Does intensity modulated radiation therapy (IMRT) prevent additional toxicity of treating the pelvic lymph nodes compared to treatment of the prostate only?
BACKGROUND
To evaluate the risk of rectal, bladder and small bowel toxicity in intensity modulated radiation therapy (IMRT) of the prostate only compared to additional irradiation of the pelvic lymphatic region.


METHODS
For ten patients with localized prostate cancer, IMRT plans with a simultaneous integrated boost (SIB) were generated for treatment of the prostate only (plan-PO) and for additional treatment of the pelvic lymph nodes (plan-WP). In plan-PO, doses of 60 Gy and 74 Gy (33 fractions) were prescribed to the seminal vesicles and to the prostate, respectively. Three plans-WP were generated with prescription doses of 46 Gy, 50.4 Gy and 54 Gy to the pelvic target volume; doses to the prostate and seminal vesicles were identical to plan-PO. The risk of rectal, bladder and small bowel toxicity was estimated based on NTCP calculations.


RESULTS
Doses to the prostate were not significantly different between plan-PO and plan-WP and doses to the pelvic lymph nodes were as planned. Plan-WP resulted in increased doses to the rectum in the low-dose region </= 30 Gy, only, no difference was observed in the mid and high-dose region. Normal tissue complication probability (NTCP) for late rectal toxicity ranged between 5% and 8% with no significant difference between plan-PO and plan-WP. NTCP for late bladder toxicity was less than 1% for both plan-PO and plan-WP. The risk of small bowel toxicity was moderately increased for plan-WP.


CONCLUSIONS
This retrospective planning study predicted similar risks of rectal, bladder and small bowel toxicity for IMRT treatment of the prostate only and for additional treatment of the pelvic lymph nodes.
Guckenberger
Matthias
M
Department of Radiation Oncology, Julius-Maximilians University, Wuerzburg, Germany. Guckenberger_M@klinik.uni-wuerzburg.de
Baier
Kurt
K
Richter
Anne
A
Vordermark
Dirk
D
Flentje
Michael
M
D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects*; D008198:Lymph Nodes / Q000528:radiation effects*; D008297:Male; D010388:Pelvis / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D012007:Rectum / Q000528:radiation effects*; D012189:Retrospective Studies; D012669:Seminal Vesicles / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects*