New approaches for imaging and therapy of solid cancer

Radionuclide therapy is a systemic treatment that aims to deliver cytotoxic radiation to cancer cells. Due to their properties, antibodies have been considered as suitable agent for the delivery of therapeutic radioisotopes, radioimmunotherapy (RIT). This article gives an overview of new approaches for imaging and therapy of solid cancer with particular attention to strategies to enhance treatment success. Examples of increased antibody uptake by targeting stromal constituent of tumor microenvironment such as fibronectin (FN) an important tumor-associated angiogenesis targeting agent, with specifically designed antibody format will be provided. Strategies oriented to identify patients most likely to benefit from RIT including identification of radiosensitivity profiles, in vivo target identification by teragnostic approach and better prediction of dosimetric estimates would be presents. Combination regimens such as with chemo-radiotherapy and immunotherapy would be also discussed as an approach to enhance RIT success.

Development of anthropomorphic hand phantoms for personal dosimetry in 90Y-Zevalin preparation and patient delivering

Anthropomorphic tissue-equivalent hand phantoms were achieved to measure the extremity dose involved in Zevalin (90)Y-labelling and patient delivering procedure for radioimmunotherapy treatment of non-Hodgkin lymphoma. The extremity doses to hands and wrists of operators were measured by using thermoluminescent detectors mounted on the developed phantoms. Measurements of chest- and lens-equivalent doses performed on a Rando phantom are also reported.

Personalization of radioiodine treatment for Graves' disease: a prospective, randomized study with a novel method for calculating the optimal 131I-iodide activity based on target reduction of thyroid mass

AIM

There is no consensus regarding the most appropriate dosimetric approach to cure Graves' disease. This study describes a personalized approach based on the desired therapy-induced volume (mass) reduction in order to define the activity of 131I-iodide to be administered, based on the MIRD approach and the radiobiological Linear Quadratic Model.

METHODS

A model for calculating the "optimal" final thyroid mass has been developed and published in the past years. Based on this model, it is possible to predict the thyroid absorbed dose following administration of a certain activity as a function of desired reduction of the starting mass of the gland. A total of 147 Graves' disease patients were randomly divided into four groups based on the absorbed thyroid dose, respectively 100 Gy (Group A, N.=29), 200 Gy (Group B, N.=25), and 400 Gy (Group C, N.=29), while patients of Group D (n=64) received a 131I-iodide activity calculated based on the desired "optimal" final thyroid mass.

RESULTS

At one-year follow-up, 48% of patients in Group A, 64% in Group B, 97% in Group C, and 94% in Group D were cured. There was no statistical difference between cure rate in Group C versus Group D. The administered 131I-iodide activity for Group C was significantly higher than for Group D (524 ± 201 MBq versus 386 ± 173 MBq, P<0.001).

CONCLUSION

These results demonstrate that the proposed method allows to optimize 131I-iodide therapy for Graves' disease patients on an individual basis, avoiding the administration of unjustified higher activities.

Accuracy and optimal timing of activity measurements in estimating the absorbed dose of radioiodine in the treatment of Graves' disease

Calculation of the therapeutic activity of radioiodine (131)I for individualized dosimetry in the treatment of Graves' disease requires an accurate estimate of the thyroid absorbed radiation dose based on a tracer activity administration of (131)I. Common approaches (Marinelli-Quimby formula, MIRD algorithm) use, respectively, the effective half-life of radioiodine in the thyroid and the time-integrated activity. Many physicians perform one, two, or at most three tracer dose activity measurements at various times and calculate the required therapeutic activity by ad hoc methods. In this paper, we study the accuracy of estimates of four 'target variables': time-integrated activity coefficient, time of maximum activity, maximum activity, and effective half-life in the gland. Clinical data from 41 patients who underwent (131)I therapy for Graves' disease at the University Hospital in Pisa, Italy, are used for analysis. The radioiodine kinetics are described using a nonlinear mixed-effects model. The distributions of the target variables in the patient population are characterized. Using minimum root mean squared error as the criterion, optimal 1-, 2-, and 3-point sampling schedules are determined for estimation of the target variables, and probabilistic bounds are given for the errors under the optimal times. An algorithm is developed for computing the optimal 1-, 2-, and 3-point sampling schedules for the target variables. This algorithm is implemented in a freely available software tool. Taking into consideration (131)I effective half-life in the thyroid and measurement noise, the optimal 1-point time for time-integrated activity coefficient is a measurement 1 week following the tracer dose. Additional measurements give only a slight improvement in accuracy.

