A possible abscopal effect of post-irradiation immunotherapy in two patients with metastatic lung tumors

A long-term survival case of bladder cancer with distant metastases: abscopal effect of brain metastases after stereotactic radiotherapy with immune checkpoint blockade therapy to lung metastases

Brain metastases from bladder cancer are rare, with a poor prognosis. There is no standard treatment for bladder cancer with brain metastases; thus, palliative therapy is generally provided. We report a case of abscopal effect in a single brain metastasis from bladder cancer in a patient treated with focal stereotactic radiotherapy (total dose = 52 Gy, administered in eight fractions) with immune checkpoint blockade therapy for lung metastases, who achieved long-term disease-free survival (> 4 years). To our knowledge, although there have been some reports on abscopal effects in bladder cancer, there are no previous reports on patients with brain metastases. To date, the brain metastasis, which showed an "abscopal effect," continues to maintain complete regression.

Abscopal Effect on Bone Metastases from Solid Tumors: A Systematic Review and Retrospective Analysis of Challenge within a Challenge

BACKGROUND

Abscopal effect (AE) describes the ability of radiotherapy (RT) to induce immune-mediated responses in nonirradiated distant metastasis. Bone represents the third most frequent site of metastasis and an immunologically favorable environment for the proliferation of cancer cells. We revised the literature, searching documented cases of AE involving bone metastases (BMs) and evaluated the incidence of AE involving BMs in patients requiring palliative RT on BMs or non-BMs treated at our department.

METHODS

Articles published in the PubMed/MEDLINE database were selected using the following search criteria: ((abscopal effect)) AND ((metastases)). Patients with BMs, who underwent performed bone scintigraphy before and at least 2-3 months after RT, were selected and screened between January 2015 and July 2022. AE was defined as an objective response according to the scan bone index for at least one nonirradiated metastasis at a distance > 10 cm from the irradiated lesion. The primary endpoint was the rate of AE on BMs.

RESULTS

Ten cases experiencing AE of BMs were identified from the literature and eight among our patients.

CONCLUSIONS

The analysis performed here suggests the use of hypofractionated radiotherapy as the only triggering factor for AE of BMs through the activation of the immune response.

A Patient-Level Data Meta-analysis of the Abscopal Effect

Purpose

The abscopal effect is defined when a form of local therapy causes tumor regression of both the target lesion and any untreated tumors. Herein cases of the abscopal effect were systematically reviewed and a patient-level data analysis was performed for clinical predictors of both duration of response and survival.

Methods and Materials

The Population, Intervention, Control, Outcome, Study (PICOS) design approach, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) literature selection process, and Meta-analysis of Observational Studies in Epidemiology (MOOSE) were used to find articles published before September 2019 in MEDLINE/PubMed and Google Scholar. Inclusion criteria were (1) population: patients with reported abscopal response; (2) intervention: documented treatment(s); (3) control: none; (4) outcomes: overall and progression-free survival; and (5) setting: retrospective case reports. Time from treatment until abscopal response and time from abscopal response until progression/death were calculated. Univariate and multivariate analyses were conducted for survival outcomes.

Results

Fifty studies (n = 55 patients) were included. Median age was 65 years (interquartile range [IQR], 58-70) and 62% were male. Fifty-four (98%) patients received radiation therapy, 34 (62%) received radiation therapy alone, 5 (9.1%) underwent surgery, 4 (7.3%) received chemotherapy, and 11 (20%) received immunotherapy. Median total dose was 32 Gy (IQR, 25.5-48 Gy) and median dose per fraction was 3 Gy (IQR, 2-7.2). Median time until abscopal response was 4 months (IQR, 1-5; min 0.5, max 24). At 5 years, overall survival was 63% and distant progression-free survival was 45%. No variables had statistical significance in predicting duration of response or survival.

Conclusions

Almost all reported cases of the abscopal response are after radiation therapy; however, there are no known predictors of duration of response or survival in this population.

