A Novel Radiotherapeutic Approach to Treat Bulky Metastases Even From Cutaneous Squamous Cell Carcinoma: Its Rationale and a Look at the Reliability of the Linear-Quadratic Model to Explain Its Radiobiological Effects

Feasibility of optimal vertex size and spacing for lattice radiotherapy implementation using helical tomotherapy

Purpose

Lattice radiotherapy (LRT), a type of spatially fractionated radiotherapy (SFRT), delivers high dose at specific volumes of lattice structure within the tumor to create a low valley-to-peak dose ratio (VPDR). This study aims to evaluate the feasibility of implementing SFRT using helical tomotherapy and to investigate the effects of vertex size and spacing for attaining the VPDR.

Methods

A three-dimensional lattice structure with 3×3×3 vertices was designed in a cheese phantom. Vertex sizes of 0.5 cm, 1.0 cm, and 2.0 cm were assessed, with spacing from 1.0 cm to 5.0 cm. The prescribed dose was set to 20 Gy to the vertices in a single fraction. VPDR was calculated from dose profiles along lines connecting three vertices in the anterior-posterior (AP), lateral (LAT), and superior-inferior (SI) directions. The minimum, maximum, and mean dose for each vertex, as well as conformity, homogeneity and monitor unit (MU) analysis were also performed.

Results

VPDR decreased significantly with increasing vertex size and spacing. While the AP and LAT directions showed similar VPDR values, the SI direction consistently exhibited lower VPDR values across all configurations. Vertex sizes of 0.5 cm, 1.0 cm, and 2.0 cm required spacing of at least 3.0 cm, 2.0 cm, and 1.0 cm, respectively, to achieve VPDR values below 0.4. The conformity indices ranged from 1.0 to 4.02, and the homogeneity indices ranged from 1.20 to 1.57 across all configurations. Additionally, the MUs increased with both vertex size and spacing.

Conclusions

This study quantitatively analyzed the impact of various vertex sizes and spacings on VPDR in lattice radiotherapy using helical tomotherapy. VPDR decreased with increasing vertex size and spacing, with consistently lower values in the SI direction. These findings provide crucial insights for optimizing LRT plans. The identified relationships between the parameters and VPDR offer a foundation for developing more effective LRT protocols in helical tomotherapy, potentially improving therapeutic outcomes.

Emerging Radiotherapy Technologies for Head and Neck Squamous Cell Carcinoma: Challenges and Opportunities in the Era of Immunotherapy

Radiotherapy (RT) is an integral component in the multidisciplinary management of patients with head and neck squamous cell carcinoma (HNSCC). Significant advances have been made toward optimizing tumor control and toxicity profiles of RT for HNSCC in the past two decades. The development of intensity modulated radiotherapy (IMRT) and concurrent chemotherapy established the standard of care for most patients with locally advanced HNSCC around the turn of the century. More recently, selective dose escalation to the most radioresistant part of tumor and avoidance of the most critical substructures of organs at risk, often guided by functional imaging, allowed even further improvement in the therapeutic ratio of IMRT. Other highly conformal RT modalities, including intensity modulated proton therapy (IMPT) and stereotactic body radiotherapy (SBRT) are being increasingly utilized, although there are gaps in our understanding of the normal tissue complication probabilities and their relative biological effectiveness. There is renewed interest in spatially fractionated radiotherapy (SFRT), such as GRID and LATTICE radiotherapy, in both palliative and definitive settings. The emergence of immune checkpoint inhibitors (ICIs) has revolutionized the treatment of patients with recurrent and metastatic HNSCC. Novel RT modalities, including IMPT, SBRT, and SFRT, have the potential to reduce lymphopenia and immune suppression, stimulate anti-tumor immunity, and synergize with ICIs. The next frontier in the treatment of HNSCC may lie in the exploration of combined modality treatment with new RT technologies and ICIs.

Effectiveness of radiotherapy in delaying treatment changes in primary or secondary immunorefractory oligoprogressive patients: preliminary results from a single-center study

AIMS

To investigate whether the addition of radiotherapy could be an appropriate option to delay the time-to-next systemic treatment (TTNsT) in patients with oligoprogressive solid tumors who had acquired or innate resistance to immune checkpoint inhibitors (ICIs).

MATERIAL AND METHODS

Patients with oligoprogressive disease treated with ICIs and radiotherapy at our Institute from January 2019 to June 2023 were retrospectively identified. Patients were stratified as primary or secondary immunorefractory according to the time of onset of ICI resistance. TTNsT and Time-To-Resistance (TTR) were the primary outcomes. Secondary outcomes included: post-radiotherapy first progression-free survival (pR-PFS), Local Control (LC), Overall Survival (OS), and treatment-related toxicities. In addition, out-of-field effects (such as the abscopal effect) of radiotherapy have been hypothesized. The survival rates were analyzed using the Kaplan-Meier method and long-rank test.

RESULTS

40 out of 105 screened patients with oligoprogressive disease met the inclusion criteria. Of these, 28 had an acquired drug resistance while 12 had an innate drug resistance. Radiotherapy was offered as a local treatment approach in all patients. RT techniques were classified into three regimens: standard palliative hypofractionated radiotherapy (hypo-RT), stereotactic radiotherapy (SRS/SBRT), and lattice radiotherapy (LRT). After a median follow-up of 22.5 months, the median TTR was 4 months (range 3-4) in patients with innate resistance vs 14 months (range 7-36) in patients with acquired resistance. Median TTNsT among patients with acquired and those with innate resistance was not reached (NR) vs 24 months (range 7-72). Overall, only six patients suffered from a local failure. Although out-of-field effects of radiotherapy were hypothesized, we were unable to record them as they did not occur during the observation period. Regardless of the radiation dose, there was no observable ≥ Grade 2 acute or late treatment-related toxicity.

