Marta Cremonesi

Receptor radionuclide therapy with 90Y-[DOTA]0-Tyr3-octreotide (90Y-DOTATOC) in neuroendocrine tumours.

Somatostatin receptors are over-expressed in many tumours, mainly of neuroendocrine origin, thus enabling treatment with somatostatin analogues. Almost a decade of clinical experience of receptor radionuclide therapy with the analogue 90Y-[DOTA]0-Tyr3-octreotide [90Y-DOTATOC] has now been obtained at a few centres of excellence. This review reports on the present state of the art of receptor radionuclide therapy and discusses new perspectives.

Sentinel node biopsy in early vulvar cancer

Lymph node pathologic status is the most important prognostic factor in vulvar cancer; however, complete inguinofemoral node dissection is associated with significant morbidity. Lymphoscintigraphy associated with gamma-probe guided surgery reliably detects sentinel nodes in melanoma and breast cancer patients. This study evaluates the feasibility of the surgical identification of sentinel groin nodes using lymphoscintigraphy and a gamma-detecting probe in patients with early vulvar cancer. Technetium-99m-labelled colloid human albumin was administered perilesionally in 37 patients with invasive epidermoid vulvar cancer (T1–T2) and lymphoscintigraphy performed the day before surgery. An intraoperative gamma-detecting probe was used to identify sentinel nodes during surgery. A complete inguinofemoral node dissection was then performed. Sentinel nodes were submitted separately to pathologic evaluation. A total of 55 groins were dissected in 37 patients. Localization of the SN was successful in all cases. Eight cases had positive nodes: in all the sentinel node was positive; the sentinel node was the only positive node in five cases. Twenty-nine patients showed negative sentinel nodes: all of them were negative for lymph node metastases. Lymphoscintigraphy and sentinel-node biopsy under gamma-detecting probe guidance proved to be an easy and reliable method for the detection of sentinel node in early vulvar cancer. This technique may represent a true advance in the direction of less aggressive treatments in patients with vulvar cancer.

Biokinetics and dosimetry in patients administered with 111In-DOTA-Tyr3-octreotide: implications for internal radiotherapy with 90Y-DOTATOC

Abstract. Recent advances in receptor-mediated tumour imaging have resulted in the development of a new somatostatin analogue, DOTA-dPhe1-Tyr3-octreotide. This new compound, named DOTATOC, has shown high affinity for somatostatin receptors, ease of labelling and stability with yttrium-90 and favourable biodistribution in animal models. The aim of this work was to evaluate the biodistribution and dosimetry of DOTATOC radiolabelled with indium-111, in anticipation of therapy trials with 90Y-DOTATOC in patients. Eighteen patients were injected with DOTATOC (10 µg), labelled with 150–185 MBq of 111In. Blood and urine samples were collected throughout the duration of the study (0–2 days). Planar and single-photon emission tomography images were acquired at 0.5, 3–4, 24 and 48 h and time-activity curves were obtained for organs and tumours. A compartmental model was used to determine the kinetic parameters for each organ. Dose calculations were performed according to the MIRD formalism. Specific activities of >37 GBq/ µmol were routinely achieved. Patients showed no acute or delayed adverse reactions. The residence time for 111In-DOTATOC in blood was 0.9±0.4 h. The injected activity excreted in the urine in the first 24 h was 73%±11%. The agent localized primarily in spleen, kidneys and liver. The residence times in source organs were: 2.2±1.8 h in spleen, 1.7±1.2 h in kidneys, 2.4±1.9 h in liver, 1.5±0.3 h in urinary bladder and 9.4±5.5 h in the remainder of the body; the mean residence time in tumour was 0.47 h (range: 0.03–6.50 h). Based on our findings, the predicted absorbed doses for 90Y-DOTATOC would be 7.6±6.3 (spleen), 3.3±2.2 (kidneys), 0.7±0.6 (liver), 2.2±0.3 (bladder), 0.03±0.01 (red marrow) and 10.1 (range: 1.4–31.0) (tumour) mGy/MBq. These results indicate that high activities of 90Y-DOTATOC can be administered with low risk of myelotoxicity, although with potentially high radiation doses to the spleen and kidneys. Tumour doses were high enough in most cases to make it likely that the disired therapeutic response desired would be obtained.

