Somsak Wanwilairat

High-dose-rate afterloading brachytherapy in carcinoma of the cervix : An experience of 1992 patients

PURPOSE To report the results of radiation therapy in carcinoma of the cervix treated by external irradiation and high-dose-rate (HDR) intracavitary brachytherapy. METHODS AND MATERIALS This is a retrospective analysis of 2,063 patients with histologically proven carcinoma of the cervix treated by external irradiation and HDR intracavitary brachytherapy between March 1985-December 1991. The Kaplan-Meier method was used for survival and disease-free survival analysis. Late complications in the bowel and bladder were calculated actuarially. RESULTS There were 71 patients who did not complete the course of irradiation so only 1992 patients were retrospectively analyzed for survival. There were 2 patients (0.1%) in Stage IA, 211 (10.2%) Stage IB, 225 (10.9%) in Stage IIA, 902 (43. 7%) in Stage IIB, 14 (0.7%) in Stage IIIA, 675 (32.7%) in Stage IIIB, 16 (0.8%) in Stage IVA, and 16 (0.8%) in Stage IVB. The median follow-up time was 96 months. The actuarial 5-year disease-free survival rate was 79.5%, 70.0%, 59.4%, 46.1%, 32.3%, 7.8%, and 23.1% for Stage IB, IIA, IIB, IIIA, IIIB, IVA, and IVB respectively. The actuarial 5-year disease-free survival rate for Stage IB(1) and IB(2) squamous cell carcinoma was 88.7% and 67.0%. The actuarial 5-year overall survival rate was 86.3%, 81.1%, 73.0%, 50.3%, 47.8%, 7.8%, and 30.8% for Stage IB, IIA, IIB, IIIA, IIIB, IVA, and IVB respectively. Pattern of failure revealed 20.8% local recurrence, 18. 7% distant metastases, and 4% in both. The late complication rate Grade 3 and 4 (RTOG) for bowel and bladder combined was 7.0% with 1. 9% Grade 4. CONCLUSION HDR brachytherapy used in this series produced pelvic control and survival rates comparable to other LDR series.

Dosimetric verification of radiotherapy treatment planning systems: Results of IAEA pilot study

BACKGROUND AND PURPOSE The methodology developed by IAEA for dosimetric quality control of treatment planning systems has been tested in different hospitals through a pilot study. The aim was to verify the methodology and observe the range of deviations between planned and delivered doses in 3D conformal radiotherapy in situations close to a clinical setting. MATERIAL AND METHODS The methodology was based on an anthropomorphic phantom representing the human thorax, and simulates the whole chain of external beam radiotherapy treatment planning activities. The phantom was scanned using computed tomography and eight test cases were planned on treatment planning systems which imitate different irradiation geometries found in conformal radiotherapy. The doses were measured with ion chambers, and the deviation between measured and treatment planning system calculated doses was reported. This methodology, which employs the same phantom and the same set of test cases, was tested in 17 different hospitals which were using 14 different algorithms/inhomogeneity correction methods implemented in different treatment planning systems. RESULTS A total of 53 clinical test case datasets for different energies and calculation algorithms were produced. Most of the systems with advanced algorithms complied with predefined agreement criteria. Dose differences more than 20% were discovered for some of the simple algorithms and high energy X-ray beams. The number of deviations outside agreement criteria increases with the beam energy and decreases with advancement of the treatment planning system calculation algorithm. CONCLUSIONS Large deviations exist in some simple dose calculation algorithms, therefore more advanced algorithms would be preferable and therefore should be implemented in clinical practice. The test cases that could be performed in reasonable time would help the users to appreciate the possibilities of their system and understand its limitations.

Intermediate-term results of image-guided brachytherapy and high-technology external beam radiotherapy in cervical cancer: Chiang Mai University experience

OBJECTIVE To evaluate the outcomes of image-guided brachytherapy combined with 3D conformal or intensity modulated external beam radiotherapy (3D CRT/IMRT) in cervical cancer at Chiang Mai University. METHODS From 2008 to 2011, forty-seven patients with locally advanced cervical cancer were enrolled in this study. All patients received high-technology (3D CRT/IMRT) whole pelvic radiotherapy with a total dose of 45-46 Gy plus image-guided High-Dose-Rate intracavitary brachytherapy 6.5-7 Gy × 4 fractions to a High-Risk Clinical Target Volume (HR-CTV) according to GEC-ESTRO recommendations. The dose parameters of the HR-CTV for bladder, rectum and sigmoid colon were recorded, as well as toxicity profiles. In addition, the endpoints for local control, disease-free, metastasis-free survival and overall survival were calculated. RESULTS At the median follow-up time of 26 months, the local control, disease-free survival, and overall survival rates were 97.9%, 85.1%, and 93.6%, respectively. The mean dose of HR-CTV, bladder, rectum and sigmoid were 93.1, 88.2, 69.6, and 72 Gy, respectively. In terms of late toxicity, the incidence of grade 3-4 bladder and rectum morbidity was 2.1% and 2.1%, respectively. CONCLUSIONS A combination of image-guided brachytherapy and IMRT/3D CRT showed very promising results of local control, disease-free survival, metastasis-free survival and overall survival rates. It also caused a low incidence of grade 3-4 toxicity in treated study patients.

