Conventional Conformal Radiotherapy Research Articles

Radiation source personalization for nanoparticle-enhanced radiotherapy using dynamic contrast-enhanced MRI in the treatment planning process

Nanoparticle-enhanced radiotherapy offers the potential to selectively increase the radiation dose imparted to the tumor while at the same time sparing the healthy structures around it. Among the recommendations of an interdisciplinary group for the clinical translation of this treatment modality, is the developing of methods to quantify the effects that the nanoparticle concentration has on the radiation dosimetry and incorporate these effects into the treatment planning process. In this work, using Monte Carlo simulations and dynamic contrast-enhanced MRI images, treatment plans for nanoparticle-enhanced radiotherapy are calculated in order to evaluate the effects that realistic distributions of the nanoparticles have on the resultant plans and to devise treatment strategies to account for these effects, including the selection of the proper x-ray source configuration in terms of energy and collimation. Dynamic contrast-enhanced MRI studies were obtained for two treatment sites, namely brain and breast. A model to convert the MRI signal to contrast agent concentration was applied to each set of images. Two treatment modalities, 3D conformal radiotherapy and Stereotactic Body Radiation Therapy, were evaluated at three different x-ray spectra, namely 6 MV from a linear accelerator, 110 kVp and 220 kVp from a tungsten target. For the breast patient, as the nanoparticle distribution varies markedly with time, the treatment plans were obtained at two different times after administration. It was determined that maximum doses to the healthy structures around the tumor are mostly determined by the minimum nanoparticle concentration in the tumor. The presence of highly hypoxic or necrotic tissue, which fails to accumulate the nanoparticles, or leakage of the contrast agent into the surrounding healthy tissue, make irradiation with conventional conformal radiotherapy unfeasible for kilovoltage beam energies, as the uniform beam apertures lack the ability to compensate for the non-uniform distribution of the nanoparticles. Therefore, proper quantification of the nanoparticle distribution not only in the target volume but also in the surrounding tissues and structures is crucial for the proper planning of nanoparticle-enhanced radiotherapy and a treatment delivery with a high-degree of freedom, such as small-field stereotactic body radiotherapy, should be the method of choice for this treatment modality.

Association of 3D-CRT and IMRT accelerated hyperfractionated radiotherapy with local control rate and 5-year survival in esophageal squamous cell carcinoma patients.

This retrospective study examined the relevance and prognostic factors of whole-course conformal radiotherapy (CRT) and late-course accelerated hyperfractionation radiotherapy (LCAFRT) for esophageal squamous cell carcinoma (ESCC). A total of 110 patients with ESCC received whole-course CRT and LCAFRT between May 2004 and January 2015. All patients received conventional CRT of 2 Gy per day, up to 30-40 Gy, followed by LCAFRT using reduced fields at 1.5 Gy/fraction twice a day, up to 24-39 Gy, for a total dose of 60-69 Gy. The median follow-up was 85 months. The whole groups 1-, 3-, and 5-year survival rates were 81.8%, 46.4%, and 41.8%, respectively. The local control rates for the whole group at 1, 3, and 5 years were 82.7%, 70.0%, and 68.2%, respectively. There were no significant differences among survival rates and local control rates between the 3D-CRT and intensity-modulated radiotherapy (IMRT) groups. The main reactions to acute radiotherapy were acute radiation tracheitis, esophagitis, and pneumonia. The tumor location and TNM stage were independent prognostic factors for overall survival. The results showed that whole-course CRT and LCAFRT for ESCC can improve survival and local control with a tolerable acute reaction compared to previous studies. Local recurrence and distant metastasis are the main failure modes of treatment. Whole-course CRT and LCAFRT for ESCC can improve the survival and local control rate compared with previous studies from the 2DRT era. It might provide another treatment for patients with inoperable ESCC or refusing surgery.

Biological Evaluation of Grid versus 3D Conformal Radiotherapy in Bulky Head and Neck Cancer.

