Abstract
Background
In treatment planning for proton therapy a constant Relative Biological Effectiveness (RBE) of 1.1 is used, disregarding variations with linear energy transfer, clinical endpoint, ...or fractionation.
Purpose
To present a methodology to analyze the variation of RBE with fractionation from clinical data of tumor control probability (TCP) and to apply it to study the response of prostate cancer to proton therapy.
Methods and materials
We analyzed the dependence of the RBE on the dose per fraction by using the LQ model and the Poisson TCP formalism. Clinical tumor control probabilities for prostate cancer (low and intermediate risk) treated with photon and proton therapy for conventional fractionation (2 Gy(RBE)×37 fractions), moderate hypofractionation (3 Gy(RBE)×20 fractions) and hypofractionation (7.25 Gy(RBE)×5 fractions) were obtained from the literature and analyzed aiming at obtaining the RBE and its dependence on the dose per fraction.
Results
The theoretical analysis of the dependence of the RBE on the dose per fraction showed three distinct regions with RBE monotonically decreasing, increasing or staying constant with the dose per fraction, depending on the change of (
α
,
β
) values between photon and proton irradiation (the equilibrium point being at
(α
p
/β
p
)
=
(α
X
/β
X
)(α
X
/α
p
)
). An analysis of the clinical data showed RBE values that decline with increasing dose per fraction: for low risk RBE≈1.124, 1.119, and 1.102 for 1.82 Gy, 2.73 Gy and 6.59 Gy per fraction (physical proton doses), respectively; for intermediate risk RBE≈1.119 and 1.102 for 1.82 Gy and 6.59 Gy per fraction (physical proton doses), respectively. These values are nonetheless very close to the nominal 1.1 value.
Conclusions
In this study, we have presented a methodology to analyze the RBE for different fractionations, and we used it to study clinical data for prostate cancer and evaluate the RBE versus dose per fraction. The analysis shows a monotonically decreasing RBE with increasing dose per fraction, which is expected from the LQ formalism and the changes in (
α
,
β
) values between photon and proton irradiation. However, the calculations in this study have to be considered with care as they may be biased by limitations in the modeling assumptions and/or by the clinical data set used for the analysis.
Aims
To estimate the prevalence of lower urinary tract symptoms (LUTS) in patients with prostate cancer scheduled to receive LHRH analogs, and to assess the effectiveness of LHRH analogs on LUTS in ...patients presenting moderate/severe symptoms.
Methods
Prospective, noninterventional, multicenter study conducted at 28 centers in Spain and Portugal. LUTS were evaluated using the International Prostate Symptom Score (IPSS) at baseline, 24 and 48 weeks after initiation of treatment. Subanalyses were performed according to age and concomitant treatment (radiotherapy, alpha‐blockers, and antiandrogens).
Results
A total of 354 patients were treated with LHRH analogs for 48 weeks. The percentage of patients with moderate/severe LUTS (IPSS > 7) decreased from 60.2% (n = 213/354) at baseline to 52.8% (n = 187/354) at Week 48. Among patients with moderate/severe LUTS at baseline: 73.7% (n = 157/213) still had moderate/severe LUTS at Week 48; percentage reductions of patients with LUTS at Week 48 were statistically significant (p < 0.05) overall and by age or concomitant treatment, except for alpha‐blockers (84.2% patients receiving them still had moderate/severe LUTS at Week 48). All IPSS items, including quality of life for urinary symptoms, improved throughout the study. The only predictor of response to treatment with LHRH analogs that improved IPSS by 3 points after 48 weeks was baseline testosterone levels. Lower baseline testosterone levels were associated with greater improvement in IPSS after treatment with LHRH analogs (odds ratio 0.998, 95% confidence interval 0.996–1.000, p = 0.0277).
Conclusion
LHRH analogs have a positive effect in patients with locally advanced or metastatic prostate cancer presenting moderate/severe LUTS regardless of age or concomitant treatment received (radiotherapy, antiandrogens, or alpha‐blockers).
This article summarizes the current status of CT perfusion in oncologic imaging, including lesion characterization, staging, prediction of patient outcome or response to therapy, assessment of ...response to different therapies, and evaluation of tumor relapse. Technical limitations and drawbacks of CT perfusion are also discussed.
Tumor angiogenesis is essential for cancer growth and provides an attractive target for oncologic therapies. CT perfusion is an emerging imaging tool that provides both qualitative and quantitative information regarding tumor angiogenesis.
•NSCLC dose–response curves show evidence of indirect cell damage at large doses.•Brain metastases dose–response curves show evidence of damage saturation at large doses.•Dose prescription to such ...tumors might be re-evaluated according to the reported evidence.
