High-dose rate brachytherapy using inverse planning simulated annealing for locoregionally advanced cervical cancer: a clinical report with 2-year follow-up

High-dose-rate brachytherapy using inverse planning optimization with tandem and ovoid applicators for locally advanced cervical cancer: a simulation study

The purpose of this study was to evaluate the dosimetric advantage of inverse planning optimization (IPO) in locally advanced cervical cancer using high-dose-rate (HDR) brachytherapy (BT). IPO was compared with point A plan and geometric optimization (GO). The three planning methods were evaluated using doses to the virtual organ-at-risk (OAR) and D90 (the minimum dose covering of 90% of the volume) to the virtual high-risk clinical target volume (HR-CTV) based on quantitative analysis. HR-CTV structures measuring 38.5 cm³ and 59.5 cm³ were created based on the outcomes of a European Group cohort study. The HR-CTVs were located either at the center of the cervix (cervical center model) or shifted toward the left (extensive disease model). The distances from the HR-CTVs to the rectum were set at 0 mm, 3 mm, 5 mm, 8 mm, 10 mm, and 15 mm. We analyzed 336 conditions in this study. All doses were evaluated by conversion to doses in 2-Gy fractions of conventional radiotherapy. The D90 of the HR-CTV using GO and IPO could achieve the desired dose in all conditions, providing better results than that of point A plan. IPO makes it possible to deliver a sufficient dose for the D90 of the HR-CTV while reducing OAR doses with smaller HR-CTV values (< 38.5 cm³) in HDR BT. However, taking into consideration the whole treatment planning time, IPO should be used only when the HR-CTV-to-rectum distance is ≤ 5 mm, and the use of GO cannot spare OARs.

Comparison of two inverse planning algorithms for cervical cancer brachytherapy

PURPOSE

To compare two inverse planning algorithms, the hybrid inverse planning optimization (HIPO) algorithm and the inverse planning simulated annealing (IPSA) algorithm, for cervical cancer brachytherapy and provide suggestions for their usage.

MATERIAL AND METHODS

This study consisted of 24 cervical cancer patients treated with CT image-based high-dose-rate brachytherapy using various combinations of tandem/ovoid applicator and interstitial needles. For fixed catheter configurations, plans were retrospectively optimized with two methods: IPSA and HIPO. The dosimetric parameters with respect to target coverage, localization of high dose volume (LHDV), conformal index (COIN), and sparing of organs at risk (OARs) were evaluated. A plan assessment method which combines a graphical analysis and a scoring index was used to compare the quality of two plans for each case. The characteristics of dwell time distributions of the two plans were also analyzed in detail.

RESULTS

Both IPSA and HIPO can produce clinically acceptable treatment plans. The rectum D_2cc was slightly lower for HIPO as compared to IPSA (P = 0.002). All other dosimetric parameters for targets and OARs were not significantly different between the two algorithms. The generated radar plots and scores intuitively presented the plan properties and enabled to reflect the clinical priorities for the treatment plans. Significant different characteristics were observed between the dwell time distributions generated by IPSA and HIPO.

CONCLUSIONS

Both algorithms could generate high-quality treatment plans, but their performances were slightly different in terms of each specific patient. The clinical decision on the optimal plan for each patient can be made quickly and consistently with the help of the plan assessment method. Besides, the characteristics of dwell time distribution were suggested to be taken into account during plan selection. Compared to IPSA, the dwell time distributions generated by HIPO may be closer to clinical preference.

IRIDIUM-192 RADIOTHERAPY BENEFITS IN THE MANAGEMENT OF GYNECOLOGICAL TUMORS

BACKGROUND

Application of the most advanced radiation technologies of brachytherapy featuring the high dose ratesources i.e. 60Co and 192Ir within contemporary management protocols for gynecological cancer provides maximum dosedistribution in the clinical target along with minimal radiation exposure on surrounding organs and tissues. It involvesirradiation of large spaces with delivery of high therapeutic doses at the tolerance bound of «critical» organs (bladder,rectum) and tissues. Thus minimization of the early and late radiation complications, life span extent and quality oflife increase remain just the issues in contemporary radiation oncology requiring therefore the elaboration of radiobiological criteria along with substantiation of physiсо-engineering properties of the radiation sources. Taking intoaccount the basic radiobiological patterns will ensure a definitive further progress in the field of radiation oncology.

