[Conformal radiotherapy in prostate cancer: for whom and how?]

Radiothérapie pelvienne pour récidive biochimique isolée après prostatectomie pour cancer de prostate : quels volumes ?

After prostatectomy, radiotherapy is a potential curable treatment. From the surgery series, it is possible to identify all the localization at risk in case of biochemical relapse after prostatectomy. The target volume of irradiation has to be defined according to the pathological findings. The CTV is limited to the pelvic fascia laterally, to the anterior wall of the rectum behind. The inferior limit includes the anastomosis, and the superior is easier to define with the length of the prostatic gland. The inclusion of area of seminal vesicles and pelvic node areas should be discussed. The use of surgical clips on the anastomosis and image fusionning techniques including the preoperative imaging would help physicians to define the CTV's limits.

[Pilot study of conformal intensity modulated radiation therapy for localized prostate cancer]

PURPOSE

- To report our experience on treatment planning and acute toxicity in 16 patients suffering from clinically localized prostate cancer treated with high-dose intensity-modulated radiation therapy (IMRT).

PATIENTS AND METHODS

- Between March 2001 and October 2002, 16 patients with clinically localized prostate cancer were treated with IMRT. Treatment planning included an inverse-planning approach, and the desired beam intensity profiles were delivered by dynamic multileaf collimation. All patients received the entire treatment course with IMRT to a prescribed dose of 78 Gy. All IMRT treatment plans were compared with a theoretical conventional three-dimensional conformal radiation therapy (3D-CRT). Acute lower gastro-intestinal (GI) and genito-urinary (GU) toxicity was evaluated in all patients and graded according to the Common Toxicity Criteria for Adverse Events version 3.0 (CTCAE v. 3.0). A relationship between dose volume and clinical toxicity was evaluated.

RESULTS

- Ninety-five percent of the PTV2 received more than 76 Gy using IMRT or 3D-CRT with no difference between both methods. The dose-volume histogram mean obtained for the PTV2 was not different between IMRT and 3D-CRT. IMRT improved homogeneity of the delivered dose to the PTV2 as compared with 3D-CRT (7.5 vs 9%, respectively). Ninety-five percent of the PTV1 received 5 Gy more using IMRT with protection of the bladder and the rectum walls. The benefit was considered below 75 and 70 Gy for the wall of the bladder and the rectum, respectively. Grade 2 GI and GU toxicity was observed in four (25%) and five (31%) patients, respectively. No grade 3 toxicity was observed. There was a trend towards a relationship between the mean rectal dose and acute rectal toxicity but without statistical significant difference (P =0.09).

CONCLUSION

- Dose escalation with IMRT is feasible with no grade 3 or higher acute GI or GU toxicity. Examination of a larger cohort and longer-term follow-up are warranted in the future.