Does help structures play a role in reducing the variation of dwell time in IPSA planning for gynaecological brachytherapy application?

Purpose: To report our experience of dosimetric comparison of IPSA and manual plans, with a focus on the use ofhelp structures (HS) during optimization. Material and methods: 33 patients who underwent MR image-based HDR intracavitary-brachytherapy for cervixcancer based on GYN-ESTRO recommendations were selected for evaluation. Tandem/ovoid (T/O) and Vienna applicatorswere used. HS of diameter of 5 mm were drawn around the tandem/needles/ovoid and ring. Three plans weregenerated: manual optimized plan (MOPT), IPSA without help structures (IPSA_woHS) and IPSA with help structures(IPSA_wHS). Dose-volume parameters and the loading pattern were evaluated. Results: For T/O, the use of HS did not make significant impact in the dose-volume parameters and in the loadingof tandem and ovoids, however steep variation was found in the individual dwell time. In case of Vienna applicator,inclusion of HS in the optimization made a significant impact in loading of needles. The percentage ratio oftotal time of needles to the tandem (TN/T%) was found to be 14 ± 2.5, 53 ± 9, 22 ± 6 for MOPT, IPSA_woHS andIPSA_wHS, respectively, which implies that in IPSA_woHS the dwell time in needles were half of the dwell time inthe tandem, while in MOPT the needles were loaded only in 14%, and in IPSA_wHS it was 22% of the dwell timeof tandem. Inclusion of HS in the optimization has reduced the contribution of dwell time of needle in IPSA_wHS.The individual variation of dwell time was also reduced in IPSA_wHS, however drawing of HS is a time consumingprocedure and may not be practical for a routine practice. Conclusion: The role of HS was evaluated for IPSA for T/O and Vienna-applicator, the use of HS may be beneficialin case of combined intracavitary – interstitial approach

Treatment outcome with low-dose-rate interstitial brachytherapy in early-stage oral tongue cancers

Purpose : Although radical radiotherapy is known to be equally effective for early-stage oral tongue cancers (T1-2 N0) with the added advantage of organ and function preservation, surgery remains the preferred treatment. We present outcome of patients treated with brachytherapy (BT) either radical or boost. Materials and Methods : Fifty-seven patients (T1/T2 31/26) were studied. Seventeen patients (30%) were treated with radical BT (50-67 Gy) while 40 (70%) with external beam radiation therapy (EBRT) + BT (36-56 Gy + 15-38 Gy]. Low-dose-rate (LDR) BT was delivered with 192 Ir wires, using plastic bead technique with varied dose rates (< 60 cGy/h in 29 patients, 60-90 cGy/h in 17, and> 90 cGy/h in 11). Results : The overall local control (LCR) was achieved in 59.7% (34/57) patients. LCR for T1 and T2 was 67.8% and 50%, respectively. A total of 23 patients had failures [local: 20 (T1: 8; T2: 12 patients), node: 5 (T1:2; T2: 3), and local + nodal: 3]. Overall 5-year disease-free survival and overall survival (OAS) were 51% and 67%, respectively and those for T1 and T2 was 64.5/77.4% and 38.5/54% respectively (P = 0.002). All 16 patients were salvaged. Median survival after salvage treatment was 13.5 months (6-100 months). Soft tissue necrosis was observed in 12.3% (7/57) and osteoradionecrosis in two patients. Conclusion : BT, as an integral part of radical radiation therapy in early-stage tongue cancers, appears to be an effective alternative treatment modality with preservation of the organ and function without jeopardizing the outcome

Treatment outcome with low-dose-rate interstitial brachytherapy in early-stage oral tongue cancers

Purpose : Although radical radiotherapy is known to be equally effective for early-stage oral tongue cancers (T1-2 N0) with the added advantage of organ and function preservation, surgery remains the preferred treatment. We present outcome of patients treated with brachytherapy (BT) either radical or boost. Materials and Methods : Fifty-seven patients (T1/T2 31/26) were studied. Seventeen patients (30%) were treated with radical BT (50-67 Gy) while 40 (70%) with external beam radiation therapy (EBRT) + BT (36-56 Gy + 15-38 Gy]. Low-dose-rate (LDR) BT was delivered with 192 Ir wires, using plastic bead technique with varied dose rates (< 60 cGy/h in 29 patients, 60-90 cGy/h in 17, and> 90 cGy/h in 11). Results : The overall local control (LCR) was achieved in 59.7% (34/57) patients. LCR for T1 and T2 was 67.8% and 50%, respectively. A total of 23 patients had failures [local: 20 (T1: 8; T2: 12 patients), node: 5 (T1:2; T2: 3), and local + nodal: 3]. Overall 5-year disease-free survival and overall survival (OAS) were 51% and 67%, respectively and those for T1 and T2 was 64.5/77.4% and 38.5/54% respectively (P = 0.002). All 16 patients were salvaged. Median survival after salvage treatment was 13.5 months (6-100 months). Soft tissue necrosis was observed in 12.3% (7/57) and osteoradionecrosis in two patients. Conclusion : BT, as an integral part of radical radiation therapy in early-stage tongue cancers, appears to be an effective alternative treatment modality with preservation of the organ and function without jeopardizing the outcome

