Synergies Radiotherapy-Immunotherapy in Head and Neck Cancers. A New Concept for Radiotherapy Target Volumes-"Immunological Dose Painting"

Immunotherapy with PD-1 Inhibitor Nivolumab in Recurrent/Metastatic Platinum Refractory Head and Neck Cancers-Early Experiences from Romania and Literature Review

Prognosis in recurrent/metastatic head and neck squamous-cell carcinoma (HNSCC) refractory to platinum-based chemotherapy is poor, making therapy optimization a priority. Anti-programmed cell death protein 1 (anti-PD-1) monoclonal antibody Nivolumab was approved in such cases. We present the early experience with Nivolumab immunotherapy at three cancer clinics from south and northeast Romania, aiming to describe the main characteristics and outcomes relative to literature reports, and to suggest patient selection criteria. Diagnostic, clinical, biological, therapeutic, and outcomes-related data from January 2020 until March 2023 were analyzed retrospectively. Eighteen patients with platinum refractory HNSCC (85.7% men, median age 58.9) were administered Nivolumab for 1-14 months (median 5.6 months) in addition to other treatments (surgery, radiotherapy, chemotherapy), and monitored for up to 25 months. Median neutrophil-to-lymphocyte ratio (NLR) ranged from 2.72 initially to 6.01 during treatment. Overall survival (OS) was 16 months, and patients who died early had the sharpest NLR increases (13.07/month). There were no severe immune-related adverse events. Lower NLR values and combined intensive chemotherapy, radiotherapy, and immunotherapy were related to better outcomes. To our knowledge, we also report the first two cases of second primary malignancy (SPM) in the head and neck region treated with Nivolumab in Romania (for which the sequential administration of radiotherapy and immunotherapy seems better). The work of other Romanian authors on the role of HPV status in HNC is also discussed. Multi-center trials are needed in order to investigate and confirm these observations.

Safety and potential increased risk of toxicity of radiotherapy combined immunotherapy strategy

Accumulating interest has emerged in exploring the toxicity profiles of the combination strategy of radiotherapy (RT) and immune checkpoint inhibitors (ICIs). Much remains unknown regarding safety and the potential increased risk of toxicity of a combined treatment. ICI prolongs survival but can induce immune-related adverse events as well. To increase awareness of adverse effect and support immediate and successful management, we go over the literature on the safety of RT combined immunotherapy strategy. Representative evidence relevant to RT combined with ICI in the brain, lung, head and neck, and pelvic malignance was reviewed respectively. Given radiation doses and fractionation, the irradiated volume, the timing of RT, and ICI would significantly affect the safety and efficiency of ICI+RT combination therapy, and no consensus had been reached about how to arrange RT delivery in the combined contexture, we went over the available literature and tried to address these challenges including the timing of RT, optimal dose and fractionations, RT target and target volume, and potential biomarkers to predict toxicity. We found even though RT+ICI combination therapy might augment toxicities, the majority of patients experienced grade 4 or 5 AE are relatively rare and no significant difference could be found between combination group and monotherapy group. Sometimes the acute toxicity with ICI is much less predictable and often life threatening and in some can give rise to permanent effects. Clinicians across disciplines should be aware of these uncommon lethal complications induced by ICI+RT. Early recognition is the key to successful treatment, reversibility of organ dysfunction, and in some cases even prevention of fatal outcome. If recognized early, managed properly, and no fatal AE occurs, the development of irAE indicates a good prognosis. It should be noted that nothing is known about potential late effects because very few studies have 5-year follow-up. The nature of irAE is the attack of activated immune cells on normal tissues. The nature of RT-induced AE is the DNA damage on normal tissue, which is related with the dose delivered and volume irradiated and the tolerance of surrounding normal tissues. The immune-modulating effect of SBRT may augment the damage on normal tissues. To maximize the antitumor immune response, 8-12 Gy/fraction is preferred when conducting RT. The available clinical evidence suggest RT of this dose/fractionated strategy combined with ICI have a tolerable AE profile, which need further validation by more clinical trials in the future. The combination strategy of RT with anti-PD1/PDL1 anti-body is supposed to be concurrent or RT followed by anti-PD1/PDL1 antibody. Although RT and ipilimumab combination sequence is controversial, ipilimumab prior to or concurrent with RT might be proper, which need more clinical validation. Under the concept of immunological dose painting, SBRT work as a trigger of immune response. It has been observed that SBRT of partially radiated tumors combined with ICI could induce similar tumor control compared with total tumor irradiation. The side effects of RT may be mitigated potentially due to the reduction of irradiated volume. The antitumor efficiency and safety profile of immunological RT dose painting+ICI deserve further investigation. Clinical predictive factors for irAE risk remain unclear, and more investigation deserves to be conducted about the irAE prediction.