Grid radiotherapy is one of the treatment techniques applied to treat patients with advanced bulky tumors.Purpose:This study aims to estimate the difference in biological and dosimetric parameters of the grid radiotherapy technique for the treatment of bulky head and neck (H and N) tumors and compare it with conventional conformal radiotherapy.Subjects and Methods:Three-dimensional conformal and grid radiotherapy were designed by the Monaco treatment planning system (TPS). Eight bulky tumors of (H and N) cases were selected, using a single fraction 15–20 Gy. Dose-volume histogram of the tumors and organs at risk (OARs) used to calculate the equivalent uniform dose (EUD) (Gy) by Matlab program. Furthermore, dosimetric parameters of the tumors from the TPS were compared for two techniques (grid radiotherapy and the conventional conformal radiotherapy).Results:Grid attained a lower EUD (Gy) in tumors and OARs as compared to conformal therapy, as Grid principle protects about half of the tumor area from the radiation leads to less coverage of the tumor. Also, where OARs in closed with tumors and the shielding by multi-leaf (1 cm) were more effective than other techniques, lead to a decrease of radiobiological values according to its definition by Niemierko. Radiobiological results showed significant differences between the two methods, and dosimetric data obtained by the TPS for tumours for two plans were P < 0.05.Conclusions:The grid plan achieves lower values of EUDs than the conformal technique for OARs. Hence, it achieves more sparing and fewer complications for these organs.

A planning study to optimise a simultaneously integrated boost treatment of larynx cancer with seven intensity-modulated radiation therapy (IMRT) beams

AbstractBackgroundIntensity-modulated radiation therapy (IMRT) is one of the most reported techniques for head and neck cancer treatment, as it allows a good coverage of the planning target volume (PTV) while sparing the surrounding organs at risk (OAR) better than conventional conformal radiotherapy. The objective of this work is to optimise an IMRT technique for the simultaneously integrated boost (SIB) treatment of larynx cancer delivering a total dose of 69·96 Gy to the boost volume and 54·45 Gy to the elective volume in 33 fractions.MethodsThree IMRT techniques, each using seven equally spaced beams, were planned for a sample of 10 patients. The first two techniques (IMRT-0 and IMRT-26) differ only for the starting angle of the seven beams, whereas the third (IMRT-CT) combines both these techniques by delivering IMRT-0 in the first half of treatment, and IMRT-26 in the second half, thus taking advantage of using 14 beams in total while using seven at a time only. The planning results were compared according to the dose coverage, homogeneity and conformity of the two PTVs, as well as to the dose to OARs, that is, spinal cord, parotids, mandible, brainstem and healthy tissue (defined as the body volume minus the sum of PTVs).ResultsBasically the PTV coverage resulted acceptable and comparable with all the three techniques. Concerning OARs, statistically better results are obtained in IMRT-CT when compared with IMRT-26 and IMRT-0.ConclusionThe IMRT-CT technique, combining two different seven-beam setups, delivered in two treatment phases, improves dose distribution without increasing delivery time.

Adherence to 'Choosing Wisely' recommendations for radiation therapy in a commercially insured breast cancer population.

e18267 Background: ASTRO ‘Choosing Wisely recommendations’ (CWr) note radiation therapy (RT) interventions lacking evidence of benefit in cancer care. This study evaluates adherence to the 2013 CWr to ‘not routinely use intensity modulated radiotherapy (IMRT) to deliver whole breast radiotherapy as part of breast conservation therapy’ using a novel linkage between the Western WA Cancer Surveillance System (CSS) and claims from two large commercial insurance plans. No studies have evaluated adherence to this CWr in a commercial insurance setting. Methods: CSS records for first primary Stage I/II breast cancer cases (2008-2015) were linked with Premera Blue Cross and Regence Blue Shield claims. Included cases had coverage for ≥12-months before/after diagnosis (or until death), lumpectomy within 6 months of diagnosis, and RT within 6 months of lumpectomy. We used generalized estimating equations (GEE) to evaluate associations between demographic (age, race) and tumor (grade, laterality, diagnosis year) variables and use of IMRT vs conventional conformal RT within 1 year of diagnosis. Results: We identified 1,048 first primary Stage I/II breast cancer cases that met inclusion criteria. Mean age was 61, 91% were white, 52% were left-side cases. The non-adherent proportions are in the table below. In GEE analysis, only left-side cases (OR=6.4, p&lt;0.001) and years of age (OR=1.03, p&lt;0.01) were independently associated with IMRT use. Conclusions: Patients with IMRT vs. conventional conformal RT after lumpectomy may incur additional cost without commensurate clinical benefit. In the first study of adherence to a CWr against IMRT in this setting, we found that left-side cases were 6-fold more likely to be non-adherent vs right-side cases. This association suggests that IMRT is being used to reduce radiation dose to the heart, though not supported by evidence. Overall, the small non-adherent proportion before/after the CWr suggests alignment between guidelines and use of IMRT in Western WA. Future studies should evaluate IMRT use in other regions and develop strategies to improve CWr adherence in left-side cases. [Table: see text]

Myelodysplastic Syndromes and Acute Myeloid Leukemia After Radiotherapy for Prostate Cancer: A Population-Based Study.