Influence of total-body mass on the scaling ofS-factors for patient-specific, blood-based red-marrow dosimetry

To perform patient-specific, blood-based red-marrow dosimetry, dose conversion factors (the S factors in the MIRD formalism) have to be scaled by patients' organ masses. The dose to red marrow includes both self-dose and cross-irradiation contributions. Linear mass scaling for the self-irradiation term only is usually applied as a first approximation, whereas the cross-irradiation term is considered to be mass independent. Recently, the need of a mass scaling correction on both terms, not necessarily linear and dependent on the radionuclide, has been highlighted in the literature. S-factors taking into account different mass adjustments of organs are available in the OLINDA/EXM code. In this paper, a general algorithm able to fit the mass-dependent factors S(rm<--tb) and S(rm<--rm) is suggested and included in a more general equation for red-marrow dose calculation. Moreover, parameters to be considered specifically for therapeutic radionuclides such as (131)I, (90)Y and 177Lu are reported. The red-marrow doses calculated by the traditional and new algorithms are compared for (131)I in ablation therapy (14 pts), 177Lu- (13 pts) and (90)Y- (11 pts) peptide therapy for neuroendocrine tumours, and (90)Y-Zevalin therapy for NHL (21 pts). The range of differences observed is as follows: -36% to -10% for (131)I ablation, -22% to 5% for 177Lu-DOTATATE, -9% to 11% for (90)Y-DOTATOC and -8% to 6% for (90)Y-Zevalin. All differences are mostly due to the activity in the remainder of the body contributing to cross-irradiation. This paper quantifies the influence of mass scaling adjustment on usually applied therapies and shows how to derive the appropriate parameters for other radionuclides and radiopharmaceuticals.

A dosimetric algorithm for patient-specific131I therapy of thyroid cancer based on a prescribed target-mass reduction

(131)I therapy is used in the treatment of differentiated thyroid cancer both to ablate the post-surgical thyroid remnant and to treat recurrent or metastatic cancer. The optimum administered activity for ablation remains controversial: the most commonly used method is the administration of a fixed radioiodine activity (1110-3700 MBq or more); an alternative is the administration of an activity individually calculated to deliver a prescribed absorbed dose (usually 300 Gy for remnant ablation and 80 Gy for treatment of metastasis). Neither of these two approaches is based on a theoretical model and for this reason the debate on the optimization of (131)I therapy of thyroid cancer could have a weak grounding. In this paper, the meaning of the fixed value of target absorbed dose (Gy) is discussed and a mathematical model for remnant/metastasis optimum absorbed dose calculation is presented. This model is based on the desired reduction of the volume of the target (remnant or metastasis) and allows one to calculate individually the value of the optimum target absorbed dose (Gy) and consequently the optimum therapeutic activity to administer to the patient.

Transtympanic steroids in refractory sudden hearing loss. Personal experience

The treatment of choice for sudden sensorineural hearing loss is still lacking. Many drugs have been used over the years, with varying results and steroids have proven to be effective in clinical trials, albeit systemic administration is associated with untoward side-effects and cannot be used in all patients. The transtympanic approach presents two main advantages: first, it allows higher concentrations in the inner ear environment and, second, it minimizes systemic absorption. Aim of the present investigation was to establish the effectiveness of transtympanic steroid treatment for sudden sensorineural hearing loss in patients in whom conventional treatment had failed. For this purpose, a prospective, non-randomized study was designed to evaluate hearing improvement in sudden sensorineural hearing loss patients treated with transtympanic steroids. A solution of methyl-prednisolone and sodium bicarbonate was administered, via a transtympanic injection, in 10 patients. Hearing levels were evaluated before treatment and on days 1, 7 and 30, thereafter. Improvement in hearing was observed in 70% of patients, moreover, in patients not usually considered amenable to this kind of treatment. Transtympanic steroid treatment is an effective and safe option for patients with sudden sensorineural hearing loss when conventional treatment regimens have failed. Further studies are needed to define the optimal dosage, route of administration and type of steroids.

