Place of low-dose total body irradiation in the treatment of localized follicular non-Hodgkin's lymphoma: results of a pilot study

Effect of triple therapy with low-dose total body irradiation and hypo-fractionated radiation plus anti-programmed cell death protein 1 blockade on abscopal antitumor immune responses in breast cancer

Immunostimulatory effects of radiotherapy can be synergistically augmented with immune checkpoint blockade to act both on irradiated tumor lesions and distant, non-irradiated tumor sites. Our hypothesis was that low-dose total body irradiation (L-TBI) combined with hypo-fractionated radiotherapy (H-RT) and anti-programmed cell death protein 1 (aPD-1) checkpoint blockade would enhance the systemic immune response. We tested the efficacy of this triple therapy (L-TBI + H-RT + aPD-1) in BALB/c mice with bilateral breast cancer xenografts. The L-TBI dose was 0.1 Gy. The primary tumor was treated with H-RT (8 Gy × 3). The PD-1 monoclonal antibody was injected intraperitoneally, and the secondary tumors not receiving H-RT were monitored for response. The triple therapy significantly delayed both primary and secondary tumor growths, improved survival rates, and reduced the number of lung metastasis lesions. It increased the activated dendritic and CD8⁺ T cell populations and reduced the infiltration of myeloid-derived suppressor cells in the secondary tumor microenvironment relative to other groups. Thus, L-TBI could be a potential therapeutic modality, and when combined with H-RT and aPD-1, the therapeutic effect could be enhanced significantly.

Low-Dose Radiation Therapy (LDRT) against Cancer and Inflammatory or Degenerative Diseases: Three Parallel Stories with a Common Molecular Mechanism Involving the Nucleoshuttling of the ATM Protein?

Very early after their discovery, X-rays were used in multiple medical applications, such as treatments against cancer, inflammation and pain. Because of technological constraints, such applications involved X-ray doses lower than 1 Gy per session. Progressively, notably in oncology, the dose per session increased. However, the approach of delivering less than 1 Gy per session, now called low-dose radiation therapy (LDRT), was preserved and is still applied in very specific cases. More recently, LDRT has also been applied in some trials to protect against lung inflammation after COVID-19 infection or to treat degenerative syndromes such as Alzheimer's disease. LDRT illustrates well the discontinuity of the dose-response curve and the counterintuitive observation that a low dose may produce a biological effect higher than a certain higher dose. Even if further investigations are needed to document and optimize LDRT, the apparent paradox of some radiobiological effects specific to low dose may be explained by the same mechanistic model based on the radiation-induced nucleoshuttling of the ATM kinase, a protein involved in various stress response pathways.

Combination therapy of lymphatic drug delivery and total body irradiation in a metastatic lymph node and lung mouse model

Chemotherapy using a lymphatic drug delivery system (LDDS) targeting lymph nodes (LNs) in the early stage of metastasis has a superior antitumor effect to systemic chemotherapy. An LDDS produces a higher drug retention rate and tissue selectivity in LNs. To expand the therapeutic coverage of LDDS from local treatment of metastatic LNs to prevention of distant metastases, the combination of treatment with therapies that enhance systemic tumor immune effects is an important therapeutic strategy. Recently, total body irradiation (TBI) has been shown to activate immune responses and alter the tumor microenvironment. Here we show that combination therapy with TBI and LDDS improves the antitumor effect of metastatic LNs and lung metastasis. Tumor cells were inoculated into the subiliac LN (SiLN) to induce metastasis into the proper axillary LN (PALN) and lung in a mouse model. TBI was carried out on day 4 after inoculation using a gamma irradiator. Lymphatic drug delivery into the accessory axillary LN was used to treat PALN. In vivo bioluminescence imaging, high-frequency ultrasound, and histology showed that combination therapy using TBI (total dose 1.0 Gy once) and the LDDS suppressed tumor growth in LNs and lung metastases and was more effective than using LDDS or TBI alone. Quantitative RT-PCR of spleens after combination therapy revealed increased expression of CD4, CD8, and IL-12b, indicating an activated immune response. The results show that combination therapy with TBI and LDDS is a method to improve the efficacy of LN metastases and distant metastases therapy and is a promising novel approach to treat cancer patients.

Hematological Changes Following Low Dose Radiation Therapy and Comparison to Current Standard of Care Cancer Treatments

Cancer is the second leading cause of mortality worldwide accounting for almost 10 million deaths in 2020. Current standard of care treatment varies depending on the type and stage of disease, but commonly includes surgery, chemotherapy, and/or radiation therapy. There is evidence that whole- and half-body exposure to low dose ionizing radiation can also be an effective therapeutic due to its stimulation of anti-cancer immunity. One of the limiting factors for past clinical trials using low dose radiation therapy has been adverse hematological events. However, similar hematological changes are also frequently reported following standard of care treatments in oncology. This review summarizes the effects of various cancer therapies on hematologic toxicity through the evaluation of complete blood count reports. The reviewed literature elucidates hematological trends in patients undergoing chemotherapy, and both high and low dose radiation therapy. In general, high dose radiation and chemotherapy can result in widespread changes in blood counts, with the most severe effects related to leukopenia. Overall, compared to standard of care treatments, low dose radiation results in similar, yet more mild hematological changes. Taken together, hematological toxicities should not be a limiting factor in the applicability of low dose radiation as a cancer therapeutic.

Radiophobia Overreaction: College of Chiropractors of British Columbia Revoke Full X-Ray Rights Based on Flawed Study and Radiation Fear-Mongering

Fears over radiation have created irrational pressures to dissuade radiography use within chiropractic. Recently, the regulatory body for chiropractors practicing in British Columbia, Canada, the College of Chiropractors of British Columbia (CCBC), contracted Pierre Côté to review the clinical use of X-rays within the chiropractic profession. A "rapid review" was performed and published quickly and included only 9 papers, the most recent dating from 2005; they concluded, "Given the inherent risks of radiation, we recommend that chiropractors do not use radiographs for the routine and repeat evaluation of the structure and function of the spine." The CCBC then launched an immediate review of the use of X-rays by chiropractors in their jurisdiction. Member and public opinion were gathered but not presented to their members. On February 4, 2021, the College announced amendments to their Professional Conduct Handbook that revoked X-ray rights for routine/repeat assessment and management of patients with spine disorders. Here, we highlight current and historical evidence that substantiates that X-rays are not a public health threat. We also point out critical and insurmountable flaws in the single paper used to support irrational and unscientific policy that discriminates against chiropractors who practice certain forms of evidence-based X-ray-guided methods.