CONCLUSION

Our preliminary results seem to confirm that the integration of radiotherapy and ICIs may allow for the continuation of systemic therapy beyond progression, which can have a subsequent benefit in terms of survival outcomes even in patients with innate resistance.

LatticeOpt: An automatic tool for planning optimisation of spatially fractionated stereotactic body radiotherapy

PURPOSE

Lattice radiotherapy (LRT) is a three dimensional (3D) implementation of spatially fractionated radiation therapy, based on regular spatial distribution of high dose spheres (vertices) inside the target. Due to tumour shape heterogeneity, finding the best lattice arrangement is not trivial. The aim of this study was to develop the LatticeOpt tool to generate the best lattice structures on clinical cases for treatment planning.

METHODS

Developed in MATLAB, LatticeOpt finds the 3D-spatial configurations that maximize the number of vertices within the gross target volume (GTV). If organs at risk (OARs) are considered, it chooses the solution that minimizes the overlapping volume histograms (OVH). Otherwise, the lattice structure with the minimum Hausdorff distance between vertices and GTV boundary is chosen to avoid unpopulated regions. Different lattice structures were created for 20 patients, with (OVHopt) and without (OVHunopt) OVH minimization. Imported into TPS (Eclipse, Varian), corresponding plans were generated and evaluated in terms of OAR mean and maximum doses, GTV vertex coverage and dose gradients, as well as pre-clinical plan dosimetry.

RESULTS

Plans based on an optimized lattice structure (OVHopt, OVHunopt) had similar dose distributions in terms of vertex coverage and gradient index score. OAR sparing was observed in all patients, with a 4 % and 9 % difference for mean and max dose (both p-values <0.01), respectively. The best vertices dimensions and their relative distances were patient dependent.

CONCLUSIONS

LatticeOpt was able to reduce the time-consuming procedures of LRT, as well as to achieve standardized and reproducible results, useful for multicentre studies.

Cutaneous Squamous Cell Carcinoma in Patients with Solid-Organ-Transplant-Associated Immunosuppression

The management of advanced cutaneous squamous cell carcinoma (CSCC) has been revolutionized by the introduction of immunotherapy. Yet, successful treatment with immunotherapy relies on an adequate antitumor immune response. Patients who are solid-organ transplant recipients (SOTRs) have a higher incidence of CSCC compared to the general population. This review discusses the current knowledge of epidemiology, pathophysiology, and management of patients with CSCC who are immunocompromised because of their chronic exposure to immunosuppressive medications to prevent allograft rejection. First, we discuss the prognostic impact of immunosuppression in patients with CSCC. Next, we review the risk of CSCC development in immunosuppressed patients due to SOT. In addition, we provide an overview of the biological immune disruption present in transplanted immunosuppressed CSCC patients. We discuss the available evidence on the use of immunotherapy and provide a framework for the management approach with SOTRs with CSCC. Finally, we discuss potential novel approaches that are being investigated for the management of immunosuppressed patients with CSCC.

The Promising Effects of Lattice Radiotherapy for Large, Fungating, or Ulcerating Breast Cancers: A Prospective Single-center Study

BACKGROUND/AIM

To evaluate the safety and efficacy of lattice radiotherapy (LRT) for large, inoperable breast cancers.

PATIENTS AND METHODS

In this prospective study, patients who underwent LRT for breast tumors that were ulcerating/fungating/extensively eroding the chest wall, and were ineligible/unwilling for surgery, were enrolled from May 2021 to Nov 2023. Baseline Eastern Cooperative Oncology Group (ECOG) status, pre- and post-LRT numerical rating scale (NRS), and post-LRT changes in quality of life (QoL) were recorded. Survival outcomes were reported at 6 months and 1-year. Median rates of survival and dosimetric parameters were calculated. Kaplan-Meier curves for overall survival (OS), cancer-specific survival (CSS), and failure of local control (LC) were constructed.

RESULTS

Ten patients (8 females) underwent LRT. The median age was 76 years (range=57-99 years) and the median ECOG performance status was 2.5 (range=1-4). The planned schedule was completed by 9/10 patients, accounting for a 90% compliance rate. Among patients with pain (n=7), NRS rapidly reduced from 7 (range=5-10) to 3 (range=1-6). The median equivalent uniform dose was 0.71 Gy (0.09-1.59 Gy). The actuarial rates of 6-month LC, CSS, and OS were 75%, 89%, and 61%, respectively, with only LC rate changing to 50% at 1 year. Two patients had local relapse at the six-month and 1-year follow-up, respectively, after having achieved a complete response at three months, and two others died of COVID-19 infection and ischemic stroke.

CONCLUSION

LRT was found to be effective and safe in palliating symptoms among patients with large inoperable breast tumors.

Time-Related Outcome Following Palliative Spatially Fractionated Stereotactic Radiation Therapy (Lattice) of Large Tumors - A Case Series

Purpose

Lattice radiation therapy (LRT), a form of spatially fractionated radiation therapy, holds promise for treating large tumors. Despite its introduction in clinical practice around 2010, there remains limited information on its time-related outcomes despite consistently high response rates and tolerability. We assessed the time-related outcome of our palliative LRT cohort.

