Radiotherapeutic techniques for prostate cancer, dose escalation and brachytherapy

Regression Analysis of Rectal Cancer and Possible Application of Artificial Intelligence (AI) Utilization in Radiotherapy

Artificial Intelligence (AI) has been widely employed in the medical field in recent years in such areas as image segmentation, medical image registration, and computer-aided detection. This study explores one application of using AI in adaptive radiation therapy treatment planning by predicting the tumor volume reduction rate (TVRR). Cone beam computed tomography (CBCT) scans of twenty rectal cancer patients were collected to observe the change in tumor volume over the course of a standard five-week radiotherapy treatment. In addition to treatment volume, patient data including patient age, gender, weight, number of treatment fractions, and dose per fraction were also collected. Application of a stepwise regression model showed that age, dose per fraction and weight were the best predictors for tumor volume reduction rate.

Prostate Cancer, Version 2.2019, NCCN Clinical Practice Guidelines in Oncology

The NCCN Guidelines for Prostate Cancer include recommendations regarding diagnosis, risk stratification and workup, treatment options for localized disease, and management of recurrent and advanced disease for clinicians who treat patients with prostate cancer. The portions of the guidelines included herein focus on the roles of germline and somatic genetic testing, risk stratification with nomograms and tumor multigene molecular testing, androgen deprivation therapy, secondary hormonal therapy, chemotherapy, and immunotherapy in patients with prostate cancer.

Artificial intelligence in radiotherapy

Artificial intelligence (AI) has already been implemented widely in the medical field in the recent years. This paper first reviews the background of AI and radiotherapy. Then it explores the basic concepts of different AI algorithms and machine learning methods, such as neural networks, that are available to us today and how they are being implemented in radiotherapy and diagnostic processes, such as medical imaging, treatment planning, patient simulation, quality assurance and radiation dose delivery. It also explores the ongoing research on AI methods that are to be implemented in radiotherapy in the future. The review shows very promising progress and future for AI to be widely used in various areas of radiotherapy. However, basing on various concerns such as availability and security of using big data, and further work on polishing and testing AI algorithms, it is found that we may not ready to use AI primarily in radiotherapy at the moment.

Automatic matching using intraprostatic calcifications as a volume of interest in CBCT images during prostate radiotherapy: a comparative study

Aim:

The study aimed to assess the clinical feasibility of employing an automatic match during cone beam computed tomography (CBCT) imaging using prostatic calcifications within the 95% isodose set as the region of interest.

Materials and methods:

CBCT images were analysed on the 5th fraction in 34 patients evaluating the difference between standard manual soft tissue anatomy matching versus auto calcification matching. An assessment of the clinical feasibility of using prostatic calcifications during matching alongside considering the effect a more automated matching process has been conducted on interobserver variability.

Results:

The standard deviation values of the difference between the soft tissue match (baseline) versus automatic calcification matches fluctuated around 1 mm in all three axes for all of the matches carried out. The interobserver variability observed between the two radiographers was 0·055, 0·065 and 0·045 cm in the vertical, longitudinal and lateral axes, respectively.

Findings:

The clarity of the calcifications on the CBCT images might explain the low interobserver variability displayed by the two matching radiographers. A calcification provides a clear starting point for image matching before commencing a check of volumetric coverage, if the matching process begins in the same place, it can allow for a standardisation of matching technique between radiographers.

Use of metrics to quantify IMRT and VMAT treatment plan complexity: A systematic review and perspectives

PURPOSE

Fixed-field intensity modulated radiation therapy (FF-IMRT) or volumetric modulated arc therapy (VMAT) beams complexity is due to fluence fluctuation. Pre-treatment Quality Assurance (PTQA) failure could be linked to it. Several plan complexity metrics (PCM) have been published to quantify this complexity but in a heterogeneous formalism. This review proposes to gather different PCM and to discuss their eventual PTQA failure identifier abilities.

