Radioimmunotherapy for Non-Hodgkin’s Lymphoma

SPECT performance evaluation on image of Yttrium 90 - Bremsstrahlung using Monte Carlo simulation

Yttrium-90 (⁹⁰Y) is one of the most widely used radionuclides in Nuclear Medicine practice. However, characteristic energy of this beta emitter constitutes a difficulty for dose planning using SPECT imaging. This work aimed to study bremsstrahlung X-rays effects produced by ⁹⁰Y beta particles during SPECT image acquisition using Monte Carlo code MCNPX. Several simulations were carried out to evaluate different aspects that could affect SPECT image quality, such as: collimator type, source-collimator distance and composition of each interacting material. Two configurations of ⁹⁰Y sources were simulated: a point source in several spheres of different materials (soft tissue, water, articular cartilage, and bone) and dimensions with radius ranging from 1 to 20 mm; and a uniformly distributed source in a Lucite cylindrical phantom filled with water. It was evaluated the bremsstrahlung photon emission generated inside different materials; for this was considered the number photons that passing through every different sphere's surface for each radii and material. In case of cylindrical phantom filled with water, in order to obtain the energy deposited over NaI (Tl) crystal detector; there was considered Median Energy General Purpose (MEGP) and Low Energy High Resolution (LEHR) collimators. Moreover, using TMESH routine available in the MCNPX Monte Carlo code, energy distribution images according to the collimator type and the source-collimator distance were obtained. The simulation was validated by comparing with the spectral distribution of the ⁹⁰Y bremsstrahlung X-rays obtained experimentally from an acrylic cylindrical phantom. Results corroborated the importance of Monte Carlo simulation method to evaluate a performance of SPECT image acquisition with ⁹⁰Y. The best resolution was obtained with MEGP collimator independent of source-collimator distance.

Dosimetric analysis of 177Lu-DOTA-rituximab in patients with relapsed/refractory non-Hodgkin's lymphoma

OBJECTIVE

Radioimmunotherapy targeting CD20 receptors in lymphoma using radiolabeled chimeric antibodies may lead to better therapeutic responses than cold anti-CD20 antibodies. This study aimed to assess the biodistribution and present reasonable estimates of normal organ doses, including red marrow using Lu-DOTA-rituximab.

MATERIALS AND METHODS

Patients with relapsed/refractory CD20+ B-cell non-Hodgkin's lymphoma were recruited into this prospective study. In-house labeling of Lu-DOTA-rituximab was performed and administered after quality assurance. Rituximab (375 mg/m), followed by 50 mCi (1850 MBq) of Lu-DOTA-rituximab was administered as a slow intravenous infusion and emission images were acquired. Regions of interest were drawn for kidney, liver, heart, bladder, spleen, and tumor lesions on both anterior and posterior images. Internal dose estimation was performed using OLINDA v1.0 software.

RESULTS

The mean age of the 10 patients (eight men and two women) was 52±13 years. The uptake of radiolabeled antibody was visualized within 30 min of administration in the liver, kidneys, heart, spleen, and bladder. The coefficient of determination (R) was greater than 0.95 for organs and the whole body in all patients. The effective half-life of radioimmunoconjugate was 100±28 h (42-126 h). The critical organ in our study was the red marrow. The average total body dose, effective dose, and effective dose equivalent calculated in all 10 patients were 0.13±0.02, 0.15±0.03, and 0.22±0.04 mGy/MBq, respectively.

CONCLUSION

There may be considerable interindividual differences in absorbed doses of organs and generalization or extrapolation of doses in the clinical setting at present is not feasible with Lu-DOTA-rituximab in non-Hodgkin's lymphoma patients. Patient-specific dosimetry is thus recommended to eliminate the variations and reduce the possibility of dose-limiting toxicity.

Pharmacotherapy of large B-cell lymphoma

BACKGROUND

Constituting approximately 30% of lymphoid malignancies, diffuse large B-cell lymphoma (DLBCL) is the most common aggressive lymphoma in adults worldwide. The clinical and biologic heterogeneity that exists in DLBCL suggests that this entity might actually be comprised of several distinct neoplasms that could require different therapeutic approaches. DLBCL was considered incurable until combination chemotherapy became available.

OBJECTIVE

Current treatment strategies for the treatment of untreated and relapsed advanced-stage DLBCL are reviewed; novel treatments for DLBCL are discussed.

METHODS

Relevant literature was identified using the PubMed search engine and by reviewing abstracts from major conference proceedings.

RESULTS/CONCLUSION

Recently, novel therapeutic strategies, including the incorporation of immunotherapy to combination chemotherapy, have improved outcome for patients with DLBCL with cure rates exceeding 50%, especially in younger patients.