Ion recombination correction for very high dose-per-pulse high-energy electron beams

The parallel-plate ionization chamber is the recommended tool for the absorbed dose measurement in pulsed high-energy electron beams. Typically, the electron beams used in radiotherapy have a dose-per-pulse value less then 0.1 cGy/pulse. In this range the factor to correct the response of an ionization chamber for the lack of complete charge collection due to ion recombination (ksat) can be properly evaluated with the standard "two voltage" method proposed by the international dosimetric reports. Very high dose-per-pulse electron beams are employed in some special Linac dedicated to the Intra-Operatory-Radiation-Therapy (IORT). The high dose-per-pulse values (3-13 cGy/pulse) characterizing the IORT electron beams allow to deliver the therapeutic dose (10-20 Gy) in less than a minute. This considerably reduces the IORT procedure time, but some dosimetric problems arise because the standard method to evaluate ksat overestimates its value by 20%. Moreover, if the dose-per-pulse value >1 cGy/pulse, the dependence of ksat on the dose-per-pulse value cannot be neglected for relative dosimetry. In this work the dependence of ksat on the dose-per-pulse value is derived, based on the general equation that describes the ion recombination in the Boag theory. A new equation for ksat, depending on known or measurable quantities, is presented. The new ksat equation is experimentally tested by comparing the absorbed doses to water measured with parallel-plate ionization chambers (Roos and Markus) to that measured using dose-per-pulse independent dosimeters, such as radiochromic films and chemical Fricke dosimeters. These measurements are performed in the high dose-per-pulse (3-13 cGy/pulse) electron beams of the IORT dedicated Linac Hitesys Novac7 (Aprilia-Latina, Italy). The dose measurements made using the parallel-plate chambers and those made using the dose-per-pulse independent dosimeters are in good agreement (<3%). This demonstrates the possibility of using the parallel-plate ionization chambers also for the very high dose-per-pulse (> 1 cGy/pulse) electron-beam dosimetry.

A minimally invasive method to evaluate 131I kinetics in blood

The dose limiting factor for 131I therapy in patients with thyroid cancer is myelotoxicity, thus an accurate determination of radioiodine activity in the red marrow is of paramount importance. The reference method for red marrow dosimetry in radiometabolic therapy is based on the measurement of radioiodine kinetics, particularly the activity/time curve in blood. Such a measurement requires withdrawal of blood samples at various times after 131I administration. This procedure involves some potential risk from the radiation protection point of view, such as possible contamination of personnel with blood and disposal of the radioactive blood samples (and syringes). We present here a minimally invasive method to evaluate radioiodine kinetics in the blood, which only requires one blood sample and a set of measurements on the patient's thigh made with a collimated NaI(Tl) probe. The method has been validated in four patients treated with 131I for thyroid cancer.

A theoretical model for prescription of the patient-specific therapeutic activity for radioiodine therapy of Graves' disease

A fundamental function of the thyroid is to extract iodine from the blood, synthesize it into thyroid hormones, and release it into the circulation under feedback control by pituitary-secreted hormones. This capability of the thyroid, termed as functionality, can in principle be related to the severity of hyperthyroidism in individual patients. In this paper the uptake and release of 131I by the thyroid following the administration of 131I therapy for Graves' disease has been theoretically studied. The kinetics of iodine in the thyroid and blood have been evaluated using a two-compartment model. This simplified model appears to be adequate for dosimetry purposes and allows one to correlate levels of increased thyroid functionality (hyperthyroidism) with clinically measurable kinetic parameters. An expression has been derived for the rate of change of thyroid mass following therapy; this has the same form as an empirical relationship described in an earlier work. A method is presented for calculation of the amount of radioiodine activity to be administered to individual patients in order to achieve the desired final functionality of the gland. The activity to be administered is based on measurements of 131I kinetics after the administration of a 'low-activity' (1850 kBq) tracer for treatment planning.