METHODS AND MATERIALS

A systematic literature search and outcome extraction from MEDLINE/PubMed (National Center for Biotechnology Information, NCBI) was performed. First, a list and a synthesis of available PCM is made in a homogeneous formalism. Second, main results relying on the link between PCM and PTQA results but also on other uses are listed.

RESULTS

A total of 163 studies were identified and n = 19 were selected after inclusion and exclusion criteria application. Difference is made between fluence and degree of freedom (DOF)-based PCM. Results about the PCM potential as PTQA failure identifier are described and synthesized. Others uses are also found in quality, big data, machine learning and audit procedure.

CONCLUSIONS

A state of the art is made thanks to this homogeneous PCM classification. For now, PCM should be seen as a planning procedure quality indicator although PTQA failure identifier results are mitigated. However limited clinical use seems possible for some cases. Yet, addressing the general PTQA failure prediction case could be possible with the big data or machine learning help.

Large-Scale Production of 119mTe and 119Sb for Radiopharmaceutical Applications

Radionuclides find widespread use in medical technologies for treating and diagnosing disease. Among successful and emerging radiotherapeutics, ¹¹⁹Sb has unique potential in targeted therapeutic applications for low-energy electron-emitting isotopes. Unfortunately, developing ¹¹⁹Sb-based drugs has been slow in comparison to other radionuclides, primarily due to limited accessibility. Herein is a production method that overcomes this challenge and expands the available time for large-scale distribution and use. Our approach exploits high flux and fluence from high-energy proton sources to produce longer lived ^119mTe. This parent isotope slowly decays to ¹¹⁹Sb, which in turn provides access to ¹¹⁹Sb for longer time periods (in comparison to direct ¹¹⁹Sb production routes). We contribute the target design, irradiation conditions, and a rapid procedure for isolating the ^119mTe/¹¹⁹Sb pair. To guide process development and to understand why the procedure was successful, we characterized the Te/Sb separation using Te and Sb K-edge X-ray absorption spectroscopy. The procedure provides low-volume aqueous solutions that have high ^119mTe-and consequently ¹¹⁹Sb-specific activity in a chemically pure form. This procedure has been demonstrated at large-scale (production-sized, Ci quantities), and the product has potential to meet stringent Food and Drug Administration requirements for a ^119mTe/¹¹⁹Sb active pharmaceutical ingredient.

Radioresistance of Brain Tumors

Radiation therapy (RT) is frequently used as part of the standard of care treatment of the majority of brain tumors. The efficacy of RT is limited by radioresistance and by normal tissue radiation tolerance. This is highlighted in pediatric brain tumors where the use of radiation is limited by the excessive toxicity to the developing brain. For these reasons, radiosensitization of tumor cells would be beneficial. In this review, we focus on radioresistance mechanisms intrinsic to tumor cells. We also evaluate existing approaches to induce radiosensitization and explore future avenues of investigation.

Integral dose: Comparison between four techniques for prostate radiotherapy

AIM

Comparisons of integral dose delivered to the treatment planning volume and to the whole patient body during stereotactic, helical and intensity modulated radiotherapy of prostate.

BACKGROUND

Multifield techniques produce large volumes of low dose inside the patient body. Delivered dose could be the result of the cytotoxic injuries of the cells even away from the treatment field. We calculated the total dose absorbed in the patient body for four radiotherapy techniques to investigate whether some methods have a potential to reduce the exposure to the patient.

MATERIALS AND METHODS

We analyzed CyberKnife plans for 10 patients with localized prostate cancer. Five alternative plans for each patient were calculated with the VMAT, IMRT and TomoTherapy techniques. Alternative dose distributions were calculated to achieve the same coverage for PTV. Integral Dose formula was used to calculate the total dose delivered to the PTV and whole patient body.

RESULTS

Analysis showed that the same amount of dose was deposited to the treated volume despite different methods of treatment delivery. The mean values of total dose delivered to the whole patient body differed significantly for each treatment technique. The highest integral dose in the patient's body was at the TomoTherapy and CyberKnife treatment session. VMAT was characterized by the lowest integral dose deposited in the patient body.