To investigate the possible contribution of indirect damage and damage saturation to tumour control obtained with SBRT/SRS treatments for early-stage NSCLC and brain metastases.
We have constructed a dataset of early-stage NSCLC and brain metastases dose–response. These data were fitted to models based on the linear-quadratic (LQ), the linear-quadratic-linear (LQL), and phenomenological modifications of the LQ-model to account for indirect cell damage. We use the Akaike-Information-Criterion formalism to compare performance, and studied the stability of the results with changes in fitting parameters and perturbations on dose/TCP values.
In NSCLC, a modified LQ-model with a beta-term increasing with dose yields the best-fits for α/β = 10 Gy. Only the inclusion of very fast accelerated proliferation or low α/β values can eliminate such superiority. In brain, the LQL model yields the best-fits, and the ranking is not affected by variations of fitting parameters or dose/TCP perturbations.
For α/β = 10 Gy, a modified LQ-model with a beta-term increasing with dose provides better fits to NSCLC dose–response curves. For brain metastases, the LQL provides the best fit. This might be interpreted as a hint of indirect damage in NSCLC, and damage saturation in brain metastases. The results for NSCLC are strongly dependent on the value of α/β and may require further investigation, while those for brain seem to be clearly significant. Our results can assist in the design of improved radiotherapy for NSCLC and brain metastases, aiming at avoiding over/under-treatment.
There is increasing evidence that high doses of radiotherapy, like those delivered in stereotactic body radiotherapy (SBRT), trigger indirect mechanisms of cell death. Such effect seems to be ...two-fold. High doses may trigger an immune response and may cause vascular damage, leading to cell starvation and death. Development of mathematical response models, including indirect death, may help clinicians to design SBRT optimal schedules. Despite increasing experimental literature on indirect tumor cell death caused by vascular damage, efforts on modeling this effect have been limited. In this work, we present a biomathematical model of this effect. In our model, tumor oxygenation is obtained by solving the reaction-diffusion equation; radiotherapy kills tumor cells according to the linear-quadratic model, and also endothelial cells (EC), which can trigger loss of functionality of capillaries. Capillary death will affect tumor oxygenation, driving nearby tumor cells into severe hypoxia. Capillaries can recover functionality due to EC proliferation. Tumor cells entering a predetermined severe hypoxia status die according to a hypoxia-death model. This model fits recently published experimental data showing the effect of vascular damage on surviving fractions. It fits surviving fraction curves and qualitatively reproduces experimental values of percentages of functional capillaries 48 hours postirradiation, and hypoxic cells pre- and 48 hours postirradiation. This model is useful for exploring aspects of tumor and EC response to radiotherapy and constitutes a stepping stone toward modeling indirect tumor cell death caused by vascular damage and accounting for this effect during SBRT planning. SIGNIFICANCE: A novel biomathematical model of indirect tumor cell death caused by vascular radiation damage could potentially help clinicians interpret experimental data and design better radiotherapy schedules.
The purpose of this work was to investigate the response of prostate cancer to different radiotherapy schedules, including hypofractionation, to evaluate potential departures from the ...linear-quadratic (LQ) response, to obtain the best-fitting parameters for low-(LR), intermediate-(IR), and high-risk (HR) prostate cancer and to investigate the effect of ADT on the radiobiological response. We constructed a dataset of the dose-response containing 87 entries/16,536 patients (35/5181 LR, 32/8146 IR, 20/3209 HR), with doses per fraction ranging from 1.8 to 10 Gy. These data were fit to tumour control probability models based on the LQ model, linear-quadratic-linear (LQL) model, and a modification of the LQ (LQmod) model accounting for increasing radiosensitivity at large doses. Fits were performed with the maximum likelihood expectation methodology, and the Akaike information criterion (AIC) was used to compare the models. The AIC showed that the LQ model was superior to the LQL and LQmod models for all risks, except for IR, where the LQL model outperformed the other models. The analysis showed a low α/β for all risks: 2.0 Gy for LR (95% confidence interval: 1.7-2.3), 3.4 Gy for IR (3.0-4.0), and 2.8 Gy for HR (1.4-4.2). The best fits did not show proliferation for LR and showed moderate proliferation for IR/HR. The addition of ADT was consistent with a suppression of proliferation. In conclusion, the LQ model described the response of prostate cancer better than the alternative models. Only for IR, the LQL model outperformed the LQ model, pointing out a possible saturation of radiation damage with increasing dose. This study confirmed a low α/β for all risks.
