Local treatment in initially unresected non-rhabdomyosarcoma soft-tissue sarcomas of children and adolescents: A retrospective single-center experience.

BACKGROUND: Pediatric non-rhabdomyosarcoma soft-tissue sarcomas (NRSTS) are a heterogeneous group of aggressive tumors. Patients with locally advanced/initially unresected disease represent a subset of patients with unsatisfactory outcome: limited data are available on the best treatment approach, in particular regarding local therapy. METHODS: This retrospective analysis concerned 71 patients < 21 years old with nonmetastatic, initially unresected adult-type NRSTS, treated at a referral center for pediatric sarcomas from 1990 to 2021. Patients were treated using a multimodal approach, based on the protocols adopted at the time of their diagnosis. RESULTS: The series included a selected group of patients with unfavorable clinical characteristics, i.e., most cases had high-grade and large tumors, arising from axial sites in 61% of cases. All patients received neoadjuvant chemotherapy, 58 (82%) had delayed surgery (R0 in 45 cases), and 50 (70%) had radiotherapy. Partial response to chemotherapy was observed in 46% of cases. With a median follow-up of 152 months (range, 18-233), 5-year event-free survival (EFS) and overall survival (OS) were 39.9% and 56.5%, respectively. Survival was significantly better for patients who responded to chemotherapy, and those who had a delayed R0 resection. Local relapse at 5 years was 7.7% for patients who did not undergo delayed surgery. CONCLUSIONS: Our series underscores the unsatisfactory outcome of initially unresected NRSTS patients. Improving the outcome of this patient category requires therapeutic strategies able to combine novel effective systemic therapies with a better-defined local treatment approach to offer patients the best chances to have R0 surgery.

Treatment at relapse for synovial sarcoma of children and adolescents: A multi-institutional European retrospective analysis.

PURPOSE: Though the prognosis for pediatric patients with localised synovial sarcoma (SS) is generally good, the chances of being cured after relapse are limited. This study describes a retrospective multi-institutional series of relapsing SS patients treated at six selected European referral centers for pediatric sarcoma. PATIENTS AND METHODS: The study included 41 patients <21 years with relapsing SS, treated between 2002 and 2022. The analysis included patient's characteristics at first diagnosis, first-line treatments, clinical findings at relapse, and second-line treatment modalities. RESULTS: The first relapse occurred within 3-132 months (median 18 months) after first diagnosis and was local in 34%, metastatic in 54%, and both in 12%. Treatment at first relapse included surgery in 56% of cases, radiotherapy in 34%, and systemic therapy in 88%. In all, 36 patients received second-line medical treatment, that was chemotherapy in 32 cases (with 10 different regimens) and targeted therapy in four. No patient was included in an early-phase clinical trial as second-line therapy-line therapy. Overall response rate was 42%. Median event-free survival (EFS) was 12 months, postrelapse 5-year EFS was 15.8%. Median overall survival (OS) was 30 months, postrelapse 5-year OS was 22.2%. At the Cox's multivariable regression analysis, OS was significantly associated with time and type of relapse. CONCLUSION: Pediatric patients with relapsed SS have a poor prognosis and generally receive an individualized approach, due to the lack of a uniform standardized approach. New comprehensive strategies are needed to improve the knowledge on the biologic landscape of SS and develop tailored prospective clinical trials.

Optimizing reirradiation for relapsed medulloblastoma: identifying the ideal patient and tumor profiles.