CONCLUSIONS

The highest total dose absorbed in normal tissue was observed with the use of a robotic radiosurgery system and TomoTherapy. These results demonstrate that the exposure of healthy tissue is a dosimetric factor which differentiates the dose delivery methods.

Phase I/II trial of definitive carbon ion radiotherapy for prostate cancer: evaluation of shortening of treatment period to 3 weeks

BACKGROUND

The purpose of this study was to evaluate the feasibility of a new shortened 3-week treatment schedule of carbon ion radiotherapy (CIRT) for prostate cancer.

METHODS

Beginning in May 2010, patients with T1b-T3bN0M0, histologically proven prostate adenocarcinoma were enrolled in the phase II trial of CIRT. Patients received 51.6 GyE in 12 fractions over 3 weeks (protocol 1002). The primary end point was defined as the incidence of late adverse events that were evaluated based on the Common Terminology Criteria for Adverse Events version 4.0. Biochemical failure was determined using the Phoenix definition (nadir +2.0 ng ml(-1)).

RESULTS

Forty-six patients were enrolled, and all patients were included in the analysis. The number of low-, intermediate-, and high-risk patients was 12 (26%), 9 (20%), and 25 (54%), respectively. The median follow-up period of surviving patients was 32.3 months. Two patients had intercurrent death without recurrence, and the remaining 44 patients were alive at the time of this analysis. In the analysis of late toxicities, grade 1 (G1) rectal haemorrhage was observed in 3 (7%) patients. The incidence of G1 haematuria was observed in 6 (13%) patients, and G1 urinary frequency was observed in 17 (37%) patients. No ⩾G2 late toxicities were observed. In the analysis of acute toxicities, 2 (4%) patients showed G2 urinary frequency, and no other G2 acute toxicities were observed.

CONCLUSIONS

The new shortened CIRT schedule over 3 weeks was considered as feasible. The analysis of long-term outcome is warranted.

Sonablate®-500: transrectal high-intensity focused ultrasound for the treatment of prostate cancer

Prostate cancer (PCa) is the most common cancer in men and the second leading cause of death from malignancy in the UK. The number of men diagnosed with PCa is increasing, due in part to an increased willingness of men to visit their family doctors with lower urinary tract symptoms, and also a willingness of physicians to test for it. As the demographic of men diagnosed with PCa becomes younger and better informed, so the demand for a less-invasive alternative to standard therapies becomes greater. The Sonablate-500 is one of only two high-intensity focused ultrasound (HIFU) devices commercially available to treat PCa. HIFU is an attractive treatment option as it is the only form of therapy that neither involves direct instrumentation of the prostate nor ionizing radiation. This article describes the unique features of both the Sonablate-500 system hardware and software, and the outcome data from this device in the context of current standard therapies. Finally, a view into the future attempts to outline where this technology is heading and how a paradigm shift in the way that PCa is considered may make HIFU even more relevant.

Tissue biomarkers for prostate cancer radiation therapy

Prostate cancer is the most common cancer and second leading cause of cancer deaths among men in the United States. Most men have localized disease diagnosed following an elevated serum prostate specific antigen test for cancer screening purposes. Standard treatment options consist of surgery or definitive radiation therapy directed by clinical factors that are organized into risk stratification groups. Current clinical risk stratification systems are still insufficient to differentiate lethal from indolent disease. Similarly, a subset of men in poor risk groups need to be identified for more aggressive treatment and enrollment into clinical trials. Furthermore, these clinical tools are very limited in revealing information about the biologic pathways driving these different disease phenotypes and do not offer insights for novel treatments which are needed in men with poor-risk disease. We believe molecular biomarkers may serve to bridge these inadequacies of traditional clinical factors opening the door for personalized treatment approaches that would allow tailoring of treatment options to maximize therapeutic outcome. We review the current state of prognostic and predictive tissue-based molecular biomarkers which can be used to direct localized prostate cancer treatment decisions, specifically those implicated with definitive and salvage radiation therapy.

