A dosimetric analysis comparing treatment of low-risk prostate cancer with TomoTherapy versus static field intensity modulated radiation therapy.
OBJECTIVE
Static field intensity modulated radiation therapy (IMRT) has demonstrated dosimetric and clinical benefits over 3-dimensional conformal radiation therapy. TomoTherapy is a unique form of IMRT that may offer further improvements.


METHODS
The study population consisted of 15 patients with low-risk prostate cancer treated at Rush University with TomoTherapy (n = 7) or IMRT (n = 8). For each patient, both a TomoTherapy plan and an IMRT plan were generated using identical planning objectives. The planning target volume (PTV) was defined as the prostate and proximal seminal vesicles plus a margin. The prescription dose was 7740 cGy in 43 fractions. Radiation Therapy Oncology Group (RTOG) normal tissue guidelines were used as constraints, and the PTV coverage was made equivalent for the paired plans by equalizing the PTV V100. RTOG benchmark DVH values for the rectum and bladder and mean dose to the penile bulb were recorded. The volume of PTV receiving ≥ 105% of the prescription dose was measured.


RESULTS
The mean DVH values for each of the RTOG constraints for rectum and bladder were significantly improved using TomoTherapy. The volume of the PTV that received at least 105% of the dose was higher with IMRT (11.7% vs. 0.2%, <0.001). The mean dose to the penile bulb was higher with TomoTherapy (40.4 Gy vs. 27.4 Gy, P = 0.005).


CONCLUSIONS
TomoTherapy offers a more favorable dose distribution to the bladder and rectum, as well as improved target homogeneity in comparison with IMRT.
Shah
Anand P
AP
Department of Radiation Oncology, Rush University Medical Center, Chicago, IL, USA. anand_shah@rush.edu
Chen
Sea S
SS
Strauss
Jonathan B
JB
Kirk
Michael C
MC
Coleman
Joy L
JL
Coon
Alan B
AB
Miller
Cheryl
C
Dickler
Adam
A
D006801:Humans; D008297:Male; D011467:Prostate / Q000000981:diagnostic imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D012306:Risk; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000528:radiation effects