BACKGROUND: First-line therapies for medulloblastoma(MBL) are obtaining higher survival-rates while decreasing late-effects, but treatment at relapse is not standardized. We report here the experience with MBL re-irradiation(re-RT), its timing and outcome in different clinical settings and tumor groups. METHODS: Patient's staging/treatment at diagnosis, histotypes/molecular subgroups, relapse site/s, re-treatments outcome are reported. RESULTS: 25 patients were included, with a median age of 11.4 years; 8 had metastases. According to 2016-2021 WHO-classification, 14 had SHH subgroup tumors(six TP53 mutated,one + MYC,one + NMYC amplification), 11 non-WNT/non-SHH (two with MYC/MYCN amplification).Thirteen had received HART-CSI, 11 standard-CSI, one HFRT; all post-radiation chemotherapy(CT), 16 also pre-RT. Median time to relapse (local-LR in nine, distant-DR in 14, LR + DR in two) was 26 months. Fourteen patients were re-operated, in five cases excising single DR-sites, thereafter three received CT, two after re-RT; out of 11 patients not re-operated, four had re-RT as first treatment and seven after CT. Re-RT was administered at median 32 months after first RT: focally in 20 cases, craniospinal-CSI in five. Median post-relapse-PFS/after re-RT was 16.7/8.2 months, while overall survival-OS was 35.1/23.9 months, respectively. Metastatic status both at diagnosis/relapse negatively affected outcome and re-surgery was prognostically favorable. PD after re-RT was however significantly more frequent in SHH (with a suggestive association with TP53 mutation, p = 0.050). We did not observe any influence of biological subgroups on PFS from recurrence while SHH showed apparently worse OS compared to non-WNT/non-SHH group. CONCLUSIONS: Re-surgery + reRT can prolong survival; a substantial fraction of patients with worse outcome belongs to the SHH-subgroup.

Relapse after non-metastatic rhabdomyosarcoma: The impact of routine surveillance imaging on early detection and post-relapse survival.

BACKGROUND: Patients with rhabdomyosarcoma (RMS) whose disease relapses have little chance of being cured, so front-line treatments are usually followed up with surveillance imaging in an effort to detect any recurrences as early as possible, and thereby improve post-relapse outcomes. The real benefit of such routine surveillance imaging in RMS remains to be demonstrated, however. This retrospective, single-center study examines how well surveillance imaging identifies recurrent tumors and its impact on post-relapse survival. METHODS: The analysis concerned 79 patients <21 years old treated between 1985 and 2020 whose initially localized RMS relapsed. Clinical findings, treatment modalities, and survival were analyzed, comparing patients whose relapse was first suspected from symptoms they developed (clinical symptoms group) with those whose relapse was identified by radiological surveillance (routine imaging group). RESULTS: Tumor relapses came to light because of clinical symptoms in 42 cases, and on routine imaging in 37. The time to relapse was much the same in the two groups. The median overall survival (OS) and 5-year OS rate were, respectively, 10 months and 12.6% in the clinical symptoms group, and 11 months and 27.5% in the routine imaging group (p-value .327). Among patients with favorable prognostic scores, survival was better for those in the routine imaging group (5-year OS 75.0% vs. 33.0%, p-value .047). CONCLUSION: It remains doubtful whether surveillance imaging has any real impact on RMS relapse detection and patients' post-relapse survival. Further studies are needed to establish the most appropriate follow-up recommendations, taking the potentially negative effects of regular radiological exams into account.

Relapse after nonmetastatic rhabdomyosarcoma: Salvage rates and prognostic variables.

BACKGROUND: Patients with relapsing rhabdomyosarcoma (RMS) pose a therapeutic challenge, and the survival rate is reportedly poor. We describe a retrospective series of relapsing RMS patients treated at a referral center for pediatric sarcoma, investigating the pattern of relapse, salvage rates, and factors correlating with final outcomes. METHODS: The analysis concerned 105 patients <21 years old treated from 1985 to 2020 with initially localized RMS at first relapse. For risk-adapted stratification purposes, patient outcomes were examined using univariable and multivariable analyses based on patients' clinical features at first diagnosis, first-line treatments, clinical findings at first relapse, and second-line treatments. RESULTS: First relapses occurred 0.08-4.8 years (median 1 year) following initial diagnosis and were local/locoregional in 59% of cases. Treatment at first relapse included chemotherapy in all but two cases, radiotherapy in 38, and surgery in 21. Median event-free survival (EFS) after first relapse was 4 months, while 5-year EFS was 16.3%; median overall survival (OS) was 9 months, while 5-year OS was 16.7%. Several variables influenced survival rates. Considering only clinical findings and treatment at relapse, Cox's multivariable analysis showed that OS correlated significantly with time to relapse, radiotherapy administered at relapse, response to chemotherapy, and whether a second remission was achieved. CONCLUSION: Survival following first relapse of patients with localized RMS at initial diagnosis is poor. The variables found to influence survival can be utilized in a risk-adapted model to estimate the chances of salvage to guide decisions for second-line treatments.