Methods and Materials

We conducted an analysis of our LRT program, which involved 45 palliative patients with 56 lesions larger than 7 cm, treated between January 2022 and November 2023. Prospectively defined treatment protocols included delivering 20 to 25 Gy/5 fractions to the tumor with a stereotactic simultaneously integrated boost (SIB) of 60 to 65 Gy to lattice vertices (n = 45/56) or, mainly in preirradiated lesions, single fraction stereotaxy with 1 × 15 to 20 Gy to vertices only (n = 11/56). Follow-up (FU) intervals were determined based on clinical considerations, considering the mostly highly palliative situation of included patients. Outcome assessments focused on subjective benefit and objective radiologic FU response.

Results

The mean/median FU was 5.5/4.0 months (0.3-21 months). A total of 25/45 (56%) patients died after a mean/median of 3.9/2.0 months (0.3-14 months). Fourteen of 56 lesions (25%) were previously irradiated, with a mean/median of 18/13 months (4-72 months) prior to LRT. The mean/median gross tumor volume (GTV) measured 797/415 cc (54-4027 cc) and 14/13 cm (7-28 cm). Subjective statements at LRT completion were available from 37 symptomatic patients: 32/37 (87%) reported fast symptom relief, and 5/37 felt no change under LRT or at LRT completion. Early tolerance was excellent (G0-1). FU imaging was available from 40/56 lesions (71%): progression in 3/40 at first exam one at 1.5 and 4 months post-LRT, and stable disease (±10%) in 5/40 assessed at 2, 3, 3, and 4 months post-LRT. First measure shrinkage of 48%/30% (10%-100%) was found in 32/40 lesions (80%) after a mean/median of 2.8/3 months (0.3-7 months). Maximum shrinkage over time based on 21 cases with at least 1 FU imaging measured a mean/median of 62%/60% after 6.2/5.5 months. The duration of radiologic response was a mean/median of 7.4/7.0 months (1-21 months).

Conclusions

Short-course LRT emerged as an effective and well-tolerated palliative option for very large lesions, whether treatment-naïve or previously irradiated. Nearly 90% of symptomatic patients reported significant subjective benefit, and 80% of assessed lesions demonstrated tumor shrinkage ≥10%, with a mean response duration of >6 months.

The Immunomodulatory Potential of Concurrent High-Dose Radiotherapy and Immune Checkpoint Inhibitor Cemiplimab in Advanced Cutaneous Squamous Cell Carcinoma: Initial Results

In this retrospective case series, we investigate the synergistic effect and the immunomodulatory potential of combination radiotherapy and immunotherapy on 11 patients affected by locally advanced or metastatic cutaneous squamous cell carcinoma (CSCC), treated at our institution between 2020 and 2023. The primary endpoints of this study are objective tumor response, assessed by Immunotherapy Response Evaluation Criteria in Solid Tumors (iRECIST), and time to treatment failure (disease progression). In all patients, surgery was deemed not amenable, due to its potential functional and aesthetic impact. Therefore, upon multidisciplinary agreement, radiotherapy and immunotherapy with cemiplimab were alternatively administered. After 6 months, an early objective tumor response was observed in 9/11 patients, with 17/20 cutaneous lesions (85%) presenting either a complete or partial response. Only 2/11 patients, with a total of 3/20 cutaneous lesions (15%), had stable disease. These benefits persisted at a longer follow-up (21.4 ± 9.7 months), with no patients presenting disease progression. Despite the retrospective nature of this study and small sample size, our experience highlights the ability of concomitant radiotherapy and cemiplimab to promote an early objective response in patients with advanced CSCC. Moreover, in our population, the clinical benefits were also related to a longer progression-free survival, without any safety alert reported.

Mathematical modeling of the synergistic interplay of radiotherapy and immunotherapy in anti-cancer treatments

Introduction

While radiotherapy has long been recognized for its ability to directly ablate cancer cells through necrosis or apoptosis, radiotherapy-induced abscopal effect suggests that its impact extends beyond local tumor destruction thanks to immune response. Cellular proliferation and necrosis have been extensively studied using mathematical models that simulate tumor growth, such as Gompertz law, and the radiation effects, such as the linear-quadratic model. However, the effectiveness of radiotherapy-induced immune responses may vary among patients due to individual differences in radiation sensitivity and other factors.

Methods

We present a novel macroscopic approach designed to quantitatively analyze the intricate dynamics governing the interactions among the immune system, radiotherapy, and tumor progression. Building upon previous research demonstrating the synergistic effects of radiotherapy and immunotherapy in cancer treatment, we provide a comprehensive mathematical framework for understanding the underlying mechanisms driving these interactions.

Results

Our method leverages macroscopic observations and mathematical modeling to capture the overarching dynamics of this interplay, offering valuable insights for optimizing cancer treatment strategies. One shows that Gompertz law can describe therapy effects with two effective parameters. This result permits quantitative data analyses, which give useful indications for the disease progression and clinical decisions.

Discussion

Through validation against diverse data sets from the literature, we demonstrate the reliability and versatility of our approach in predicting the time evolution of the disease and assessing the potential efficacy of radiotherapy-immunotherapy combinations. This further supports the promising potential of the abscopal effect, suggesting that in select cases, depending on tumor size, it may confer full efficacy to radiotherapy.

