Dosimetric comparison of manual forward planning with uniform dwell times versus volume-based inverse planning in interstitial brachytherapy of cervical malignancies.

AIM: Dosimetic comparison of manual forward planning(MFP) with inverse planning(IP) for interstitial brachytherapy(ISBT) in cervical carcinoma. BACKGROUND: Brachytherapy planning by MFP is more reliable but time-consuming method, whereas IP has been explored more often for its ease and rapidness. The superiority of either is yet to be established. METHODOLOGY: Two plans were created on data sets of 24 patients of cervical carcinoma who had undergone ISBT, one by MFP with uniform dwell times and another IP on BrachyVision 13.7 planning system with a dose prescription of 600 cGy. Isodose shaper was used for improving conformity & homogeneity. Dosimetric parameters for target and organs at risk (OARs) were recorded. Conformity index (COIN), dose homogeneity index (DHI), overdose index (OI), Coverage index (CI) and dose nonuniformity ratio (DNR) were calculated. RESULTS: Mean high risk clinical target volume: 73.05(±20.7)cc, D90: 5.51 Gy vs. 5.6 Gy (p = 0.017), V100: 81.77 % vs. 83.74 % (p = 0.002), V150: 21.7 % vs. 24.93 % (p = 0.002), V200: 6.3 % vs. 6.4 % (p=0.75) for IP and MFP, respectively. CI: 0.81(IP) and 0.83(MFP) (p = 0.003); however, COIN was 0.79 for both plans. D2cc of OARs was statistically better with IP (bladder 54.7 % vs. 56.1 %, p = 0.03; rectum 63 % vs. 64.7 %, (p = 0.0008). CONCLUSION: Both MFP and IP are equally acceptable dosimetrically. With higher dose achieved to the target, for a similar OAR dose, MFP provides greater user flexibility of dwell positions within the target as well as better optimization. Isodose shaper may be carefully used for fine tuning. Larger sample sizes and clinical correlation will better answer the superiority of one over the other.

Quantification of uncertainties in conventional plan evaluation methods in Intensity Modulated Radiation Therapy.

PURPOSE: In Intensity Modulated Radiation Therapy (IMRT) dose distributions tend to be more complex and heterogeneous because of the modulated fluences in each beamlet of every single beam. These dose-volume (DV) parameters derived from the dose volume histogram (DVH) are physical quantities, thought to correlate with the biological response of the tissues. The aim of this study was to quantify the uncertainty of physical dose metrics to predict clinical outcomes of radiotherapy. METHODS: The radiobiological estimates such as tumor control probability (TCP) and Normal Tissue Complication Probability (NTCP) were made for a cohort of 40 cancer patients (10 brain;19 head & neck;11 cervix) using the DV parameters. Statistical analysis was performed to determine the correlation of physical plan quality indicators with radiobiological estimates. RESULTS: The correlation between conformity index (CI) and TCP was found to be good and the dosimetric parameters for optic nerves, optic chiasm, brain stem, normal brain and parotids correlated well with the NTCP estimates. A follow up study (median duration 18 months) was also performed. There was no grade 3 or 4 normal tissue complications observed. Local tumor control was found to be higher in brain (90%) and pelvic cases (95%), whereas a decline of 70% was noted with head & neck cancer cases. CONCLUSIONS: The equivalent uniform dose (EUD) concept of radiobiological model used in the software determines TCP and NTCP values which can predict outcomes precisely using DV data in the voxel level. The uncertainty of using physical dose metrics for plan evaluation is quantified with the statistical analysis. Radiobiological evaluation is helpful in ranking the rival treatment plans also.

Comparison of dosimetric analysis of organs at risk and target volumes for ovoids and cylinders in endometrial carcinoma.

Purpose: To compare dose volume parameters of target and organs at risk in vaginal vault brachytherapy using ovoids or cylinder in post-operative endometrial carcinoma. Material and methods: The study was done among 25 histologically proven post-operative endometrial carcinoma patients requiring vaginal brachytherapy. All patients underwent both cylinder and ovoids application alternatively on weekly basis. Ovoids size ranged from 2 to 3 cm diameter. Diameters of cylinder ranged between 2.5 and 3.5 cm. Bladder, rectum, urethra, and clinical target volume (CTV) were contoured on CT simulation images. Prescribed dose was 6-7 Gy in 2-3 fractions at 0.5 cm from the surface of applicator. Results: The mean values of D90, D50, V150, V100, V90, and V50 of CTV were comparable between cylinder and ovoids plans. The mean dose of CTV was significantly higher with cylinder than with ovoids, and D100 was significantly higher with ovoids (mean = 15.63 Gy vs. 14.64 Gy, p = 0.016, and D100 = 37.82% vs. 42.86%, p = 0.042, for cylinder vs. ovoids). In the dosimetry of the vault, D90, D50, V100, V90, V50, and mean of the vault did not show any significant difference between cylinder and ovoids. The V150 was significantly higher with cylinder plans than ovoids, and D100 of the vault was significantly higher with ovoids plans (V150 = 14.81% vs. 6.86%, p = 0.02, and D100 = 37.77% vs. 44.80%, p = 0.029, for cylinder vs. ovoids). D0.1cc, D1cc, D2cc, and mean for the bladder, rectum, and urethra were comparable between the cylinder and ovoid plans. Conclusions: The present study showed that the dose to organs at risk, most of the dosimetric parameters of CTV, and vault were comparable between the cylinder and ovoid plans. Both applicators provide good reproducibility. The choice of applicator will ultimately depend on the institutional policies and oncologist decision. However, in patients with dog-ear configuration of the vagina, ovoids may be preferred as per ABS guidelines.

