Dosimetric comparison of intensity-modulated, conformal, and four-field pelvic radiotherapy boost plans for gynecologic cancer: a retrospective planning study

Abstract

Purpose: To evaluate intensity-modulated radiation therapy (IMRT) as an alternative to conformal radiotherapy (CRT) or 4-field box boost (4FB) in women with gynecologic malignancies who are unsuitable for brachytherapy for technical or medical reasons.Methods: Dosimetric and toxicity information was analyzed for 12 patients with cervical (8), endometrial (2) or vaginal (2) cancer previously treated with external beam pelvic radiotherapy and a CRT boost. Optimized IMRT boost treatment plans were then developed for each of the 12 patients and compared to CRT and 4FB plans. The plans were compared in terms of dose conformality and critical normal tissue avoidance. Results:The median planning target volume (PTV) was 151 cm 3 (range 58-512 cm 3 ). The median overlap of the contoured rectum with the PTV was 15 (1-56) %, and 11 (4-35) % for the bladder. Two of the 12 patients, both with large PTVs and large overlap of the contoured rectum and PTV, developed grade 3 rectal bleeding. The dose conformity was significantly improved with IMRT over CRT and 4FB (p ≤ 0.001 for both). IMRT also yielded an overall improvement in the rectal and bladder dose-volume distributions relative to CRT and 4FB. The volume of rectum that received the highest doses (>66% of the prescription) was reduced by 22% (p < 0.001) with IMRT relative to 4FB, and the bladder volume was reduced by 19% (p < 0.001). This was at the expense of an increase in the volume of these organs receiving doses in the lowest range (<33%). Conclusion:These results indicate that IMRT can improve target coverage and reduce dose to critical structures in gynecologic patients receiving an external beam radiotherapy boost. This dosimetric advantage will be integrated with other patient and treatment-specific factors, particularly internal tumor movement during fractionated radiotherapy, in the context of a future image-guided radiation therapy study.

Dosimetric study comparing intensity modulated and conformal pelvic radiotherapy boost plans in locally advanced cancer cervix

“…In our study it was found that 30% of the volume of the rectum received about 70% of the prescribed dose by the IMRT field while in CRT 30% of the rectal volume received 95%of the dose, this is in concordance to what was reported by Philip Chan et al 2006 [5] where there was rectal volume reduction by about 22% on using the 8 fields IMRT.…”

“…In our study it was found that the IMRT technique reduces the volume of the bladder receiving the dose by about 30% than that of the 3DCRT which is in concordance to what was reported by Philip Chan et al 2006 [5] who reported reduction in the bladder volume by 19% on using the 8 fields IMRT.…”

“…Philip Chan et al 2006 [5] showed that the use of IMRT significantly improved the conformality relative to CRT treatment both the 95% isodose line encompassed 95% or more of the PTV in both of the IMRT and CRT plans which is similar to our results which showed that the V99 was nearly the same for 3D plane and for IMRT plane. In our study normal tissue avoidance was assessed using cumulative DVH for both bladder and rectum.…”

“…The dose-volume constraints for the portions of the rectum, bladder and both femoral heads outside of the PTV were set so that 30% of the OAR-received less than 66% of the prescribed dose, and 70% of the OAR-received less than 33% of the dose [5] .…”

Should helical tomotherapy replace brachytherapy for cervical cancer? Case report

“…IMRT and 3-dimensional conformal radiotherapy (3DCRT) are now widely used radiotherapy techniques for various cancers and have been shown to be acceptable alternatives to brachytherapy for the treatment of gynecologic malignancies [5,9]. …”