Purpose: Our institution offered patients brachytherapy with the single (SCVC) or multichannel vaginal cylinder (MCVC) for vaginal cancer and with the tandem and ring (TR) for cervical and endometrial cancer treatment. Each modality has advantages in some aspects over others. A combination of multichannel vaginal cylinder with intrauterine tube (MCVC-IUT) has shown a superior capability of treating vaginal, cervical and endometrial cancer in one procedure over to two procedures using, respectively, TR and cylinder applicators. The current work presents dosimetric evaluation and clinical application of MCVC-IUT applicator set in treating vaginal, cervical and endometrial cancer.
Methods: Three sizes of MCVC in diameter 25, 30 and 35 mm and three types of intrauterine tubes of 20mm/15 deg, 40mm/30deg and 60mm/45deg were offered to patients. Each was assessed with physical measurements and CT scanning. The dwell source position of the cuffed catheters and intrauterine tubes was verified with a source position simulator and Gafchromic film EBT3. An Elekta Oncentra version 4.5.3 was served as a planning system. Radiation was delivered by an Elekta Flexitron. Radiation dose was prescribed either to the depth or the planned treatment volume (PTV) and point A. IPSA was used for radiation dose optimization.
Results: Radiation dose 700cGy for a MCVC-IUT system was prescribed to the point A and PTV at 5mm away from the surface of a 25mm-MCVC with treatment length of 50mm. A Smit Sleeve was used for guiding intrauterine tube and identifying cervix. MCVC was able to sculpture radiation dose to the PTV while sparing dose to nearby organs at risk such as rectum and bladder. A final dose distribution featured a joint dose distribution of tandem and ring with a cylinder.
Conclusion: MCVC IUT applicators integrated outstanding dosimetric features from TR and MCVC in an effective treatment of vaginal, cervical and endometrial cancers.