Effects of gamma-ray-induced free radicals on the metal content and amino acid composition of human metallothionein-1

Metallothioneins (MTs), a low-mass class of metalloproteins, are characterized by a high thiolate sulphur and metal content. MTs are involved in metal homeostasis and heavy metal detoxification, and are efficient scavengers of free radicals. This article describes zinc release from human MT-1 and modification of its amino acid composition when subjected to free radicals generated during gamma ray radiolysis. The effect of gamma ray radiolysis of untreated and metal-depleted human MT-1 was tested under multiple aerobic and anaerobic conditions at increasing irradiation doses. Under all conditions, a rapid increase of serine in the early stages of irradiation was observed. Irradiation for longer times led to cysteic acid formation, except under argon atmosphere. Several other amino acid concentrations gradually decreased. Formation of limited amounts of hydroxyproline, hydroxylysine and ornithine as well as some less common derivatives such as cystathionine occurred as side-effects.

Magnetic resonance imaging for adaptive cobalt tomotherapy: A proposal

Magnetic resonance imaging (MRI) provides excellent soft tissue contrast for oncology applications. We propose to combine a MRI scanner with a helical tomotherapy (HT) system to enable daily target imaging for improved conformal radiation dose delivery to a patient. HT uses an intensity-modulated fan-beam that revolves around a patient, while the patient slowly advances through the plane of rotation, yielding a helical beam trajectory. Since the use of a linear accelerator to produce radiation may be incompatible with the pulsed radiofrequency and the high and pulsed magnetic fields required for MRI, it is proposed that a radioactive Cobalt-60 ((60)Co) source be used instead to provide the radiation. An open low field (0.25 T) MRI system is proposed where the tomotherapy ring gantry is located between two sets of Helmholtz coils that can generate a sufficiently homogenous main magnetic field.It is shown that the two major challenges with the design, namely acceptable radiation dose rate (and therefore treatment duration) and moving parts in strong magnetic field, can be addressed. The high dose rate desired for helical tomotherapy delivery can be achieved using two radiation sources of 220TBq (6000Ci) each on a ring gantry with a source to axis-of-rotation distance of 75 cm. In addition to this, a dual row multi-leaf collimator (MLC) system with 15 mm leaf width at isocentre and relatively large fan beam widths between 15 and 30 mm per row shall be employed. In this configuration, the unit would be well-suited for most pelvic radiotherapy applications where the soft tissue contrast of MRI will be particularly beneficial. Non-magnetic MRI compatible materials must be used for the rotating gantry. Tungsten, which is non-magnetic, can be used for primary collimation of the fan-beam as well as for the MLC, which allows intensity modulated radiation delivery. We propose to employ a low magnetic Cobalt compound, sycoporite (CoS) for the Cobalt source material itself.Rotational delivery is less susceptible to problems related to the use of a low energy megavoltage photon source while the helical delivery reduces the negative impact of the relatively large penumbra inherent in the use of Cobalt sources for radiotherapy. On the other hand, the use of a (60)Co source ensures constant dose rate with gantry rotation and makes dose calculation in a magnetic field as easy as the range of secondary electrons is limited.The MR-integrated Cobalt tomotherapy unit, dubbed 'MiCoTo,' uses two independent physical principles for image acquisition and treatment delivery. It would offer excellent target definition and will allow following target motion during treatment using fast imaging techniques thus providing the best possible input for adaptive radiotherapy. As an additional bonus, quality assurance of the radiation delivery can be performed in situ using radiation sensitive gels imaged by MRI.

Dosimetric comparison between 3D conformal and intensity-modulated radiation therapy for prostate cancer

Background and Purpose: Intensity-modulated radiation therapy (IMRT) is considered by many to be the standard of care in the delivery of external-beam radiotherapy treatments to the prostate. The purpose of this study is to assess the validity of the purported benefits of IMRT.

Materials and Methods: Treatment plans were produced for 10 patients using both 3D conformal radiation therapy (3D-CRT) and IMRT, utilising the dose constraints recommended by the Radiation Therapy Oncology Group (RTOG) 0415 protocol. Three IMRT modalities used in this study were linear accelerator based IMRT, helical tomotherapy, and serial tomotherapy. The prescription to the target, 76 Gy, was the same for all plans.

