Interstitial high-dose-rate brachytherapy using cobalt-60 source for cervical cancer: dosimetric and clinical outcomes from a single institute.

PURPOSE: To record and report dosimetric and clinical outcomes of interstitial brachytherapy using cobalt-60 (60Co) source in cervical cancer. MATERIAL AND METHODS: Seventy patients who underwent external beam radiotherapy with dose of 45 Gy in 25 fractions, followed by interstitial brachytherapy (ISBT) 6.5 Gy × 4 fractions were included into this study. The ISBT applicators were inserted under combined spinal and epidural anesthesia. Computed tomography (CT) simulation was performed and axial CT images were transferred to treatment planning system. High-risk clinical target volume (CTVHR) and organs at risks (OARs) were contoured. Four fractions of 6.5 Gy were prescribed to CTVHR using inverse planning technique. Patients were followed-up for 3 years. Dosimetric parameters and clinical outcomes were recorded and compared with available literature. RESULTS: Seventy patients with FIGO stage IIB-IVA were included in the study. The median EQD2 of 2 cm3 of bladder, rectum, sigmoid and D90 CTVHR were 70 Gy (53-75 Gy), 64 Gy (51-71 Gy), 48 Gy (44-72 Gy), and 77 Gy (70-86 Gy), and dose homogeneity index (DHI), dose non-uniformity ratio (DNR), coverage index (CI), overdose volume index (OI), and conformal index (COIN) were 0.58 (0.39-0.78), 0.42 (0.22-0.61), 0.87 (0.59-0.97), 0.19 (0.09-0.30) and 0.74 (0.52-0.85), respectively. Local control rate at 2 years was 87.14%. Eight patients had local recurrence and one patient had lung metastasis. Also, two patients with local recurrence had recto-vaginal fistula. Two patients had grade 2 proctitis (2.8%) and one patient developed grade 3 proctitis (1.4%). There was no grade 2 or higher bladder toxicity. CONCLUSIONS: The dosimetric parameters, local control and toxicities of high-dose-rate interstitial brachytherapy in cervical cancer patients treated by 60Co radioactive source are similar, compared to available literature using iridium-192 (192Ir) source.

One thousand cases of cobalt-based high dose rate brachytherapy treated at a tertiary care center: A retrospective study.

PURPOSE: This is a study of our experience with Co-60 high dose rate brachytherapy (HDR BT) from a tertiary care center. MATERIALS AND METHODS: One thousand patients were treated with Cobalt-based HDR BT for more than 6 years. The practice of BT was analyzed for clinical outcome, physical, radiobiological, and technical aspects. RESULTS: Among those 1000 patients, 906 (90.6%) patients had gynecologic cancer, 29 (2.9%) patients had intraluminal BT, 63 (6.3%) hadhead &neck (2.1%), keloid (2.1%) and mold BT (2.1%), and 2 (0.2%) had sarcoma. Dose rate decreased by 48.9%, and treatment time increased from 9.33 to 18.27 min over 5 years. No patients treatment was abandoned because of machine-related problems. CONCLUSION: Cobalt-based HDR BT is preferable in terms of lesser source exchanges, relatively uniform treatment time, quality assurance requirement, and cost.

Inter-institutional comparison of treatment practice for cervical cancer with special emphasis on brachytherapy.

PURPOSE: To compare the cervical cancer treatment outcome and toxicities between two different institutions. MATERIAL AND METHODS: We analysed the clinical outcome of cervical cancer patients treated at two different centres from January 2015 to December 2016. Centre A treated 72 patients by external beam radiotherapy (EBRT) to a dose of 45 Gy in 25 fractions followed by intracavitary brachytherapy (ICBT) 6.5 Gy × 4 fractions and centre B treated 89 patients by EBRT to a dose of 50.4 Gy in 28 fractions followed by ICBT 9 Gy × 2 fractions. The local control, distant metastases and treatment toxicities were compared. RESULTS: The median follow-up in centre A was 12 months and in centre B was 18 months. The median overall treatment time in centre A was 52 days and in centre B was 61 days. The mean equieffective doses in 2 Gy (EQD2) for high risk target volume (CTVHR) and point A in centre A were 84.59 and 64.5 Gy, respectively. The mean EQD2 for point A in centre B was 78.5 Gy. One patient out of 72 (1.38%) had local recurrence in centre A and five patients out of 89 (5.6%) had local recurrence in centre B. Local control in centre A was 98.6% and in centre B was 94.3%. The local recurrence rate was higher in centre B but it was not statistically significant (p = 0.15). One patient developed brain metastasis in centre B. One patient developed grade 3 proctitis in centre A. CONCLUSIONS: A high dose rate brachytherapy fractionation schedule of 6.5 Gy × 4 fractions over 2 days for CTVHR is associated with reduced overall treatment time, a slightly higher local control rate and lesser dose to OARs compared to 9 Gy × 2 fractions given one week apart to point A.

Impact of different dose prescription schedules on EQD2 in high-dose-rate intracavitary brachytherapy of carcinoma cervix.

PURPOSE: To observe the effect of different high-dose-rate (HDR) intracavitary brachytherapy dose schedules on equieffective dose in 2 Gy per fraction (EQD2). MATERIAL AND METHODS: It is a retrospective study involving 50 cervical cancer patients, who received external radiotherapy of 45 Gy in 25 fractions and underwent intracavitary brachytherapy (ICBT). Computed tomography (CT) simulation was done after insertion of the applicators. High-risk clinical target volume (CTVHR) and organs at risk (OARs) such as bladder, rectum, and sigmoid were contoured. Four different plans were generated for each patient, with dose prescriptions of 5.5 Gy × 5 fractions (plan A), 6.5 Gy × 4 fractions (plan B), 7 Gy × 4 fractions (plan C), and 9 Gy × 2 fractions (plan D), delivered to CTVHR. The total EQD2 for 0.1 cm3 and 2 cm3 of bladder, rectum, and sigmoid as well as dose received by 90% of the CTVHR (D90) and point A were calculated. The values were analyzed and compared with available literature. RESULTS: The mean CTVHR volume was 47.12 ±13.8 cm3. All plans delivered similar EQD2 for 0.1 cm3 and 2 cm3 of sigmoid. Plan D delivered lesser EQD2 compared to other plans for bladder, rectum, D90 CTVHR, and point A (p = 0.0001). Plan C delivered higher EQD2 to OARs compared to other plans (p = 0.001). Plan A, B, and plan C delivered similar EQD2 for D90 CTVHR and point A. CONCLUSIONS: EQD2 of bladder, rectum, sigmoid, D90 CTVHR, and point A were similar with 5.5 Gy × 5 fractions, 6.5 Gy × 4 fractions, and 7 Gy × 4 fractions, whereas EQD2 of 9 Gy × 2 fractions was significantly unfavorable compared to other schedules. Further clinical studies are recommended to observe clinical outcomes.