OBJECTIVE

to study and compare the biological effects of 192Ir with the effects of the reference gamma radiation 60Coand increase the effectiveness of brachytherapy using a 192Ir source.

MATERIALS AND METHODS

Radiobiological dosimetry on the basis of a test system of peripheral blood lymphocytesfrom the gynecological cancer patients with subsequent cytogenetic analysis of radiation-induced chromosomeaberrations was performed to study and compare the biological effects of 192Ir and reference 60Со γ-radiation, and toenhance the efficiency of 192Ir brachytherapy.

RESULTS

Radiation markers, i.e. dicentric chromosomes with an accompanying paired fragment prevailed in thespectrum of radiation-induced damage. Variability of individual cytogenetic parameters of peripheral lymphocytesupon the first fraction of irradiation at the same dose of 5 Gy indicated an individual sensitivity of patients to the192Ir γ-irradiation. Comprehensive conservative treatment with adjuvant radiotherapy was applied to the patients(n = 98) having got secondary vaginal cancer stage II-III, T2-3N0-1M0. The high dose-rate (HDR) brachytherapy using 192Ir radiation sources was applied in the main study group (n = 37), HDR brachytherapy using 60Co radiation sourceswas applied in the control group (n = 35).

CONCLUSION

The HDR brachytherapy with 192Ir and 60Co sources on the up-to-date technology intensive devices provides a high accuracy of dose distributions when irradiating the malignant neoplasms with minimized radiationexposure to the «critical» tissues. Treatment results are improved therefore. The use of 192Ir radiation sources compared with 60Co ones resulted in an increased throughput of treatment, enhanced tumor regression, and reduced incidence of radiation effects on the critical organs. Currently we perform the radiobiological studies on somatic cellsfrom cancer patients at the genetic, biochemical, biophysical, and cytological levels in order to receive a biologicalindication of radiation damage under the impact of 192Ir isotope. Continuation of clinical trials with radiobiologicalsupport will provide an opportunity to predict the early and late radiation complications and thus to provide a personalized approach in brachytherapy of cancer patients using the 192Ir sources of γ-rays.

Influence of dwell time homogeneity error weight parameter on treatment plan quality in inverse optimized high-dose-rate cervix brachytherapy using SagiPlan

Purpose

Restricting the gradients of dwell times between adjacent dwell positions can potentially be beneficial in reducing the probability of unwanted hot/cold spots occurring, if the planned applicators/anatomy relative positions change before or during treatment. This constraint, however, may degrade plan quality. This study, for the first time, aims to quantify the impact of modulation restriction on plan quality indices in inverse optimization for cervix high-dose-rate (HDR) brachytherapy using the BEBIG SagiPlan treatment planning system.

Material and methods

Ten cervical cancer patient plans were optimized for treatment with a BEBIG SagiNova ⁶⁰Co HDR afterloader using the min/max inverse planning method, with dwell time homogeneity error weight (DTHEW) parameter values of 0 to 10. Dwell time homogeneity and gradients as well as various plan quality indices were analyzed.

Results

For DTHEW = 0, min/max-based optimization yielded higher HR-CTV D₉₀ values than the variance-based option (p < 0.001) and was therefore selected for this study. Averaging over all patients, selecting non-zero DTHEWs resulted in a general increase in dwell time homogeneity and decrease in mean and maximum adjacent dwell time gradients, especially between DTHEWs of 0 and 1. For DTHEW > 1, an increase of this parameter did not always result in more homogeneous dwell times or reduced gradients in individual patients. There was a negative correlation between DTHEW and both HR-CTV D₉₀ and V₁₀₀ (p < 0.001, r = –0.91). Increasing DTHEW also negatively affected conformity index (p < 0.001, r = –0.99). Changes in rectum and sigmoid colon D_2cc were insignificant. There was a strong positive relationship between bladder D_2cc and DTHEW (p < 0.001, r = 0.99).