Results: In general the 3D-CRT plans satisfied the RTOG criteria for planning target volume (PTV) coverage, and met or bettered the dose criteria for the organs at risk. PTV coverage was more homogeneous for the IMRT plans than the 3D-CRT plans but not significantly improved.

Conclusions: Technically, because the IMRT plans required greater effort for the optimisation, longer treatment times and higher monitor units, the use of IMRT for the fulfilment of the protocol’s dosimetric goals was not justified using these constraints.

Updated results of high-dose rate brachytherapy and external beam radiotherapy for locally and locally advanced prostate cancer using the RTOG-ASTRO Phoenix definition

PURPOSE

To evaluate the prognostic factors for patients with local or locally advanced prostate cancer treated with external beam radiotherapy (RT) and high dose rate brachytherapy (HDR) according to the RTOG-ASTRO Phoenix Consensus Conference.

MATERIALS AND METHODS

The charts of 209 patients treated between 1997 and 2005 with localized RT and HDR as a boost at the Department of Radiation Oncology, AC Camargo Hospital, Sao Paulo, Brazil were reviewed. Clinical and treatment parameters i.e.: patient's age, Gleason score, clinical stage, initial PSA (iPSA), risk group (RG) for biochemical failure, doses of RT and HDR were evaluated. Median age and median follow-up time were 68 and 5.3 years, respectively. Median RT and HDR doses were 45 Gy and 20 Gy.

RESULTS

Disease specific survival (DSS) at 3.3 year was 94.2%. Regarding RG, for the LR (low risk), IR (intermediate risk) and HR (high risk), the DSS rates at 3.3 years were 91.5%, 90.2% and 88.5%, respectively. On univariate analysis prognostic factors related to DSS were RG (p=0.040), Gleason score <or= 6 ng/mL (p=0.002), total dose of HDR >or= 20 Gy (p<0.001) On multivariate analysis the only statistical significant predictive factor for biochemical control (bNED) was the RG, p<0.001 (CI-1.147-3.561).

CONCLUSIONS

Although the radiation dose administered to the prostate is an important factor related to bNED, this could not be established with statistical significance in this group of patients. To date, in our own experience, HDR associated to RT could be considered a successful approach in the treatment of prostate cancer.

The clinical applications of high intensity focused ultrasound in the prostate

PURPOSE

To review the current status of high intensity focused ultrasound (HIFU) therapy in the prostate, in particular the treatment of prostate cancer.

MATERIALS AND METHODS

Two trans-rectal devices are currently in clinical use; the SonablateR500 and AblathermR. These devices are compared and similarities and differences highlighted.

RESULTS

Outcomes from the primary treatment of prostate cancer, and HIFU as a salvage therapy are discussed. The rate of adverse events are described after each of these, and the role and safety of other therapies after primary HIFU failure are outlined. Factors which may influence outcome such as use of neo-adjuvant androgen suppression are discussed.

CONCLUSIONS

Trans-rectal HIFU for prostate cancer is a promising technique with medium-term oncological results broadly comparable to standard therapies. It is the only form of therapy which is non-invasive and does not utilise ionising radiation. This is an exiciting field undergoing rapid developments, both in the technology and the way in which prostate cancer as a disease is managed.

The relationship between the biochemical control outcomes and the quality of planning of high-dose rate brachytherapy as a boost to external beam radiotherapy for locally and locally advanced prostate cancer using the RTOG-ASTRO Phoenix definition

PURPOSE

To evaluated prognostic factors and impact of the quality of planning of high dose rate brachytherapy (HDR-BT) for patients with local or locally advanced prostate cancer treated with external beam radiotherapy (EBRT) and HDR-BT.