Secondary osteosarcoma: a challenge indeed.

BACKGROUND: The risk of survivors developing a secondary bone sarcoma after being treated for pediatric cancers is well established. The aim of this study was to examine the clinical characteristics and outcomes of patients with secondary osteosarcoma (SOS). METHODS: The study concerns survivors of childhood and adolescence primary neoplasms (PN) treated with chemotherapy, with or without radiotherapy and surgery, subsequently diagnosed with SOS. RESULTS: We identified 26 patients (13 females, 13 males) who developed SOS a median 7.3 years after being diagnosed with a PN (5/7 of these patients tested for Li-Fraumeni and found positive for the syndrome). The sample's median age was 8.0 and 15.0 years when their PN and SOS were diagnosed, respectively. To treat their PN, 24 out of 26 patients had been given radiotherapy, and 19 had received chemotherapy including doxorubicin. A considerable number of SOS occurred at unfavorable sites (nine hip bone, six skull). All but one patient received chemotherapy with tailored schedules, omitting doxorubicin in 19 cases. Eighteen of the 26 patients underwent surgery. The 5- and 10-year overall survival and probabilities after the diagnosis of SOS (95% confidence interval) were 50% (32.7-76.5%) and 38.9% (22.4-67.4%); 5- and 10-year progression-free survival was 47% (29.9-73.7%) and 35.2% (19.3-64.4%), respectively. CONCLUSIONS: The survival rates after SOS are lower than in patients with primary osteosarcoma, but not negligible. It is therefore mandatory to discuss the best choice of treatment for such patients at a referral center, in terms of their chances of cure and quality of life.

How ten-years of reirradiation for paediatric high-grade glioma may shed light on first line treatment.

PURPOSE: Recurrence incidence for paediatric/adolescent high-grade glioma (HGG) exceeds 80%. Reirradiation (reRT) palliates symptoms and delays further progression. Strategies for reRT are scarce: we retrospectively analysed our series to develop rational future approaches. METHODS: We re-evaluated MRI + RT plans of 21 relapsed HGG-patients, accrued 2010-2021, aged under 18 years. All underwent surgery and RT + chemotherapy at diagnosis. Pathologic/molecular re-evaluation allowed classification based on WHO 2021 criteria in 20/21 patients. Survival analyses and association with clinical parameters were performed. RESULTS: Relapse after 1st RT was local in 12 (7 marginal), 4 disseminated, 5 local + disseminated. Re-RT obtained 8 SD, 1 PR, 1PsPD, 1 mixed response, 10 PD; neurological signs/symptoms improved in 8. Local reRT was given to 12, followed again by 6 local (2 marginal) and 4 local + disseminated second relapses in 10/12 re-evaluated. The 4 with dissemination had 1 whole brain, 2 craniospinal irradiation (CSI), 1 spine reRT and further relapsed with dissemination and local + dissemination in 3/four assessed. Five local + disseminated tumours had 3 CSI, 1 spine reRT, further progressing locally (2), disseminated (1), n.a. (1). Three had a third RT; three were alive at 19.4, 29, 50.3 months after diagnosis. Median times to progression/survival after re-RT were 3.7 months (0.6-16.2 months)/6.9 months (0.6-17.9 months), improved for longer interval between 1st RT and re-RT (P = 0.017) and for non-PD after reRT (P < 0.001). First marginal relapse showed potential association with dissemination after re-RT (P = 0.081). CONCLUSIONS: This is the biggest series of re-RT in paediatric HGG. Considering the dissemination observed at relapse, our results could prompt the investigation of different first RT fields in a randomized trial.

