Long-term toxicity following 3D conformal radiation therapy for prostate cancer from the RTOG 9406 phase I/II dose escalation study.
OBJECTIVE
To update the incidence of late toxicity of RTOG 9406, a three-dimensional conformal radiation therapy (3DCRT) dose escalation trial for prostate cancer.


METHODS
A total of 1,084 men were registered to this Phase I/II trial of 3DCRT (eligible patients, 1,055). The dose for level I was 68.4 Gy; 73.8 Gy for level II; 79.2 Gy for level III; 74 Gy for level IV; and 78 Gy for level V. Patients in levels I to III received 1.8 Gy/fraction, and those in levels IV to V received 2.0 Gy/fraction. Disease group I patients were treated at the prostate only, group 2 patients were treated at the prostate and at the seminal vesicles with a prostate boost, and group 3 patients were treated at the prostate and seminal vesicles. The median follow-up period for surviving patients was 6.1 y (level V) to 12.1 y (level I).


RESULTS
The incidence rates of RTOG grade 3 or less gastrointestinal or genitourinary toxicity were 3%, 4%, 6%, 7%, and 9% in group 1 and 6%, 2%, 6%, 9%, and 12% in group 2 at dose levels of I, II, III, IV, and V, respectively. In group 1, level V patients had a higher probability of grade 2 late or greater gastrointestinal or genitourinary toxicity than those in levels I, II, and III (hazard ratio [HR] = 1.93, p = 0.0101; HR = 2.29, p = 0.0007; HR = 2.52, p = 0.0002, respectively). In group 2, dose level V patients had a higher probability of grade 2 or greater late gastrointestinal or genitourinary toxicity than those in dose levels II, III, and IV (HR = 2.61, p = 0.0002; HR = 2.22, p = 0.0051; HR = 1.60, p = 0.0276, respectively).


CONCLUSIONS
Tolerance to high-dose 3DCRT remains excellent. There is significantly more grade 2 or greater toxicity with a dose of 78 Gy at 2 Gy/fraction than with 68.4 Gy to 79.2 Gy at 1.8 Gy/fraction and with 74 Gy at 2 Gy/fraction.
Michalski
Jeff M
JM
Radiation Oncology, Washington University Medical School, St. Louis, MO 63110, USA. michalski@wustl.edu
Bae
Kyounghwa
K
Roach
Mack
M
Markoe
Arnold M
AM
Sandler
Howard M
HM
Ryu
Janice
J
Parliament
Matthew B
MB
Straube
William
W
Valicenti
Richard K
RK
Cox
James D
JD
D000368:Aged; D005500:Follow-Up Studies; D041981:Gastrointestinal Tract / Q000528:radiation effects*; D006801:Humans; D008297:Male; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D011467:Prostate / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000473:pathology* / Q000517:prevention & control; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D012007:Rectum / Q000528:radiation effects; D012669:Seminal Vesicles / Q000528:radiation effects; D016896:Treatment Outcome; D047368:Tumor Burden; D001743:Urinary Bladder / Q000528:radiation effects; D014566:Urogenital System / Q000528:radiation effects*