years was 71% in each group (hazard ratio [HR] = 0.99; P = .96). Biochemical progression or progressive disease occurred in 391 patients: 221 (57%) in the standard-dose treatment arm and 170 (43%) in the intense-dose treatment arm. At 10 years, biochemical progression-free survival was 43% in the standard-dose treatment arm compared with 55% in the intense-dose treatment arm (HR = 0.69; P = .0003).

“These efficacy data for escalated-dose treatment must be weighed against the increase in acute and late toxicities associated with the escalated dose and emphasize the importance of use of appropriate modern radiotherapy methods to reduce side effects,” cautioned the authors in their conclusion. However, few men had severe side effects and those who received the intense dose regimen were not as likely to require hormone therapy as a follow-up, which also has side effects.

The 5-year results of this study had shown the positive benefits of a higher-intensity radiotherapy regimen and had been part of the evidence used to change the standard radiotherapy regimen recommended in the United Kingdom for men with localized prostate cancer.

“Radiotherapy in general is both a safe and an effective treatment for localized prostate cancer,” said Dr. Dearnaley, in a statement. “Almost three quarters of men treated with either the more or less intensive radiotherapy regimens are still alive after 10 years, and of the men who have died, less than half actually died from prostate cancer.”