Accelerated partial breast irradiation using external beam radiotherapy-A feasibility study based on dosimetric analysis.

AIM: To investigate the feasibility of using External Beam radiotherapy for accelerated partial breast irradiation by a comparative tumour and normal tissue dose volume analysis with that of high dose rate interstitial brachytherapy. BACKGROUND: Accelerated Partial Breast Irradiation (APBI) is more clinically appealing because of the reduced treatment course duration and the irradiated area. Brachytherapy application is more dependent on the clinician's expertise when it is practised free hand without image guidance and a template. It happens to be an invasive procedure with the use of local anaesthesia which adds patient discomfort apart from its cost compared to External Beam Radiotherapy. But APBI with brachytherapy is more commonly practised procedure compared to EBRT owing to its previous reults. Hence in this research study, we intend to explore the use of EBRT with the radiobiological corrections for APBI in the place of brachytherapy. It is done as a dosimetric comparison of Brachytherapy treatment plans with that of EBRT plans. MATERIALS AND METHODS: The computed tomography images of 15 patients undergoing ISBT planning were simulated with conformal photon fields. Various dose volume parameters of each structure were obtained from the DVH generated in the brachytherapy and the simulated external beam planning which can correlate well with the late toxicity. The plan quality indices such as conformity index and homogeneity index for the target volume were computed from the dosimetric factors. The statistical p values for CI, HI and normal tissue dosimetric parameters were calculated and the confidence levels achievable were analysed. The dose prescribed in brachytherapy was 3400cGy in ten fractions. The equivalent prescription dose for the external beam radiotherapy planning was 3000cGy in five fractions applied with radiobiological correction. RESULTS: All the fifteen patients were with complete lung data and six were with left sided tumours having complete cardiac data. The lung dosimetry data and the cardiac dosimetry data of the patients were studied. Lower percentages of lung and cardiac V 20 and V 5 volumes were obtained with conformal planning. The conformity of radiation dose to the tumour volume was akin to the interstitial brachytherapy planning. Moreover the external beam planning resulted in more homogenous dose distribution. For the sampled population, the statistical analysis showed a confidence level of 95% for using EBRT as an alternate to multi catheter ISBT. CONCLUSION: The EBRT planning for Accelerated Partial Breast Irradiation was found to be technically feasible in the institution where the interstitial brachytherapy happens to be the only available technique as evident from the dose volume parameters and the statistical analysis.

Clinical profile and outcomes in cervical cancer: An audit from a tertiary cancer center.

Background: Carcinoma cervix contributes to a major proportion of cancer treatment in tertiary oncology centers. The outcomes are dependent on multiple factors. We conducted an audit to establish the pattern of treatment practiced for carcinoma cervix at the institute and suggest changes thereof to improve the quality of care. Methodology: A retrospective observational study of 306 diagnosed cases of carcinoma cervix was carried out for the year 2010. Data was collected with regards to diagnosis, treatment, and follow-up. Statistical analysis was performed using Statistical Package for Social Sciences (SPSS) version 20. Results: Out of 306 cases, 102 (33.33%) patients received only radiation therapy and 204 (66.66%) patients received concurrent chemotherapy. The most common chemotherapy used was weekly cisplatin 99 (48.52%), followed by weekly carboplatin 60 (29.41%) and three weekly cisplatin 45 (22.05%). Disease-free survival (DFS) at 5 years was 36.6% with patients of overall treatment time (OTT) of <8 weeks and >8 weeks showing DFS of 41.8% and 34% (P = 0.149), respectively. Overall survival (OS) was 34%. Concurrent chemoradiation improved overall survival by a median of 8 months (P = 0.035). There was a trend towards improved survival with three weekly cisplatin regimen, however, insignificant. Stage correlated with improved overall survival significantly with stage I and II showing 40% and stage III and IV showing 32% (P < 0.05) OS. Acute toxicity (grade I-III) was higher in the concurrent chemoradiation group (P < 0.05). Conclusion: This audit was a first of its kind in the institute and threw light on the treatment and survival trends. It also revealed the number of patients lost to follow-up and prompted us to review the reasons for it. It has laid the foundation for future audits and recognized the importance of electronic medical records in the maintenance of data.

Prostate permanent implant brachytherapy with BARC I-125 Ocu-Prosta seeds.