Time to rejuvenate ultra-low dose whole-body radiotherapy of cancer

The results of clinical trials performed from the 1930s until the end of the 20th century in which total-body ultra-low level ionizing radiation (TB-LLR) was used demonstrate that this form of treatment can be equal or superior to other systemic anti-neoplastic modalities in terms of the rates of remissions, toxicity, and side effects. In this review, we provide the rationale for TB-LLR and analyze the results of reliable clinical trials in patients with predominantly lymphoproliferative disorders but also advanced solid cancers. The doses used in these trials did not exceed 0.1-0.2 Gy per fraction and cumulative totals ranged from 1 to 4 Gy. Based on the reviewed results we conclude that it is appropriate to revive interest in and resume clinical investigations of TB-LLR in order to refine and improve the effectiveness of such treatment, whether employed alone or in combination with other anticancer strategies.

Radiophobic Fear-Mongering, Misappropriation of Medical References and Dismissing Relevant Data Forms the False Stance for Advocating Against the Use of Routine and Repeat Radiography in Chiropractic and Manual Therapy

There is a faction within the chiropractic profession passionately advocating against the routine use of X-rays in the diagnosis, treatment and management of patients with spinal disorders (aka subluxation). These activists reiterate common false statements such as "there is no evidence" for biomechanical spine assessment by X-ray, "there are no guidelines" supporting routine imaging, and also promulgate the reiterating narrative that "X-rays are dangerous." These arguments come in the form of recycled allopathic "red flag only" medical guidelines for spine care, opinion pieces and consensus statements. Herein, we review these common arguments and present compelling data refuting such claims. It quickly becomes evident that these statements are false. They are based on cherry-picked medical references and, most importantly, expansive evidence against this narrative continues to be ignored. Factually, there is considerable evidential support for routine use of radiological imaging in chiropractic and manual therapies for 3 main purposes: 1. To assess spinopelvic biomechanical parameters; 2. To screen for relative and absolute contraindications; 3. To reassess a patient's progress from some forms of spine altering treatments. Finally, and most importantly, we summarize why the long-held notion of carcinogenicity from X-rays is not a valid argument.

5 Reasons Why Scoliosis X-Rays Are Not Harmful

Radiographic imaging for scoliosis screening, diagnosis, treatment, and management is the gold standard assessment tool. Scoliosis patients receive many repeat radiographs, typically 10-25 and as many as 40-50, equating to a maximum 50 mGy of cumulative exposure. It is argued this amount of radiation exposure is not carcinogenic to scoliosis patients for 5 main reasons: 1. Estimated theoretical cumulative effective doses remain below the carcinogenic dose threshold; 2. Scoliosis patient x-rays are delivered in serial exposures and therefore, mitigate any potential cumulative effect; 3. Linear no-threshold cancer risk estimates from scoliosis patient cohorts are flawed due to faulty science; 4. Standardized incidence/mortality ratios demonstrating increased cancers from aged scoliosis cohorts are confounded by the effects of the disease entity itself making it impossible to claim cause and effect resulting from low-dose radiation exposures from spinal imaging; 5. Children are not more susceptible to radiation damage than adults. Radiophobia concerns from patients, parents, and doctors over repeat imaging for scoliosis treatment and management is not justified; it adds unnecessary anxiety to the patient (and their parents) and interferes with optimal medical management. X-rays taken in the evidence-based management of scoliosis should be taken without hesitation or concern about negligible radiation exposures.

Are Restrictive Medical Radiation Imaging Campaigns Misguided? It Seems So: A Case Example of the American Chiropractic Association's Adoption of "Choosing Wisely"

Since the 1980s, increased utilization of medical radiology, primarily computed tomography, has doubled medically sourced radiation exposures. Ensuing fear-mongering media headlines of iatrogenic cancers from these essential medical diagnostic tools has led the public and medical professionals alike to display escalating radiophobia. Problematically, several campaigns including Image Gently, Image Wisely, and facets of Choosing Wisely propagate fears of all medical radiation, which is necessary for the delivery of effective and efficient health care. Since there are no sound data supporting the alleged risks from low-dose radiation and since there is abundant evidence of health benefits from low-doses, these imaging campaigns seem misguided. Further, thresholds for cancer are 100 to 1000-fold greater than X-rays, which are within the realm of natural background radiation where no harm has ever been validated. Here, we focus on radiographic imaging for use in spinal rehabilitation by manual therapists, chiropractors, and physiotherapists as spinal X-rays represent the lowest levels of radiation imaging and are critical in the diagnosis and management of spine-related disorders. Using a case example of a chiropractic association adopting "Choosing Wisely," we argue that these campaigns only fuel the pervasive radiophobia and continue to constrain medical professionals, attempting to deliver quality care to patients.

Death of the ALARA Radiation Protection Principle as Used in the Medical Sector

ALARA is the acronym for "As Low As Reasonably Achievable." It is a radiation protection concept borne from the linear no-threshold (LNT) hypothesis. There are no valid data today supporting the use of LNT in the low-dose range, so dose as a surrogate for risk in radiological imaging is not appropriate, and therefore, the use of the ALARA concept is obsolete. Continued use of an outdated and erroneous principle unnecessarily constrains medical professionals attempting to deliver high-quality care to patients by leading to a reluctance by doctors to order images, a resistance from patients/parents to receive images, subquality images, repeated imaging, increased radiation exposures, the stifling of low-dose radiation research and treatment, and the propagation of radiophobia and continued endorsement of ALARA by regulatory bodies. All these factors result from the fear of radiogenic cancer, many years in the future, that will not occur. It has been established that the dose threshold for leukemia is higher than previously thought. A low-dose radiation exposure from medical imaging will likely upregulate the body's adaptive protection systems leading to the prevention of future cancers. The ALARA principle, as used as a radiation protection principle throughout medicine, is scientifically defunct and should be abandoned.

Light and shadows of a new technique: is photon total-skin irradiation using helical IMRT feasible, less complex and as toxic as the electrons one?

