Article
Intensity modulated radiotherapy (IMRT) for high risk prostate cancer based on sentinel node optimized target volume definition
Search Medline for
Authors
Published: | March 20, 2006 |
---|
Outline
Text
Objective: Whereas cure rates for patients (pts.) with low/intermediate risk prostate cancer (PC) are good, the situation is more problematic in high risk PC. In parallel with risk of distant seeding, the probability of locoregional lymph node metastasis increases. The RTOG 94-13 provided evidence that pts. with high risk of pelvic node involvement benefit from an additional radiotherapy (RT) to the pelvic nodes combined with hormonal ablation. Since the physiological lymphatic drainage is highly variable, the optimal target volume definition for the adjuvant nodes is problematic. To overcome this limitation, we tried to optimize our target volume definition by including information derived from pelvic sentinel nodes (SN) identification.
Material and Methods: Pts. with histologically proven high risk PC, cN0 stage, were included. To permit a three-dimensional (3D) localisation of SN transmission- and emission data were acquired using a double-headed gamma camera with an integrated X-Ray device (Millennium VG & Hawkeye®, GE) 1.5-3 hours after injection of 250 MBq 99mTc-Nanocoll. Numbers and 3D-localisations of SN were analysed. IMRT planning was done with Hyperion® based on 3 CT’s, definition of clinical/planning target volumes (CTV/PTV) and risk organs with image fusion of 3 data sets. All SN localisations were included into the pelvic CTV additionally. Dose prescriptions were 50,4 Gy (1,8 Gy/d) to the pelvis and 70,0 Gy (2 Gy/d) to the prostate/seminal vesicles.
Results: Since 08/2003 17 pts. with cT1c-4 stage were treated. No patient (pat.) had undergone a staging lymphadenectomy. All pts. had detectable SN, the numbers of SN per pat. ranged from 2 to 9. A total of 91 SN could be identified for all 17 pts. together. Most common localisations were ext. iliac (36), followed by int. iliac (15), perirectal lymph. plexus (10), common iliac (8), seminal vesicle lymph. plexus (6), sacral (5), left paraaortic (3), int. pudendal (2), perivesical lymph. plexus (2), sup. rectal (1), inf. rectal (1), deep inguinal (1) and right paraaortic (1). IMRT planning could be completed in all pts. with acceptable doses to risk organs and prescribed doses to the target volumes. 11 of 17 pts. showed SN localisations (total 31 SN) that would not have been treated adequately with only CT-based planning (‘geographical miss’). The comparison between dose-volume-histograms of IMRT- and conventional CT-planning in regard to the risk organs demonstrated clear superiority of IMRT when all SN were included. No gastrointestinal or genitourinary acute toxicity Grade 3 or 4 (RTOG) occurred.
Conclusion: IMRT based on SN identification is feasible and reduces the probability of a geographical miss. Furthermore IMRT allows a pronounced sparing of normal tissue irradiation. Thus the chosen approach will help to increase the curative potential of RT in high risk PC pts.