Computational Approach for Spatially Fractionated Radiation Therapy (SFRT) and Immunological Response in Precision Radiation Therapy

The field of precision radiation therapy has seen remarkable advancements in both experimental and computational methods. Recent literature has introduced various approaches such as Spatially Fractionated Radiation Therapy (SFRT). This unconventional treatment, demanding high-precision radiotherapy, has shown promising clinical outcomes. A comprehensive computational scheme for SFRT, extrapolated from a case report, is proposed. This framework exhibits exceptional flexibility, accommodating diverse initial conditions (shape, inhomogeneity, etc.) and enabling specific choices for sub-volume selection with administrated higher radiation doses. The approach integrates the standard linear quadratic model and, significantly, considers the activation of the immune system due to radiotherapy. This activation enhances the immune response in comparison to the untreated case. We delve into the distinct roles of the native immune system, immune activation by radiation, and post-radiotherapy immunotherapy, discussing their implications for either complete recovery or disease regrowth.

Hypofractionated radiotherapy combined with lenalidomide improves systemic antitumor activity in mouse solid tumor models

Background: Hypofractionated radiotherapy (hRT) can induce a T cell-mediated abscopal effect on non-irradiated tumor lesions, especially in combination with immune checkpoint blockade (ICB). However, clinically, this effect is still rare, and ICB-mediated adverse events are common. Lenalidomide (lena) is an anti-angiogenic and immunomodulatory drug used in the treatment of hematologic malignancies. We here investigated in solid tumor models whether lena can enhance the abscopal effect in double combination with hRT. Methods: In two syngeneic bilateral tumor models (B16-CD133 melanoma and MC38 colon carcinoma), the primary tumor was treated with hRT. Lena was given daily for 3 weeks. Besides tumor size and survival, the dependence of the antitumor effects on CD8+ cells, type-I IFN signaling, and T cell costimulation was determined with depleting or blocking antibodies. Tumor-specific CD8+ T cells were quantified, and their differentiation and effector status were characterized by multicolor flow cytometry using MHC-I tetramers and various antibodies. In addition, dendritic cell (DC)-mediated tumor antigen cross-presentation in vitro and directly ex vivo and the composition of tumor-associated vascular endothelial cells were investigated. Results: In both tumor models, the hRT/lena double combination induced a significant abscopal effect. Control of the non-irradiated secondary tumor and survival were considerably better than with the respective monotherapies. The abscopal effect was strongly dependent on CD8+ cells and associated with an increase in tumor-specific CD8+ T cells in the non-irradiated tumor and its draining lymph nodes. Additionally, we found more tumor-specific T cells with a stem-like (TCF1+ TIM3- PD1+) and a transitory (TCF1- TIM3+ CD101- PD1+) exhausted phenotype and more expressing effector molecules such as GzmB, IFNγ, and TNFα. Moreover, in the non-irradiated tumor, hRT/lena treatment also increased DCs cross-presenting a tumor model antigen. Blocking type-I IFN signaling, which is essential for cross-presentation, completely abrogated the abscopal effect. A gene expression analysis of bone marrow-derived DCs revealed that lena augmented the expression of IFN response genes and genes associated with differentiation, maturation (including CD70, CD83, and CD86), migration to lymph nodes, and T cell activation. Flow cytometry confirmed an increase in CD70+ CD83+ CD86+ DCs in both irradiated and abscopal tumors. Moreover, the hRT/lena-induced abscopal effect was diminished when these costimulatory molecules were blocked simultaneously using antibodies. In line with the enhanced infiltration by DCs and tumor-specific CD8+ T cells, including more stem-like cells, hRT/lena also increased tumor-associated high endothelial cells (TA-HECs) in the non-irradiated tumor. Conclusions: We demonstrate that lena can augment the hRT-induced abscopal effect in mouse solid tumor models in a CD8 T cell- and IFN-I-dependent manner, correlating with enhanced anti-tumor CD8 T cell immunity, DC cross-presentation, and TA-HEC numbers. Our findings may be helpful for the planning of clinical trials in (oligo)metastatic patients.

Development of an automated treatment planning approach for lattice radiation therapy

BACKGROUND

Lattice radiation therapy (LRT) alternates regions of high and low doses within the target. The heterogeneous dose distribution is delivered to a geometrical structure of vertices segmented inside the tumor. LRT is typically used to treat patients with large tumor volumes with cytoreduction intent. Due to the geometric complexity of the target volume and the required dose distribution, LRT treatment planning demands additional resources, which may limit clinical integration.

PURPOSE

We introduce a fully automated method to (1) generate an ordered lattice of vertices with various sizes and center-to-center distances and (2) perform dose optimization and calculation. We aim to report the dosimetry associated with these lattices to help clinical decision-making.

METHODS

Sarcoma cancer patients with tumor volume between 100 cm3 and 1500 cm3 who received radiotherapy treatment between 2010 and 2018 at our institution were considered for inclusion. Automated segmentation and dose optimization/calculation were performed by using the Eclipse Scripting Application Programming Interface (ESAPI, v16, Varian Medical Systems, Palo Alto, USA). Vertices were modeled by spheres segmented within the gross tumor volume (GTV) with 1 cm/1.5 cm/2 cm diameters (LRT-1 cm/1.5 cm/2 cm) and 2 to 5 cm center-to-center distance on square lattices alternating along the superior-inferior direction. Organs at risk were modeled by subtracting the GTV from the body structure (body-GTV). The prescription dose was that 50% of the vertice volume should receive at least 20 Gy in one fraction. The automated dose optimization included three stages. The vertices optimization objectives were refined during optimization according to their values at the end of the first and second stages. Lattices were classified according to a score based on the minimization of body-GTV max dose and the maximization of GTV dose uniformity (measured with the equivalent uniform dose [EUD]), GTV dose heterogeneity (measured with the GTV D90%/D10% ratio), and the number of patients with more than one vertex inserted in the GTV. Plan complexity was measured with the modulation complexity score (MCS). Correlations were assessed with the Spearman correlation coefficient (r) and its associated p-value.

