Use of low-value radiotherapy practices in Canada: an analysis of provincial cancer registry data

BACKGROUND

As part of Choosing Wisely Canada (a national campaign to encourage patient-provider conversations about unnecessary medical tests, treatments, and procedures), a list of ten oncology practices that could be low-value in some instances was developed. Of those practices, two were specific to radiation therapy (rt): conventional fractionation as part of breast-conserving therapy (bct) for women with early-stage breast cancer, and multifraction radiation for palliation of uncomplicated painful bone metastases. Here, we report baseline findings for the current utilization rates of those two rt practices in Canada.

RESULTS

The use of conventional fractionation as part of bct varied substantially from province to province. Of women 50 years of age and older, between 8.8% (Alberta) and 36.5% (Saskatchewan) received radiation in 25 fractions (excluding boost irradiation) as part of bct. The use of hypofractionated rt (that is, 16 fractions excluding boost irradiation)-a preferred approach for many patients-was more common in all 6 reporting provinces, ranging from 43.2% in Saskatchewan to 94.7% in Prince Edward Island. The use of multifraction rt for palliation of bone metastases also varied from province to province, ranging from 40.3% in British Columbia to 69.0% in Saskatchewan. The most common number of fractions delivered to bone metastases was 1, at 50.2%; the second most common numbers were 2-5 fractions, at 41.7%.

CONCLUSIONS

Understanding variation in the use of potentially low-value rt practices can help to inform future strategies to promote higher-value care, which balances high-quality care with the efficient use of limited system resources. Further work is needed to understand the factors contributing to the interprovincial variation observed and to develop benchmarks for the appropriate rate of use of these rt practices.

Computational analysis of drug transport in tumor microenvironment as a critical compartment for nanotherapeutic pharmacokinetics

Over the last decade, nanotherapeutics gained increasingly important role in drug delivery because of their frequently beneficial pharmacokinetics (PK) and lower toxicity when compared to classical systemic drug delivery. In view of therapeutic payload delivery, convective transport is crucial for systemic distribution via circulatory system, but the target domain is tissue outside vessels where transport is governed by diffusion. Here, we have computationally investigated the understudied interplay of physical transports to characterize PK of payload of nanotherapeutics. The analysis of human vasculature tree showed that convective transport is still 5 times more efficient than diffusion suggesting that circulating and payload releasing drug vectors can contribute mostly to systemic delivery. By comparing payload delivery using systemic circulation and drug vectors to microenvironment, internalized vectors were the most efficient and showed Area under the Curve almost 100 higher than in systemic delivery. The newly introduced zone of influence parameter indicated that vectors, especially internalized, lead to the largest tissue fraction covered with therapeutically significant payload concentration. The internalization to microenvironment minimizes effects of plasma domain on payload extravasation from nanotherapeutics. The computed results showed that classical PK, which mostly relies on concentration profiles in plasma, sometimes might be inadequate or not sufficient in explaining therapeutic efficacy of nanotherapeutics. These results provide a deeper look into PK of drug vectors and can help in the design of better drug delivery strategies.

Mass release curves as the constitutive curves for modeling diffusive transport within biological tissue

In diffusion governed by Fick's law, the diffusion coefficient represents the phenomenological material parameter and is, in general, a constant. In certain cases of diffusion through porous media, the diffusion coefficient can be variable (i.e. non-constant) due to the complex process of solute displacements within microstructure, since these displacements depend on porosity, internal microstructural geometry, size of the transported particles, chemical nature, and physical interactions between the diffusing substance and the microstructural surroundings. In order to provide a simple and general approach of determining the diffusion coefficient for diffusion through porous media, we have introduced mass release curves as the constitutive curves of diffusion. The mass release curve for a selected direction represents cumulative mass (per surface area) passed in that direction through a small reference volume, in terms of time. We have developed a methodology, based on numerical Finite Element (FE) and Molecular Dynamics (MD) methods, to determine simple mass release curves of solutes through complex media from which we calculate the diffusion coefficient. The diffusion models take into account interactions between solute particles and microstructural surfaces, as well as hydrophobicity (partitioning). We illustrate the effectiveness of our approach on several examples of complex composite media, including an imaging-based analysis of diffusion through pancreatic cancer tissue. The presented work offers an insight into the role of mass release curves in describing diffusion through porous media in general, and further in case of complex composite media such as biological tissue.

Hypoxia Marker GLUT-1 (Glucose Transporter 1) is an Independent Prognostic Factor for Survival in Bladder Cancer Patients Treated with Radical Cystectomy

BACKGROUND

Tumour hypoxia, which is frequent in many cancer types, is associated with treatment resistance and poor prognosis. The role of hypoxia in surgically treated bladder cancer (BC) is not well described. We studied the role of hypoxia in two independent series of urothelial bladder cancers treated with radical cystectomy.

METHODS

279 patients from the University Hospital Network (UHN), Toronto, Canada, and Turku University, Finland were studied. Hypoxia biomarkers (HIF1-α, CAIX, GLUT-1) and proliferation marker Ki-67 were analyzed with immunohistochemistry using defined tissue microarrays. Kaplan-Meier methods and Cox proportional hazards regression models were used to investigate prognostic role of the factors.

