Intensity-modulated radiotherapy for adenocarcinoma of the prostate: A point of view

Percutaneous radiotherapy for low-risk prostate cancer: options for 2007

Technical developments of radiotherapy (RT) over the recent years yielded in better conformation to the target volume thus increasing the therapeutic ratio and decreasing side effects. This paper discusses these options for low-risk prostate cancer. There has been evidence from randomized trials, that for low-risk PCA doses >70 Gy are significant better in case of biochemical disease-free survival (bNED). Image-guided radiotherapy (IGRT) has been proven in several studies for reduced safety margins around the prostate target volume. Intensity-modulated radiotherapy (IMRT) allow treatment with higher doses and 5-year results are reported from several studies. Data from several randomized trials about adjuvant RT after radical prostatectomy (RP) have been reported. In two phase-III trials a significant advantage of 20% bNED was demonstrated for doses between 76 and 79 Gy compared with 70 Gy. Using IGRT, the safety margin around the prostate can be reduced for about 30-50%. Doses of >80 Gy can be given safely to the prostate with IMRT and <5% grade-III/IV late side effects. Adjuvant RT for positive margins after RP has been of proven advantage. Three phase-III trials achieved a significant better bNED of 20% for 5 years. The effect of doses >70 Gy have been proven for low-risk PCA. IGRT resulted in reduced safety margins and a decrease of acute and late side effects. The addition of IMRT allowed higher doses to the prostate. Adjuvant RT after RP for positive margins achieved a significant better bNED.

Dose distribution in 3-dimensional conformal radiotherapy for prostate cancer: Comparison of two treatment techniques (six coplanar fields and two dynamic arcs)

PURPOSE

To compare dose distribution for two techniques of 3-dimensional conformal radiotherapy (RT): 6-field technique (6F) and 2-dynamic arc therapy (2DA).

METHODS AND MATERIALS

Thirty nonmetastatic prostate cancer patients were included. In each patient, two treatment plans were prepared: with six coplanar fields (45 degrees , 90 degrees , 135 degrees , 225 degrees , 270 degrees , 315 degrees ) and with two dynamic lateral 100 degrees -wide arcs (40-140 degrees , 220-320 degrees ). Dose-volume histograms (DVHs) were computed and mean area under curve (AUC) values were calculated for the DVHs of Planning Target Volume (PTV), rectum, urinary bladder and femoral heads. Doses given to 30% of rectum (DR(30)), to 60% of rectum (DR(60)), to 50% of bladder (DB(50)), to 50% of femoral head (DF(50)) and to 95% of PTV (DPTV(95)) were reported as a percentage of the total dose.

RESULTS

Mean DR(30) and DR(60) for 6F and 2DA were 75.8%, 51.5% and 72.2%, 37.2%, respectively. Mean DB(50) for 6F and 2DA were 68% and 64.2%, respectively. Mean right DF(50) for 6F and 2DA were 35.4% and 45.5%, respectively. Mean DPTV(95) for 6F and 2DA were 99% and 99.2%, respectively. Mean AUCs of DVHs of rectum and urinary bladder were significantly higher for 6F (this was more evident for small PTV and in the intermediate dose range). Mean AUC of DVHs of PTV and femoral heads were significantly higher for 2DA.

CONCLUSIONS

Both 6F and 2DA offer good dose distribution for PTV. 2DA allows for significantly better sparing of rectum and urinary bladder with slightly worse femoral head dose distribution. Further study is warranted in order to establish the clinical relevance of these differences.