RESULTS

Thirty-three patients with GTV volumes between 150 and 1350 cm3 (median GTV volume = 494 cm3 , IQR = 272-779 cm3 were included. The median time required for segmentation/planning was 1 min/21 min. The number of vertices was strongly correlated with GTV volume in each LRT lattice for each center-to-center distance (r > 0.85, p-values < 0.001 in each case). Lattices with center-to-center distance = 2.5 cm/3 cm/3.5 cm in LRT-1.5 cm and center-to-center distance = 4 cm in LRT-1 cm had the best scores. These lattices were characterized by high heterogeneity (median GTV D90%/D10% between 0.06 and 0.19). The generated plans were moderately complex (median MCS ranged between 0.19 and 0.40).

CONCLUSIONS

The automated LRT planning method allows for the efficacious generation of vertices arranged in an ordered lattice and the refinement of planning objectives during dose optimization, enabling the systematic evaluation of LRT dosimetry from various lattice geometries.

Immune Priming with Spatially Fractionated Radiation Therapy

PURPOSE OF REVIEW

This review aims to summarize the current preclinical and clinical evidence of nontargeted immune effects of spatially fractionated radiation therapy (SFRT). We then highlight strategies to augment the immunomodulatory potential of SFRT in combination with immunotherapy (IT).

RECENT FINDINGS

The response of cancer to IT is limited by primary and acquired immune resistance, and strategies are needed to prime the immune system to increase the efficacy of IT. Radiation therapy can induce immunologic effects and can potentially be used to synergize the effects of IT, although the optimal combination of radiation and IT is largely unknown. SFRT is a novel radiation technique that limits ablative doses to tumor subvolumes, and this highly heterogeneous dose deposition may increase the immune-rich infiltrate within the targeted tumor with enhanced antigen presentation and activated T cells in nonirradiated tumors. The understanding of nontargeted effects of SFRT can contribute to future translational strategies to combine SFRT and IT. Integration of SFRT and IT is an innovative approach to address immune resistance to IT with the overall goal of improving the therapeutic ratio of radiation therapy and increasing the efficacy of IT.

Absolute oxygen-guided radiation therapy improves tumor control in three preclinical tumor models

Background

Clinical attempts to find benefit from specifically targeting and boosting resistant hypoxic tumor subvolumes have been promising but inconclusive. While a first preclinical murine tumor type showed significant improved control with hypoxic tumor boosts, a more thorough investigation of efficacy from boosting hypoxic subvolumes defined by electron paramagnetic resonance oxygen imaging (EPROI) is necessary. The present study confirms improved hypoxic tumor control results in three different tumor types using a clonogenic assay and explores potential confounding experimental conditions.

Materials and methods

Three murine tumor models were used for multi-modal imaging and radiotherapy: MCa-4 mammary adenocarcinomas, SCC7 squamous cell carcinomas, and FSa fibrosarcomas. Registered T2-weighted MRI tumor boundaries, hypoxia defined by EPROI as pO2 ≤ 10 mmHg, and X-RAD 225Cx CT boost boundaries were obtained for all animals. 13 Gy boosts were directed to hypoxic or equal-integral-volume oxygenated tumor regions and monitored for regrowth. Kaplan-Meier survival analysis was used to assess local tumor control probability (LTCP). The Cox proportional hazards model was used to assess the hazard ratio of tumor progression of Hypoxic Boost vs. Oxygenated Boost for each tumor type controlling for experimental confounding variables such as EPROI radiofrequency, tumor volume, hypoxic fraction, and delay between imaging and radiation treatment.

Results

An overall significant increase in LTCP from Hypoxia Boost vs. Oxygenated Boost treatments was observed in the full group of three tumor types (p < 0.0001). The effects of tumor volume and hypoxic fraction on LTCP were dependent on tumor type. The delay between imaging and boost treatments did not have a significant effect on LTCP for all tumor types.

Conclusion

This study confirms that EPROI locates resistant tumor hypoxic regions for radiation boost, increasing clonogenic LTCP, with potential enhanced therapeutic index in three tumor types. Preclinical absolute EPROI may provide correction for clinical hypoxia images using additional clinical physiologic MRI.

The Role of Radiotherapy in the Management of Vaginal Melanoma: A Literature Review with a Focus on the Potential Synergistic Role of Immunotherapy

Among the mucosal melanomas, vaginal melanomas are very rare tumors, accounting for less than 20% of melanomas arising from the female genital tract. They occur most frequently in women in post-menopausal age, but younger patients may also experience this neoplasm, mainly located in the lower third of the vagina or the anterior wall. The optimal management of this tumor remains controversial, with surgery reported as the most frequently adopted approach. However, a clear benefit of surgical treatment in terms of survival has not yet been demonstrated. Conversely, radiotherapy may represent an attractive non-invasive alternative, and there are several favorable reports of the role of radiation therapy, either delivered with photons, brachytherapy, or hadrontherapy. A wide range of techniques and fractionation regimens are reported with substantially good tolerance to the treatment, and acute G3 or higher toxicities are reported only in the case of concurrent immunotherapy. Of note, due to the rarity of the disease, there is a lack of high-level evidence for the optimal therapeutic option. In this scenario, recent studies theorize the possibility of developing combinatorial approaches of radiotherapy with immunotherapy based on cutaneous melanomas reports. In this review, we aim to summarize the evidence available in the literature supporting the role of definitive radiotherapy for vaginal melanomas, with a focus on the combination of RT with immunotherapy, in terms of optimal timing and biological rationale.