Conclusions

Assuming a static geometry, statistically significant degradation of plan quality can result from restricting the dwell time homogeneity in min/max-based optimization of cervix HDR brachytherapy plans using SagiPlan. Therefore, setting DTHEW to zero is indicated for the type of patient plans considered in this study.

American Brachytherapy Task Group Report: A pooled analysis of clinical outcomes for high-dose-rate brachytherapy for cervical cancer

PURPOSE

Advanced imaging used in combination with brachytherapy (BT) has revolutionized the treatment of patients with cervical cancer. We present a comprehensive review of the literature for definitive radiation with high-dose-rate (HDR) BT. In addition, we investigate potential outcome improvement with image-based brachytherapy (IBBT) compared to studies using traditional Point A dosing. This review extensively investigates acute and late toxicities.

METHODS AND MATERIALS

This study reviews the literature from 2000 to 2015 with an emphasis on modern approaches including concurrent chemotherapy (chemoRT), radiation, and HDR BT and IBBT. Descriptive statistics and pelvic control (PC), disease-free survival (DFS), and overall survival (OS) outcomes were calculated using weighted means to report pooled analysis of outcomes.

RESULTS

Literature search yielded 16 prospective, 51 retrospective studies that reported survival outcomes, and 13 retrospective studies that focused on acute and late toxicity outcomes regardless of applicator type. There are 57 studies that report Point A dose specification with 33 having chemoRT, and 10 studies that use IBBT, 8 with chemoRT. Patients receiving radiation and chemoRT with HDR BT in the prospective studies, with >24 months followup, rates of PC were: for RT: 73%, SD: 11; CRT: 82%, SD: 8; DFS-RT: 55%, SD: 10; CRT: 65%, SD: 7; OS-RT: 66%, SD: 7; CRT: 70%, SD: 11. In the retrospective studies, the PC rates (weighted means) for the radiation and chemoradiation outcomes are 75% vs. 80%, and for DFS, the values were 55% vs. 63%, respectively. Comparing patients receiving chemoRT and IBBT to traditional Point A dose specification, there is a significant improvement in PC (p < 0.01) and DFS (p < 0.01) with IBBT. The range of genitourinary late toxicity reported for radiation was Grade 3: 1-6% and for chemoRT 2-20%. The range of late gastrointestinal toxicity for radiation was Grade 3: 4-11% and for chemoRT, 1-11%. For the late gynecologic toxicity, only 1 of the 16 prospective trials report a Grade 1-2 of 17% for radiation and 9% for chemoRT effects.

CONCLUSIONS

We present concise outcomes of PC, DFS, OS, and toxicity for cervical cancer patients treated with chemoradiation and HDR BT. Our data suggest an improvement in outcomes with the use of IBBT compared with traditional Point A dose prescriptions. In conclusion, HDR BT is a safe, effective modality when combined with IBBT.

Comparison of manual and inverse optimisation techniques in high dose rate intracavitary brachytherapy of cervical cancer: A dosimetric study

AIMS AND OBJECTIVES

To compare dosimetrically the manual optimisation with IPSA using dose volume histograms (DVH) among patients treated for carcinoma of cervix with intracavitary brachytherapy.

BACKGROUND

With the advent of advanced imaging modalities, there has been a shift from conventional X-ray based planning to three-dimensional planning. Manual optimisation is widely used across various institutions but it is time consuming and operator dependant. Inverse planning simulated annealing (IPSA) is now available in various brachytherapy planning systems. But there is a paucity of studies comparing manual optimisation and IPSA in treatment of carcinoma cervix with intracavitary brachytherapy and hence this study.