p53 Modulates Radiosensitivity in Head and Neck Cancers-From Classic to Future Horizons

p53, initially considered a tumor suppressor, has been the subject of research related to cancer treatment resistance in the last 30 years. The unfavorable response to multimodal therapy and the higher recurrence rate, despite an aggressive approach, make HNSCC a research topic of interest for improving therapeutic outcomes, even if it is only the sixth most common malignancy worldwide. New advances in molecular biology and genetics include the involvement of miRNA in the control of the p53 pathway, the understanding of mechanisms such as gain/loss of function, and the development of different methods to restore p53 function, especially for HPV-negative cases. The different ratio between mutant p53 status in the primary tumor and distant metastasis originating HNSCC may serve to select the best therapeutic target for activating an abscopal effect by radiotherapy as a "booster" of the immune system. P53 may also be a key player in choosing radiotherapy fractionation regimens. Targeting any pathway involving p53, including tumor metabolism, in particular the Warburg effect, could modulate the radiosensitivity and chemo-sensitivity of head and neck cancers.

Immunotherapy and Radiotherapy as an Antitumoral Long-Range Weapon-A Partnership with Unsolved Challenges: Dose, Fractionation, Volumes, Therapeutic Sequence

Immunotherapy, the modern oncological treatment with immune checkpoint inhibitors (ICIs), has been part of the clinical practice for malignant melanoma for more than a decade. Anti-cytotoxic T-lymphocyte antigen 4 (CTLA4), anti-programmed cell death Protein 1 (PD-1), or anti programmed death-ligand 1 (PD-L1) agents are currently part of the therapeutic arsenal of metastatic or relapsed disease in numerous cancers; more recently, they have also been evaluated and validated as consolidation therapy in the advanced local stage. The combination with radiotherapy, a treatment historically considered loco-regional, changes the paradigm, offering-via synergistic effects-the potential to increase immune-mediated tumor destruction. However, the fragile balance between the tumoricidal effects through immune mechanisms and the immunosuppression induced by radiotherapy means that, in the absence of ICI, the immune-mediated potentiation effect of radiotherapy at a distance from the site of administration is rare. Through analysis of the preclinical and clinical data, especially the evidence from the PACIFIC clinical trial, we can consider that hypofractionated irradiation and reduction of the irradiated volume, in order to protect the immune-infiltrated tumor microenvironment, performed concurrently with the immunotherapy or a maximum of 2 weeks before the start of ICI treatment, could bring maximum benefits. In addition, avoiding radiation-induced lymphopenia (RILD) by protecting some anatomical lymphoid structures or large blood vessels, as well as the use of irradiation of partial tumor volumes, even in plurimetastatic disease, for the conversion of a "cold" immunological tumor into a "hot" immunological tumor are modern concepts of radiotherapy in the era of immunotherapy. Low-dose radiotherapy could also be proposed in plurimetastatic cases, the effect being different (modeling of the TME) from that of high doses per fraction irradiation (cell death with release of antigens that facilitates immune-mediated cell death).