METHODS AND MATERIALS

Between 1997 and 2005, 209 patients with biopsy proven prostate adenocarcinoma were treated with localized EBRT and HDR-BT at the Department of Radiation-Oncology, Hospital A. C. Camargo, Sao Paulo, Brazil. Patient's age, Gleason score (GS), clinical stage (CS), initial PSA (iPSA), risk group for biochemical failure (GR), doses of EBRT and HDR-BT, use of three-dimensional planning for HDR-BT (3DHDR) and the Biological Effective Dose (BED) were evaluated as prognostic factors for biochemical control (bC).

RESULTS

Median age and median follow-up time were 68 and 5.3 years, respectively. Median EBRT and HDR-BT doses were 45 Gy and 20 Gy. The crude bC at 3.3 year was 94.2%. For the Low, intermediate and high risk patients the bC rates at 3.3 years were 91.5%, 90.2% and 88.5%, respectively. Overall survival (OS) and disease specific survival rates at 3.3 years were 97.8% and 98.4%, respectively. On univariate analysis the prognostic factors related bC were GR (p= 0.040), GS < or = 6 (p= 0.002), total dose of HDR-BT > or = 20 Gy (p< 0.001), 3DHDR (p< 0.001), BED-HDR > or = 99 Gy(1.5) (p<0.001) and BED-TT > or = 185 (p<0.001). On multivariate analysis the statistical significant predictive factors related to bC were RG (p< 0.001), HDR-BT > or = 20 Gy (p=0.008) and 3DHDR (p<0.001).

CONCLUSIONS

we observed that the bC rates correlates with the generally accepted risk factors described in the literature. Dose escalation, evaluated through the BED, and the quality of planning of HDR-BT are also important predictive factors when treating prostate cancer.

Thermoluminescence dosimetry for in-vivo verification of high dose rate brachytherapy for prostate cancer

It was the aim of the study to verify dose delivered in urethra and rectum during High Dose Rate brachytherapy boost (HDRBB) of prostate cancer patients. During the first fraction of HDRBB measurement catheters were placed in the urethra and rectum of prostate cancer patients. These contained LiF:Mg,Ti Thermoluminescence Dosimetry (TLD) rods of 1 mm diameter, with up to 11 detectors positioned every 16 mm separated by radio-opaque markers. A Lorentzian peak function was used to fit the data. Measurements from 50 patients were evaluated and measured doses were compared with predictions from the treatment planning system (Plato Vs 13.5 to 14.1). Prospective urinary and rectal toxicity scores were collected following treatment. In more than 90% of cases, the Lorentzian peak function provided a good fit to both experimental and planning urethral data (r2 > 0.9). In general there was good agreement between measured and predicted doses with the average difference between measured and planned maximum dose being 0.1 Gy. No significant association between dose and any clinical endpoints was observed in 43 patients available for clinical evaluation. An average inferior shift of 2 mm between the plan and the measurement performed approximately 1 hour after the planning CT scan was found for the dose distribution in the cohort of patients for the urethra measurements. Rectal measurements proved to be more difficult to interpret as there is more variability of TLD position between planning and treatment. TLD in-vivo measurements are easily performed in urethra and rectum during HDR brachytherapy of prostate patients. They verify the delivery and provide information about the dose delivered to critical structures. The latter may be of particular interest if higher doses are to be given per fraction such as in HDR monotherapy.

Is the α/β Value for Prostate Tumours Low Enough to be Safely Used in Clinical Trials?

There has been an intense debate over the past several years on the relevant alpha/beta value that could be used to describe the fractionation response of prostate tumours. Previously it has been assumed that prostate tumours have high alpha/beta values, similar to most other tumours and the early reacting normal tissues. However, the proliferation behaviour of the prostate tumours is more like that of the late reacting tissues, with slow doubling times and low alpha/beta values. The analyses of clinical results carried out in the past few years have indeed suggested that the alpha/beta value that characterises the fractionation response of the prostate is low, possibly even below the 3 Gy commonly assumed for most late complications, and hence that hypofractionation of the radiation treatment might improve the therapeutic ratio (better control at the same or lower complication rate). However, hypofractionation might also increase the complication rates in the surrounding late responding tissues and if their alpha/beta value is not larger that of prostate tumours it could even lead to a decrease in the therapeutic ratio. Therefore, the important question is whether the alpha/beta value for the prostate is lower than the alpha/beta values of the surrounding late responding tissues at risk. This paper reviews the clinical and experimental data regarding the radiobiological differential that might exist between prostate tumours and the late normal tissues around them. Several prospective hypofractionated trials that have been initiated recently in order to determine the alpha/beta value or the range of values that describe the fractionation response of prostate tumours are also reviewed. In spite of several confounding factors that interfere with the derivation of a precise value, it seems that most data support a trend towards lower alpha/beta values for prostate tumours than for rectum or bladder.