BACKGROUND

Radiotherapy is one of the standard treatments for cutaneous lymphoma and Total Skin Electrons Beam Irradiation (TSEBI) is generally used to treat diffuse cutaneous lymphoma and some cases of localized disease. Helical IMRT (HI) allows to treat complex target with optimal dose distribution and organ at risk sparing, so helical tomotherapy has been proposed as alternative technique to TSEBI but only one preliminary report has been published.

METHODS

Three patients treated (from May 2013 to December 2014) with Helical IMRT, with a total dose between 24 and 30 Gy, were retrospectively evaluated. Data about dosimetric features, response and acute toxicity were registered and analyzed. Planned target coverage was compared with daily in vivo measures and dose calculation based on volumetric images used for set up evaluation as well.

RESULTS

The patients had a mean measured surface fraction dose ranging from 1.54 Gy up to 2.0 Gy. A planned target dose ranging from 85 to 120% of prescription doses was obtained. All doses to Organs At Risk were within the required constraints. Particular attention was posed on "whole bone marrow" planned V10Gy, V12Gy and V20Gy values, ranging respectively between 23 and 43%, 20.1 and 38% and 9.8 and 24%. A comparison with the theoretical homologous values obtained with TSEBI has shown much lower values with TSEBI. Even if treatment was given in sequence to the skin of the upper and lower hemi-body, all the patients had anaemia, requiring blood transfusions, leukopenia and thrombocytopenia.

CONCLUSION

Based on our limited results TSEBI should still be considered the standard method to treat total skin because of its pattern of acute and late toxicities and the dose distribution. In this particular case the better target coverage obtained with HI can be paid in terms of worse toxicity. Helical IMRT can instead be considered optimal in treating large, convex, cutaneous areas where it is difficult to use multiple electrons fields in relation with the clinical results and the limited and reversible toxicities.

Cancer immunotherapy: how low-level ionizing radiation can play a key role

The cancer immunoediting hypothesis assumes that the immune system guards the host against the incipient cancer, but also "edits" the immunogenicity of surviving neoplastic cells and supports remodeling of tumor microenvironment towards an immunosuppressive and pro-neoplastic state. Local irradiation of tumors during standard radiotherapy, by killing neoplastic cells and generating inflammation, stimulates anti-cancer immunity and/or partially reverses cancer-promoting immunosuppression. These effects are induced by moderate (0.1-2.0 Gy) or high (>2 Gy) doses of ionizing radiation which can also harm normal tissues, impede immune functions, and increase the risk of secondary neoplasms. In contrast, such complications do not occur with exposures to low doses (≤0.1 Gy for acute irradiation or ≤0.1 mGy/min dose rate for chronic exposures) of low-LET ionizing radiation. Furthermore, considerable evidence indicates that such low-level radiation (LLR) exposures retard the development of neoplasms in humans and experimental animals. Here, we review immunosuppressive mechanisms induced by growing tumors as well as immunomodulatory effects of LLR evidently or likely associated with cancer-inhibiting outcomes of such exposures. We also offer suggestions how LLR may restore and/or stimulate effective anti-tumor immunity during the more advanced stages of carcinogenesis. We postulate that, based on epidemiological and experimental data amassed over the last few decades, whole- or half-body irradiations with LLR should be systematically examined for its potential to be a viable immunotherapeutic treatment option for patients with systemic cancer.

Reappraisal of total body irradiation followed by bone marrow transplantation as a therapy for inflammatory bowel disease

The main current therapies for inflammatory bowel diseases (IBD) are aimed at controlling the exacerbated inflammation in the gut. Although these therapies have been successful, they are not curative and it is not possible to predict whether a beneficial response will occur or which patients will be refractory to the treatment. Total body irradiation (TBI) associated with chemotherapy is the first choice in the treatment of some hematological disorders and is an applicable option in the preparation of patients with hematologic diseases for hematopoietic stem cell transplantation. Then, in this study we investigated the association of TBI as immunosuppressive therapy and bone marrow cell (BMC) transplantation as a strategy to induce colitis recovery and immune reconstitution in the TNBS model of intestinal inflammation. TNBS mice treated with TBI associated with BMC transplantation presented elevated gain of weight and an overall better outcome of the disease when compared to those treated only with TBI. In addition, TBI associated or not with BMC reduced the frequency of inflammatory cells in the gut and restored the goblet cell counts. These results were accompanied by a down regulation in the production of inflammatory cytokines in the colon of mice treated with TBI alone or in association with BMC transplantation. The BMC infused were able to repopulate the ablated immune system and accumulate in the site of inflammation. However, although both treatments (TBI or TBI+BMC) were able to reduce gut inflammation, TBI alone was not enough to fully restore mice weight and these animals presented an extremely reduced survival rate when their immune system was not promptly reconstituted with BMC transplantation. Finally, these evidences suggest that the BMC transplantation is an efficient strategy to reduce the harmful effects of TBI in the colitis treatment, suggesting that radiotherapy may be an important immunosuppressive therapy in patients with IBD, by modulating the local inflammatory response.

Low-dose radiation therapy of cancer: role of immune enhancement

The efficacy of conventional radiation therapy, one of the most widely used treatment modalities of cancer, is limited by resistance of tumors as well as normal tissue toxicity. In the last decade, several studies have shown that protocols using low-dose radiation (LDR) are more effective in providing local tumor control with negligible normal tissue toxicity. LDR stimulates antioxidant capacity, repair of DNA damage, apoptosis and induction of immune responses, which might be collectively responsible for providing effective local tumor control. This article focuses on the immunostimulatory effects of LDR in in vivo models and its clinical efficacy, supporting the use of LDR regimens (alone or as adjuvant) as an anticancer treatment.

Treatment strategies in limited stage follicular NHL

Limited stage (I-II) follicular lymphoma is an uncommon entity, since most patients with this disease have generalized adenopathy (stage III) or bone marrow involvement (stage IV). Although patients who present with stage III-IV disease often are considered to be incurable, ~50% of patients with limited disease will enjoy long-term freedom-from progression, usually following treatment with radiation therapy. Relapse among these patients is uncommon after 10 years and exceedingly rare after 15 years. Radiation treatment is generally restricted to the involved nodal region(s) with modest (~5 cm.) extension proximally and distally. Radiation dose is generally 30 Gy, but may be boosted slightly (36 Gy total) in the presence of bulky disease. Randomized clinical trials have been insufficiently powered to define the value of any additional treatment beyond radiation therapy, although single arm studies suggest a benefit to the addition of chemotherapy. There have been no reported experiences with chemo-immunotherapy or radioimmunotherapy. Patients should be monitored during follow up to identify transformation to a more aggressive lymphoma.

