Abscopal Response in Irradiated Patients: Results of a Proof of Principle Trial

Advances in non and minimal-invasive transcutaneous delivery of immunotherapy for cancer treatment

Cancer research has focused on figuring out what was the difference between cancer cells and the tissues within which cancer arose and developing targeted treatments for those differences. With FDA-approved treatments for more ten different cancers and more than thousand new clinical trials, immunotherapy has recently emerged as the most promising area of cancer research by improving efficacy and controlling the adverse effects. Transcutaneous delivery drug delivery offers a number of advantages for the patient because of not only its noninvasive and convenient nature but also factors such as avoidance of first-pass metabolism and prevention of gastrointestinal degradation. The purpose of this review was to highlight technological recent approaches to non and minimal-invasive delivery of immunotherapy for cancer treatment. Finally, some practical considerations and discussions for future studies in the field of transdermal immunomodulation are also included.

The immunology of ablative radiation

Radiation has been a staple of cancer therapy since the early 20th century and is implemented in nearly half of current cancer treatment plans. Originally, the genotoxic function of radiation led to a focus on damage and repair pathways associated with deoxyribonucleic acid as important therapeutic targets to augment radiation efficacy. However, in recent decades, the participation of endogenous immune responses in modifying radiation effects have been widely documented and exploited in both preclinical and clinical settings. In particular, preclinical studies have highlighted the capacity of hypofractionated-radiation dose schedules to modify endogenous immune responses raising interest in the use of hypofractionation in the clinical setting to harness the indirect immune effects of radiation and improve clinical responses. We review the current literature regarding the immunomodulatory effects of hypofractionated "ablative" radiation with a primary focus on the preclinical literature but also highlight examples from the clinical literature.

Present and future of immune checkpoint blockade: Monotherapy to adjuvant approaches

Immune regulation of aggressive tumor growth is often outpaced by tumor up-regulation of ligands that inhibit effector immune responses through the activation of immune checkpoints. A few of such checkpoints include programmed death-1 (PD-1), cytotoxic T lymphocyte associated antigen-4 (CTLA-4), lymphocyte activation gene-3, T-cell immunoglobulin and mucin protein-3, Glucocorticoid-induced TNFR family-related receptor (GITR), and killer cell immunoglobulin like receptor. With the exception of GITR, after binding to their respective ligands these checkpoints induce down-modulation of immune responses to prevent autoimmunity. However, such immune mechanisms are co-opted by tumors to allow rapid tumor cell proliferation. Pre-clinical studies in antibody blockade of PD-1 and CTLA-4 have led to promising augmentation of effector immune responses in murine tumor models, and human antibodies against PD-1 and CTLA-4 alone or in combination have demonstrated tumor regression in clinical trials. The development of immune checkpoint blockade as a potential future immunotherapy has led to increasing interest in combining treatment modalities. Combination checkpoint blockade with chemotherapy and radiation therapy has shown synergistic effects in pre-clinical and clinical studies, and combination checkpoint blockade with bacterial vaccine vectors have produced increased effector immune responses in pre-clinical models. The future of immune checkpoint blockade may be as a powerful adjuvant alongside the current standard of care.

Surgery or ablative radiotherapy for breast cancer oligometastases

Precisely focused radiation or surgical resection of limited metastases resulted in long-term disease control and survival in multiple studies of patients with oligometastatic breast cancer. The integration of these ablative techniques into standard systemic therapy regimens has the potential to be paradigm shifting, leaving many patients without evidence of disease. Although an attractive treatment option, the utility of these therapies have not been proven in controlled studies, and improved outcomes may be because of patient selection or favorable biology alone. Ongoing studies continue to refine radiation techniques and determine the role for ablative therapies in the management of patients with metastatic breast cancer (MBC). Additionally, patient selection for metastasis-directed therapies is based on clinical criteria, with many not benefiting from therapies that may have substantial toxicities. Recent reports are beginning to uncover the biology of oligometastatic cancer, but much work is needed. Current and developing trials that integrate both clinical and translational endpoints have the potential to transform management strategies in women with limited MBC.

