Outpatient 131I-Rituximab Radioimmunotherapy for Non-Hodgkin Lymphoma: A Study in Safety

Radiopharmaceutical Treatments for Cancer Therapy, Radionuclides Characteristics, Applications, and Challenges

Advances in the field of molecular biology have had an impact on biomedical applications, which provide greater hope for both imaging and therapeutics. Work has been intensified on the development of radionuclides and their application in radiopharmaceuticals (RP_S) which will certainly influence and expand therapeutic approaches in the future treatment of patients. Alpha or beta particles and Auger electrons are used for therapy purposes, and each has advantages and disadvantages. The radionuclides labeled drug delivery system will deliver the particles to the specific targeting cell. Different radioligands can be chosen to uniquely target molecular receptors or intracellular components, making them suitable for personal patient-tailored therapy in modern cancer therapy management. Advances in nanotechnology have enabled nanoparticle drug delivery systems that can allow for specific multivalent attachment of targeted molecules of antibodies, peptides, or ligands to the surface of nanoparticles for therapy and imaging purposes. This review presents fundamental radionuclide properties with particular reference to tumor biology and receptor characteristic of radiopharmaceutical targeted therapy development.

Relevance of radiobiological concepts in radionuclide therapy of cancer

PURPOSE

Radionuclide therapy (RNT) is a rapidly growing area of clinical nuclear medicine, wherein radionuclides are employed to deliver cytotoxic dose of radiation to the diseased cells/tissues. During RNT, radionuclides are either directly administered or delivered through biomolecules targeting the diseased site. RNT has been clinically used for diverse range of diseases including cancer, which is the focus of the review.

CONCLUSIONS

The major emphasis in RNT has so far been given towards developing peptides/antibodies and other molecules to conjugate a variety of therapeutic radioisotopes for improved targeting/delivery of radiation dose to the tumor cells. Despite that, many of the RNT approaches have not achieved their desired therapeutic success probably due to poor knowledge about complex and dynamic (i) fate of radiolabeled molecules; (ii) radiation dose delivered; (iii) cellular heterogeneity in tumor mass; and (iv) cellular radiobiological response. Based on understanding gathered during recent years, it may be stated that besides the absorbed dose, the net radiobiological response of tumor/normal cells also determines the clinical response of radiotherapeutic modalities including RNT. The radiosensitivity of tumor/normal cells is governed by radiobiological phenomenon such as radiation-induced bystander effect, genomic instability, adaptive response and low dose hyper-radiosensitivity. These concepts have been well investigated in the context of external beam radiotherapy, but their clinical implications during RNT have received meagre attention. In this direction, a few studies performed using in vitro and in vivo models envisage the possibilities of exploiting the radiobiological knowledge for improved therapeutic outcome of RNT.

Radiation exposure to caregivers from patients undergoing common radionuclide therapies: a review

The contribution of radionuclide therapies (RNTs) to effective patient treatment is widely appreciated. The administration of high doses has necessitated investigating the potential radiation hazard to caregivers from patients undergoing RNTs. This work aimed to review the literature regarding measured effective doses to caregivers from such patients. The main selection criterion was the presence of real radiation exposure measurements. The results were categorised according to the treatment protocol and dose parameters. Analysis of the collected data demonstrated that the measured effective dose values were within the dose constraints defined by the International Commission on Radiological Protection, provided that the radiation protection instructions were followed by both patients and caregivers. In conclusion, the radiation risk for caregivers was almost negligible. In this context, treatments could be administered more often on an outpatient basis, once cost-effectiveness criteria were established and radiation protection training and procedures were appropriately applied.

Phase II study of first-line (131)I-rituximab radioimmunotherapy in follicular non-Hodgkin lymphoma and prognostic (18)F-fluorodeoxyglucose positron emission tomography

First-line (131)I-anti-CD20 radioimmunotherapy of indolent non-Hodgkin lymphoma (NHL) achieves durable remission with low toxicity. The phase II INITIAL study comprised 68 patients with follicular NHL followed up to 7 years (median 4 years) after outpatient (131)I-rituximab radioimmunotherapy (RIT) in conjunction with rituximab, followed by maintenance therapy for 1 year. Baseline and 3-month (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) imaging, analyzed according to Deauville criteria, was used to evaluate response and predict prognosis. The overall response rate at 3 months was 99%, with 88% achieving Deauville category 1-3. These satisfactory responders did not reach median time-to-next-treatment, versus a median of 29 months for a category 4-5 response (p < 0.0001). Grade IV hematological toxicity (9%) was self-limited without clinical sequelae. (131)I-rituximab radioimmunotherapy in newly diagnosed, advanced stage, symptomatic follicular NHL is an effective, practical and affordable alternative to existing conventional chemotherapies, with lower toxicity and durable remissions. Response assessment at 3 months by (18)F-FDG PET Deauville five-point scale permits prognostic stratification.