To understand the impact of radiotherapy on the development of myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) among elderly prostate cancer patients. We performed a retrospective cohort study of elderly prostate cancer patients diagnosed during 1999-2011 by using the National Cancer Institute's Surveillance, Epidemiology and End Results-Medicare linked database. Competing risk analyses adjusting for patient characteristics were conducted to assess the impact of radiotherapy on the development of subsequent MDS/AML, compared with surgery. Of 32,112 prostate cancer patients, 14,672 underwent radiotherapy, and 17,440 received surgery only. The median follow-up was 4.68 years. A total of 157 (0.47%) prostate cancer patients developed subsequent MDS or AML, and the median time to develop MDS/AML was 3.30 (range: 0.16-9.48) years. Compared with prostate cancer patients who received surgery only, patients who underwent radiotherapy had a significantly increased risk of developing MDS/AML (hazard ratio [HR] =1.51, 95% confidence interval [CI]: 1.07-2.13). When radiotherapy was further categorized by modalities (brachytherapy, conventional conformal radiotherapy, and intensity-modulated radiotherapy [IMRT]), increased risk of second MDS/AML was only observed in the IMRT group (HR = 1.66, 95% CI: 1.09-2.54). Our findings suggest that radiotherapy for prostate cancer increases the risk of MDS/AML, and the impact may differ by modality. Additional studies with longer follow-up are needed to further clarify the role of radiotherapy in the development of subsequent myeloid malignancies. A better understanding may help patients, physicians, and other stakeholders make more informed treatment decisions. Prostate 77:437-445, 2017. © 2016 Wiley Periodicals, Inc.

Hypofraction radiotherapy by helical tomotherapy for unresectable but confined intrahepatic hepatocellular carcinoma is efficient and safe in comparison with conventional 3-dimension conformal radiotherapy

Objective To evaluate the safety of helical tomotherapy (HT) for hepatocellular carcinoma confined to the liver, and to investigate the efficacy of HT by comparison with three-dimensional conformal radiotherapy (3DCRT). Methods In June 2011, hypofractionated HT was performed in 35 patients with unresectable hepatocellular carcinoma confined to the liver who had no distant metastasis or tumor thrombosis. The dose in each fraction increased from 2.4 Gy to 5.0 Gy with a median dose of 3.2 Gy. The median dose for the total treatment was 50.0 Gy. Within the same period, 45 patients received conventionally fractionated 3DCRT with a median dose of 54.0 Gy. The adverse reactions, clinical outcomes, and survival time were compared between the two groups. The survival rate was calculated with Kaplan-Meier method, and log-rank test was used to estimate statistical significance of survival differences. Multivariate analysis of survival was carried out with Cox’s regression model. Results There were no significant differences in adverse reactions between the two groups. The objective response rate was significantly higher in the HT group than in the 3DCRT group (60% vs. 33%, P=0.024). There was no significant difference in the disease control rate between the two groups (94% vs. 89%, P=0.459). The HT group showed significantly higher 1-, 2-, and 3-year overall survival rates than the 3DCRT group (97% vs. 80%, P=0.025; 81% vs. 55%, P=0.008; 67% vs. 50%, P=0.048). The multivariate analysis indicated that tumor smaller than 8 cm, transarterial chemoembolization before radiotherapy, and HT were associated with improved survival (P=0.005; P=0.000; P=0.002). Conclusions HT shows an advantage in precise treatment of hepatocellular carcinoma confined to the liver. With acceptable toxicity, hypofractionated HT shortens the treatment duration and improves the survival in patients. Key words: Liver neoplasms/radiotherapy; Radiotherapy, helicaltomo; Radiotherapy, three-dimensional conformal; Prognosis

Dosimetric comparison of 3D conformal conventional radiotherapy versus intensity-modulated radiation therapy both in conventional and high dose radiation for prostate carcinoma