Different radiosensitivity of CD4(+)CD25(+) regulatory T cells and effector T cells to low dose gamma irradiation in vitro

PURPOSE

To determine the radiosensitivity difference of human Cluster of Differentiation (CD)4(+)CD25(+) regulatory T cells (Treg) and effector T cells to low dose gamma ray and elucidate the underlying mechanisms in vitro.

MATERIALS AND METHODS

Blood samples were collected from five health subjects and five patients with advanced hepatocellular carcinoma (HCC). Treg and CD4(+)CD25⁻ T cells were selected using magnetic microbeads. The proliferative profiles, cytokine secretion, and differential expressions of apoptosis-related proteins in Treg and CD4(+)CD25⁻ T cells were compared using [³H]-thymidine incorporation, Luminex assay and flow cytometry when treated with various low doses of γ-ray.

RESULTS

A dose-dependent reduction of proliferation in response to irradiation which paralleled the induction of apoptosis existed in Treg and CD4(+)CD25⁻ T cells. Treg were more radiosensitive to low-dose irradiation (0.94 Gray [Gy]) than effector T cells. The interferon-γ (IFNγ) was significantly upregulated and interleukin 10 (IL-10) was significantly downregulated in irradiated Treg. An enhanced immune response to low dose gamma ray existed in the peripheral blood in patients with advanced HCC. Higher levels of active caspase-3, CD95, B cell lymphoma 2 (Bcl-2)-associated X protein (Bax) expression were observed in Treg compared to CD4(+)CD25⁻ T cells. In addition, gamma irradiation activated CD4(+)CD25⁻ T cells to express CD25.

CONCLUSIONS

These studies revealed that Treg were more radiosensitive than CD4(+)CD25⁻ T cells to low dose irradiation. Higher expressions of apoptosis-related proteins such as caspase-3, CD95 and Bax were observed in Treg when compared to CD4(+)CD25⁻ T cells. Our results suggest that treatment with low doses of gamma irradiation may be a viable strategy to enhance immune response in patients with advanced HCC.

Postconditioning hormesis put in perspective: an overview of experimental and clinical studies

A beneficial effect of applying mild stress to cells or organisms, that were initially exposed to a high dose of stress, has been referred to as 'postconditioning hormesis'. The initial high dose of stress activates intrinsic self-recovery mechanisms. Modulation of these endogenous adaptation strategies by administration of a subsequent low dose of stress can confer effects that are beneficial to the biological system. Owing to its potentially therapeutic applications, postconditioning hormesis is subject to research in various scientific disciplines. This paper presents an overview of the dynamics of postconditioning hormesis and illustrates this phenomenon with a number of examples in experimental and clinical research.

Low-dose radiation-induced hormetic effect on hematopoietic reconstitution

PURPOSE

To investigate the effects on hematopoietic reconstitution of recipient mice receiving bone marrow cells (BMC) of donor pre-exposed to low-dose radiation (LDR).

MATERIALS AND METHODS

BMC were irradiated in vitro at various low-dose X-rays radiation. Tritiated thymidine ((3)H-TdR) incorporation was adopted to measure the proliferation of the BMC in vitro, and then the optimal radiation doses were selected for further study in vivo. Irradiated recipient mice (7.5 Gy) were infused by BMC exposed to 6 and 8 cGy. The counts of recipients' peripheral blood cells (PBC) and bone marrow mononuclear cells (BMMNC) were monitored at the 5th, 10th, 15th, and 30th day after BMC infusion. The colony-forming units in the recipient spleens (CFU-S) were calculated at the 10th day after infusion.

RESULTS

Exposed to 6 and 8 cGy, BMC demonstrated significant proliferative activities in vitro. When the recipient mice receiving BMC pre-exposed to low dose radiation (6 and 8 cGy), the counts of white blood cell (WBC), BMMNC and CFU-S were consistently higher than those in control.

CONCLUSIONS

BMC of donor irradiated by LDR in vitro may facilitate the hematopoietic reconstitution of the recipient mice.

Nuclear energy and health: and the benefits of low-dose radiation hormesis

Energy needs worldwide are expected to increase for the foreseeable future, but fuel supplies are limited. Nuclear reactors could supply much of the energy demand in a safe, sustainable manner were it not for fear of potential releases of radioactivity. Such releases would likely deliver a low dose or dose rate of radiation, within the range of naturally occurring radiation, to which life is already accustomed. The key areas of concern are discussed. Studies of actual health effects, especially thyroid cancers, following exposures are assessed. Radiation hormesis is explained, pointing out that beneficial effects are expected following a low dose or dose rate because protective responses against stresses are stimulated. The notions that no amount of radiation is small enough to be harmless and that a nuclear accident could kill hundreds of thousands are challenged in light of experience: more than a century with radiation and six decades with reactors. If nuclear energy is to play a significant role in meeting future needs, regulatory authorities must examine the scientific evidence and communicate the real health effects of nuclear radiation. Negative images and implications of health risks derived by unscientific extrapolations of harmful effects of high doses must be dispelled.

Low-dose radioimmuno-therapy of cancer

Four decades of genomic, cellular, animal and human data have shown that low-dose ionizing radiation stimulates positive genomic and cellular responses associated with effective cancer prevention and therapy and increased life span of mammals and humans.( 1-8) Nevertheless, this data is questioned because it seems to contradict the well demonstrated linear relation between ionizing radiation dose and damage to DNA without providing a clear mechanistic explanation of how low-dose radiation could produce such beneficial effects. This apparent contradiction is dispelled by current radiobiology that now includes DNA damage both from ionizing radiation and from endogenous metabolic free radicals, and coupled with the biological response to low-dose radiation. Acceptance of current radiobiology would invalidate long established recommendations and regulations of worldwide radiation safety organizations and so destroy the basis of the very expensive existing system of regulation and remediation. More importantly, current radiobiology would facilitate urgently needed clinical trials of low dose radiation (LDR) cancer therapy.