Dosimetric evaluation of rectum and bladder using image-based CT planning and orthogonal radiographs with ICRU 38 recommendations in intracavitary brachytherapy

The purpose is to compare CT-based dosimetry with International Commission on Radiation Units and Measurements (ICRU 38) bladder and rectum reference points in patients of carcinoma of uterine cervix treated with intracavitary brachytherapy (ICA). Twenty-two consecutive patients were evaluated. Orthogonal radiographs and CT images were acquired and transferred to PLATO planning system. Bladder and rectal reference points were identified according to ICRU 38 recommendations. Dosimetry was carried out based on Manchester system. Patient treatment was done using ¹⁹² Iridium high dose rate (HDR) remote after-loading machine based on the conventional radiograph-based dosimetry. ICRU rectal and bladder point doses from the radiograph plans were compared with D₂ , dose received by 2 cm³ of the organ receiving maximum dose from CT plan. V₂ , volume of organ receiving dose more than the ICRU reference point, was evaluated. The mean (&#x00B1;standard deviation) volume of rectum and bladder was 60 (&#x00B1;28) cm³ and 138 (&#x00B1;41) cm³ respectively. The mean reference volume in radiograph and CT plan was 105 (&#x00B1;7) cm³ and 107 (&#x00B1;7) cm³ respectively. It was found that 6 (&#x00B1;4) cm³ of rectum and 16 (&#x00B1;10) cm³ of bladder received dose more than the prescription dose. V₂ of rectum and bladder was 7 (&#x00B1;1.7) cm³ and 20.8 (&#x00B1;6) cm³ respectively. Mean D₂ of rectum and bladder was found to be 1.11 (&#x00B1;0.2) and 1.56 (&#x00B1;0.6) times the mean ICRU reference points respectively. This dosimteric study suggests that comparison of orthogonal X-ray-based and CT-based HDR ICA planning is feasible. ICRU rectal point dose correlates well with maximum rectal dose, while ICRU bladder point underestimates the maximum bladder dose

Additional rectal and sigmoid mucosal points and doses in high dose rate intracavitary brachytherapy for carcinoma cervix: A dosimetric study

Background: Late rectal and sigmoid toxicities seen in cervical cancer patients are attributed to brachytherapy despite rectal doses within tolerance limits. The purpose of this study was to identify additional dosimetric points which may better forecast rectal complications. Materials and Methods: Fifteen high dose rate intracavitary brachytherapy (ICA-HDR) applications with conventional X-ray and computed tomography (CT) based planning were studied. In addition to International Commission on Radiation Units and Measurement (ICRU) rectal and bladder points, proximal and distal rectal and sigmoid points were digitized on CT scans and dose volume histograms′ (DVHs′) parameters were computed and correlated. Results: The mean ICRU, additional distal, proximal and sigmoid point doses were 486 ± 152 cGy, 527 ± 156 cGy, 401 ± 149 cGy and 838 ± 254 cGy, respectively, for a prescription of 700 cGy to point A. The mean sigmoid point dose was significantly higher than the ICRU rectal point doses (P=0.001). The high-dose sigmoid points were situated at a mean -8 mm (range -22.95 to 10.43 mm) lateral, 10 mm posterior (range -15.87 to 27.82 mm) and 31 mm (range 8.08-62.91 mm) cranial to the intracavitary applicator flange of central tandem. Conclusions: Our dosimetric study suggests that sigmoid points and 0.1 cm 3 receive significantly higher doses than rectal points during ICA-HDR in carcinoma of the uterine cervix. No definite conclusion on reproducible spatial distribution on orthogonal X-rays could be achieved. To document and reduce sigmoid doses, some form of 3D image-based planning is necessary