Background: Radiotherapy plays an important role in the management of prostate cancer. There are ongoing efforts to deliver the optimum radiation dose to the prostate while minimizing it to at risk pelvic structures. Aim: To compare the dose coverage of planning target volume (PTV) and organs-at-risk (OAR) between intensity-modulated radiation therapy (IMRT) and conventional three dimensional conformal radiotherapy (3D-CRT) for the same plan of prostate cancer patients in both conventional dose and high dose. Methods: Plans of 15 prostate cancer patients with low- or intermediate risk, treated by 3D-CRT, were compared with IMRT to the same dose and to a higher dose. We used XIO- treatment planning system for 3D-CRT and Monaco treatment planning system for IMRT. Results: Mean and minimum dose to PTV were equal, but the mean maximum dose was significantly higher in IMRT (72Gy) than 3D-CRT. Doses to critical organs in IMRT plans were lower than 3D-CRT, even in the increased dose of 80Gy. Conclusion: IMRT is recommended as the standard of care in treatment of prostate carcinoma. Applying escalated dose is recommended.

Health-Related Quality of Life in Head-and-Neck Cancer Treated With Radiation Therapy With or Without Chemotherapy: A Systematic Review

Health-related quality of life (HRQoL) is a subjective measure of patients' experience of disease and treatment. We systematically reviewed the literature to identify high quality manuscripts reporting HRQoL outcomes in adults with squamous cell carcinoma of the head and neck (HNSCC) treated with an organ-sparing curative regimen of radiation therapy with or without chemotherapy. Assessments were performed independently by two reviewers; a third reviewer resolved disputes. High quality reports were reviewed in detail to identify trends in HRQoL outcomes. MEDLINE and EMBASE searching yielded 276 distinct reports, plus 24 added via hand search. Of these, 53 met eligibility criteria and 18 were deemed high quality reports on the basis of a quality assessment tool. HRQoL declines after treatment but recovers to baseline levels, generally within 12months. However, xerostomia-related HRQoL deficits may remain long-term. Combined chemoradiotherapy showed a trend toward worse HRQoL compared with RT alone. Intensity modulated radiotherapy (IMRT) yields better HRQoL compared with conventional or three-dimensional conformal radiotherapy. Baseline HRQoL may independently predict local-regional control and overall survival. Future research should incorporate HRQoL into phase III trials. However, adequate effort and journal space must be afforded to the HRQoL results of these studies to ensure proper reporting methods are followed, allowing clinicians to incorporate HRQoL into patient counseling and clinical decision making.

Comparative Effectiveness of Intensity-Modulated Radiotherapy and Conventional Conformal Radiotherapy in the Treatment of Prostate Cancer After Radical Prostatectomy

Comparative effectiveness research of prostate cancer therapies is needed because of the development and rapid clinical adoption of newer and costlier treatments without proven clinical benefit. Radiotherapy is indicated after prostatectomy in select patients who have adverse pathologic features and in those with recurrent disease. To examine the patterns of use of intensity-modulated radiotherapy (IMRT), a newer, more expensive technology that may reduce radiation dose to adjacent organs compared with the older conformal radiotherapy (CRT) in the postprostatectomy setting, and to compare disease control and morbidity outcomes of these treatments. Data from the Surveillance, Epidemiology, and End Results-Medicare-linked database were used to identify patients with a diagnosis of prostate cancer who had received radiotherapy within 3 years after prostatectomy. Patients who received IMRT or CRT. The outcomes of 457 IMRT and 557 CRT patients who received radiotherapy between 2002 and 2007 were compared using their claims through 2009. We used propensity score methods to balance baseline characteristics and estimate adjusted incidence rate ratios (RRs) and their 95% CIs for measured outcomes. Use of IMRT increased from zero in 2000 to 82.1% in 2009. Men who received IMRT vs CRT showed no significant difference in rates of long-term gastrointestinal morbidity (RR, 0.95; 95% CI, 0.66-1.37), urinary nonincontinent morbidity (0.93; 0.66-1.33), urinary incontinence (0.98; 0.71-1.35), or erectile dysfunction (0.85; 0.61-1.19). There was no significant difference in subsequent treatment for recurrent disease (RR, 1.31; 95% CI, 0.90-1.92). Postprostatectomy IMRT and CRT achieved similar morbidity and cancer control outcomes. The potential clinical benefit of IMRT in this setting is unclear. Given that IMRT is more expensive, its use for postprostatectomy radiotherapy may not be cost-effective compared with CRT, although formal analysis is needed.

