Dose escalation using a hypofractionated, intensity-modulated radiation therapy boost for localized prostate cancer: preliminary results addressing concerns of high or low alpha/beta ratio.
OBJECTIVE
The possibility that prostate cancers have a low alpha/beta ratio led to a schedule including a hypofractionated boost. The purpose of this study was to analyze the outcomes of this regimen.


METHODS
Between 2002 and 2007, 125 patients with localized prostate cancer were treated. Median follow-up was 33 months. Radiation therapy was delivered to a planning target volume including the prostate and seminal vesicles with a 1-1.5 cm margin to block edge using a 6-field technique to 45 Gy in 25 fractions. This was followed by a 2.5-Gy/fraction intensity-modulated radiation therapy boost to the prostate alone to a total dose of 75 Gy in 61 low-risk patients and 77.5 Gy to the prostate and seminal vesicles in 64 high- and intermediate-risk patients.


RESULTS
There have been 2 (1.6%) biochemical failures, 1 death from prostate cancer, and 1 death in a patient with no evidence of disease. Rates of acute genitourinary and gastrointestinal toxicity (grade 1 and 2) for the whole group were 31.2% and 16%, respectively. Rates of chronic genitourinary and gastrointestinal toxicity (grade 1 and 2) for the whole group were 30.4% and 27.2%, respectively. There were 2 patients (1.6%) with grade 3 gastrointestinal toxicity at 12 and 18 months' follow-up. They had radiation proctitis requiring laser cauterization.


CONCLUSIONS
The preliminary results of this novel schedule were excellent. Given that the alpha/beta ratio is still in question, this technique addresses concerns regarding low and high ratios. This technique is a suitable alternative method of dose escalation in the treatment of localized prostate cancer.
Shridhar
Ravi
R
Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL 33612, USA. ravi.shridhar@moffitt.org
Bolton
Sue
S
Joiner
Michael C
MC
Forman
Jeffrey D
JD
D000328:Adult; D000369:Aged, 80 and over; D005767:Gastrointestinal Diseases / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000473:pathology; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods*; D016896:Treatment Outcome