The role of surgery and ablative radiotherapy in oligometastatic breast cancer

The ability to deliver precise focused radiation, combined with improved surgical techniques, has led to multiple reports of long-term survivors in patients with oligometastatic breast cancer. The removal or ablation of known metastases, often present after systemic therapy regimens has the potential to be paradigm shifting rendering many patients without evidence of disease. However, the utility of these therapies has not been proven in phase III studies. Additionally, patient selection for metastasis-directed therapies is based on clinical criteria, with many patients not benefiting from these therapies. Refinements of radiation techniques are continuing, and discoveries are uncovering the biology of breast cancer in the oligometastatic state among patients. Integrated into ongoing studies, and those in development, they have the potential to alter standard management strategies in oligometastatic patients.

Radical irradiation of extracranial oligometastases

Advances in radiotherapy planning and delivery have been used to treat patients with limited metastatic disease. With these techniques, high rates of treated metastasis control and low toxicity have been reported. Some patients have long disease-free intervals after radiotherapy similar to those seen after surgical resection. Ongoing studies will determine the benefit of these irradiation techniques to treat limited metastases, identify appropriate candidates, and assist in integrating these treatments into management strategies for specific diseases.

Oligometastases treated with stereotactic body radiotherapy: long-term follow-up of prospective study

PURPOSE

To analyze the long-term survival and tumor control outcomes after stereotactic body radiotherapy (SBRT) for metastases limited in number and extent.

METHODS AND MATERIALS

We prospectively analyzed the long-term overall survival (OS) and cancer control outcomes of 121 patients with five or fewer clinically detectable metastases, from any primary site, metastatic to one to three organ sites, and treated with SBRT. Freedom from widespread distant metastasis (FFDM) was defined as metastatic disease not amenable to local therapy (i.e., resection or SBRT). Prognostic variables were assessed using log-rank and Cox regression analyses.

RESULTS

For breast cancer patients, the median follow-up was 4.5 years (7.1 years for 16 of 39 patients alive at the last follow-up visit). The 2-year OS, FFDM, and local control (LC) rate was 74%, 52%, and 87%, respectively. The 6-year OS, FFDM, and LC rate was 47%, 36%, and 87%, respectively. From the multivariate analyses, the variables of bone metastases (p = .057) and one vs. more than one metastasis (p = .055) were associated with a fourfold and threefold reduced hazard of death, respectively. None of the 17 bone lesions from breast cancer recurred after SBRT vs. 10 of 68 lesions from other organs that recurred (p = .095). For patients with nonbreast cancers, the median follow-up was 1.7 years (7.3 years for 7 of 82 patients alive at the last follow-up visit). The 2-year OS, FFDM, and LC rate was 39%, 28%, and 74%, respectively. The 6-year OS, FFDM, and LC rate was 9%, 13%, and 65%, respectively. For nonbreast cancers, a greater SBRT target volume was significantly adverse for OS (p = .012) and lesion LC (p < .0001). Patients whose metastatic lesions, before SBRT, demonstrated radiographic progression after systemic therapy experienced significantly worse OS compared with patients with stable or regressing disease.

CONCLUSIONS

Select patients with limited metastases treated with SBRT are long-term survivors. Future research should address the therapeutic benefit of SBRT for these patients.

Systemic effects of local radiotherapy

Radiotherapy is generally used to treat a localised target that includes cancer. Increasingly, evidence indicates that radiotherapy recruits biological effectors outside the treatment field and has systemic effects. We discuss the implications of such effects and the role of the immune system in standard cytotoxic treatments. Because the effects of chemotherapy and radiotherapy are sensed by the immune system, their combination with immunotherapy presents a new therapeutic opportunity. Radiotherapy directly interferes with the primary tumour and possibly reverses some immunosuppressive barriers within the tumour microenvironment-ideally, recovering the role of the primary tumour as an immunogenic hub. Local radiation also triggers systemic effects that can be used in combination with immunotherapy to induce responses outside the radiation field.