Image-guided brachytherapy (IGBT) combined with whole pelvic intensity-modulated radiotherapy (WP-IMRT) for locally advanced cervical cancer: a prospective study from Chiang Mai University Hospital, Thailand

Purpose A report of preliminary results and toxicity profiles using image-guided brachytherapy (IGBT) combined with whole pelvic intensity-modulated radiation therapy (WP-IMRT) for locally advanced cervical cancer. Material and methods Fifteen patients with locally advanced cervical cancer were enrolled into the study. WP-IMRT was used to treat the Clinical Target Volume (CTV) with a dose of 45 Gy in 25 fractions. Concurrent cisplatin (40 mg/m2) was prescribed during radiotherapy (RT) on weekly basis. IGBT using computed tomography was performed at the dose of 7 Gy × 4 fractions to the High-Risk Clinical Target Volume (HR-CTV). Results The mean cumulative doses – in terms of equivalent dose of 2 Gy (EQD2) – of IGBT plus WP-IMRT to HR-CTV, bladder, rectum, and sigmoid colon were 88.3, 85.0, 68.2 and 73.6 Gy, respectively. In comparison with standard (point A prescription) dose-volume histograms, volume-based image-guided brachytherapy improved the cumulative doses for bladder of 67%, rectum of 47% and sigmoid of 46%. At the median follow-up time of 14 months, the local control, metastasis-free survival and overall survival rates were 93%, 100% and 93%, respectively. No grade 3-4 acute and late toxicities were observed. Conclusion The combination of image-guided brachytherapy and intensity-modulated radiotherapy improved the dose distribution to tumor volumes and avoided overdose in OARs which could be converted in excellent local control and toxicity profiles.

Two-year results of transabdominal ultrasound-guided brachytherapy for cervical cancer

PURPOSE To report the preliminary results of transabdominal ultrasound (TAUS)-guided brachytherapy (BT) in cervical cancer. METHODS AND MATERIALS Twenty-nine patients with cervical cancer Stage IB-IVA according to The International Federation of Gynecology and Obstetrics staging were treated by radical radiotherapy from February 2012 to December 2012. Treatment was composed of WPRT to 50 Gy in 25 fractions and central shielding after 44 Gy in combination with TAUS-guided BT to optimize the total dose (equivalent dose of 2 Gy [EQD2]) to the minimal dose at cervical points (in EQD2 concepts) defined by TAUS ≥80 Gy while maintaining low doses to the ICRU report no. 38 bladder and rectal points. The treatment results and toxicity profiles were reported. RESULTS At median followup time of 19 months (range, 17-27), the local control and disease-free survival rates were 93.1% and 86.2%, respectively. One episode of Grade 3 vaginal toxicity was observed in this followup period. The mean applied doses to cervix, bladder, and rectal points were 82.6, 72.5, and 75 Gy, respectively. TAUS-guided planning reduced bladder (defined as >80 Gy in EQD2) and rectal overdose (defined as >75 Gy in EQD2) in 44.9% and 34.5% of patients, respectively. CONCLUSION The 2-year results demonstrate that TAUS-guided BT is feasible and associated with excellent tumor control/toxicity rates in cervical cancer.

The association of rectal equivalent dose in 2 Gy fractions (EQD2) to late rectal toxicity in locally advanced cervical cancer patients who were evaluated by rectosigmoidoscopy in Faculty of Medicine, Chiang Mai University.

Purpose To evaluate association between equivalent dose in 2 Gy (EQD2) to rectal point dose and gastrointestinal toxicity from whole pelvic radiotherapy (WPRT) and intracavitary brachytherapy (ICBT) in cervical cancer patients who were evaluated by rectosigmoidoscopy in Faculty of Medicine, Chiang Mai University. Materials and Methods Retrospective study was designed for the patients with locally advanced cervical cancer, treated by radical radiotherapy from 2004 to 2009 and were evaluated by rectosigmoidoscopy. The cumulative doses of WPRT and ICBT to the maximally rectal point were calculated to the EQD2 and evaluated the association of toxicities. Results Thirty-nine patients were evaluated for late rectal toxicity. The mean cumulative dose in term of EQD2 to rectum was 64.2 Gy. Grade 1 toxicities were the most common findings. According to endoscopic exam, the most common toxicities were congested mucosa (36 patients) and telangiectasia (32 patients). In evaluation between rectal dose in EQD2 and toxicities, no association of cumulative rectal dose to rectal toxicity, except the association of cumulative rectal dose in EQD2 >65 Gy to late effects of normal tissue (LENT-SOMA) scale ≥ grade 2 (p = 0.022; odds ratio, 5.312; 95% confidence interval, 1.269-22.244). Conclusion The cumulative rectal dose in EQD2 >65 Gy have association with ≥ grade 2 LENT-SOMA scale.