Considerations on surgery invasiveness and response and toxicity patterns in classic palliative radiotherapy for acrometastases of the hand: a hint for a potential role of stereotactic body radiation therapy? A case report and literature review

Background

The rarity of hand acrometastases hampers the consensus-building for their optimal management among the involved oncology professionals. In the current literature, demolitive surgery overcomes the use of palliative radiotherapy, which proved to be ineffective in more than 30% of cases treated with classic palliative dose schemes, carrying also a not negligible radiation-related adverse event rate. Against this background, stereotactic body radiation therapy (SBRT) could emerge as a well-balanced therapeutic option.

Case summary

Here we describe the methods and outcomes of a SBRT treatment of a painful and function-limiting hand acrometastasis in a patient with a history of stage IIIB lung adenocarcinoma. We delivered a total dose of 30 Gy in five daily fractions to a soft-tissue metastasis abutting the fifth metacarpal bone through the SBRT protocol generally used for intracranial treatments. A few weeks later, the patient reported a clinical complete response with acrometastasis and pain disappearance, function recovery, and no significant toxicity. The acrometastasis was the first sign of an atypical cancer progression.

Conclusions

SBRT for hand acrometastases is feasible and might have the best therapeutic profile among the currently available treatment options for this rare clinical scenario. Larger investigations are needed to confirm the present single-case experience.

Forecasting Individual Patients' Best Time for Surgery in Colon-Rectal Cancer by Tumor Regression during and after Neoadjuvant Radiochemotherapy

The standard treatment of locally advanced rectal cancer is neoadjuvant chemoradiotherapy before surgery. For those patients experiencing a complete clinical response after the treatment, a watch-and-wait strategy with close monitoring may be practicable. In this respect, the identification of biomarkers of the response to therapy is extremely important. Many mathematical models have been developed or used to describe tumor growth, such as Gompertz's Law and the Logistic Law. Here we show that the parameters of those macroscopic growth laws, obtained by fitting the tumor evolution during and immediately after therapy, are a useful tool for evaluating the best time for surgery in this type of cancer. A limited number of experimental observations of the tumor volume regression, during and after the neoadjuvant doses, permits a reliable evaluation of a specific patient response (partial or complete recovery) for a later time, and one can evaluate a modification of the scheduled treatment, following a watch-and-wait approach or an early or late surgery. Neoadjuvant chemoradiotherapy effects can be quantitatively described by applying Gompertz's Law and the Logistic Law to estimate tumor growth by monitoring patients at regular intervals. We show a quantitative difference in macroscopic parameters between partial and complete response patients, reliable for estimating the treatment effects and best time for surgery.

Introducing Radiotherapy in Metastatic Merkel Cell Carcinoma Patients with Limited Progression on Avelumab: An Effective Step against Primary and Secondary Immune Resistance?

PURPOSE

To investigate the ability of radiotherapy (RT) to prolong progression-free survival (PFS) and to report treatment-related toxicities among oligoprogressive metastatic Merkel cell carcinoma (mMCC) patients on avelumab.

METHODS

We retrospectively collected clinical data on mMCC patients who underwent radiotherapy for limited progression on avelumab. Patients were categorized as primary or secondary immune refractory depending on the time of onset of resistance to immunotherapy (at the first or subsequent follow-up visits after avelumab initiation). Pre- and post-RT PFS were calculated. Overall survival (OS) from the first progression treated with RT was also reported. Radiological responses and toxicities were evaluated according to the irRECIST criteria and RTOG scoring system, respectively.

RESULTS

Eight patients, including five females, with a median age of 75 years, met our inclusion criteria. The median gross tumor and clinical target volumes at first progression on avelumab were 29.85 cc and 236.7 cc, respectively. The treatment sites included lymph node, skin, brain, and spine metastases. Four patients received more than one course of RT. Most patients were treated with palliative radiation doses (mainly 30 Gy in 3 Gy/day fractions). Two patients were treated with stereotactic RT. Five/eight patients were primary immune refractory. The objective response rate at the first post-RT assessment was 75%, whereas no local failure was reported. The median pre-RT PFS was 3 months. The pre-RT PFS was 37.5% at 6 months and 12.5% at 1 year. The median post-RT PFS was not reached. The post-RT PFS was 60% at 6 months and 1 year. The post-RT OS was 85.7% at 1 year and 64.3% at 2 years. No relevant treatment-related toxicity was observed. After a median follow-up of 18.5 months, 6/8 patients are still alive and continuing on avelumab therapy.

CONCLUSIONS

Adding radiotherapy to mMCC patients with limited progression on avelumab seems to be safe and effective in prolonging the successful use of immunotherapy, regardless of the type of immune refractoriness.