This review presents challenges and recommendations on different aspects related to the management of patients with localized muscle-invasive bladder cancer (MIBC), which were discussed by a group of ...experts of a Spanish Oncology Genitourinary (SOGUG) Working Group within the framework of the Genitourinary Alliance project (12GU). It is necessary to clearly define which patients are candidates for radical cystectomy and which are candidates for undergoing bladder-sparing procedures. In older patients, it is necessary to include a geriatric assessment and evaluation of comorbidities. The pathological report should include a classification of the histopathological variant of MIBC, particularly the identification of subtypes with prognostic, molecular and therapeutic implications. Improvement of clinical staging, better definition of prognostic groups based on molecular subtypes, and identification of biomarkers potentially associated with maximum benefit from neoadjuvant chemotherapy are areas for further research. A current challenge in the management of MIBC is improving the selection of patients likely to be candidates for immunotherapy with checkpoint inhibitors in the neoadjuvant setting. Optimization of FDG-PET/CT reliability in staging of MIBC and the selection of patients is necessary, as well as the design of prospective studies aimed to compare the value of different imaging techniques in parallel.
Radiogenomics in lung cancer: Where are we? Aguado-Barrera, Miguel E.; Sosa-Fajardo, Paloma; Gómez-Caamaño, Antonio ...
Lung cancer (Amsterdam, Netherlands),
February 2023, 2023-02-00, Letnik:
176
Journal Article
Recenzirano
•Forty-six publications on radiogenomic analyses of lung cancer were included in this review.•All these studies used candidate gene approach; time has come to advance to GWAS.•Most SNPs from ...inflammation and DNA repair pathways, 12 good biomarker candidates.•Bigger sample size cohorts and uniformity in the reporting of data are required.•Clinical application of genomic biomarkers of radiation induced toxicity is needed.
Huge technological and biomedical advances have improved the survival and quality of life of lung cancer patients treated with radiotherapy. However, during treatment planning, a probability that the patient will experience adverse effects is assumed. Radiotoxicity is a complex entity that is largely dose-dependent but also has important intrinsic factors. One of the most studied is the genetic variants that may be associated with susceptibility to the development of adverse effects of radiotherapy. This review aims to present the current status of radiogenomics in lung cancer, integrating results obtained in association studies of SNPs (single nucleotide polymorphisms) related to radiotherapy toxicities. We conclude that despite numerous publications in this field, methodologies and endpoints vary greatly, making comparisons between studies difficult. Analyzing SNPs from the candidate gene approach, together with the study in cohorts limited by the sample size, has complicated the possibility of having validated results. All this delays the incorporation of genetic biomarkers in predictive models for clinical application. Thus, from all analysed SNPs, only 12 have great potential as esophagitis genetic risk factors and deserve further exploration. This review highlights the efforts that have been made to date in the radiogenomic study of radiotoxicity in lung cancer.
Purpose Androgen deprivation therapy may promote the development of the metabolic syndrome in patients with prostate cancer. We assessed the prevalence of the full metabolic syndrome and its ...components during the first year of androgen deprivation therapy. Materials and Methods This observational, multicenter, prospective study included 539 patients with prostate cancer scheduled to receive 3-month depot luteinizing hormone-releasing hormone analogs for more than 12 months. Waist circumference, body mass index, lipid profile, blood pressure and fasting glucose were evaluated at baseline and after 6 and 12 months. The metabolic syndrome was assessed according to NCEP ATP III criteria (2001) and 4 other definitions (WHO 1998, AACE 2003, AHA/NHLBI 2005 and IDF 2005). Results At 6 and 12 months after the initiation of androgen deprivation therapy, significant increases were observed in waist circumference, body mass index, fasting glucose, triglycerides, total cholesterol, and high-density and low-density lipoprotein cholesterol. No significant changes in blood pressure 130/85 or greater were detected. A nonsignificant increase of 3.9% in the prevalence of the full metabolic syndrome (ATP III) was observed (22.9% at baseline vs 25.5% and 26.8% at 6 and 12 months, respectively). The prevalence of the metabolic syndrome at baseline varied according to the definition used, ranging from 9.4% (WHO) to 50% (IDF). At 12 months significant increases in prevalence were observed with the WHO (4.1%) and AHA/NHLBI (8.1%) definitions. Conclusions Androgen deprivation therapy produces significant early effects on waist circumference, body mass index, fasting glucose, triglycerides and cholesterol. The prevalence of and increase in the metabolic syndrome depend on the defining criteria. Counseling patients on the prevention, early detection and treatment of specific metabolic alterations is recommended.
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