Low cost high resolution thermoluminescence spectrometer

A high-resolution thermoluminescence dosimetry (TLD) spectroscopy reader has been developed in order to perform detailed quantitative studies of the kinetics of TLD materials. The key features of this system are high wavelength resolution (1.3 nm), low cost, and compact size. In addition, the spectrometer is fiber optic coupled to the sample material isolating the system from thermal influences and electrical noise generated by the heating system. Temperature rate control can be computer set with a heat rate accuracy of better than 0.12% and a temperature readout accuracy of 1 °C or better. Analysis of all three parameters: temperature, wavelength, and intensity, is easily visualized with integrated 2D/3D analysis software. Preliminary analysis on TLD300 samples irradiated with 60Co from 5 to 60 Gy show temperature peaks and wavelength locations consistent with other published measurements. Details of the hardware system and software are discussed along with sample results.

The effect of central shielding in the dose reporting for cervical cancer in EQD2 era.

Purpose To evaluate the cumulative dose at point A for three and four centimeters central shielding. Material and methods The plans of external beam radiotherapy plus conventional intracavitary brachytherapy were performed. Three or four centimeters central shieldings (after 44 Gy) were applied to the standard whole pelvis irradiation. Additional intracavitary brachytherapy 4 × 7 Gy at point A was prescribed, and the cumulative dose in EQD2 (α/β = 10) of 3 cm and 4 cm central shielding were evaluated. Results The cumulative dose at point A in EQD2 (α/β = 10) of 3 cm central shielding were 95.7 Gy for AR and 95.5 Gy for AL, while the cumulative dose at point As in EQD2 (α/β = 10) of 4 cm central shielding were 90.8 Gy for AR and 91.2 Gy for AL. Conclusions The 3 cm central shielding caused higher cumulative dose (in terms of EQD2 [α/β = 10]) than 4 cm central shielding.

Measurement of the dose components of fast and thermal neutrons and photons from a 0.1 mg 252Cf source in water for brachytherapy treatment planning.

The use of 252Cf in brachytherapy is expected to be more effective with the therapy of bulky tumors than the conventional therapy with photons. For treatment planning a code developed for calculation of gamma dose was used to generate the dose distributions of fast and 10B enhanced thermal neutrons and photons. Dose distributions of these components measured with ionization chambers and a GM counter were fitted to analytical functions as required by the modified treatment planning program. A comparison of these experimental results and the treatment planning output indicate good agreement. Therefore, the program may be used to optimize the brachytherapy procedure considering all three dose components. A realistic case of a patient being treated with conventional brachytherapy has been used to calculate the dose distribution that would be obtained by use of the 252Cf source.

A dosimetric comparison of two-phase adaptive intensity-modulated radiotherapy for locally advanced nasopharyngeal cancer.

The purpose of this investigation was to evaluate the potential dosimetric benefits of a two-phase adaptive intensity-modulated radiotherapy (IMRT) protocol for patients with locally advanced nasopharyngeal cancer (NPC). A total of 17 patients with locally advanced NPC treated with IMRT had a second computed tomography (CT) scan after 17 fractions in order to apply and continue the treatment with an adapted plan after 20 fractions. To simulate the situation without adaptation, a hybrid plan was generated by applying the optimization parameters of the original treatment plan to the anatomy of the second CT scan. The dose–volume histograms (DVHs) and dose statistics of the hybrid plan and the adapted plan were compared. The mean volume of the ipsilateral and contralateral parotid gland decreased by 6.1 cm3 (30.5%) and 5.4 cm3 (24.3%), respectively. Compared with the hybrid plan, the adapted plan provided a higher dose to the target volumes with better homogeneity, and a lower dose to the organs at risk (OARs). The Dmin of all planning target volumes (PTVs) increased. The Dmax of the spinal cord and brainstem were lower in 94% of the patients (1.6–5.9 Gy, P < 0.001 and 2.1–9.9 Gy, P < 0.001, respectively). The Dmean of the contralateral parotid decreased in 70% of the patients (range, 0.2–4.4 Gy). We could not find a relationship between dose variability and weight loss. Our two-phase adaptive IMRT protocol improves dosimetric results in terms of target volumes and OARs in patients with locally advanced NPC.