Low-dose radiation and its clinical implications: diabetes

Induction of hormesis and adaptive response by low-dose radiation (LDR) has been extensively indicated. Adaptive response induced by LDR was not only resistant to damage caused by a subsequently high-dose radiation, but also cross-resistant to other non-radiation challenges, such as chemicals. Mechanisms by which LDR induces the preventive effect on radiation- or chemical-induced tissue damage include induced or up-regulated expression of protective proteins, such as heat shock proteins and antioxidants. Since oxidative damage to tissues is a major pathogenesis of many human diseases including diabetes, this review will summarize the available data with an emphasis of the preventive effect of LDR on the development of diabetes and the therapeutic effect of LDR on diabetic cardiovascular complications. The available data indicated that pre-exposure of mice to LDR reduced the incidence of alloxan-induced diabetes, and also delayed the onset of hyperglycaemia in diabetes-prone non-obese diabetic mice. Experiments with animals indicated the effectively therapeutic effect of low-intensity or power laser (LIL or LPL) radiation on skin wound healing, which has stimulated clinical use of LIL to cure skin ulcer in diabetic patients. Mechanisms by which LDR prevents diabetes, though are unclear now, may include the induction of pancreatic antioxidants to prevent beta cell from oxidative damage and immunomodulation to preserve pancreatic function. For LIL therapeutic effect on diabetic wound healing, mechanisms may include its antioxidant action, immunomodulation, cell proliferation stimulation as well as improvement of systemic and wound-regional microcirculation. Therefore, although only a few studies indicating LDR prevention of the development of diabetes, many studies have demonstrated LDR, specifically LIL, therapeutic effectiveness of diabetic wound healing. These preliminary results are really encouraging for us to further pursue the clinical implication of LDT to diabetes-related areas.

Sparsely ionizing diagnostic and natural background radiations are likely preventing cancer and other genomic-instability-associated diseases

Routine diagnostic X-rays (e.g., chest X-rays, mammograms, computed tomography scans) and routine diagnostic nuclear medicine procedures using sparsely ionizing radiation forms (e.g., beta and gamma radiations) stimulate the removal of precancerous neo-plastically transformed and other genomically unstable cells from the body (medical radiation hormesis). The indicated radiation hormesis arises because radiation doses above an individual-specific stochastic threshold activate a system of cooperative protective processes that include high-fidelity DNA repair/apoptosis (presumed p53 related), an auxiliary apoptosis process (PAM process) that is presumed p53-independent, and stimulated immunity. These forms of induced protection are called adapted protection because they are associated with the radiation adaptive response. Diagnostic X-ray sources, other sources of sparsely ionizing radiation used in nuclear medicine diagnostic procedures, as well as radioisotope-labeled immunoglobulins could be used in conjunction with apoptosis-sensitizing agents (e.g., the natural phenolic compound resveratrol) in curing existing cancer via low-dose fractionated or low-dose, low-dose-rate therapy (therapeutic radiation hormesis). Evidence is provided to support the existence of both therapeutic (curing existing cancer) and medical (cancer prevention) radiation hormesis. Evidence is also provided demonstrating that exposure to environmental sparsely ionizing radiations, such as gamma rays, protect from cancer occurrence and the occurrence of other diseases via inducing adapted protection (environmental radiation hormesis).

Radiobiological basis of low-dose irradiation in prevention and therapy of cancer

Antimutagenic DNA damage-control is the central component of the homeostatic control essential for survival. Over eons of time, this complex DNA damage-control system evolved to control the vast number of DNA alterations produced by reactive oxygen species (ROS), generated principally by leakage of free radicals from mitochondrial metabolism of oxygen. Aging, mortality and cancer mortality are generally accepted to be associated with stem cell accumulation of permanent alterations of DNA, i.e., the accumulation of mutations. In a young adult, living in a low LET background of 0.1 cGy/y, the antimutagenic system of prevention, repair and removal of DNA alterations reduces about one million DNA alterations/cell/d to about one mutation/cell/d. DNA alterations from background radiation produce about one additional mutation per 10 million cells/d. As mutations accumulate and gradually degrade the antimutagenic system, aging progresses at an increasing rate, mortality increases correspondingly, and cancer increases at about the fourth power of age. During the past three decades, genomic, cellular, animal and human data have shown that low-dose ionizing radiation, including acute doses up to 30 cGy, stimulates each component of the homeostatic antimutagenic control system of antioxidant prevention, enzymatic repair, and immunologic and apoptotic removal of DNA alterations. On the other hand, high-dose ionizing radiation suppresses each of these antimutagenic protective components. Populations living in high background radiation areas and nuclear workers with increased radiation exposure show lower mortality and decreased cancer mortality than the corresponding populations living in low background radiation areas and nuclear workers without increased radiation exposure. Both studies of cancer in animals and clinical trials of patients with cancer also show, with high statistical confidence, the beneficial effects of low-dose radiation.

A phase II trial of low-dose total body irradiation and subcutaneous interleukin-2 in metastatic melanoma

BACKGROUND AND PURPOSE

Our own experimental data suggests a therapeutic synergism between low-dose total body irradiation (LTBI) and interleukin-2 (IL-2).

PATIENTS AND METHODS

Forty-five patients received a maximum of 2 cycles of high dose subcutaneous (s.c.) IL-2 and LTBI. One treatment cycle included 5 weeks treatment followed by 2 weeks break and composed of a single radiation fraction 0.1 Gy on days 1, 8, 22 and 30 and IL-2: 18 MU x 2 daily s.c. on days 2 to 5 and days 16-19 as well as 9 MU x 2 daily s.c. on days 9-12 and 31-34. In 17 patients, flow cytometric analyses of the various subpopulations of immune cells were done on blood samples before the first LTBI fraction and 24h after LTBI as well as after the first week of treatment.

RESULTS

Two patients (4.4%) had a partial response (PR) and 13 patients (29%) had stable disease (SD). The duration of the partial remission and stable disease did not exceed 3 months. The median overall survival was 5.8 months (95% CI, 4-8 months). Thirty-four of the 58 treatment cycles (74%) were given in 100% of the intended dose without modification or delay. The dose was modified in 15 cycles (26%) because of progression (6), liver toxicity (3), CNS toxicity (2), thrombocytopenia (1), lung morbidity (1) and itching (1). There were no treatment-related deaths. Flowcytometry data showed a significant increase in the percentage of cells carrying the beta chain of IL-2 receptor (CD122+), a significant increase in the percentage of NK cells (CD56+ cells) as well as a significant reduction in the percentage of B cells (CD20+) and monocytes (CD14+).