Comparative Effectiveness of Intensity-Modulated Radiotherapy and Conventional Conformal Radiotherapy in the Treatment of Prostate Cancer After Radical Prostatectomy

Comparative Effectiveness of Intensity-Modulated Radiotherapy and Conventional Conformal Radiotherapy in the Treatment of Prostate Cancer After Radical Prostatectomy

La radiothérapie avec modulation d’intensité rotationnelle apporte-t-elle un avantage dosimétrique dans le traitement du cancer bronchique localement évolué ?

PurposeTo analyse the dosimetric differences between the conventional conformal radiation therapy (CR) and the volumetric modulated arc therapy (VMAT) for non-small-cell locally advanced lung cancer (NSCLC). Patients and methodsTwo plans (CR and VMAT) were calculated for ten NSCLC patients. Dose to PTV, organs at risk and external contours (body), conformity index (PTV volume/volume of the 95% reference isodose) and homogeneity index ([maximal dose−minimal dose]/dose prescription) were compared. ResultsDoses delivered to PTV (homogeneity index, maximal, minimal and mean dose) are similar with both techniques but conformity index is improved by 60% with VMAT: from 0.55±0.07 with CR to 0.89±0.07 with VMAT (P=0.002). Pulmonary protection is improved with VMAT: with CR and VMAT, respectively, the mean lung dose is 14.1±5.2Gy and 12.2±4.5Gy, the lung volume which receives at least 30Gy (V30) is 20±8% and 14±5%, and the V20 is 24±11% and 20±10% (P=0.002). The mean dose received by the body is also 9% lower (P=0.004) and V5 is 13% higher (P=0.004) with VMAT. V10 and V15 were similar with both modalities. From 20Gy and higher, irradiated body volume is larger with CR than with VMAT. The relative difference increases with the dose: from 10% for 20Gy (P=0.014) up to 39% for 62.7Gy (P=0.002). ConclusionCompared to CR, VMAT greatly improves conformity and reduces mean dose and dose delivered from 20Gy and higher to the lungs and the body.

Intérêts dosimétriques et cliniques de la radiothérapie asservie à la respiration des cancers du poumon et du sein : résultats du Stic 2003

PurposeTo compare respiratory-gated conformal radiotherapy versus conventional conformal radiotherapy for the irradiation of non-small cells lung cancer and breast cancer. Patients and methodsThe STIC 2003 project was a comparative, non-randomized, multicenter and prospective study that included in 20 French centers between April 2004 and June 2008, 634 evaluable patients, 401 non-small cells lung cancer and 233 breast cancers. ResultsThe final results confirmed the feasibility and good reproducibility of the various respiratory-gated conformal radiotherapy systems regardless of tumour location. The results of this study demonstrated a marked reduction of dosimetric parameters predictive of pulmonary, cardiac and esophageal toxicity, especially for non-small cells lung cancer, as a result of the various respiratory gating techniques. These dosimetric benefits were mainly observed with deep inspiration breath-hold techniques (ABC and SDX), which markedly increased the total lung volume compared to the inspiration-synchronized system based on tidal volume (RPM). For non-small cells lung cancer, these theoretical dosimetric benefits were correlated with a significant reduction in clinically acute and late toxicities, especially the pulmonary. For breast cancer, although less clear due to the lower total dose, there was a decrease in the dose delivered to the heart, potentially reducing the risk of cardiac toxicity in the long-term, especially during the irradiation of the left breast, and a reduction in dose to the contra lateral breast. ConclusionRespiratory-gated radiotherapy appears to be essential to reduce the risk of acute and late toxicities, especially for lungs and heart, during irradiation of non-small cells lung cancer and breast cancers.

Contribution of Respiratory Gating Techniques for Optimization of Breast Cancer Radiotherapy

A comparative, nonrandomized, multicenter, and prospective analysis were performed between April 2004 and June 2008 in 20 French centers in order to compare clinical aspects of respiratory-gated conformal radiotherapy (RGRT) during breast cancer irradiation versus conventional conformal radiotherapy. The final results based on 233 evaluable patients at 48 months confirm the feasibility and good reproducibility of the RGRT systems. The main results demonstrated a marked reduction of dosimetric parameters predictive of lungs and cardiac toxicities in the RGRT group; especially the dose delivered to the heart during irradiation of the left breast; mostly observed with deep inspiration breath-hold techniques.