Metastatic rhabdomyosarcoma: Evidence of the impact of radiotherapy on survival. A retrospective single-center experience.

BACKGROUND: The prognosis for patients with metastatic rhabdomyosarcoma (RMS) remains largely unsatisfactory despite the adoption of intensive multimodal therapy. To assess the role of different treatments adopted over the years, we retrospectively analyzed a cohort of patients <21 years old with metastatic RMS, treated from 1990 to 2020 at a referral center for pediatric sarcomas. METHODS: Patients were treated using a multimodal approach that included surgery, radiotherapy, and chemotherapy (both high-dose chemotherapy and maintenance therapy in some cases). The type of radiotherapy administered was categorized as radical (to all sites of disease); partial (to at least one, but not all sites of disease); or none. A landmark analysis was used to examine the impact of radiotherapy on survival, that is, patients who had an event before day 221 were excluded from the analysis. RESULTS: The series included 80 patients. Event-free survival (EFS) and overall survival (OS) rates at 5 years were 17.3% and 21.3%, respectively. Survival was significantly associated with radiotherapy to metastatic sites, and with the radiotherapy category. In particular, 5-year EFS and OS rates were 70.6% and 76.0% for patients given radical radiotherapy, and 4.8% and 10.7%, respectively, for those given partial radiotherapy or none. Using the Cox multivariable analysis, OS correlated significantly with radiotherapy category. CONCLUSIONS: While confirming the poor overall outcome of patients with metastatic RMS, this study identified radiotherapy-when given to all sites of disease (including metastases)-as the main variable influencing survival.

Proton beam versus photon beam dose to the heart and left anterior descending artery for left-sided breast cancer.

PURPOSE: The purpose of this study was to compare the dose to heart, left anterior descending (LAD) artery and lung between proton and photon beam irradiation for left-sided early stage breast cancer. MATERIAL AND METHODS: Ten women with early stage left-sided breast cancer were treated with breast conserving surgery and radiation. Whole breast radiation was delivered for actual treatment via a tangential technique with deep inspiration breath hold (DIBH) utilizing inverse planned intensity-modulated radiation therapy (IMRT). Each patient was replanned on an Institutional Review Board (IRB)-approved prospective study using en face proton beam radiation with both uniform scanning (US) and pencil beam scanning (PBS) techniques. RESULTS: Both PBS (0.011 Gy) and US (0.009 Gy) proton plans resulted in a significantly lower mean heart dose compared to IMRT (1.612 Gy) (p < 0.05 for PBS vs. IMRT and US vs. IMRT). The Dmean, Dmin, Dmax, and D0.2cm(3) of the LAD with either proton technique were significantly lower (p = 0.005) compared to IMRT. Both US and PBS reduced the mean dose to the lungs compared to IMRT. The coverage of the breast planning target volume was comparable between photon and proton plans. CONCLUSIONS: The dose to whole heart was relatively low in this study of patients treated under conditions of DIBH. However, proton beam radiation was associated with lower minimum, maximum, and dose to 0.2 cm(3) of the LAD, which is the critical structure for late radiation therapy effects, compared to even the most optimized photon beam plan with DIBH and IMRT.

Proton therapy for pediatric malignancies: Indications and challenges focusing on the oncological landscape.

Advances in therapeutic techniques and multimodal approaches have significantly improved the success rates of treatment for pediatric malignancies, with cure rates now close to 80%. This has led to an increase in long-term survival, with 0.10-0.15% of the general population being survivors of childhood cancer. In Italy, cancer registry data suggest that 75% of treated children become long-term survivors. However, these survivors face significant risks of late adverse events, including chronic diseases and severe conditions, highlighting the need for specialized follow-up care.Radiotherapy, a cornerstone of pediatric cancer treatment, contributes to late toxicities due to the susceptibility of growing tissues. Proton therapy offers advantages in reducing treatment-related toxicity, reducing the risk of secondary cancers, and allowing dose escalation for radioresistant tumors. Comparative studies suggest that proton therapy is superior in sparing healthy tissues and reducing long-term toxicities.Despite these benefits, challenges such as the high cost, limited proton therapy centers, and the need for clinical trials hinder the widespread adoption of proton therapy. Efforts to centralize care in high-ranking centers and ensure equitable access to proton therapy are crucial. In Italy, pediatric solid tumors are now eligible for proton therapy under national health policies, ensuring free access for all children.Dedicated proton therapy centers must provide comprehensive care involving multidisciplinary teams and supportive environments for pediatric patients and their families. Addressing current limitations and enhancing care environments are essential for improving outcomes for pediatric oncology patients.

