In the epub edition of Radiotherapy and Oncology, Dr. Ishikawa and colleagues from the National Institute of Radiological Sciences, Chiba, Japan report on carbon ion (C-ion) beam radiotherapy for prostate cancer (CaP). With short-term follow-up they found it safe, potentially effective and with low toxicity.

C-ion beam radiotherapy has potential advantages to photon or proton beam radiotherapy. C-ions have high relative biological effectiveness due to high linear energy transfer (LET) with an estimated cytocidal effect about 3-times that of photons or protons. C-ions exhibit a spread-out Bragg peak similar to protons, providing a better dose distribution for the target volume by beam modulations.

Based upon dose escalation studies, a dose of 66Gy was selected and administered to 175 CaP patients between 2000 and 2003. Patients were defined as low-risk (PSA<20ng/ml and Gleason score <7, cT1/T2N0M0) or high-risk (PSA>20ng/ml and Gleason score >7, cT2b/T3). Androgen-deprivation therapy (ADT) was given in high-risk patients for 2-6 months as neoadjuvant treatment and for 12 months or more as adjuvant therapy. The primary endpoint was the biochemical relapse-free survival (bNED), local control and toxicities. Median follow-up was 46 months and median duration of ADT was 22 months in the high-risk group. Median patient age was 70 years.

The mean PSA level prior to treatment was 30.6ng/ml with values greater than 50ng/ml in 29 patients. The high-risk group included 142 patients (81%). There were no Grade 2-3 toxicities and 33% experienced Grade 1 urinary toxicity. The 4-year overall survival was 91% and the cancer-specific survival was 97%. Stratified by risk-group, the OS and CSS survivals were 94% and 100% for low-risk, respectively and 91% and 97% for high-risk, respectively. The 4-year bNED for all patients was 88% and relapses occurred in 11%. In the 8 patients with documented recurrences, most were in the lymph nodes.

Functional assessment of quality of life did not demonstrate a decrease from before to after treatment. While encouraging, this study needs further validation, especially in light of 81% of patients receiving ADT for a median of 22 months, which could significantly affect the data at 4-years follow-up. Also, no decrease in QOL with so many patients on ADT is unusual.

By Christopher P. Evans, M.D.

Radiotherapy and Oncology<.i> 2006
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