Abstract
BackgroundInterstitial brachytherapy (ISBT) is an optional treatment for locally advanced gynecological tumours for which conventional intracavitary brachytherapy (ICBT) would result in suboptimal dose coverage. However, ISBT with Martinez Universal Perineal Interstitial Template (MUPIT), in which ~10-20 needles are usually applied, is more time-consuming and labor-intensive than ICBT alone, making it a burden on both practitioners and patients. Therefore, here we investigated the applicability of a combined intracavitary/interstitial (IC/IS) approach in image-guided adaptive brachytherapy for bulky and/or irregularly shaped gynecological tumours for which interstitial brachytherapy (ISBT) was performed.MethodsTwenty-one consecutive patients with gynecological malignancies treated with computed tomography-guided ISBT using MUPIT were analyzed as cases for this dosimetric study. For each patient, the IC/IS plan using a tandem and 1 or 2 interstitial needles, which was modeled after the combined IC/IS approach, was generated and compared with the IS plan based on the clinical ISBT plan, while the IC plan using only the tandem was applied as a simplified control. Maximal dose was prescribed to the high-risk clinical target volume (HR-CTV) while keeping the dose constraints of D2cc bladder < 7.0 Gy and D2cc rectum < 6.0 Gy. The plan with D90 HR-CTV exceeding 6.0 Gy was considered acceptable.ResultsThe average D90 HR-CTV was 77%, 118% and 140% in the IC, IC/IS and IS plans, respectively, where 6 Gy corresponds to 100%. The average of the ratio of D90 HR-CTV to D2cc rectum (gain factor (GF) rectum) in the IC, IC/IS and IS plans was 0.8, 1.3 and 1.5 respectively, while GFbladder was 0.9, 1.4 and 1.6, respectively. In the IC/IS plan, D90 HR-CTV, GFrectum and GFbladder exceeded 100%, 1.0 and 1.0, respectively, in all patients.ConclusionsThese data demonstrated that the combined IC/IS approach could be a viable alternative to ISBT for gynecological malignancies with bulky and/or irregularly shaped tumours.Electronic supplementary materialThe online version of this article (doi:10.1186/s13014-014-0222-6) contains supplementary material, which is available to authorized users.
Highlights
Interstitial brachytherapy (ISBT) is an optional treatment for locally advanced gynecological tumours for which conventional intracavitary brachytherapy (ICBT) would result in suboptimal dose coverage
Average ± standard deviation (SD) of high-risk clinical target volume (CTV) (HR-CTV) in the present study was 60 ± 32 cm3, which was similar to the values of patients with locally advanced cervical cancer treated with combined IC/IS by the Utrecht group (66 ± 34 cm3) [8]
The IC plans with only the tandem resulted in insufficient high-risk clinical target volume (HR-CTV) coverage as expected (Figure 2a-e, Figure 3a, Table 1)
Summary
Interstitial brachytherapy (ISBT) is an optional treatment for locally advanced gynecological tumours for which conventional intracavitary brachytherapy (ICBT) would result in suboptimal dose coverage. ISBT with Martinez Universal Perineal Interstitial Template (MUPIT), in which ~10-20 needles are usually applied, is more time-consuming and labor-intensive than ICBT alone, making it a burden on both practitioners and patients. We have been treating patients with locally advanced cervical tumours and other gynecological malignancies using in-room and in-situ computed tomography (CT)-guided adaptive high dose rate (HDR) ISBT with Martinez Universal Perineal Interstitial Template (MUPIT, Nucleotron) [2]. ISBT with MUPIT, in which ~10-20 needles are usually applied, is more time-consuming and laborintensive than ICBT alone, making it a burden on practitioners Patients receiving this treatment must bear the hardship of keeping interstitial needles implanted for several days. These aspects have prompted us to explore alternative treatment strategies for bulky and/or irregularly shaped tumours
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