Proton Therapy in Non-Rhabdomyosarcoma Soft Tissue Sarcomas of Children and Adolescents.

This paper provides insights into the use of Proton Beam Therapy (PBT) in pediatric patients with non-rhabdomyosarcoma soft tissue sarcomas (NRSTS). NRSTS are a heterogeneous group of rare and aggressive mesenchymal extraskeletal tumors, presenting complex and challenging clinical management scenarios. The overall survival rate for patients with NRSTS is around 70%, but the outcome is strictly related to the presence of various variables, such as the histological subtype, grade of malignancy and tumor stage at diagnosis. Multimodal therapy is typically considered the preferred treatment for high-grade NRSTS. Radiotherapy plays a key role in the treatment of children and adolescents with NRSTS. However, the potential for radiation-induced side effects partially limits its use. Therefore, PBT represents a very suitable therapeutic option for these patients. The unique depth-dose characteristics of protons can be leveraged to minimize doses to healthy tissue significantly, potentially allowing for increased tumor doses and enhanced preservation of surrounding tissues. These benefits suggest that PBT may improve local control while reducing toxicity and improving quality of life. While clear evidence of therapeutic superiority of PBT over other modern photon techniques in NRSTS is still lacking-partly due to the limited data available-PBT can be an excellent treatment option for young patients with these tumors. A dedicated international comprehensive collaborative approach is essential to better define its role within the multidisciplinary management of NRSTS. Shared guidelines for PBT indications-based on the patient's age, estimated outcome, and tumor location-and centralization in high-level referral centers are needed to optimize the use of resources, since access to PBT remains a challenge due to the limited number of available proton therapy facilities.

Machine Learning Analysis in Diffusion Kurtosis Imaging for Discriminating Pediatric Posterior Fossa Tumors: A Repeatability and Accuracy Pilot Study.

Background and purpose: Differentiating pediatric posterior fossa (PF) tumors such as medulloblastoma (MB), ependymoma (EP), and pilocytic astrocytoma (PA) remains relevant, because of important treatment and prognostic implications. Diffusion kurtosis imaging (DKI) has not yet been investigated for discrimination of pediatric PF tumors. Estimating diffusion values from whole-tumor-based (VOI) segmentations may improve diffusion measurement repeatability compared to conventional region-of-interest (ROI) approaches. Our purpose was to compare repeatability between ROI and VOI DKI-derived diffusion measurements and assess DKI accuracy in discriminating among pediatric PF tumors. Materials and methods: We retrospectively analyzed 34 children (M, F, mean age 7.48 years) with PF tumors who underwent preoperative examination on a 3 Tesla magnet, including DKI. For each patient, two neuroradiologists independently segmented the whole solid tumor, the ROI of the area of maximum tumor diameter, and a small 5 mm ROI. The automated analysis pipeline included inter-observer variability, statistical, and machine learning (ML) analyses. We evaluated inter-observer variability with coefficient of variation (COV) and Bland-Altman plots. We estimated DKI metrics accuracy in discriminating among tumor histology with MANOVA analysis. In order to account for class imbalances, we applied SMOTE to balance the dataset. Finally, we performed a Random Forest (RF) machine learning classification analysis based on all DKI metrics from the SMOTE dataset by partitioning 70/30 the training and testing cohort. Results: Tumor histology included medulloblastoma (15), pilocytic astrocytoma (14), and ependymoma (5). VOI-based measurements presented lower variability than ROI-based measurements across all DKI metrics and were used for the analysis. DKI-derived metrics could accurately discriminate between tumor subtypes (Pillai's trace: p < 0.001). SMOTE generated 11 synthetic observations (10 EP and 1 PA), resulting in a balanced dataset with 45 instances (34 original and 11 synthetic). ML analysis yielded an accuracy of 0.928, which correctly predicted all but one lesion in the testing set. Conclusions: VOI-based measurements presented improved repeatability compared to ROI-based measurements across all diffusion metrics. An ML classification algorithm resulted accurate in discriminating PF tumors on a SMOTE-generated dataset. ML techniques based on DKI-derived metrics are useful for the discrimination of pediatric PF tumors.