Pre-Targeted Locoregional Radioimmunotherapy with 90Y-biotin in Glioma Patients: Phase I Study and Preliminary Therapeutic Results

The aim of this study was to determine the maximum-tolerated dose, of a pre-targeting three-step (3-S) method employing 90Y-biotin in the locoregional radioimmunotherapy (RIT) of recurrent high grade glioma, and to investigate the antitumor efficacy of this new treatment. Twenty-four patients with recurrent glioma underwent second surgical debulking and implantation of a catheter into the surgical resection cavity (SRC), in order to introduce the radioimmunotherapeutic agents [biotinylated monoclonal antibody (MoAb), avidin and 90Y-biotin]. Eight patients with anaplastic astrocytoma (AA) and 16 patients with glioblastoma (GBM) were injected with biotinylated anti-tenascin MoAb (2 mg), then with avidin (10 mg; 24 h later) and finally 90Y-biotin (18 h later). Each patient received two of these treatments 8-10 weeks apart. The injected activity ranged from 0.555 to 1.110 GBq (15-30 mCi). Dosage was escalated by 0.185 GBq (5 mCi) in four consecutive groups. The treatment was well tolerated without acute side effects up to 0.740 GBq (20 mCi). The maximum tolerated activity was 1.110 GBq (30 mCi) limited by neurological toxicity. None of the patients developed hematologic toxicity. In three patients infection occurred around the catheter. The average absorbed dose to the normal brain was minimal compared with that received at the SRC interface. At first control (after 2 months), partial (PR) and minor (MR) responses were observed in three GBM (1 PR; 2 MR) and three AA patients (1 PR; 2 MR) with an overall objective response rate of 25%. Stable disease (SD) was achieved in seven GBM and five AA patients (50%). There was disease progression in six GBM patients (25%), but in none of the AA patients. At the dosage of 0.7-0.9 GBq per cycle, locoregional 3-S-RIT was safe and produced an objective response in 25% of patients. Based on these encouraging results, phase II studies employing 3-S-RIT soon after first debulking are justified.

MIRD pamphlet no. 20: The effect of model assumptions on kidney dosimetry and response - Implications for radionuclide therapy

Renal toxicity associated with small-molecule radionuclide therapy has been shown to be dose-limiting for many clinical studies. Strategies for maximizing dose to the target tissues while sparing normal critical organs based on absorbed dose and biologic response parameters are commonly used in external-beam therapy. However, radiopharmaceuticals passing though the kidneys result in a differential dose rate to suborgan elements, presenting a significant challenge in assessing an accurate dose–response relationship that is predictive of toxicity in future patients. We have modeled the multiregional internal dosimetry of the kidneys combined with the biologic response parameters based on experience with brachytherapy and external-beam radiation therapy to provide an approach for predicting radiation toxicity to the kidneys. Methods: The multiregion kidney dosimetry model of MIRD pamphlet no. 19 has been used to calculate absorbed dose to regional structures based on preclinical and clinical data. Using the linear quadratic model for radiobiologic response, we computed regionally based surviving fractions for the kidney cortex and medulla in terms of their concentration ratios for several examples of radiopharmaceutical uptake and clearance. We used past experience to illustrate the relationship between absorbed dose and calculated biologically effective dose (BED) with radionuclide-induced nephrotoxicity. Results: Parametric analysis for the examples showed that high dose rates associated with regions of high activity concentration resulted in the greatest decrease in tissue survival. Higher dose rates from short-lived radionuclides or increased localization of radiopharmaceuticals in radiosensitive kidney subregions can potentially lead to greater whole-organ toxicity. This finding is consistent with reports of kidney toxicity associated with early peptide receptor radionuclide therapy and 166Ho-phosphonate clinical investigations. Conclusion: Radionuclide therapy dose–response data, when expressed in terms of biologically effective dose, have been found to be consistent with external-beam experience for predicting kidney toxicity. Model predictions using both the multiregion kidney and linear quadratic models may serve to guide the investigator in planning and optimizing future clinical trials of radionuclide therapy.

