Intensity modulated radiation therapy (IMRT) in the radiotherapy treatment of colo-rectal cancer: the influence of profile smoothing on the efficiency of delivery

2002 ◽  
Vol 2 (4) ◽  
pp. 189-198 ◽  
Author(s):  
W. Laub ◽  
D. Yan ◽  
J. Robertson ◽  
A. Martinez
Keyword(s):  
Rectal Cancer ◽  
Radiation Therapy ◽  
Small Bowel ◽  
Intensity Modulated Radiation Therapy ◽  
Smoothing Function ◽  
Treatment Technique ◽  
Intensity Modulated ◽  
Treatment Implementation ◽  
Close Proximity ◽  
Radiotherapy Treatment

Small bowel toxicity due to radiotherapy treatment of rectal cancer is common. The potential use of intensity modulated radiation therapy (IMRT) to reduce the volume of small bowel irradiated during radiation therapy (RT) for cancer has previously been reported. However, IMRT treatment implementation is relatively difficult for these patients. The PTV is large and has a concave shape, with the small bowel in very close proximity. Therefore, the intensity profile calculated by an inverse planning engine could be highly modulated and complicated to deliver.In this study, two methods were used to optimise IMRT plans for rectal cancer patients. Scatter contribution when backprojecting dose values to fluence values and a smoothing function were only implemented in the optimisation searching of one method. A common arrangement of five beams, each separated by equal gantry angle, was adopted. With both methods used, the dose coverage of the PTV was satisfactory. Small bowel irradiated to a dose of 95 % was reduced by about 70% as compared to a 3D conformal 3-field treatment technique. However, incorporation of scatter contribution and a smoothing function in the iteration of optimisation searching greatly reduced the degree of modulation in the two-dimensional intensity profiles. Instead of 120–160 step-and-shoot MLC segments only 30–60 segments were necessary to deliver the five intensity profiles. The number of monitor units per fraction was reduced accordingly to about one half. Therefore, by controlling the smoothness of the intensity profiles during optimisation, the produced IMRT plans could be delivered more efficiently. Moreover, the possibility to account for overlap of organs was found to be very valuable to avoid hot spots in these regions and to get the full DVHs of all organs at the same time.

Intensity-modulated radiation therapy (IMRT): Differences in target volumes and improvement in clinically relevant doses to small bowel in rectal carcinoma.

2011 ◽  
Vol 29 (4_suppl) ◽  
pp. 586-586
Author(s):  
H. Mok ◽  
C. H. Crane ◽  
T. Briere ◽  
S. Beddar ◽  
M. E. Delclos ◽  
...  
Keyword(s):  
At Risk ◽  
Rectal Cancer ◽  
Radiation Therapy ◽  
Small Bowel ◽  
Rectal Carcinoma ◽  
Organs At Risk ◽  
Intensity Modulated Radiation Therapy ◽  
Preoperative Treatment ◽  
Conformal Radiation Therapy ◽  
Intensity Modulated

586 Background: In the treatment of rectal cancer, a strong dose-volume relationship exists between the amount of small bowel receiving low- to intermediate-doses of radiation and the rates of acute, severe gastrointestinal toxicity. Highly conformal treatment approaches, such as intensity-modulated radiation therapy (IMRT), may reduce dose to adjacent organs-at-risk (OAR). We performed a dosimetric evaluation of IMRT compared to 3-dimensional conformal radiation therapy (3DCRT) in standard, preoperative treatment for rectal cancer. Methods: Using RTOG consensus contouring atlas, treatment volumes were generated for ten patients treated preoperatively, with IMRT plans compared to 3DCRT plans derived from classic anatomic landmarks, as well as modified 3DCRT plans treating the RTOG consensus volume. The patients were all T3, were node-negative (N=1) or node–positive (N=9), and were planned to a total dose of 45-Gy. Bowel displacement was achieved using a carbon-fiber bellyboard apparatus with prone positioning. Results: IMRT plans had superior PTV coverage, dose homogeneity, and conformality in treatment of the gross disease and at-risk nodal volume, in comparison to 3DCRT. Additionally, in comparison to the modified 3DCRT plans, IMRT achieved a concomitant reduction in doses to the bowel, bladder, pelvic bones, and femoral heads, with an improvement in absolute volumes of small bowel receiving dose levels known to induce clinically-relevant acute toxicity. In the six patients with the highest volume of small bowel (range: 209-537-cc), the volume of bowel receiving 15-Gy was reduced from a median of 224-cc in the modified 3DCRT plans to 185-cc with IMRT. Also, the IMRT volumes were typically larger than that covered by classic 3DCRT fields, without incurring penalty with respect to adjacent OAR. Conclusions: For rectal carcinoma, IMRT, compared to 3DCRT, yielded plans with superior target coverage, homogeneity, and conformality, while lowering dose to adjacent OAR. This is despite treating larger volumes, raising the possibility of a clinically-relevant improvement in the therapeutic ratio through the use of IMRT with a belly-board apparatus. No significant financial relationships to disclose.

National trends in intensity modulated radiation therapy (IMRT) use for rectal cancer.

2019 ◽  
Vol 37 (4_suppl) ◽  
pp. 648-648
Author(s):  
Zachary D. Horne ◽  
Stephen Abel ◽  
Shaakir Hasan ◽  
Alexander V. Kirichenko ◽  
Rodney E Wegner
Keyword(s):  
Rectal Cancer ◽  
Radiation Therapy ◽  
Surgical Resection ◽  
Locally Advanced ◽  
Multivariable Analysis ◽  
Rectal Adenocarcinoma ◽  
Intensity Modulated Radiation Therapy ◽  
Treatment Technique ◽  
Current Standard ◽  
Intensity Modulated

648 Background: Neoadjuvant chemoradiation represents the current standard of care for locally advanced rectal cancer prior to surgical resection. Traditionally, 3D conformal radiation therapy (3D CRT) was used in this setting. With advancing technology, intensity modulated radiation therapy (IMRT) was developed with the goal of delivering a more conformal radiation dose, with the potential for reduced toxicity providing a potential advantage across many disease sites. We sought to use the national cancer database (NCDB) to examine trends and predictors for IMRT use in rectal cancer. Methods: We queried the NCDB from 2004-2015 for patients with rectal adenocarcinoma treated with neoadjuvant concurrent chemoradiation to a standard doses (50.4-54Gy) followed by surgical resection. Odds ratios were used to determine predictors of IMRT use. Univariable and multivariable cox regressions were used to determine potential predictors of overall survival (OS). Propensity matching was used to account for any indication bias. Results: We identified 21,490 patients satisfying eligibility criteria, of which 3,131 were treated with IMRT. IMRT use increased from 1% in 2004 to 22% in 2014. Predictors for IMRT use included increased N stage, more recent treatment year, treatment at an academic facility, increased income, and higher educational level. On multivariable analysis including propensity score male gender, increased distance to facility, higher comorbidity score, IMRT technique, government insurance, African American race, and non-metro location were predictive of worse OS. Of note, the complete response rate at time of surgery was 28% with non-IMRT and 21% with IMRT. Conclusions: IMRT use has steadily increased in the treatment of rectal cancer, but still remains only a fraction of overall treatment technique. IMRT use correlated with worse survival likely due to utilization in higher stages and patients with worse disease features.

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