Dosimetric Comparison Between Proton and Photon Radiation Therapies for Pediatric Neuroblastoma.

Purpose: The aim of this study is to determine the most beneficial radiation treatment technique for pediatric patients with thoracic and abdominal neuroblastoma (NBL), through a dosimetric comparison between photon Volumetric Modulated Arc Therapy and proton Intensity-Modulated Proton Therapy treatment plans. Materials and Methods: A retrospective analysis was conducted on a multicentre case series of 19 patients with thoracic and/or abdominal NBL who underwent radiation therapy, following the recommendations of the European protocol for high-risk NBL (HR-NBL2/SIOPEN). The prescribed dose was 21.6 Gy in 12 fractions (1.8 Gy/fraction) delivered over the preoperative disease volume. The dose volume histograms were analyzed for each patient, and a Wilcoxon signed-rank test with a significance level of 0.01 was employed to assess statistical differences between the dosimetric parameters investigated. Two homogeneity indices (HI and newHI) were compared to evaluate the uniformity in dose, delivered to the adjacent vertebrae (VBs_Adj). Results: Both radiation techniques conform to the protocol regarding CTV/PTV coverage for every location. Proton therapy resulted in statistically significant dose sparing for the heart and lungs in supradiaphragmatic locations and for the contralateral kidney, liver, spleen, and bowel in subdiaphragmatic locations. For both techniques, sparing the non-adjacent vertebrae (VBs_NAdj) results more challenging, although promising results were obtained. Furthermore, the dose delivered to the VBs_Adj was not statistically different, in terms of homogeneity, for the 2 radiation techniques that both met the protocol's requirements. Conclusion: This dosimetric analysis highlights the potential of protons to reduce radiation dose to healthy tissue. These findings apply to all the investigated patients, regardless of primary tumor location, making proton therapy a valuable option for the treatment of neuroblastoma. However, a multidisciplinary assessment of each case is essential to ensure the selection of the most effective and suitable treatment modality.

Long-term outcome of the Milano-HART strategy for high-risk medulloblastoma, including the impact of molecular subtype.

BACKGROUND: We applied the strategy for M+ medulloblastoma across all high-risk subgroups, including LC/A histology, TP53 mutations, MYC/MYCN amplification. METHODS: Patients over 3-years-old received,after surgery,staging and histo-biological analysis,sequential high-dose-methotrexate(HD-MTX),high-dose-etoposide(HD-VP16),high-dose-cyclophosphamide(HD-Cyclo),high-dose-carboplatin(HD-Carbo).Hyperfractionated-accelerated-radiotherapy-craniospinal(HART-CSI),administered in twice daily 1.3 Gy-fractions reached a total dose tailored to the patients' age and pre-radiation response to chemotherapy(CT): 31.2 Gy if under 10-years-old and complete response(CR) or partial response(PR) obtained or absence of metastatic disease,39 Gy in other/older patients.Boosts to posterior fossa/residual metastatic(M+) deposits were given up to a total dose of 60 Gy/9 Gy,respectively,but avoided if metastatic nodules were very big or patients very young.Two courses of high-dose-thiotepa were delivered in case of not CR/PR after pre-radiotherapy(RT) phase and in all M0 patients either - pre/post HART.Subgrouping was performed where tissue was available. RESULTS: Eighy-nine patients were enrolled,median age 8.8 years,median follow up 136 months.Overall-survival(OS) and event-free-survival(EFS) at 5/15 years were 75.9/66.5% and 68.2/65.3%, respectively;5/28 fatal events were not related to relapse(three developed secondary malignancies).Sex,age less than 10 years,histological subtype,presence of MYC/MYCN amplification,reduction in CSI dose,omission of RT-boosts,implementation of myeloablative therapy,presence/absence of metastases did not impact prognosis.Patients progressing after pre-HART CT(14/89) and stable-disease(SD)+PD after HART(10/89) negatively affected outcome(P<0.001).Subgrouping in 66/89 patients' samples demonstrated a significantly worse EFS for patients with Sonic Hedgehog(SHH)-tumors(#15, 2 with constitutional TP53-mutations) vs. group 3 and 4(15 and 29 patients, respectively, group3/4 in 7).Patients younger than 10 received lower CSI doses if stratified according to CT response. CONCLUSIONS: This strategy, partly adopted in the ongoing SIOPE protocol,confirmed improved EFS and OS over previously reported outcomes in all high-risk categories;SHH tumors appeared the most aggressive.