Risk of Myelopathy Following Second Local Treatment after Initial Irradiation of Spine Metastasis

Metastatic lesions of the spine occur in up to 40% of cancer patients and are a frequent source of pain and neurologic deficit due to cord compression. Palliative radiotherapy is the main first-intent local treatment in the form of single-fraction radiotherapy or fractionated courses. Reirradiation is a viable option for inoperable patients where spinal decompression is needed but with an increased risk of radiation-induced myelopathy (RM) and subsequent neurologic damage. This review summarizes reported data on local treatment options after initial irradiation in patients with relapsed spine metastasis and key dosimetric correlations between the risk of spinal cord injury and reirradiation technique, total dose, and time between treatments. The Linear Quadratic (LQ) model was used to convert all the published doses into biologically effective doses and normalize them to EQD2. For 3D radiotherapy, authors used cumulative doses from 55.2 Gy2/2 to 65.5 Gy2/2 EQD2 with no cases of RM mentioned. We found little evidence of RM after SBRT in the papers that met our criteria of inclusion, usually at the median reported dose to critical neural tissue around 93.5 Gy2/2. There is a lack of consistency in reporting the spinal cord dose, which leads to difficulty in pooling data.

Neoadjuvant Stereotactic Radiotherapy for Brain Metastases: Systematic Review and Meta-Analysis of the Literature and Ongoing Clinical Trials

Simple Summary

The available treatment strategies for patients with brain metastases remain suboptimal, with current research focused on identifying therapies intended to improve patient outcomes while reducing the risk of treatment-related complications. Several studies have investigated the role of pre-operative neoadjuvant stereotactic radiotherapy, and have proposed it as a valid alternative to post-operative adjuvant stereotactic radiotherapy. The aim of our systematic review was to comprehensively analyze the current literature and ongoing clinical trials evaluating neoadjuvant stereotactic radiotherapy in patients with brain metastases, describing treatment protocols and related outcomes. Early evidence suggests that neoadjuvant stereotactic radiotherapy may offer rates of local control and overall survival comparable to those obtained with adjuvant postoperative SRS, but comparative studies are currently lacking. In addition, neoadjuvant stereotactic radiotherapy shows low rates of post-treatment radiation necrosis and leptomeningeal metastases. Ongoing clinical trials aim to evaluate long-term outcomes in large patient cohorts, with some focused on comparing neoadjuvant stereotactic radiotherapy to adjuvant stereotactic radiosurgery.

Abstract

Background: Brain metastases (BMs) carry a high morbidity and mortality burden. Neoadjuvant stereotactic radiotherapy (NaSRT) has shown promising results. We systematically reviewed the literature on NaSRT for BMs. Methods: PubMed, EMBASE, Scopus, Web-of-Science, Cochrane, and ClinicalTrial.gov were searched following the PRISMA guidelines to include studies and ongoing trials reporting NaSRT for BMs. Indications, protocols, and outcomes were analyzed using indirect random-effect meta-analyses. Results: We included 7 studies comprising 460 patients with 483 BMs, and 13 ongoing trials. Most BMs originated from non-small lung cell carcinoma (41.4%), breast cancer (18.7%) and melanoma (43.6%). Most patients had single-BM (69.8%) located supratentorial (77.8%). Patients were eligible if they had histologically-proven primary tumors and ≤4 synchronous BMs candidate for non-urgent surgery and radiation. Patients with primary tumors clinically responsive to radiotherapy, prior brain radiation, and leptomeningeal metastases were deemed non-eligible. Median planning target volume was 9.9 cm³ (range, 2.9–57.1), and NaSRT was delivered in 1-fraction (90.9%), 5-fraction (4.8%), or 3-fraction (4.3%), with a median biological effective dose of 39.6 Gy10 (range, 35.7–60). Most patients received piecemeal (76.3%) and gross-total (94%) resection after a median of 1-day (range, 1–10) post-NaSRT. Median follow-up was 19.2-months (range, 1–41.3). Actuarial post-treatment rates were 4% (95%CI: 2–6%) for symptomatic radiation necrosis, 15% (95%CI: 12–18%) and 47% (95%CI: 42–52%) for local and distant recurrences, 6% (95%CI: 3–8%) for leptomeningeal metastases, 81% (95%CI: 75–87%) and 59% (95%CI: 54–63%) for 1-year local tumor control and overall survival. Conclusion: NaSRT is effective and safe for BMs. Ongoing trials will provide high-level evidence on long-term post-treatment outcomes, further compared to adjuvant stereotactic radiotherapy.

Impressive Results after "Metabolism-Guided" Lattice Irradiation in Patients Submitted to Palliative Radiation Therapy: Preliminary Results of LATTICE_01 Multicenter Study

Purpose: To evaluate feasibility, toxicities, and clinical response in Stage IV patients treated with palliative “metabolism-guided” lattice technique. Patients and Methods: From June 2020 to December 2021, 30 consecutive clinical stage IV patients with 31 bulky lesions were included in this study. All patients received palliative irradiation consisting of a spatially fractionated high radiation dose delivered in spherical deposits (vertices, Vs) within the bulky disease. The Vs were placed at the edges of tumor areas with different metabolisms at the PET exam following a non-geometric arrangement. Precisely, the Vs overlapped the interfaces between the tumor areas of higher 18F-FDG uptake (>75% SUV max) and areas with lower 18F-FDG uptake. A median dose of 15 Gy/1 fraction (range 10−27 Gy in 1/3 fractions) was delivered to the Vs. Within 7 days after the Vs boost, all the gross tumor volume (GTV) was homogeneously treated with hypo-fractionated radiation therapy (RT). Results: The rate of symptomatic response was 100%, and it was observed immediately after lattice RT delivery in 3/30 patients, while 27/30 patients had a symptomatic response within 8 days from the end of GTV irradiation. Radiation-related acute grade ≥1 toxicities were observed in 6/30 (20%) patients. The rate of overall clinical response was 89%, including 23% of complete remission. The 1-year overall survival rate was 86.4%. Conclusions: “Metabolism-guided” lattice radiotherapy is feasible and well-tolerated, being able to yield very impressive results both in terms of symptom relief and overall clinical response rate in stage IV bulky disease patients. These preliminary results seem to indicate that this kind of therapy could emerge as the best therapeutic option for this patient setting.