CONCLUSIONS

This LTBI and IL-2 regimen was well tolerated, however it cannot be recommended because of its low clinical efficacy. No indication of increased efficacy or altered toxicity was seen using LTBI.

Not all 2 gray radiation prescriptions are equivalent: Cytotoxic effect depends on delivery sequences of partial fractionated doses

PURPOSE

To test whether or not the commonly prescribed daily dose of 2 Gy (whole fraction), when delivered as various partial fraction (PF) dose sequences simulating clinical treatment fields, produces equal biologic effects.

METHODS AND MATERIALS

Eleven actively proliferating cell lines derived from human and animal tissues were used in this study. 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) and clonogenic assays were used to determine the radiation effects on cell proliferation and survival, respectively. The 2 Gy dose was divided into 2 or more PFs for delivery to simulate the delivery of clinical treatment fields. Most irradiation sequences contained two parts consisting of at least 1 small PF, denoted by S which was 0.5 Gy or less, and a large PF, denoted by L which was 1 Gy or more. Irradiation schemes were designed to include the following conditions: (a) the 2 Gy dose divided into combinations of an L-dose and one or more S-doses; (b) the L-dose given either before or after the S-doses; and (c) delivery of all partial fractions within a fixed total time.

RESULTS

Significant differences in biologic effect were observed between sequences in which the L-dose was given before or after the S-doses in both the MTT and clonogenic assays. Nearly all the latter schemes, that is S-L, produced greater cytotoxic effects than the L-S schemes.

CONCLUSIONS

These data demonstrate that the biologic effects of 2 Gy may differ in different clinical settings depending on the size and sequence of the partial fractions. The variation between cytotoxic effects is likely a result of the combination of low-dose hyper-radiosensitivity (HRS) and higher-dose increased radioresistance (IRR) effects established recently. We suggest that to ensure the optimal biologic effect of a prescribed dose of 2 Gy clinically, it is critical to consider the sequence in which the treatment fields are delivered when partial fractions of different sizes are used.

Low-dose radiation (LDR) induces hematopoietic hormesis: LDR-induced mobilization of hematopoietic progenitor cells into peripheral blood circulation

OBJECTIVE

The aim of this study was to investigate the stimulating effect of low-dose radiation (LDR) on bone marrow hematopoietic progenitor cell (HPC) proliferation and peripheral blood mobilization.

METHODS

Mice were exposed to 25- to 100-mGy x-rays. Bone marrow and peripheral blood HPCs (BFU-E, CFU-GM, and c-kit+ cells) were measured, and GM-CSF, G-CSF, and IL-3 protein and mRNA expression were detected using ELISA, slot blot hybridization, and Northern blot methods. To functionally evaluate LDR-stimulated and -mobilized HPCs, repopulation of peripheral blood cells in lethally irradiated recipients after transplantation of LDR-treated donor HPCs was examined by WBC counts, animal survival, and colony-forming units in the recipient spleens (CFUs-S).

RESULTS

75-mGy x-rays induced a maximal stimulation for bone marrow HPC proliferation (CFU-GM and BFU-E formation) 48 hours postirradiation, along with a significant increase in HPC mobilization into peripheral blood 48 to 72 hours postradiation, as shown by increases in CFU-GM formation and proportion of c-kit+ cells in the peripheral mononuclear cells. 75-mGy x-rays also maximally induced increases in G-CSF and GM-CSF mRNA expression in splenocytes and levels of serum GM-CSF. To define the critical role of these hematopoietic-stimulating factors in HPC peripheral mobilization, direct administration of G-CSF at a dose of 300 microg/kg/day or 150 microg/kg/day was applied and found to significantly stimulate GM-CFU formation and increase c-kit+ cells in the peripheral mononuclear cells. More importantly, 75-mGy x-rays plus 150 microg/kg/day G-CSF (LDR/150-G-CSF) produced a similar effect to that of 300 microg/kg/day G-CSF alone. Furthermore, the capability of LDR-mobilized donor HPCs to repopulate blood cells was confirmed in lethally irradiated recipient mice by counting peripheral WBC and CFUs-S.

CONCLUSION

These results suggest that LDR induces hematopoietic hormesis, as demonstrated by HPC proliferation and peripheral mobilization, providing a potential approach to clinical application for HPC peripheral mobilization.

Single low doses of X rays inhibit the development of experimental tumor metastases and trigger the activities of NK cells in mice

There is evidence indicating that low-level exposures to low- LET radiation may inhibit the development of tumors, but the mechanism of this effect is virtually unknown. In the present study, BALB/c mice were irradiated with single doses of 0.1 or 0.2 Gy X rays and injected intravenously 2 h later with syngeneic L1 sarcoma cells. Compared to the values obtained for sham-irradiated control mice, the numbers of pulmonary tumor colonies were significantly reduced in the animals exposed to either 0.1 or 0.2 Gy X rays. Concurrently, a significant stimulation of NK cell-mediated cytotoxic activity was detected in splenocyte suspensions obtained from irradiated mice compared to sham-exposed mice. Intraperitoneal injection of the NK-suppressive anti-asialo GM1 antibody totally abrogated the tumor inhibitory effect of the exposures to 0.1 and 0.2 Gy X rays. These results indicate that single irradiations of mice with either 0.1 or 0.2 Gy X rays suppress the development of experimental tumor metastases primarily due to the stimulation of the cytolytic function of NK cells by radiation.

The potential palliative role and possible immune modulatory effects of low-dose total body irradiation in relapsed or chemo-resistant non-Hodgkin's lymphoma

In a group of 35 patients with relapsed and/or chemo-resistant non-Hodgkin's lymphoma (NHL), low-dose total body irradiation (LTBI) (+involved-field radiotherapy to bulky sites) achieved a complete remission rate of 29%, 2-years progression-free survival of 32% and a median progression-free survival of 12 months. The 2-year survival was 42% and the median survival was 17 months. Immuno-staining and flow cytometry of peripheral blood in 14 patients showed that LTBI leads to a significant increase in the percentage of CD4+ cells with a consequent significant increase in the CD4+/CD8+ ratio. High lymphocytic percent and a high percentage of CD4+ cells before LTBI were significantly correlated with longer response duration and overall survival. These data may suggest that the palliative potential of LTBI should be investigated as an alternative to chemotherapy in NHL patients. The pre-treatment percentage of lymphocytes and CD4+ cells may be used as predictors for response to LTBI.