Clinical practice in European centres treating paediatric posterior fossa tumours with pencil beam scanning proton therapy.

BACKGROUND AND PURPOSE: As no guidelines for pencil beam scanning (PBS) proton therapy (PT) of paediatric posterior fossa (PF) tumours exist to date, this study investigated planning techniques across European PT centres, with special considerations for brainstem and spinal cord sparing. MATERIALS AND METHODS: A survey and a treatment planning comparison were initiated across nineteen European PBS-PT centres treating paediatric patients. The survey assessed all aspects of the treatment chain, including but not limited to delineations, dose constraints and treatment planning. Each centre planned two PF tumour cases for focal irradiation, according to their own clinical practice but based on common delineations. The prescription dose was 54 Gy(RBE) for Case 1 and 59.4 Gy(RBE) for Case 2. For both cases, planning strategies and relevant dose metrics were compared. RESULTS: Seventeen (89 %) centres answered the survey, and sixteen (80 %) participated in the treatment planning comparison. In the survey, thirteen (68 %) centres reported using the European Particle Therapy Network definition for brainstem delineation. In the treatment planning study, while most centres used three beam directions, their configurations varied widely across centres. Large variations were also seen in brainstem doses, with a brainstem near maximum dose (D2%) ranging from 52.7 Gy(RBE) to 55.7 Gy(RBE) (Case 1), and from 56.8 Gy(RBE) to 60.9 Gy(RBE) (Case 2). CONCLUSION: This study assessed the European PBS-PT planning of paediatric PF tumours. Agreement was achieved in e.g. delineation-practice, while wider variations were observed in planning approach and consequently dose to organs at risk. Collaboration between centres is still ongoing, striving towards common guidelines.

Clinical Insight on Proton Therapy for Paediatric Rhabdomyosarcoma.

This paper offers an insight into the use of Proton Beam Therapy (PBT) in paediatric patients with rhabdomyosarcoma (RMS). This paper provides a comprehensive analysis of the literature, investigating comparative photon-proton dosimetry, outcome, and toxicity. In the complex and multimodal scenario of the treatment of RMS, clear evidence of the therapeutic superiority of PBT compared to other modern photon techniques has not yet been demonstrated; however, PBT can be considered an excellent treatment option, in particular for young children and patients with specific primary sites, such as the head and neck area (and especially the parameningeal regions), genito-urinary, pelvic, and paravertebral regions. The unique depth-dose characteristics of protons can be exploited to achieve significant reductions in normal tissue doses and may allow an escalation of tumour doses and greater sparing of normal tissues, thus potentially improving local control while at the same time reducing toxicity and improving quality of life. However, access of children with RMS (and more in general with solid tumors) to PBT remains a challenge, due to the limited number of available proton therapy installations.

Case Report: Remarkable breakthrough: successful treatment of a rare intracranial mesenchymal, FET::CREB fusion-positive tumor treated with patient-tailored multimodal therapy.