Tc 99m-Sestamibi scintimammography in the differentiation of benign and malignant breast microcalcifications

The capability of the mammography-scintimammography combination to distinguish between benign and malignant isolated clusters of breast microcalcifications is discussed. Scintimammography using Tc 99m-Sestamibi was performed in 97 women with an isolated cluster of microcalcifications on mammograms. Seventy-two women had final histopathologic diagnoses (24 cancer and 48 benign pathology). The other 25 patients had follow-up to 3 years. The results of mammography, scintimammography and mammography-scintimammography combination were divided into five groups, based on the suspicion of malignancy. The sensitivity, specificity, false negative fraction, false positive fraction, predictive positive value, predictive negative value and diagnostic accuracy were calculated varying the diagnostic threshold. The Receiver Operating Characteristic (ROC) statistical technique was employed to compare the diagnostic value of mammography to mammography-scintimammography combination. The area under the ROC curves was calculated by the Wilcoxon statistic without any hypothesis on data distribution. The detected difference between areas under the mammography ROC curve (area=0.854, standard error=0.049) and mammography-scintimammography ROC curve (area=0.897, standard error 0.033) was statistically significant (P>0.05, one tail). The area under a ROC curve represents the probability that a randomly chosen diseased or non-diseased subject could be correctly classified. From this point of view this paper demonstrates that, if properly used, scintimammography can add to mammography in the characterization of an isolated cluster of microcalcifications, even if it is not able to replace FNAB and core biopsy.

Study of the correlation between administered activity and radiation committed dose to the thyroid in 131I therapy of Graves' disease

Substantial reduction in the thyroid volume (up to 70-80%) after 131I therapy of Graves' disease has been demonstrated and reported in the literature. Recently a mathematical model of thyroid mass reduction during the first month after therapy has been developed and a new algorithm for the radiation committed dose calculation has been proposed. Reduction of the thyroid mass and the radiation committed dose to the gland depend on a parameter k, defined for each subject. The calculation of k allows the prediction of the activity to administer, depending on the radiation committed dose chosen by the physician. In this paper a method for calculating k is proposed. The calculated values of k are compared to values derived from measurements of the changes in thyroid mass in twenty-six patients treated by 131I for Graves' disease. The radiation committed dose to the thyroid can be predicted within 21%, and the radioiodine activity to administer to the patient can be predicted within 22% using the calculated values of k. The thyroid volume reduction during the first month after therapy administration can be also predicted with good accuracy using the calculated values of k. The radiation committed dose and the radioiodine activity to administer were calculated using a new, very simple algorithm. A comparison between the values calculated by this new algorithm and the old, classical Marinelli-Quimby algorithm shows that the new method is more accurate.

Influence of thyroid volume reduction on calculated dose in radioiodine therapy of Graves' hyperthyroidism

Administration of radioactive iodine (131I) is an effective treatment for hyperthyroidism due to Graves' disease. Recently several investigators have shown that the success of this therapy may depend on the absorbed dose to the thyroid. Thyroid dose varies inversely with the mass of the gland. Much experimental evidence demonstrates that a reduction of the thyroid volume (mass) may occur after radioiodine therapy. In this work we evaluate the influence of the volume reduction on the calculation of the absorbed dose to the thyroid. A mathematical model of thyroid mass reduction after 131I therapy is presented, based on masses evaluated with ultrasonography of ten patients treated in the endocrinology department of our hospital. This model was applied to the general formula for calculation of the thyroid doses in these patients. The dose values obtained considering a reduction of thyroid mass after the treatment are often quite different from those obtained without considering change in mass (from 9% to 30% greater). We conclude that the consideration of thyroid mass reduction is important for an accurate estimation of the calculated dose.