RESULTS

In univariate analyses, strong GLUT-1 positivity and a high Ki-67 index were associated with poor survival. In multivariate model containing clinical prognostic variables, GLUT-1 was an independent prognostic factor associated with worse disease-specific survival (HR 2.9, 95% CI 0.7-12.6, Wald p = 0.15 in the Toronto cohort and HR 3.2, 95% CI 1.3-7.5, Wald p = 0.0085 in the Turku cohort).

CONCLUSION

GLUT-1 is frequently upregulated and is an independent prognostic factor in surgically treated bladder cancer. Further studies are needed to evaluate the potential role of hypoxia-based and targeted therapies in hypoxic bladder tumours.

Liposomal doxorubicin extravasation controlled by phenotype-specific transport properties of tumor microenvironment and vascular barrier

Although nanotherapeutics can be advantageous over free chemotherapy, the benefits of drug vectors can vary from patient to patient based on differences in tumor microenvironments. Although systemic pharmacokinetics (PK) of drugs is considered as the major determinant of its efficacy in clinics, recent clinical and basic research indicates that tumor-based PK can provide better representation of therapeutic efficacy. Here, we have studied the role of the tumor extravascular tissue in the extravasation kinetics of doxorubicin (DOX), delivered by pegylated liposomes (PLD), to murine lung (3LL) and breast (4T1) tumors. We found that phenotypically different 3LL and 4T1 tumors shared the similar systemic PK, but DOX extravasation in the tumor extravascular tissue was substantially different. Liquid chromatography-mass spectrometry (LC-MS) measurements showed that DOX fluorescence imaged by fluorescence microscopy could be used as a marker to study tumor microenvironment PK, providing an excellent match to DOX kinetics in tumor tissues. Our results also suggest that therapeutic responses can be closely related to the interplay of concentration levels and exposure times in extravascular tissue of tumors. Finally, the computational model of capillary drug transport showed that internalization of drug vectors was critical and could lead to 2-3 orders of magnitude more efficient drug delivery into the extravascular tissue, compared to non-internalized localization of drug vectors, and explaining the differences in therapeutic efficacy between the 3LL and 4T1 tumors. These results show that drug transport and partitioning characteristics can be phenotype- and microenvironment-dependent and are highly important in drug delivery and therapeutic efficacy.

Mass partitioning effects in diffusion transport

Frequent mass exchange takes place in a heterogeneous environment among several phases, where mass partitioning may occur at the interface of phases. Analytical and computational methods for diffusion do not usually incorporate molecule partitioning masking the true picture of mass transport. Here we present a computational finite element methodology to calculate diffusion mass transport with a partitioning phenomenon included and the analysis of the effects of partitioning. Our numerical results showed that partitioning controls equilibrated mass distribution as expected from analytical solutions. The experimental validation of mass release from drug-loaded nanoparticles showed that partitioning might even dominate in some cases with respect to diffusion itself. The analysis of diffusion kinetics in the parameter space of partitioning and diffusivity showed that partitioning is an extremely important parameter in systems, where mass diffusivity is fast and that the concentration of nanoparticles can control payload retention inside nanoparticles. The computational and experimental results suggest that partitioning and physiochemical properties of phases play an important, if not crucial, role in diffusion transport and should be included in the studies of mass transport processes.

The role of elective para-aortic lymph node irradiation in patients with locally advanced cervical cancer

AIMS

Pelvic lymph node positivity in cervical cancer is known to be an adverse prognostic factor and is associated with an elevated risk of clinically occult para-aortic lymph node metastases. The purpose of this study was to examine the benefit of elective para-aortic lymph node radiotherapy (PART) in patients with no clinical or radiographic evidence of para-aortic lymph node metastases receiving concurrent cisplatin chemotherapy.

MATERIALS AND METHODS

Patients treated with radiotherapy and concurrent cisplatin for cervical cancer from 1999 to 2009 were identified in two prospective databases. All patients received external beam pelvic radiotherapy (PRT) to a median dose of 50 Gy concurrently with weekly cisplatin 40 mg/m(2). This was followed by pulse dose rate intracavitary brachytherapy to a median dose of 40 Gy. Patients at high risk of occult para-aortic metastases also received PART to a median dose of 40 Gy.

RESULTS

There were 228 patients suitable for analysis; the median follow-up was 4.6 years. The addition of PART to PRT was not associated with a significant difference in disease-free survival (hazard ratio 1.1, confidence interval 0.7-1.8, P = 0.75) or overall survival (hazard ratio 1.6, confidence interval 0.9-2.7, P = 0.11) on multivariate analysis. There was no significant difference in the rate of para-aortic relapse with PART versus PRT (hazard ratio 2.01, confidence interval 0.79-5.12, P = 0.14). The 3 year grade 3-4 late toxicities were 11% for the PART group versus 8% for PRT (hazard ratio 1.39, confidence interval 0.58-3.37, P = 0.47).

CONCLUSIONS

These results suggest that cervical cancer patients treated with radiotherapy and concurrent cisplatin do not benefit from elective PART.