When should the seminal vesicles be included in the target volume in prostate radiotherapy?

External beam radiotherapy to the prostate and seminal vesicles as a radical treatment for prostate cancer can result in a significant dose being delivered to the rectum. This can be reduced if the target volume includes the prostate only. Using a Medline search, published studies are reviewed to show that the risk of seminal vesicle involvement can be accurately predicted using readily available pre-treatment parameters. We recommend when to exclude the seminal vesicles from a target volume, and the proportion of seminal vesicles that should be included in a target volume in higher risk patients.

Three-Dimensional Conformal Radiotherapy in Localized Carcinoma of Prostate: Preliminary Reports of Toxicity in Dose-Escalation Treatment

Purpose

Many studies confirmed the evidence of a dose-response relationship in prostate cancer. Escalation of dose using conventional techniques is however limited by rectal tolerance. IMRT and 3D-CRT have been designed to allow dose escalation while not exceeding rectal tolerance. We evaluated the acute and early late tolerance to surrounding organs upon dose escalation from 70 to 78 Gy in 3D-CRT setting, in order to introduce the IMRT process as a routine practice in prostate cancer treatment.

Materials and Methods

We compared clinical data from 35 patients with localized adenocarcinoma of the prostate, who received 70 Gy within a traditional reconstructed three-dimensional treatment planning, and data from 72 patients who received 78 Gy within a three-dimensional conformal setting. In order to respect rectal tolerance in the higher dose group, limits were set for rectum doses, and simulation procedures were standardized. We evaluated radiation morbidity (acute and late gastrointestinal and genitourinary toxicity) using the Radiation Therapy Oncology Group scoring criteria (RTOG scale).

Results

Increasing doses from 70 Gy to 78 Gy resulted in no significant difference for acute and late effects.

Conclusion

A procedural standardization aiming at minimizing day-by-day variation, as well as a more consistent dose distribution to critical organs may significantly reduce the risk of increased toxicity in dose-escalation setting.

Implications of learning effects for hospital costs of new health technologies: The case of intensity modulated radiation therapy

Objectives: The impact of learning effects on the variability of costs of new health technologies in a prospective payment system (PPS) through the case of intensity modulated radiation therapy (IMRT) was studied.

Methods: A series of consecutive patients treated in nine medical centers was enrolled in a prospective study. Direct costs were assessed from the perspective of the healthcare providers. We used a two-level model to explain the variability of costs: patients nested within centers. Learning effects at the center level were considered through a fixed effect (the learning curve slope) and a random effect (the initial cost level). Covariates were introduced to explain the patterns of variation in terms of patient characteristics.

Results: The mean direct cost of IMRT was €5,962 (range, €2,414–€24,733). Manpower accounted for 53 percent of this cost. Learning effects explained 42 percent of the variance between centers (which was 88 percent of the total variance) and were associated with a substantial decrease in treatment costs. The mean initial treatment direct cost was €6,332 in centers with a previous experience of IMRT, whereas it was €14,192 in centers implementing IMRT for the first time. Including logistics costs and overhead, the full cost of IMRT was €10,916. Average reimbursement was €6,987.

Conclusions: Learning effects are a strong confounding factor in the analysis of costs of innovative health technologies involving learning effects. In a PPS, innovative health technology involving learning effects necessitates specific reimbursement mechanisms.