MATERIALS AND METHODS

Fifteen consecutive patients treated between December 2013 and March 2014 with intracavitary brachytherapy for carcinoma of cervix were selected for this study. All patients were initially treated with external beam radiotherapy followed by intracavitary brachytherapy. The DVH was evaluated and compared between manually optimised plans and IPSA in the same set of patients.

RESULTS

There was a significant improvement in the HRCTV coverage, mean V100 of 87.75% and 82.37% (p = 0.001) and conformity index 0.67 and 0.6 (p = 0.007) for plans generated using IPSA and manual optimisation, respectively. Homogeneity index and dose to the OARs remained similar between the two groups.

CONCLUSION

The use of inverse planning in intracavitary brachytherapy of cervix has shown a significant improvement in the target volume coverage when compared with manual planning.

Automatic seed localization of iodine brachytherapy implants from CT images

Radioactive seed implantation has emerged as an effective treatment modality where small radioactive seeds are implanted into the target organ to eradicate the cancer by emitting radiation. Precise seeds localization can indicate whether those seeds deliver sufficient doses of radiation. However, it is challenging and laborious to identify all seeds manually in a short time. Therefore, our purpose in this study was to develop an automatic technique for identifying implanted seeds on any parts of body. The algorithm relies on a 3D adaptive median filter to remove bone structure; white top-hat transform to extract seeds-like objects and further seed classification analysis based on size, shape and their connection etc. Preliminary results on ten patients and seven simulated data show that this approach to be effective and accurate. It resulted in a 96.9 % detection rate with a corresponding 4.7 % false-positive rate for clinical data; a 98.5 % detection rate with a corresponding 4.1 % false-positive rate for the simulated data; and sub-millimeter accuracy for both data sets. This method can achieve robust and accurate seed segmentation through the proposed workflow.

Inverse planning for combination of intracavitary and interstitial brachytherapy for locally advanced cervical cancer

The main purpose of this study was to compare three different treatment plans for locally advanced cervical cancer: (i) the inverse-planning simulated annealing (IPSA) plan for combination brachytherapy (BT) of interstitial and intracavitary brachytherapy, (ii) manual optimization based on the Manchester system for combination-BT, and (iii) the conventional Manchester system using only tandem and ovoids. This was a retrospective study of 25 consecutive implants. The high-risk clinical target volume (HR-CTV) and organs at risk were defined according to the GEC-ESTRO Working Group definitions. A dose of 6 Gy was prescribed. The uniform cost function for dose constraints was applied to all IPSA-generated plans. The coverage of the HR-CTV by IPSA for combination-BT was equivalent to that of manual optimization, and was better than that of the Manchester system using only tandem and ovoids. The mean V100 achieved by IPSA for combination-BT, manual optimization and Manchester was 96 ± 3.7%, 95 ± 5.5% and 80 ± 13.4%, respectively. The mean D100 was 483 ± 80, 487 ± 97 and 335 ± 119 cGy, respectively. The mean D90 was 677 ± 61, 681 ± 88 and 513 ± 150 cGy, respectively. IPSA resulted in significant reductions of the doses to the rectum (IPSA D2cm(3): 408 ± 71 cGy vs manual optimization D2cm(3): 485 ± 105 cGy; P = 0.03) and the bladder (IPSA D2cm(3): 452 ± 60 cGy vs manual optimization D2cm(3): 583 ± 113 cGy; P < 0.0001). In conclusion, combination-BT achieved better tumor coverage, and plans using IPSA provided significant sparing of normal tissues without compromising CTV coverage.

A self-adaptive case-based reasoning system for dose planning in prostate cancer radiotherapy

PURPOSE

Prostate cancer is the most common cancer in the male population. Radiotherapy is often used in the treatment for prostate cancer. In radiotherapy treatment, the oncologist makes a trade-off between the risk and benefit of the radiation, i.e., the task is to deliver a high dose to the prostate cancer cells and minimize side effects of the treatment. The aim of our research is to develop a software system that will assist the oncologist in planning new treatments.