[Correlation of ultrasound and galactography in the diagnosis of nipple discharge. Preliminary results]

INTRODUCTION

Several pathologic conditions involving the breast ductal tree can cause bloody or serous nipple discharge. Galactography plays a major clinical role in identifying and localizing intraductal masses, but its sensitivity in detecting cancer is certainly suboptimal. Presently high-frequency ultrasound (US) probes allow detection and guided biopsy of intraductal lesions. We compared the specific information provided by US and galactography in the discharging breast.

MATERIAL AND METHODS

Thirty-three patients with discharging breast were submitted to both diagnostic examinations. US was performed with 13 MHz scanheads both before and after galactography. Galactography was performed with 30-31 G catheters to cannulate the discharging duct. Nonionic, water-soluble, sterile contrast material was administered. Postgalactography US was performed to investigate if it could yield further information. The final diagnosis was made at histology and 2 years' instrumental follow-up.

RESULTS

Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were evaluated for both techniques. We considered a positive finding the detection of a lesion in general (be it papilloma, papillomatosis, or cancer), as well as the detection of carcinoma only. Sensitivity was 96% for galactography and 84% for US in the former case, versus 50% and 100%, respectively, in the latter. Postgalactography US added no major information.

DISCUSSION AND CONCLUSION

US is more sensitive than galactography in cancer diagnosis and, it permits guided biopsy and preoperative localization of unpalpable ductal lesions. In our limited experience, US can be considered a complementary diagnostic tool to galactography in the discharging breast.

[Study and implementation of a computerized program for personalized prescriptions for patients treated with radioiodine to be discharged]

INTRODUCTION

Iodine-131 (131I) therapy is widely used to treat some thyroid diseases such as hyperthyroidism and thyroid carcinoma. The discharge of a radioiodine treated patient is a potential problem for the radiation protection of the general population. To keep the absorbed dose to the general population as low as possible, patients are given some recommendations, on discharge usually a quite standard list of behaviors to avoid for an amount of time depending only on the administered activity. Thus, recommendations usually consider neither the individual kinetics of 131I nor disease type, while both factors account for major differences in iodine uptake and retention. We investigated the feasibility of customizing recommendations according to recent Euratom guidelines.

MATERIAL AND METHODS

Individual 131I kinetics can be evaluated from previous work characterizing dose rate decay as a function of time for different thyroid diseases, together with measurements of iodine uptake or dose rate to the patient. Based on individual kinetics, the committed effective dose to the general population is calculated according to the kind of relationship with the patient, resulting in different amounts of time spent near him/her.

RESULTS

The calculation procedure was implemented in a user-friendly software which requires input of few data and measurements to give each patient a customized list of precautions. Using the program on patient's discharge takes no longer than 10 minutes. The precautions are in good agreement with those reported in the literature.

CONCLUSIONS

We have been using our program for nine months. Data show that most patients treated for thyroid cancer must follow the recommendations for a shorter time than hyperthyroid patients. The program is suitable for routine use in a nuclear medicine department.

[Computer-assisted combined management of physical radiation protection and quality control of X-ray diagnostic equipment]

A software for the computer-assisted management of radiation protection and quality control of radiodiagnostic equipment is described. The code was written in DB3-plus language. In addition to some independent archives on X-ray diagnostic systems identification, it includes technical and radiation protection checks, environmental dosimetry in the controlled areas and on workers. The data can be searched through a key field and periodical radiation protection reports and action reports can be printed. The software programs can also perform some "intelligent" operations such as the calculation of controlled areas range and the classification of X-ray diagnostic systems and workers. This is done by retrieving the information from the archives. The software can be updated, revised and modified very easily, due to the non-connection of the archives. It is also very simple to connect DB3-plus archives with many other software packages to process and elaborate data. This software is the core of an integrated system we are developing to store and process data from diagnostic X-ray systems control meters and from our TLD personal dosimetry equipment.