Receptor radionuclide therapy with 90Y-DOTATOC in patients with medullary thyroid carcinomas.

UNLABELLED Metastatic medullary thyroid cancer (MTC) shows a progressive course. Surgery is the only curative treatment. In advanced disease, chemo- and radiotherapy show poor results. Newly developed somatostatin analogue [DOTA0,Tyr3]octreotide (DOTATOC) labeled to 90Y is administered in patients with endocrine tumors expressing somatostatin receptors, like MTC. Preliminary studies demonstrated that 90Y-DOTATOC could be safely administered, resulting in objective responses in 27% of patients. AIMS To evaluate the efficacy of 90Y-DOTATOC therapy in metastatic MTC patients with positive OctreoScan, progressing after conventional treatments. Twenty-one patients were retrospectively evaluated after therapy, receiving 7.5-19.2 GBq in 2-8 cycles. RESULTS Two patients (10%) obtained a complete response (CR), as evaluated by CT, MRI and/or ultrasound, while a stabilization of disease (SD) was observed in 12 patients (57%); seven patients (33%) did not respond to therapy. The duration of the response ranged between 3-40 months. Using biochemical parameters (calcitonin and CEA), a complete response was observed in one patient (5%), while partial response in five patients (24%) and stabilization in three patients (14%). Twelve patients had progression (57%). Complete responses were observed in patients with lower tumor burden and calcitonin values at the time of the enrollment. CONCLUSIONS This retrospective analysis is consistent with the literature, regarding a low response rate in medullary thyroid cancers treated with 90Y-DOTATOC. Patients with smaller tumors and higher uptake of the radiopeptide tended to respond better. Studies with 90Y-DOTATOC administered in earlier phases of the disease will help to evaluate the ability of this treatment to enhance survival. New more specific peptides and new isotopes will also represent the key of a better treatment of MTC.

Radiation protection in radioguided surgery of breast cancer

The protocols for sentinel lymph node biopsy and radioguided occult lesion localization could potentially be of great value in the management of breast cancer patients. Both involve the injection of a 99Tcm-labelled radiopharmaceutical close to or into the lesion, localization of the sentinel lymph node or occult lesion by scintigraphy, and surgical removal with the aid of a hand-held gamma-ray detector. We present dosimetric data on patients and hospital personnel involved in these procedures. For evaluation of radiation protection, we measured the absorbed dose and air kerma rate. Activity levels in excised tissues and surgical instruments were also determined. For patients, the mean absorbed dose to the abdomen was 0.45 mGy, which is low compared to doses received from other diagnostic examinations. For surgeons after 100 operations, the mean absorbed dose to the hands was 0.45 mGy and the mean effective dose 0.09 mSv. Absorbed doses to all hospital personnel involved in the procedures were very low compared to recommended annual limits stipulated by the International Commission on Radiological Protection. We conclude that these procedures, performed according to protocols laid down by the European Institute of Oncology, Milan, are safe from the point of view of radiological protection and that only routine precautions are necessary.

Radioguided sentinel node biopsy to avoid axillary dissection in breast cancer.