Abscopal effect in the radio and immunotherapy

This review is devoted to a rare in clinical practice, but promising phenomenon of regression distant non-irradiated metastases in combination therapy of cancer patients. R. H. Mole in 1953 suggested introducing the term "abscopal effect" to denote the effect of ionizing radiation "at a distance from the irradiated volume but within the same organism." Currently, it is a hypothesis in the treatment of metastatic cancer, when there is a regression of untreated areas simultaneously with a decrease in the tumor. After the discovery of immune checkpoint cases were increase with patients treated with check-point blockade (especially lymphocyte associated protein 4, programmed cell death 1/programmed cell death 1 ligand 1) and which have an abscopal effect. This review systematizes works covering the time period from 1969 to 2019, which give cases of the abscopal effect at different localizations. However, abscopal effect is a poorly understood phenomenon. In this review, the authors tried to collect all information about the possible mechanisms of the abscopal effect, possible role in antitumor response and frequency abscopal effect at radio/immunotherapy or combined both.

Systemic Effects of Radiation Therapy-Induced Abscopal Responses in Patients with Advanced Lung Cancer

BACKGROUND

Out-of-field tumor regression effects of radiation therapy (abscopal response) have been sporadically observed in the past, but they have only recently gained significant importance due to the use of innovative high-precision radiation delivery devices for the treatment of various cancers including non-small cell lung cancer (NSCLC). In this study, we provide a detailed overview of the current state of knowledge and clinical experience of radiation therapy-induced abscopal effects in patients with advanced NSCLC.

SUMMARY

Peer-reviewed published clinical evidence on the abscopal effect of radiation therapy was collected using electronic databases such as MEDLINE via PubMed and Google Scholar. The clinical data on the abscopal effect of radiation therapy were reviewed and the outcomes have been summarized. Most studies describing the abscopal effects of radiation therapy in patients with advanced NSCLC have been in the form of either case reports or small cohort studies. Although the exact molecular mechanisms for the abscopal effect are yet to be established, current evidence indicates that tumor cell destruction induced by local radiation therapy releases tumor antigens, which stimulate the immune system of the host to activate the body's immune effector cells systemically and trigger the regression of distant nonirradiated cancer cells. These off-target antitumor effects of radiation therapy provide an opportunity to explore the use of the radiation therapy in combination with novel immunotherapy agents to maximize treatment outcomes in patients with advanced NSCLC and other cancers. Key Message: The findings suggest that radiation therapy has the ability to induce abscopal effects with an increased potential to boost these effects when it is used in combination with immunotherapy for the treatment of patients with advanced NSCLC and other cancers. Clinical trials investigating radiation therapy-induced abscopal effects may lead to a dramatic change in its use especially when it is combined with immunotherapy for the treatment of patients with advanced NSCLC.

Toll-like receptor 3 signal augments radiation-induced tumor growth retardation in a murine model

Radiotherapy induces anti-tumor immunity by induction of tumor antigens and damage-associated molecular patterns (DAMP). DNA, a representative DAMP in radiotherapy, activates the stimulator of interferon genes (STING) pathway which enhances the immune response. However, the immune response does not always parallel the inflammation associated with radiotherapy. This lack of correspondence may, in part, explain the radiation-resistance of tumors. Additive immunotherapy is expected to revive tumor-specific CTL facilitating radiation-resistant tumor shrinkage. Herein pre-administration of the double-stranded RNA, polyinosinic-polycytidylic acid (polyI:C), in conjunction with radiotherapy, was shown to foster tumor suppression in mice bearing radioresistant, ovalbumin-expressing Lewis lung carcinoma (LLC). Extrinsic injection of tumor antigen was not required for tumor suppression. No STING- and CTL-response was induced by radiation in the implant tumor. PolyI:C was more effective for induction of tumor growth retardation at 1 day before radiation than at post-treatment. PolyI:C targeted Toll-like receptor 3 with minimal effect on the mitochondrial antiviral-signaling protein pathway. Likewise, the STING pathway barely contributed to LLC tumor suppression. PolyI:C primed antigen-presenting dendritic cells in draining lymph nodes to induce proliferation of antigen-specific CTL. By combination therapy, CTL efficiently infiltrated into tumors with upregulation of relevant chemokine transcripts. Batf3-positive DC and CD8+ T cells were essential for therapeutic efficacy. Furthermore, polyI:C was shown to stimulate tumor-associated macrophages and release tumor necrosis factor alpha, which acted on tumor cells and increased sensitivity to radiation. Hence, polyI:C treatment prior to radiotherapy potentially induces tumor suppression by boosting CTL-dependent and macrophage-mediated anti-tumor responses. Eventually, polyI:C and radiotherapy in combination would be a promising therapeutic strategy for radiation-resistant tumors.