A Critical Overview of Predictors of Heart Sparing by Deep-Inspiration-Breath-Hold Irradiation in Left-Sided Breast Cancer Patients

Simple Summary

Adjuvant radiotherapy could damage the heart in left-sided breast cancer patients. The deep-inspiration-breath-hold technique may limit the heart exposure to radiation. As non-beneficiaries exist, there is some need to do an upfront cost-effective selection. Some easy-to-use anatomical predictors may help insiders in the treatment decision. The awareness of such findings may improve the efficiency of practitioners’ workflows.

Abstract

Radiotherapy represents an essential part of the therapeutic algorithm for breast cancer patients after conservative surgery. The treatment of left-sided tumors has been associated with a non-negligible risk of developing late-onset cardiovascular disease. The cardiac risk perception has especially increased over the last years due to the prolongation of patients’ survival owing to the advent of new drugs and an ever earlier cancer detection through screening programs. Improvements in radiation delivery techniques could reduce the treatment-related heart toxicity. The deep-inspiration-breath-hold (DIBH) irradiation is one of the most advanced treatment approaches, which requires specific technical equipment and uses inspiration to displace the heart from the tangential radiation fields. However, not all patients benefit from its use. Moreover, DIBH irradiation needs patient compliance and accurate training. Therefore, such a technique may be unjustifiably cumbersome and time-consuming as well as unnecessarily expensive from a mere healthcare cost point of view. Hence the need to early select only the true beneficiaries while tailoring more effective heart-sparing techniques for the others and streamlining the workflow, especially in high-volume radiation oncology departments. In this literature overview, we collected some possible predictors of cardiac dose sparing in DIBH irradiation for left breast treatment in an effort to provide an easy-to-consult summary of simple instruments to insiders for identifying patients actually benefitting from this technique. We critically reviewed the reliability and weaknesses of each retrieved finding, aiming to inspire new insights and discussions on this much-debated topic.

The Palliative Care in the Metastatic Spinal Tumors. A Systematic Review on the Radiotherapy and Surgical Perspective

Spine represents the most common site for metastatic disease involvement. Due to the close relationship between the spinal cord and critical structures, therapeutical management of metastatic spinal cord disease remains challenging. Spinal localization can lead to neurological sequelae, which can significantly affect the quality of life in patients with a limited life expectancy. The authors conducted a systematic literature review according to PRISMA guidelines in order to determine the impact of the most updated palliative care on spinal metastases. The initial literature search retrieved 2526 articles, manually screened based on detailed exclusion criteria. Finally, 65 studies met the inclusion criteria and were finally included in the systematic review. In the wide scenario of palliative care, nowadays, recent medical or surgical treatments represent valuable options for ameliorating pain and improving patients QoL in such this condition.

Advanced or Metastatic Cutaneous Squamous Cell Carcinoma: The Current and Future Role of Radiation Therapy in the Era of Immunotherapy

Radiation therapy (RT) is an effective therapeutic option for small localized cutaneous squamous cell carcinoma (cSCC) among patients who are not eligible for or refuse surgery. RT also has a defined role as an adjuvant treatment in cases of adverse features that predispose to tumor recurrence after local excision. Since the development of cSCC is often a late consequence of chronic sun exposure, its occurrence is more common among elderly patients whose comorbidities may contraindicate surgical procedures. These could be impeded not only by frail medical conditions but also by technical issues. Indeed, an aggressive locoregional behavior of cSCC may culminate in unresectability due to widespread invasion of neighboring tissues. Moreover, cSCC could develop distant metastases. Both locally advanced and metastatic cSCCs carry a poor prognosis. In these scenarios, recent discoveries of tumor molecular targets are promoting the use of promising systemic therapies, especially immunotherapy, over RT. However, the results from using immunotherapy and, even more so, of chemotherapy are still not optimal. By contrast, advances in radiation delivery equipment can safely treat even large and complex-shaped cSCC targets in challenging body sites. In addition, RT could also have a role in metastatic cSCC settings by enhancing the effectiveness of concomitant immunotherapy. The aim of this review is to summarize and comment on the body of literature about the use of radiotherapy for operable and inoperable locally advanced cSCCs and for metastatic ones in an attempt to define its current and future role.

Tumor Volume Regression during and after Radiochemotherapy: A Macroscopic Description

Tumor volume regression during and after chemo and radio therapy is a useful information for clinical decisions. Indeed, a quantitative, patient oriented, description of the response to treatment can guide towards the modification of the scheduled doses or the evaluation of the best time for surgery. We propose a macroscopic algorithm which permits to follow quantitatively the time evolution of the tumor volume during and after radiochemotherapy. The method, initially validated with different cell-lines implanted in mice, is then successfully applied to the available data for partially responding and complete recovery patients.