Combined therapy in advanced stages (III and IV) of follicular lymphoma increases the possibility of cure: results of a large controlled clinical trial

OBJECTIVES

We evaluate the long-term results of a randomized clinical trial in patients with advanced stages (III and IV) of follicular lymphoma using chemotherapy or combined therapy (chemotherapy following by adjuvant radiotherapy in patients with nodal bulky disease).

MATERIAL AND METHODS

Between 1981 and 1995, patients with follicular lymphoma were treated with combined chemotherapy, mostly anthracycline-based regimens; patients who achieved complete response were randomly assigned either to receive adjuvant radiotherapy to sites or to nodal bulky disease or not (control group).

RESULTS

Four hundred and sixty-nine patients were randomized; in an intent-to-treat analysis all were evaluable for efficacy and toxicity. Actuarial curves at 20yr showed that event-free survival (EFS) and overall survival (OS) in the control group were 41% [95% confidence interval (CI) 36-56%) and 71% (95% CI 65-78%), respectively; these were statistically different from results for the patients who received adjuvant radiotherapy: 68% (95% CI 62-72%) and 89% (95% CI 79-96%), respectively (P<0.01). Acute and late toxicity were minimal; only four patients (<1%) developed myelodysplastic syndrome/acute leukemia. Cardiac toxicity was 2%, but one case was lethal. Thirty-six patients (8%) died secondary to unrelated causes, in complete remission.

CONCLUSIONS

The use of adjuvant radiotherapy in patients with poor-prognosis follicular lymphoma increases EFS and OS with minimal toxicity. We feel that follicular lymphoma should be treated curatively because <80% of patients will be in first complete response at <20yr. The use of adjuvant radiotherapy will be considered in the first line of treatment in this set of patients.

Single tumor cell uptake and dosimetry of technetium-99m Fab' or minute anti-CD22 in low-grade B-cell lymphoma

BACKGROUND

A patient with follicular lymphoma was investigated with 0.5 mg Fab' or minute anti-CD22 labeled with 1100 MBq technetium-99m ((99m)Tc). A computed tomography scan performed a week later revealed regression. This unexpected response prompted an investigation of single cell dosimetry of low-energy electron emitters.

METHODS

Another patient with low-grade, unclassifiable B-cell lymphoma with a low expression of CD22 was injected with (99m)Tc anti-CD22. Blood samples were drawn 30 minutes, 4 hours, and 24 hours after injection. Lymphoma cells (CD19+) and T cells (CD3+), which served as control cells, were separated using a flow cytometer. The radioactivity of the two cell populations was measured in an NaI(Tl) well-type detector. The mean uptake per cell and absorbed dose were calculated. The CD22 expression of the patient's cells and of a B-cell lymphoma cell line (Raji) were assessed by flow cytometry for the extrapolation of the absorbed dose from the patient's cells to a cell line with higher CD22 expression.

RESULTS

The average number of (99m)Tc atoms per CD19+ and CD3+ cell 4 hours postinjection were 5.4 and 0.054, respectively. Depending on the assumed ratio between antibody and CD22 molecules (1:2 or 1:1), the CD22 expression on the patient's cells and Raji cells varied from 2800 to 5700 and from 37,000 to 74,000 per cell, respectively. The average absorbed dose per cell ranged from 4 x 10(-7) to 0.1 grays (Gy).

CONCLUSIONS

It seems feasible to assess the mean single tumor cell uptake of (99m)Tc targeted by Fab' or minute anti-CD22 in a patient's lymphoma using sorted cell populations, thereby allowing single cell dosimetry. Extrapolation of the absorbed dose from (99m)Tc to cells with higher CD22 expression was made and under certain conditions absorbed doses of 0.1 Gy were obtained, indicating the potential relevance of low-energy electron emitters to therapy.

High-dose therapy for indolent lymphoma

Stem-cell transplantation (SCT) has become the treatment of choice for patients with relapsed aggressive non-Hodgkin's lymphoma (NHL). However, the role of SCT in the management of patients with indolent NHL remains controversial. Indolent follicular lymphomas are diseases which are generally incurable with conventional therapy. Although patients can survive for prolonged periods, the median duration of first remission is approximately 3 years, and subsequent remissions are progressively shorter with time. Emerging evidence suggests that high-dose chemotherapy with SCT leads to prolonged disease-free and overall survival in a subset of patients with indolent NHL. However, there is increasing concern regarding the toxicity of SCT, especially the long-term risk of developing myelodysplastic syndrome. It is still unclear as to when this approach should be used. Poorer outcomes have been obtained in heavily pretreated patients but encouraging results are being reported for patients undergoing SCT early during the course of their disease. Investigators are now focusing on how to improve SCT efficacy in order to eradicate minimal residual disease. Many ongoing studies are especially exploring the impact of stem-cell purging and novel ablative regimens combined with allogeneic transplantation.

Management of localized low-grade follicular lymphomas

Long-term follow-up data from Stanford and other centres suggest that 40-50% of patients with clinical stages I and II follicular low-grade lymphoma can be cured by radiotherapy (RT). Relapse generally occurs outside radiation fields and most relapsed patients ultimately die from lymphoma. No randomized data exist to support adjuvant chemotherapy but only one trial of low-intensity chemotherapy was sufficiently powerful to address the question. Nevertheless, data from a large phase-II study from MD Anderson suggest that combined chemotherapy and RT can produce progression-free survival results that are far superior to historical series, with survival at 10 years to be approximately 20% superior to radiation alone. These results have encouraged the development of a joint phase III study by the Trans Tasman Radiation Oncology Group (TROG) and the Australasian Leukaemia and Lymphoma Group (ALLG) in which patients with clinical stage I/II follicular lymphoma are randomized to involved field RT with or without six cycles of cytotoxic chemotherapy. In an era of rapid development in immunological and molecular therapies the potential for improved results with new combinations of more established treatment modalities should not be forgotten. This report reviews the literature on the management of localized low-grade lymphoma and discusses the rationale for the TROG/ALLG study, which began recruitment in early 2000.