Short-term outcomes of CyberKnife therapy for advanced high-risk tumors: A report of 160 cases

The objective of the present study was to evaluate short-term outcomes of CyberKnife therapy in patients with advanced high-risk tumors. A total of 201 target areas from 341 advanced high-risk tumor lesions in 160 patients were treated with CyberKnife. A prescribed dose of 18-60 Gy to the gross tumor volume was delivered in 1-6 fractions to complete the entire treatment in 1 week. Radiographic studies and clinical examinations were performed at 1- to 3-month follow-up intervals, and the results were compared to outcomes of 160 similar advanced high-risk tumor patients who were treated by conformal radiotherapy (CRT). After CyberKnife therapy, the short-term improvement in the quality of life was significant according to radiographic study, radioimmunoassay and ZPS scores of these patients. The total rates of objective efficacy and alleviation of ascities were as high as 66.88 and 67.90%. The short-term outcomes in our series of patients with advanced high-risk tumors treated with CyberKnife appeared to be better compared to conventional CRT. CyberKnife may be an option for patients with incurable advanced high-risk tumors, although further studies of the long-term outcomes are required to confirm the validity.

Respiratory Gating Techniques for Optimization of Lung Cancer Radiotherapy

The primary objective of the STIC 2003 project was to compare the clinical and economic aspects of respiratory-gated conformal radiotherapy (RGRT), an innovative technique proposed to limit the impact of respiratory movements during irradiation, versus conventional conformal radiotherapy, the reference radiation therapy for lung cancer. A comparative, nonrandomized, multicenter, and prospective cost toxicity analysis was performed in the context of this project between April 2004 and June 2008 in 20 French centers. Only the results of the clinical study are presented here, as the results of the economic assessment have been published previously. The final results based on 401 evaluable patients confirm the feasibility and good reproducibility of the various RGRT systems. The results of this study demonstrated a marked reduction of dosimetric parameters predictive of pulmonary, cardiac and esophageal toxicity as a result of the various respiratory gating techniques. These dosimetric benefits were mainly observed with deep inspiration breath-hold (DIBH) techniques (ABC and SDX systems), which markedly increased the total lung volume compared with the inspiration-synchronized system based on tidal volume (Real-time Position Management). These theoretical dosimetric benefits were correlated clinically with a significant reduction of pulmonary acute toxicity, and the pulmonary, cardiac, and esophageal late toxicities, especially with DIBH techniques. Pulmonary function parameters, although more heterogeneous, especially DLCO, showed a tendency to reduction of pulmonary toxicity in the RGRT group. RGRT seems to be essential to reduce toxicities, especially the pulmonary, cardiac, and esophageal late toxicities with the DIBH methods.

Uncertainties and CTV to PTV margins quantitative assessment using cone-beam CT technique in clinical application for prostate, and head and neck irradiation tumours

PURPOSE To evaluate the magnitude of systematic and random errors from a subset of 100 prostate and 26 head and neck (H&N) cancer patients treated with conventional conformal radiotherapy and using image-guided radiotherapy (IGRT). After treatment, the uncertainties involved and the CTV to PTV margin were evaluated. MATERIAL AND METHODS An Elekta Synergy® linear accelerator was used, taking advantage of 3D on-board computed tomography. IGRT with no-action level (NAL) protocol was applied, reporting the 3D translation and rotation corrections. A statistical study was performed to analyse systematic, random and interobserver uncertainties, and, finally, to obtain the CTV to PTV margins. RESULTS The H&N patients' uncertainties found were smaller than those of prostate patients. The CTV to PTV margins assessed, following the guidelines found in the literature, in the three dimensions of space (right-left, superior-inferior, anterior-posterior) were (5.3, 3.5, 3.2) mm for H&N and (7.3, 7.0, 9.0) mm for prostate cancer treatments. CONCLUSIONS It was found that assessing all the involved uncertainties within radiation treatments was very revealing; their quality improves using IGRT techniques and performing extensive data analysis.