METHODS

A nonlinear case-based reasoning system is developed to capture the expertise and experience of oncologists in treating previous patients. Importance (weights) of different clinical parameters in the dose planning is determined by the oncologist based on their past experience, and is highly subjective. The weights are usually fixed in the system. In this research, the weights are updated automatically each time after generating a treatment plan for a new patient using a group based simulated annealing approach.

RESULTS

The developed approach is analyzed on the real data set collected from the Nottingham University Hospitals NHS Trust, City Hospital Campus, UK. Extensive experiments show that the dose plan suggested by the proposed method is coherent with the dose plan prescribed by an experienced oncologist or even better.

CONCLUSIONS

The developed case-based reasoning system enables the use of knowledge and experience gained by the oncologist in treating new patients. This system may play a vital role to assist the oncologist in making a better decision in less computational time; it utilizes the success rate of the previously treated patients and it can also be used in teaching and training processes.

Image guided, adaptive, accelerated, high dose brachytherapy as model for advanced small volume radiotherapy

Brachytherapy has consistently provided a very conformal radiation therapy modality. Over the last two decades this has been associated with significant improvements in imaging for brachytherapy applications (prostate, gynecology), resulting in many positive advances in treatment planning, application techniques and clinical outcome. This is emphasized by the increased use of brachytherapy in Europe with gynecology as continuous basis and prostate and breast as more recently growing fields. Image guidance enables exact knowledge of the applicator together with improved visualization of tumor and target volumes as well as of organs at risk providing the basis for very individualized 3D and 4D treatment planning. In this commentary the most important recent developments in prostate, gynecological and breast brachytherapy are reviewed, with a focus on European recent and current research aiming at the definition of areas for important future research. Moreover the positive impact of GEC-ESTRO recommendations and the highlights of brachytherapy physics are discussed what altogether presents a full overview of modern image guided brachytherapy. An overview is finally provided on past and current international brachytherapy publications focusing on "Radiotherapy and Oncology". These data show tremendous increase in almost all research areas over the last three decades strongly influenced recently by translational research in regard to imaging and technology. In order to provide high level clinical evidence for future brachytherapy practice the strong need for comprehensive prospective clinical research addressing brachytherapy issues is high-lighted.

Inverse-planned gynecologic high-dose-rate interstitial brachytherapy: clinical outcomes and dose--volume histogram analysis

PURPOSE

To present clinical outcomes and dose-volume histogram parameters of three-dimensional image-based high-dose-rate interstitial brachytherapy (HDR-ISBT) in patients with primary or recurrent gynecologic cancer unsuitable for intracavitary brachytherapy (ICB).

METHODS AND MATERIALS

Records of 43 women treated between 2001 and 2009 with iridium-192 gynecologic HDR-ISBT boost, using a Syed-Neblett template and inverse planning simulated annealing dose optimization, were reviewed. Median HDR-ISBT dose was 30Gy, delivered in 4-6Gy/fraction. Dose-volume histogram parameters recommended by the Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology for image-based ICB were analyzed. Total doses were normalized to 2Gy fractions (biologically equivalent dose in 2Gy fractions). Local control (LC) and survival were calculated using Kaplan-Meier method. Toxicities were defined according to Common Terminology Criteria for Adverse Events v3.0.

RESULTS

There were 34 primary malignancies (cervix=12, vagina=15, Bartholin's gland=5, and vulva=2) and 9 recurrences. International Federation of Gynecology and Obstetrics stage distribution for primary cancers was I=2, II=13, III=15, and IV=4. Median followup was 19.3 months (range, 0-92.2). Two-year LC was 87% for primary cancers, and 45% for recurrent cancers, respectively (p=0.0175). Median V(100), D(90), and D(100) for clinical target volume were 97.6%, 90.2, and 68.7Gy(10), respectively. Median bladder and rectal D(2)(cc) were 76.6 and 79.5Gy(3), respectively. Median urethral D(10) was 80.6Gy(3). Twelve patients experienced Grades 3 and 4 late morbidity, but toxicities were transient. Only 2 patients had persistent severe toxicities. A trend toward increased risk for vaginal necrosis was observed with a clinical target volume >84cc.