Enhancing radiotherapy for lung cancer using immunoadjuvants delivered in situ from new design radiotherapy biomaterials: a preclinical study

Studies show that radiotherapy of a primary tumor in combination with immunoadjuvants (IA) can result in increased survival or immune-mediated regression of metastasis outside the radiation field, a phenomenon known as abscopal effect. However, toxicities due to repeated systematic administration of IA have been shown to be a major obstacle in clinical trials. To minimize the toxicities and prime a more potent immune response, Ngwa et al have proposed that inert radiotherapy biomaterials such as fiducials could be upgraded to multifunctional ones loaded with IA for in situ delivery directly into the tumor sub-volume at no additional inconvenience to patients. In this preliminary study, the potential of such an approach is investigated for lung cancer using anti-CD40 antibody. First the benefit of using the anti-CD40 delivered in situ to enhance radiotherapy was tested in mice with subcutaneous tumors generated with the Lewis Lung cancer cell line LL/2 (LLC-1). The tumors were implanted on both flanks of the mice to simulate metastasis. Tumors on one flank were treated with and without anti-CD40 and the survival benefits compared. An experimentally determined in vivo diffusion coefficient for nanoparticles was then employed to estimate the time for achieving intratumoral distribution of the needed minimal concentrations of anti-CD40 nanoparticles if released from a multifuntional radiotherapy biomaterials. The studies show that the use of anti-CD40 significantly enhanced radiotherapy effect, slowing the growth of the treated and untreated tumors, and increasing survival. Meanwhile our calculations indicate that for a 2-4 cm tumor and 7 mg g^-1 IA concentrations, it would take 4.4-17.4 d, respectively, following burst release, for the required concentration of IA nanoparticles to accumulate throughout the tumor during image-guided radiotherapy. The distribution of IA could be customized as a function of loading concentrations or nanoparticle size to fit current Stereotactic Body Radiotherapy schedules. Overall, the preliminary results support ongoing work in developing multifunctional radiotherapy biomaterials for in situ delivery of immunoadjuvants such as anti-CD40 to leverage the abscopal effect, while minimizing systemic toxicities. The potential of extending such an approach to other cancer types is discussed.

The abscopal effect of local radiotherapy: using immunotherapy to make a rare event clinically relevant

BACKGROUND

Recently, immunologic responses to localized irradiation are proposed as mediator of systemic effects after localized radiotherapy (called the abscopal effect). Here, we give an overview of both preclinical and clinical data about the abscopal effect in particular and link them with the immunogenic properties of radiotherapy.

METHODS

We searched Medline and Embase with the search term "abscopal", "(non-targeted irradiation) OR (non-targeted radiotherapy)" and "distant bystander" from 1960 until July, 2014. Only papers that cover radiotherapy in an oncological setting were selected and only if no concurrent cytotoxic treatment was given. Targeted immune therapy was allowed.

RESULTS

Twenty-three case reports, one retrospective study and 13 preclinical papers were selected. Eleven preclinical papers used a combination of immune modification and radiotherapy to achieve abscopal effects. Patient age range (28-83years) and radiation dose (median total dose 32Gy) varied. Fractionation size ranged from 1.2Gy to 26Gy. Time to documented abscopal response ranged between less than one and 24months, with a median reported time of 5months. Once an abscopal response was achieved, a median time of 13months went by before disease progression occurred or the reported follow-up ended (range 3-39months).

CONCLUSION

Preclinical data points heavily toward a strong synergy between radiotherapy and immune treatments. Recent case reports already illustrate that such a systemic effect of radiotherapy is possible when enhanced by targeted immune treatments. However, several issues concerning dosage, timing, patient selection and toxicity need to be resolved before the abscopal effect can become clinically relevant.