Original ReportProposed definition of the vaginal cuff and paracolpium clinical target volume in postoperative uterine cervical cancer
Introduction
Postoperative radiation therapy is an established adjuvant treatment modality after radical hysterectomy for early-stage cervical cancer with specific adverse pathologic features.[1], [2] The conventional 3-dimensional conformal radiation technique (3DCRT) for pelvic radiation therapy involves the 4-field box technique. Although this technique includes less small bowel volume than the traditional anterior-posterior–posterior-anterior 2-field technique, a considerable part of the small bowel receives unnecessary irradiation equal in degree to the prescribed dose for target volume.
The high-precision technique of intensity modulated radiation therapy (IMRT) has the potential to irradiate the target volume while sparing adjacent risk organs. The usefulness of IMRT has been validated in several anatomic sites[3], [4], [5], [6]; however, the advantage of IMRT in the field of gynecologic cancer has not been determined clearly.[7], [8], [9], [10] The Radiation Therapy Oncology Group (RTOG) organized a multicenter, prospective, phase 2, single-arm clinical trial (RTOG 0418) using IMRT for postoperative endometrial and cervical patients,10 in which a favorable result regarding short-term bowel toxicity was demonstrated. Because of a concern about possible late severe bowel morbidity caused by the combination of surgery and radiation therapy and the favorable preliminary results for adjuvant chemotherapy alone for intermediate- and high-risk postoperative cervical cancer patients,11 some medical facilities in Japan do not use adjuvant radiation therapy for patients with early-stage high-risk postoperative cervical cancer. Instead, some medical facilities in Japan use adjuvant chemotherapy alone, even though this is not regarded as standard therapy for this population of patients.12 Therefore, the efficacy and safety of IMRT should be validated in a multi-institutional prospective clinical trial involving postoperative patients with early-stage high-risk cervical cancer.
It is possible to create a complicated, irregularly shaped dose distribution with IMRT. Thus, it is possible to focus more on the clinical target volume (CTV) with IMRT, while avoiding the organ at risk when using 3DCRT. More precise target definition is required in IMRT than conventional 3DCRT to eliminate a geographic miss, and a deeper understanding of the anatomy is essential to create high-quality IMRT plans. To aid in the definition of CTV contouring, guidelines for CTVs have been published for several anatomic sites.[13], [14], [15], [16] In the field of gynecologic cancer, the RTOG and the Radiation Therapy Study Group (RTSG) of the Japan Clinical Oncology Group (JCOG) published postoperative and intact uterus contouring guidelines[17], [18], [19], [20]; however, a clear definition of the postoperative vaginal cuff and paracolpium CTV has not been promulgated.
Therefore, in preparation for a nationwide multicenter clinical trial involving IMRT in postoperative patients with early-stage high-risk cervical cancer, a working subgroup was organized within the RTSG of the JCOG to establish guidelines for the vaginal cuff and paracolpium CTV.
Section snippets
Methods and materials
Development of a protocol for a multicenter clinical trial that would validate the efficacy and safety of IMRT in postoperative cervical cancer patients was initiated from April 2013 by the RTSG of the JCOG. In December 2013, a working subgroup was organized within this group to establish a definition for the postoperative vaginal cuff and paracolpium CTV. Five radiation oncologists who specialized in gynecologic oncology and a gynecologic oncologist made up this working group. Development of
Results
Figure 1A is a schema of preoperative anatomic components around the cervix with reference to the parametrium; Fig 2 is a schema of muscular structures that constitute the female pelvic floor; and Fig 3 is a representative magnetic resonance image of a patient who had undergone hysterectomy. As shown in Fig 1A, the internal obturator muscle forms the lateral border of the cardinal ligament. The mesorectum or mesorectal fascia forms the posterior and posteromedial borders of the cardinal
Discussion
The RTOG contouring guidelines for postoperative endometrial and cervical cancers17 do not provide clear anatomic boundaries or detailed figures for the vaginal cuff and paracolpium. This could be a possible reason for the limited unacceptable vaginal contouring in the RTOG 0418 trial,10 which could have potentially caused unfavorable clinical results. Because our group developed guidelines for the pelvic nodal CTV in postoperative cervical cancer,18 we focused on the development of definitions
Conclusion
A proposed definition for postoperative patients with cervical cancer regarding the vaginal cuff and paracolpium CTV was developed. This guideline will serve as a template for future radiation therapy clinical trial protocols, especially trials involving IMRT.
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Cited by (10)
Positional uncertainty of vaginal cuff and feasibility of implementing portable bladder scanner in postoperative cervical cancer patients
2018, Physica MedicaCitation Excerpt :Several surgical titanium clips (about 2 mm length and 1 mm diameter) were implanted in the vaginal cuff region and these were used to define the vaginal cuff CTV (mean (1σ) = 2.2 (0.9) for number of clips per patient). The nodal and vaginal cuff CTV were contoured according to contouring guidelines [25,26]. The nodal and vaginal cuff PTV received 50 Gy in 25 fractions and all patients were treated with volumetric arc therapy (VMAT) using 2 arcs and 15 MV x-rays.
A dummy-run evaluation of postoperative hypofractionated intensity-modulated radiation therapy (POHIM-RT) trials for cervical cancer
2021, Journal of Radiation Research
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Sources of support: This study was supported in part by the National Cancer Center Research and Development Fund 23A-13, 23-A-17, and 26-A-4.
Conflicts of interest: None.