Background: Intracranial mesenchymal tumors are a rare type of neoplasm (0.3% of all soft tissue tumors) characterized by a fusion of a FET family gene (usually EWSR1, rarely FUS) to CREB family genes (CREB1, ATF1, and CREM) with a slow-growing and favorable prognosis. Mesenchymal tumors are most frequently localized in the subcutaneous tissue (typically in the limbs and hands) of young adults and have rarely been diagnosed in the central nervous system. Surgery is the gold standard treatment; adjuvant radiation therapy and chemotherapy with sarcoma-based regimens have been used in rare cases when complete surgical excision was not recommended. In terms of prognosis, these tumors show a tendency for local relapse. The longest patient outcomes reported in the literature are five years. Case description: This case describes a 27-year-old woman with unconventional extracranial metastatic sites of myxoid intracranial mesenchymal tumor FET::CREB fusion-positive and high expression of PD-1 (40%) and PD-L1 (30%). Based on clinical, molecular, and histological characteristics, she underwent various local and systemic therapies, including surgery, proton beam therapy, the use of immune checkpoint inhibitors, and chemotherapy. These treatments led to a complete remission of the disease after eight years from tumor diagnosis. Conclusions: Our case sheds light on the importance of precision medicine and tailored therapy to explore new treatment opportunities for rare or unknown tumor entities.

Desmoplastic small round cell tumor: from state of the art to future clinical prospects.

INTRODUCTION: Desmoplastic small round cell tumor (DSRCT) is an extremely rare and highly aggressive soft tissue sarcoma, presenting mainly in male adolescents and young adults with multiple nodules disseminated within the abdominopelvic cavity. Despite a multimodal approach including aggressive cytoreductive surgery, intensive multi-agent chemotherapy, and postoperative whole abdominopelvic radiotherapy, the prognosis for DSRCT remains dismal. Median progression-free survival ranges between 4 and 21 months, and overall survival between 17 and 60 months, with the 5-year overall survival rate in the range of 10-20%. AREA COVERED: This review discusses the treatment strategies used for DSRCT over the years, the state of the art of current treatments, and future clinical prospects. EXPERT OPINION: The unsatisfactory outcomes for patients with DSRCT warrant investigations into innovative treatment combinations. An international multidisciplinary and multi-stakeholder collaboration, involving both pediatric and adult sarcoma communities, is needed to propel preclinical model generation and drug development, and innovative clinical trial designs to enable the timely testing of treatments involving novel agents guided by biology to boost the chances of survival for patients with this devastating disease.

Unraveling the impact of upfront chemotherapy and proton beam therapy on treatment outcome and follow-up in central nervous system germ cell tumors: a single center experience.

Background: Germ cell tumors (GCT) account for a minority of central nervous system (CNS) malignancies, highly prevalent in adolescents and young adults. Despite their aggressive biological behavior, prognosis is excellent in most cases with risk stratified treatment, consisting in a combination of chemotherapy and radiotherapy. Whole ventricular irradiation (WVI) and craniospinal irradiation, the treatment of choice for localized and metastatic disease, pose significant risk of collateral effects, therefore proton beam radiation (PBT) has been recently proposed for its steep dose fallout. Materials and methods: We report our experience in a consecutive series of 17 patients treated for CNS GCT at our Institution from 2015 to 2021. Results: Most frequent lesion location were sellar/suprasellar (35%) and bifocal germinoma (35%), followed by pineal (18%) and thalamic (12%). Two patients (12%), had evidence of disseminated disease at the time of diagnosis. At the latest follow-up all but one patient showed complete response to treatment. The only relapse was successfully rescued by additional chemotherapy and PBT. PBT was well tolerated in all cases. No visual, neurological or endocrinological worsening was documented during and after treatment. Neuropsychological evaluation demonstrated preservation of cognitive performance after PBT treatment. Conclusions: Our data, albeit preliminary, strongly support the favourable therapeutic profile of PBT for the treatment of CNS germ cell tumors.