Follicular lymphomas--a review of treatment modalities

Follicular lymphoma is the most common low-grade non Hodgkin's lymphoma and represent an homogeneous entity as defined by pathological, molecular and clinical data. This indolent disease is characterised by a slow growth pattern with possible spontaneous regression, is often disseminated but remains incurable with available treatments when disseminated. For localised stages, involved field radiotherapy remains the standard choice but other approaches remain to be investigated. In advanced disease, chemotherapy has been demonstrated to produce high response rates but recent trials with new treatment strategies including interferon and monoclonal antibodies may improve the current situation. In this article, we will review treatment of follicular lymphomas, specially emphasising published phase III trials.

The role of low-dose total body irradiation in treatment of non-Hodgkin's lymphoma: a new look at an old method

The use of low-dose total body irradiation (LTBI) in treatment of lymphomatous malignancies dates back to the 1920s. The usual practice was to give very low individual TBI fraction sizes (0.1-0. 25 Gy) several times a week to a total dose of 1.5-2 Gy. Despite this very low total dose, LTBI could induce long term remissions and was always as effective as the chemotherapy to which it was compared. In modern radiotherapy, LTBI is still a valid option in treatment of chronic lymphocytic leukaemia (CLL) and the advanced stages of indolent low-grade non-Hodgkin's lymphoma (NHL). Its use in the early stages of low-grade NHL is under investigation in a large multi-institutional trial. The efficacy of LTBI is believed to stem from three mechanisms, namely; immune-enhancement, induction of apoptosis, and the intrinsic hypersensitivity to low-radiation doses demonstrated in many cell lines and tumour systems. Thus, LTBI seems to provide 'alternative' mechanisms of action against cancer cells. This should encourage researchers to explore strategies that integrate LTBI in new and innovative experimental treatment protocols that explore the possible synergism between LTBI and chemotherapy, biological response modifiers and/or immunotherapy. The increased incidence of secondary leukaemia that occurs when LTBI is combined with alkylating agents and/or total lymphoid irradiation should be kept in mind when designing such protocols as it may limit the use of LTBI in highly curable diseases and young patients in whom long survival is expected.

The immunobiology of low-dose total-body irradiation: more questions than answers

Low-dose total-body irradiation (TBI) is used in the treatment of chronic lymphocytic leukemia and low-grade non-Hodgkin's lymphoma. The usual practice is to give very low individual fractions (0.1 to 0.25 Gy) several times a week, to a total dose of 1.5 to 2 Gy. Despite this low dose, low-dose TBI can induce long-term remissions in the majority of patients. Immune enhancement, rather than direct radiation cell killing, is one of the suggested mechanisms by which low-dose TBI can exert its effect. Data from animal experiments have shown that low-dose TBI could enhance the immune response through (1) augmenting the proliferative reactive response of the T cells to mitogenic stimulation; (2) altering cytokine release, particularly the activation of interferon gamma and Il2 production; (3) increasing the expression of Il2 receptors on the T-cell surface; (4) facilitating signal transduction in T lymphocytes; (5) increasing splenic catecholamine content and lowering the serum corticosterone level; and (6) eliminating a particularly radiosensitive subset of the suppressor T cells. Data for humans, though scarce, suggest that at least some of these mechanisms occur in patients treated with low-dose TBI. Whether these immunomodulatory effects are responsible for the clinical outcome is not yet clear. Much is still unknown about the immunobiology of low-dose TBI, its clinical potential, and the possible synergism with chemotherapy, biological response modifiers, or immunotherapy. This lack of comprehensive knowledge hampers the optimal and widespread use of this intriguing and potentially useful treatment modality in clinical practice.

Acute effects of whole-body proton irradiation on the immune system of the mouse

The acute effects of proton whole-body irradiation on the distribution and function of leukocyte populations in the spleen and blood were examined and compared to the effects of photons derived from a (60)Co gamma-ray source. Adult female C57BL/6 mice were exposed to a single dose (3 Gy at 0.4 Gy/min) of protons at spread-out Bragg peak (SOBP), protons at the distal entry (E) region, or gamma rays and killed humanely at six different times thereafter. Specific differences were noted in the results, thereby suggesting that the kinetics of the response may be variable. However, the lack of significant differences in most assays at most times suggests that the RBE for both entry and peak regions of the Bragg curve was essentially 1.0 under the conditions of this study. The greatest immunodepression was observed at 4 days postexposure. Flow cytometry and mitogenic stimulation analyses of the spleen and peripheral blood demonstrated that lymphocyte populations differ in radiosensitivity, with B (CD19(+)) cells being most sensitive, T (CD3(+)) cells being moderately sensitive, and natural killer (NK1.1(+)) cells being most resistant. B lymphocytes showed the most rapid recovery. Comparison of the T-lymphocyte subsets showed that CD4(+) T helper/inducer cells were more radiosensitive than the CD8(+) T cytotoxic/suppressor cells. These findings should have an impact on future studies designed to maximize protection of normal tissue during and after proton-radiation exposure.

Evolution of BCL-2/IgH hybrid gene RNA expression during treatment of T(14;18)-bearing follicular lymphomas

Bcl-2, the gene over-expressed in follicular lymphomas (FL), is able to block chemotherapy-induced apoptosis. Consequently, we wondered whether bcl-2/IgH expression variations during treatment of FL could predict the outcome of patients with t(14;18)-bearing FL. For this purpose, we used a reverse transcription polymerase chain reaction (RT-PCR) assay to analyse 180 serial peripheral blood samples (PBS) during 34 treatment phases in 25 patients with t(14;18)-bearing FL. In all patients but two, bcl-2/IgH gene expression was demonstrated in pre-treatment samples. During 16 out of the 34 treatment phases (47%), bcl-2/IgH expression became negative: all but one were responders to chemotherapy. This conversion was transient in six cases. In 18 treatment phases, bcl2/IgH expression remained detectable: eight were clinically considered as treatment failures, while eight others achieved PR and two achieved CR. We observed a significant correlation between treatment response and RNA PCR results (P = 0.002). Three-year overall survival of patients with stable bcl2/IgH-negative conversion was 100% compared to 54% for the remaining patients (P = 0.069); 3-year freedom from progression was respectively 87.5% and 13% (P = 0.005). These results indicate a correlation between bcl-2/IgH expression variations and both clinical response and outcome. Whether this might predict disease outcome early remains to be confirmed.