CONCLUSIONS

HDR-ISBT may achieve good LC in gynecologic cancer unsuitable for ICB, especially in primary malignancies with a 2-year LC rate higher than 85%. Delivery of such high doses has potential advantages but may predispose to adverse effects, reversible in most cases.

Patient-Specific Method of Generating Parametric Maps of Patlak K(i) without Blood Sampling or Metabolite Correction: A Feasibility Study

Currently, kinetic analyses using dynamic positron emission tomography (PET) experience very limited use despite their potential for improving quantitative accuracy in several clinical and research applications. For targeted volume applications, such as radiation treatment planning, treatment monitoring, and cerebral metabolic studies, the key to implementation of these methods is the determination of an arterial input function, which can include time-consuming analysis of blood samples for metabolite correction. Targeted kinetic applications would become practical for the clinic if blood sampling and metabolite correction could be avoided. To this end, we developed a novel method (Patlak-P) of generating parametric maps that is identical to Patlak K(i) (within a global scalar multiple) but does not require the determination of the arterial input function or metabolite correction. In this initial study, we show that Patlak-P (a) mimics Patlak K(i) images in terms of visual assessment and target-to-background (TB) ratios of regions of elevated uptake, (b) has higher visual contrast and (generally) better image quality than SUV, and (c) may have an important role in improving radiotherapy planning, therapy monitoring, and neurometabolism studies.

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 of help structures (HS) during optimization.

MATERIAL AND METHODS

33 patients who underwent MR image-based HDR intracavitary-brachytherapy for cervix cancer based on GYN-ESTRO recommendations were selected for evaluation. Tandem/ovoid (T/O) and Vienna applicators were used. HS of diameter of 5 mm were drawn around the tandem/needles/ovoid and ring. Three plans were generated: 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 loading of 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 of total time of needles to the tandem (T(N/T%)) was found to be 14±2.5, 53±9, 22±6 for MOPT, IPSA_woHS and IPSA_wHS, respectively, which implies that in IPSA_woHS the dwell time in needles were half of the dwell time in the tandem, while in MOPT the needles were loaded only in 14%, and in IPSA_wHS it was 22% of the dwell time of 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 consuming procedure 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 beneficial in case of combined intracavitary - interstitial approach.

A detailed dosimetric comparison between manual and inverse plans in HDR intracavitary/interstitial cervical cancer brachytherapy

PURPOSE

The purpose of this study was to compare two inverse planning algorithms for cervical cancer brachytherapy and a conventional manual treatment planning according to the MUW (Medical University of Vienna) protocol.

MATERIAL AND METHODS

For 20 patients, manually optimized, and, inversely optimized treatment plans with Hybrid Inverse treatment Planning and Optimization (HIPO) and with Inverse Planning Simulated Annealing (IPSA) were created. Dosimetric parameters, absolute volumes of normal tissue receiving reference doses, absolute loading times of tandem, ring and interstitial needles, Paddick and COIN conformity indices were evaluated.

RESULTS

HIPO was able to achieve a similar dose distribution to manual planning with the restriction of high dose regions. It reduced the loading time of needles and the overall treatment time. The values of both conformity indices were the lowest. IPSA was able to achieve acceptable dosimetric results. However, it overloaded the needles. This resulted in high dose regions located in the normal tissue. The Paddick index for the volume of two times prescribed dose was outstandingly low.

CONCLUSIONS

HIPO can produce clinically acceptable treatment plans with the elimination of high dose regions in normal tissue. Compared to IPSA, it is an inverse optimization method which takes into account current clinical experience gained from manual treatment planning.