AIM: The aim of this study is implementation and establishment of standard operating procedure for permanent prostate implant brachytherapy technique using BARC I-125 Ocu-Prosta seeds. MATERIALS AND METHODS: The transrectal ultrasound (US)-guided procedure was used for permanent implant procedure. The Best® Sonalis™ US Imaging System and Best NOMOS™ Treatment Planning system was used for volume study and implant procedure. The BARC provided I-125 Ocu-Pro radioactive seeds were implanted into the patient with help of Mick@ Applicator. The implant was performed based on pre-implant dosimetry and intraoperative planning performed during implant procedure. RESULTS: The necessary quality assurance tests were performed for US system before clinical use. The boost dose of 110 Gy was prescribed to the prostate volume of 34.71 cc. About 48 seeds with activity of 0.35 mCi (each) implanted into the prostate volume with reference to intraoperative planning. At the end of procedure, the patient underwent abdomen fluoroscopic examination, to ensure the seed counts in the prostate volume. The day after the implant, the patient was discharged. One month later a planning computed tomography and treatment planning was performed for seed position and dose verification. CONCLUSIONS: Low dose rate permanent implant brachytherapy has the advantage of being a one-time procedure and the existing long term follow-up supports its excellent outcome and low morbidity. BARC-BRIT is supplying the loose 125I seeds. These seeds can be easily implanted into the patient using Mick applicator. However, the pre-implant seed preparation and implant procedure may result some radiation exposure to staff involved. The radiation dose can be minimized with good practice. This report is one patient pilot study and intended to test the implant systems and standard operative procedure henceforth for permanent implant brachytherapy procedure.

Fluorescence spectral classification of iron deficiency anemia and thalassemia.

Thalassemia (Thal), sickle cell anemia, and iron deficiency anemia (IDA) are the most common blood disorders in many parts of the world, particularly in developing countries like India and Bangladesh. The well-established diagnostic procedure for them is the complete blood count (CBC); however, there is substantial confusion in discrimination between Thal and IDA blood samples based on such CBC. We propose a new spectral technique for reliable classification between the above two anemias. This is based on the identification and quantification of a certain set of fluorescent metabolites found in the blood samples of patients of Thal and IDA.

Cervical cancer detection by time-resolved spectra of blood components.

Fluorescence spectral techniques are very sensitive, and hence they are gaining importance in cancer detection. The biomarkers indicative of cancer could be identified and quantified by spectral or time domain fluorescence spectroscopy. The results of an investigation of time-resolved spectra of cellular components of blood obtained from cervical cancer patients and normal controls are given. The cancer indicative biomarker in this paper is porphyrin; it has a fluorescence decay time of 60% more in samples of cancer patients than those of normal controls. Based on such measurements, a randomized set comprising samples from cancer patients and controls (N=27 in total) could be classified with sensitivity (92%) and specificity (86%).

Treatment planning methods in high dose rate interstitial brachytherapy of carcinoma cervix: a dosimetric and radiobiological analysis.

Treatment planning is a trial and error process that determines optimal dwell times, dose distribution, and loading pattern for high dose rate brachytherapy. Planning systems offer a number of dose calculation methods to either normalize or optimize the radiation dose. Each method has its own characteristics for achieving therapeutic dose to mitigate cancer growth without harming contiguous normal tissues. Our aim is to propose the best suited method for planning interstitial brachytherapy. 40 cervical cancer patients were randomly selected and 5 planning methods were iterated. Graphical optimization was compared with implant geometry and dose point normalization/optimization techniques using dosimetrical and radiobiological plan quality indices retrospectively. Mean tumor control probability was similar in all the methods with no statistical significance. Mean normal tissue complication probability for bladder and rectum is 0.3252 and 0.3126 (P = 0.0001), respectively, in graphical optimized plans compared to other methods. There was no significant correlation found between Conformity Index and tumor control probability when the plans were ranked according to Pearson product moment method (r = -0.120). Graphical optimization can result in maximum sparing of normal tissues.

Dosimetric comparison of high dose rate brachytherapy and intensity-modulated radiation therapy for cervical carcinoma.

Intracavitary brachytherapy is an integral part of radiotherapy for locally advanced gynecologic malignancies. A dosimetric intercomparison of high dose rate intracavitary brachytherapy (HDR_BT) and intensity-modulated radiotherapy in cervical carcinoma has been made in the present study. CT scan images of 10 patients treated with HDR_BT were used for this study. A sliding-window IMRT (IMRT_SW) and step-and-shoot IMRT plans were generated using 6-MV X-rays. The cumulative dose volume histograms of target, bladder, rectum and normal tissue were analyzed for both techniques and dose distributions were compared. It was seen that the pear-shaped dose distribution characteristic of intracavitary brachytherapy with sharp dose fall-off outside the target could be achieved with IMRT. The integral dose to planning target volume was significantly higher with HDR_BT in comparison with IMRT. Significant differences between the two techniques were seen for doses to 1 cc and 2 cc of rectum, while the differences in 1 cc and 2 cc doses to bladder were not significant. The integral doses to the nontarget critical and normal structures were smaller with HDR_BT and with IMRT. It is concluded that IMRT can be the choice of treatment in case of non-availability of HDR brachytherapy facilities or when noninvasive treatments are preferred.