Background: Sentinel node (SN) biopsy may predict axillary status in breast cancer. We retrospectively analyzed more than 500 SN cases, to suggest more precise indications for the technique.Methods99mTc-labeled colloid was injected close to the tumor; lymphoscintigraphy was then performed to reveal the SN. The next day, during surgery, the SN was removed by using a gamma probe. Complete axillary dissection followed, except in later cases recruited to a randomized trial. The SN was examined intraoperatively by conventional frozen section, in later cases by sampling the entire node and using immunocytochemistry.Results: In the first series, the SN was identified in 98.7% of cases; in 6.7%, the SN was negative but other axillary nodes were positive; in 32.1%, the SN was negative by intraoperative frozen section but metastatic by definitive histology, prompting introduction of the exhaustive method. In the randomized trial, the SN was identified in all cases so far, the false-negative rate is approximately 6.5%, and in 15 cases, internal mammary chain nodes were biopsied.Conclusions: SN biopsy can reliably assess axillary status in selected patients. The problems are the SN detection rate, false negatives, and the intraoperative examination, which can miss 30% of SN metastases. Our exhaustive method overcomes the latter problem, but it is time consuming.

Quantitative Analysis of 90Y Bremsstrahlung SPECT-CT Images for Application to 3D Patient-Specific Dosimetry

AIM The aim of this study was to evaluate the accuracy of the activity quantification of single-photon emission computed tomography/computed tomography (SPECT-CT) (90)Y-Bremsstrahlung images and to validate the S-voxel method. METHODS An anthropomorphic torso phantom with radioactive inserts ((90)Y) was acquired by SPECT-CT. Constant calibration factors (cps/MBq) for the quantification were evaluated, considering different volume, shape, position inside the phantom, activity concentration and background, and distance from detectors. S-voxel values (EGSnrc) were implemented in MATLAB R0086 USA software. Dose comparisons between S-voxel and the conventional Medical Internal Radiation Dose method were repeated in a group of 11 patients administered with (90)Y-DOTATATE. RESULTS Using the appropriate calibration factors to recover the volume variability, the error about the measurement repeatability and the activity variation was within 4%. The variability of activity quantification, depending on the position in the phantom, detector distance, and background, was <10%, <5%, and <10%, respectively. The absorbed-dose values calculated by OLINDA were in agreement with the mean dose values obtained by the S-voxel method (difference, <10%). CONCLUSIONS The results confirm that, with the hybrid SPECT-CT system, quantitative analysis of SPECT (90)Y-Bremsstrahlung images and the generation of three-dimensional dose distributions are feasible. The improved analysis of Bremsstrahlung images could have a notable clinical impact, allowing to address the dosimetric verification to patients during the course of therapy.

Radioembolization of Hepatic Lesions from a Radiobiology and Dosimetric Perspective

Radioembolization (RE) of liver cancer with 90Y-microspheres has been applied in the last two decades with notable responses and acceptable toxicity. Two types of microspheres are available, glass and resin, the main difference being the activity/sphere. Generally, administered activities are established by empirical methods and differ for the two types. Treatment planning based on dosimetry is a prerogative of few centers, but has notably gained interest, with evidence of predictive power of dosimetry on toxicity, lesion response, and overall survival (OS). Radiobiological correlations between absorbed doses and toxicity to organs at risk, and tumor response, have been obtained in many clinical studies. Dosimetry methods have evolved from the macroscopic approach at the organ level to voxel analysis, providing absorbed dose spatial distributions and dose–volume histograms (DVH). The well-known effects of the external beam radiation therapy (EBRT), such as the volume effect, underlying disease influence, cumulative damage in parallel organs, and different tolerability of re-treatment, have been observed also in RE, identifying in EBRT a foremost reference to compare with. The radiobiological models – normal tissue complication probability and tumor control probability – and/or the style (DVH concepts) used in EBRT are introduced in RE. Moreover, attention has been paid to the intrinsic different activity distribution of resin and glass spheres at the microscopic scale, with dosimetric and radiobiological consequences. Dedicated studies and mathematical models have developed this issue and explain some clinical evidences, e.g., the shift of dose to higher toxicity thresholds using glass as compared to resin spheres. This paper offers a comprehensive review of the literature incident to dosimetry and radiobiological issues in RE, with the aim to summarize the results and to identify the most useful methods and information that should accompany future studies.