Carbon Ion Radiotherapy Offers Good Prostate Cancer Outcomes

VANCOUVER—Carbon ion radiotherapy is a viable option for treating prostate cancer (PCa), according to Japanese researchers.

The investigators analyzed the results of clinical trials involving 1,383 men who were treated with the relatively new modality. The treatment was associated with a 95.2% cancer-specific survival (CSS) rate and a 79.8% overall survival (OS) rate at 10 years, according to a poster presented at the 33rd Congress of the Societé Internationale d'Urologie. The patient population included men with localized and locally advanced PCa. During carbon ion radiotherapy, the whole prostate gland and the seminal vesicles are irradiated.

“Carbon ion radiotherapy is a kind of external beam radiotherapy that uses an accelerated carbon ion particle beam,” investigator Koichiro Akakura, MD, PhD, of the Tokyo Kosei Nenkin Hospital, told Renal & Urology News. “There are four institutions in Japan that have this kind of facility. I believe there are also some in Italy and there are plans to build some in Germany.”

The first generation of these machines cost approximately $330 million, he said, but the price is now in the range of $100 million to $150 million, he said. Carbon ion radiotherapy is becoming a viable alternative to proton-beam radiotherapy, which is costly and controversial.

The team, led by Jun Shimazaki, MD, PhD, analyzed results from phase 1/2 and 2 trials conducted at the National Institute of Radiological Sciences in Japan, focusing on patients with histologically confirmed T1b-3bN0M0 PCa. The modality was used in the first 250 patients at a dose of 66.0 Gy/20f. Subsequent patients received lower doses, which were found to be effective.

The 302 intermediate-risk patients in study also received androgen deprivation therapy (ADT) for six months, and the 515 high-risk patients received a total of 24 months of neoadjuvant plus adjuvant ADT.

The 10-year rates of CSS, OS, local control, and freedom from biochemical recurrence were 95.2%, 79.8%, 98.1%, and 81.2%, respectively. The worst outcomes appeared to be in high-risk men with Gleason pattern 5 disease. Their five-year biochemical recurrence-free rate was 66.9%.

The rate of grade 2 late adverse events in the rectum with the initial dose of 66.0 Gy/20f was 3.2%, and the rate of such events with this dose was 14% in the bladder/urethra (no events of grade 3 or higher were observed). The rates at the lower doses of 63.0 Gy/20f and 57.60 Gy/20f ranged from 0.4%-2.3% in the rectum and from 2.4%-6.9% in the bladder/urethra. There was one grade 3 late adverse event in the bladder/urethra, translating into an 0.5% rate.

The team also employed the Japan Cancer of the Prostate Risk Assessment (J-CAPRA)(see J Clin Oncol 2009;27:4306-4313) to analyze the outcomes. Patients with worse scores had significantly worse 10-year biochemical recurrence-free survival and cancer-specific-survival rates. Individuals with scores of 3-6 had rates of 52.4% and 93.1%, respectively, whereas those with scores of 0-2 had rates of 82% and 98.7%, respectively.

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