Impact of changing rectal dose volume parameters over time on late rectal and urinary toxicity after high-dose intensity-modulated radiotherapy for prostate cancer: A 10-years single centre experience.
BACKGROUND
External beam radiotherapy is an excellent treatment for patients with prostate cancer (PC). Assessing long-term radiotherapy-induced toxicity is important. We evaluated the impact of implementing different rectal dose volume constraints (DVC) on late rectal and urinary toxicity.


METHODS
Six hundred and thirty-seven PC patients were treated with high-dose intensity-modulated radiotherapy (IMRT) in the primary (median dose of 78 Gy to the prostate) or postoperative setting [median dose of 74 (adjuvant) and 76 Gy (salvage) to the prostatic bed]. Three groups were defined according to different DVC applied over time. The incidence of late rectal and urinary toxicity was evaluated. Three-year actuarial risk estimations of grade 2-3 rectal and urinary toxicity were calculated (Kaplan-Meier statistics).


RESULTS
Median follow-up was five years. Overall, the incidence of late grade 3 and 2 rectal toxicity was 1% and 11%. The calculated three-year actuarial risk of developing late grade≥2 rectal toxicity decreased from 16% to 7% and 5% for patients in Group 1, Group 2 and Group 3, respectively (p<0.001). Respectively, 17 (4%) and 98 (24%) patients developed grade 3 and 2 late urinary toxicity in the primary setting. In the postoperative setting, 15 (6%) and 62 (26%) patients developed grade 3 and 2 urinary toxicity, respectively. The three-year actuarial risk of developing late≥grade 2 urinary toxicity in primary- and postoperative-treated patients was 22% and 23%, respectively. This was not significantly different between the three groups.


CONCLUSIONS
The majority of patients developed no or only moderate rectal toxicity after high-dose IMRT for PC. Implementing different rectal DVC resulted in a significant decrease of late rectal toxicity without affecting urinary toxicity.
Ghent University Hospital, Department of Radiation Oncology and Experimental Cancer Research , Belgium.
Valérie
V
Fonteyne
Simin
S
Sadeghi
Piet
P
Ost
Frank
F
Vanpachtenbeke
Philippe
P
Vuye
Nicolaas
N
Lumen
Gert
G
De Meerleer
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D011832:Radiation Injuries / Q000209:etiology*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant / Q000009:adverse effects; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000639:trends; D012007:Rectum / Q000528:radiation effects*; D016879:Salvage Therapy / Q000009:adverse effects; D013997:Time Factors; D001743:Urinary Bladder / Q000528:radiation effects*