Combination of Dose Escalation with Technological Advances (Intensity-Modulated and Image-Guided Radiotherapy) Is Not Associated with Increased Morbidity for Patients with Prostate Cancer

The aim was to evaluate treatment-related morbidity after intensity-modulated (IMRT) and image-guided (IGRT) radiotherapy with a total dose of 76 Gy in comparison to conventional conformal radiotherapy (3DCRT) up to 70.2-72 Gy for patients with prostate cancer. All patients were prospectively surveyed prior to, on the last day, as well as after a median time of 2 and 16 months after RT using a validated questionnaire (Expanded Prostate Cancer Index Composite). Criteria for the 78 matched pairs after IMRT vs. 3DCRT were patient age, use of antiandrogens, treatment volume (± whole pelvis), prognostic risk group, and urinary/bowel/sexual quality of life (QoL) before treatment. QoL changes after dose-escalated IMRT were found to be similar to QoL changes after 3DCRT in all domains. Only sexual function scores more than 1 year after RT decreased slightly more after 3DCRT in comparison to IMRT (mean 9 vs. 6 points; p = 0.04), with erections firm enough for intercourse in 14% vs. 30% (p = 0.03). Painful bowel movements were reported more frequently after 3DCRT vs. IMRT 2 months after treatment (≥ once a day in 10% vs. 1%; p = 0.03), but a tendency for higher rectal bleeding rates was found after IMRT vs. 3DCRT more than 1 year after RT (≥ rarely in 20% vs. 9%; p = 0.06). Combination of dose escalation with technological advances (IMRT and IGRT) is not associated with increased morbidity for patients with prostate cancer.

Response-probability volume histograms and iso-probability of response charts in treatment plan evaluation

This study aims at demonstrating a new method for treatment plan evaluation and comparison based on the radiobiological response of individual voxels. This is performed by applying them on three different cancer types and treatment plans of different conformalities. Furthermore, their usefulness is examined in conjunction with traditionally applied radiobiological and dosimetric treatment plan evaluation criteria. Three different cancer types (head and neck, breast and prostate) were selected to quantify the benefits of the proposed treatment plan evaluation method. In each case, conventional conformal radiotherapy (CRT) and intensity modulated radiotherapy (IMRT) treatment configurations were planned. Iso-probability of response charts was produced by calculating the response probability in every voxel using the linear-quadratic-Poisson model and the dose-response parameters of the corresponding structure to which this voxel belongs. The overall probabilities of target and normal tissue responses were calculated using the Poisson and the relative seriality models, respectively. The 3D dose distribution converted to a 2 Gy fractionation, D2(GY) and iso-BED distributions are also shown and compared with the proposed methodology. Response-probability volume histograms (RVH) were derived and compared with common dose volume histograms (DVH). The different dose distributions were also compared using the complication-free tumor control probability, P+, the biologically effective uniform dose, D, and common dosimetric criteria. 3D Iso-probability of response distributions is very useful for plan evaluation since their visual information focuses on the doses that are likely to have a larger clinical effect in that particular organ. The graphical display becomes independent of the prescription dose highlighting the local radiation therapy effect in each voxel without the loss of important spatial information. For example, due to the exponential nature of the Poisson distribution, cold spots in the target volumes or hot spots in the normal tissues are much easier to be identified. Response-volume histograms, as DVH, can also be derived and used for plan comparison. RVH are advantageous since by incorporating the radiobiological properties of each voxel they summarize the 3D distribution into 2D without the loss of relevant information. Thus, more clinically relevant radiobiological objectives and constraints could be defined and used in treatment planning optimization. These measures become increasingly important when dose distributions need to be designed according to the microscopic biological properties of tumor and normal tissues. The proposed methods do not aim to replace quantifiers like the probabilities of total tissue response, which ultimately are the quantities of interest to evaluate treatment success. However, iso-probability of response charts and response-probability volume histograms illustrates more clearly the difference in effectiveness between different treatment plans than the information provided by alternative dosimetric data. The use of 3D iso-probability of response distributions could serve as a good descriptor of the effectiveness of a dose distribution indicating primarily the regions in a tissue that dominate its response.

Radiation therapy concurrent with weekly cisplatin therapy for loco-regionally advanced nasopharyngeal carcinoma: outcomes of a clinical trial

Objective The purpose of this study was to define the maximum tolerated dose (MTD) by describing the doselimiting toxicity (DLT) of weekly cisplatin concurrently with conventional plus 3-dimensional conformal radiotherapy (CT + 3DCRT) in patients with loco-regionally advanced nasopharyngeal carcinoma (NPC).