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.

PURPOSE: 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.

PATIENTS AND

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.

CONCLUSION

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.