Rationale for Harnessing the Abscopal Effect as Potential Treatment for Metastatic Uveal Melanoma

Carbon Fiducial Markers for Tumor Localization in Stereotactic Irradiation of Uveal Melanoma

PURPOSE

The aim of this study was to demonstrate the role of carbon fiducial markers (fiducials) for guiding radiotherapy in the management of uveal melanoma (UM).

METHODS

This is a retrospective interventional case series at a single-center ocular oncology practice. The medical records were reviewed retrospectively for all patients with UM treated with stereotactic radiosurgery using episcleral fiducials. We report our short-term experience with surgical placement of fiducials, UM localization, treatment outcomes, and optimization approaches.

RESULTS

We evaluated 11 cases of UM (mean age: 65 years; 64% female). The placed fiducials were numbered from 2 to 4, each secured to the sclera with a surgical microscope or surgical loupes and either 5-0 or 8-0 nylon sutures at 50% scleral depth and 3 mm beyond the tumor margin. Over a median follow-up of 11 months (range: 4.2-43.2 months), no recurrences of intraocular UM were observed. One case of enucleation after stereotactic radiosurgery developed because of radiation-related surface irritation, ocular dryness, and secondary keratopathy. Two patients (18%) with 5-0 nylon sutures required fiducial removal because of suture exposure, successfully accomplished in an outpatient setting.

CONCLUSIONS

Fiducials represent a viable alternative to tantalum rings for guiding stereotactic radiotherapy to manage UM and provide additional definition of the tumor border with linear orientation that helps optimize targeted radiation delivery. Fiducial placement with a 3-mm margin from the visible tumor border should not result in clinically important radiation dose attenuation at the tumor margins. Anteriorly placed fiducials may cause discomfort, yet they are easily removed in the outpatient setting.

Real-world efficacy of anti-PD-1 antibody or combined anti-PD-1 plus anti-CTLA-4 antibodies, with or without radiotherapy, in advanced mucosal melanoma patients: A retrospective, multicenter study

BACKGROUND

Immune checkpoint inhibitors (ICIs) have a lower efficacy in mucosal melanoma (MUM) than in cutaneous melanoma. The use of combination treatments with radiotherapy (RT) to improve the efficacy in MUM, however, requires further investigation.

METHODS

We retrospectively evaluated 225 advanced MUM patients treated with anti-PD-1 monotherapy (PD1; 115) or anti-PD-1 + anti-CTLA-4 combination therapy (PD1+CTLA4; 42) with or without RT (56 and 12, respectively). Treatment efficacy was estimated by determining the objective response rate (ORR) and survival rate with the Kaplan-Meier analysis.

RESULTS

The baseline characteristics between the two groups in each ICI cohort were similar, except for Eastern Cooperative Oncology Group performance status in the PD1 cohort. No significant differences in ORR, progression-free survival (PFS), and overall survival (OS) were observed between the PD1 alone and PD1+RT groups in the PD1 cohort (ORR 26% versus 27%, P > 0.99; median PFS 6.2 versus 6.8 months, P = 0.63; median OS 19.2 versus 23.1 months, P = 0.70) or between the PD1+CTLA alone and PD1+CTLA4+RT groups in the PD1+CTLA4 cohort (ORR 28% vs 25%, P = 0.62; median PFS 5.8 versus 3.5 months, P = 0.21; median OS 31.7 versus 19.8 months, P = 0.79). Cox multivariate analysis indicated that RT in addition to PD1 or PD1+CTLA4 did not have a positive impact on the PFS or OS.

CONCLUSIONS

A prolonged survival benefit with RT in combination with ICIs was not identified for advanced MUM patients, although RT may improve local control of the tumour and relieve local symptoms.

Radiation as an In Situ Auto-Vaccination: Current Perspectives and Challenges

Radiotherapy is generally considered to be a local treatment, but there have been reports of rare cases demonstrating abscopal effects in which antitumor effects have been observed in cancer lesions other than the irradiated site. This result is more likely to occur when immune checkpoint inhibitors are used in addition to radiotherapy. Certain radiation-induced chemokines and cytokines have immune-enhancing effects. Immune checkpoint inhibitors may strengthen these effects by stimulating antigen-presenting cells and effector cytotoxic T cells. To date, there is no consensus regarding the applicability of the abscopal effect in the clinical setting, including optimal methods for combining immune checkpoint inhibitors and irradiation. In this review, we highlight the evidence for interactions between cancer immunotherapy and radiotherapy and discuss the potential of such interactions for use in designing novel combination therapies.

Molecular mechanism of bystander effects and related abscopal/cohort effects in cancer therapy

Cancer cells subjected to ionizing radiation may release signals which can influence nearby non-irradiated cells, termed bystander effects. The transmission of bystander effects among cancer cells involves the activation of inflammatory cytokines, death ligands, and reactive oxygen/nitrogen species. In addition to bystander effects, two other forms of non-target effects (NTEs) have been identified in radiotherapy, as one is called cohort effects and the other is called abscopal effects. Cohort effects represent the phenomenon where irradiated cells can produce signals that reduce the survival of neighboring cells within an irradiated volume. The effects suggest the importance of cellular communication under irradiation with non-uniform dose distribution. In contrast, abscopal effects describe the NTEs that typically occur in non-irradiated cells distant from an irradiated target. These effects can be mediated primarily by immune cells such as T cells. Clinical trials have shown that application of radiation along with immunotherapy may enhance abscopal effects and improve therapeutic efficacy on non-target lesions outside an irradiated field. According to NTEs, cell viability is reduced not only by direct irradiation effects, but also due to signals emitted from nearby irradiated cells. A clinical consideration of NTEs could have a revolutionary impact on current radiotherapy via the establishment of more efficient and less toxic radiobiological models for treatment planning compared to conventional models. Thus, we will review the most updated findings about these effects and outline their mechanisms and potential applications in cancer treatment with a special focus on the brain, lung, and breast cancers.