Editorial Comment to Therapeutic outcomes of neoadjuvant and concurrent androgen-deprivation therapy and intensity-modulated radiation therapy with gold marker implantation for intermediate and high-risk prostate cancer.

Abstract

Radiation therapy (RT) is considered a standard treatment option for localized prostate cancer, with external beam RT (EBRT) being the most prevalent method used. EBRT evolved from 2-D conventional RT (2D-RT) to 3-D conformal RT (3D-CRT), and then to intensity-modulated RT (IMRT). In the 2D-RT era, radiation oncologists drew irradiation fields on simple roentgenographies, typically including two anterior-posterior fields with or without two lateral fields, where the radiation dose could be allowed within 70 Gy or less. In the 3D-CRT era, typically five to seven conformal irradiation fields shaped to fit the prostate with multileaf collimators, but without intensity modulation, were used, and the radiation dose could be escalated to 70–75 Gy without increasing toxicity. IMRT enabled further dose escalation; for example, to 74–86.4 Gy. IMRT requires high-quality control of multileaf collimators, which allow modulation of radiation intensity within the same field, and that can yield even a concave-shaped dose distribution that spares the rectum while covering the neurovascular bundles. Despite such high radiation doses administered in IMRT, late gastrointestinal toxicities of grade 3 or more were reported as just 0–3%.1 In the USA, 3D-CRT prevailed in the early 1990s, and IMRT began to replace it from around 2000. Sheets et al. reported a population-based study using Surveillance, Epidemiology and End Results Medicare-linked data from 2000 through 2009 for patients with non-metastatic prostate cancer. Use of IMRT versus conformal radiation therapy increased from 0.15% in 2000 to 95.9% in 2008. In propensity score-adjusted analyses (n = 12 976), men who received IMRT versus conformal radiation therapy were less likely to develop gastrointestinal morbidities, and also were less likely to receive additional cancer therapy.2 In Japan, the transition from 2D-RT through 3D-CRT to IMRT proceeded within a shorter span, or rather, all at once. Yoshioka et al. reported the change from 2D-RT to 3D-CRT in patients treated between 1998 and 2006, during which the actuarial 5-year grade 2–3 late rectal bleeding rate decreased from 23% to 7%.3 Meanwhile, around 2000, IMRT for prostate cancer began in Japan. Chiba Cancer Center, along with Kyoto University, should be recognized as pioneers in prostate IMRT in Japan.4 Kobayashi et al. reported long-term results of prostate IMRT at Chiba Cancer Center, including a successful biochemical control rate and a satisfactorily low toxicity rate.5 In 2008, the Japanese government began covering prostate IMRT under the national insurance system, and it is now rapidly becoming the prevalent therapy for prostate cancer in Japan. It should be noted that these pioneers contributed significantly to the current prevalence of IMRT in Japan. Another notable achievement of Kobayashi's study is their use of fiducial-marker guidance in the daily set-up for irradiation, which is now called image-guided RT. The authors imply that such a high-precision and high-dose IMRT should be accompanied by an accurate image-guided RT technique. This should be evaluated in the future through comparison with other image-guided RT techniques. None declared.