Radiation therapy target volume reduction in pediatric rhabdomyosarcoma

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.

The significance of margins in pediatric Non-Rhabdomyosarcoma soft tissue sarcomas: Consensus on surgical margin definition harmonization from the INternational Soft Tissue SaRcoma ConsorTium (INSTRuCT)

BACKGROUND

Margin status following surgery in children, adolescents, and young adults with soft tissue sarcomas is controversial and has been defined differently by various specialties, with definitions changing over time and by cooperative group. The International Soft Tissue Sarcoma Consortium (INSTRuCT) is a collaboration of the Children's Oncology Group (COG) Soft Tissue Sarcoma Committee, European pediatric Soft Tissue sarcoma Study Group (EpSSG), and the European Cooperative Weichteilsarkom Studiengruppe (CWS) devoted to improving patient outcomes by pooling and mining cooperative group clinical trial data.

METHODS

The INSTRuCT non-rhabdomyosarcoma soft tissue sarcoma (NRSTS) working group aimed to develop international harmonized recommendations regarding surgical margin assessment and definitions in children and adolescents with soft tissue tumors.

RESULTS AND CONCLUSION

This review addresses accepted principles and areas of controversy, including the perspectives of surgeons, pathologists, radiation oncologists, and pediatric oncologists, to develop a framework for building common guidelines for future research.

Local control of parameningeal rhabdomyosarcoma: An expert consensus guideline from the International Soft Tissue Sarcoma Consortium (INSTRuCT)

The International Soft Tissue Sarcoma Database Consortium (INSTRuCT) consists of a collaboration between the Children's Oncology Group (COG) Soft Tissue Sarcoma Committee, the European pediatric Soft Tissue Sarcoma Study Group (EpSSG), and the Cooperative Weichteilsarkom Studiengruppe (CWS). As part of the larger initiative of INSTRuCT to provide consensus expert opinions for clinical treatment of pediatric soft tissue sarcoma, we sought to provide updated, evidenced-based consensus guidelines for local treatment of parameningeal rhabdomyosarcoma using both existing literature as well as recommendations from the relevant cooperative group clinical trials. Overall, parameningeal rhabdomyosarcoma represents a distinctly challenging disease to treat, given its location near many critical structures in the head and neck, frequently advanced local presentation, and predilection for local failure. Definitive chemoradiation remains the standard treatment approach for parameningeal rhabdomyosarcoma, with surgery often limited to biopsy or salvage therapy for recurrent disease. In this consensus paper, we specifically discuss consensus guidelines and evidence for definitive local management with radiotherapy, with a focus on imaging for radiotherapy planning, dose and timing of radiation, approach for nodal irradiation, various radiation techniques, including proton therapy, and the limited role of surgical resection.

Current and Future Treatment Strategies for Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children, and can be subcategorized histologically and/or based on PAX-FOXO1 fusion gene status. Over the last four decades, there have been no significant improvements in clinical outcomes for advanced and metastatic RMS patients, underscoring a need for new treatment options for these groups. Despite significant advancements in our understanding of the genomic landscape and underlying biological mechanisms governing RMS that have informed the identification of novel therapeutic targets, development of these therapies in clinical trials has lagged far behind. In this review, we summarize the current frontline multi-modality therapy for RMS according to pediatric protocols, highlight emerging targeted therapies and immunotherapies identified by preclinical studies, and discuss early clinical trial data and the implications they hold for future clinical development.

45 GyRBE for group III orbital embryonal rhabdomyosarcoma

Purpose: Despite widespread concerns of radiotherapy toxicity in children with head and neck tumors, recent Children's Oncology Group (COG) findings suggest that the use of 45 Gy results in an unacceptably high rate of local recurrences in patients with low-risk orbital rhabdomyosarcoma. We therefore evaluated outcomes in our pediatric patients who received 45 GyRBE using proton therapy. Material and methods: To assess disease control and toxicity, we reviewed the medical records of 30 children (≤21 years old) with COG stage 1, group III embryonal orbital rhabdomyosarcoma enrolled on a prospective outcome study and treated with proton therapy between 2007 and 2018. Results: Median age at the time of radiation was 4.8 years old. Twenty-one and nine patients received ifosfamide- and cyclophosphamide-based chemotherapy according to their respective cooperative group regimens. Median duration between the start of induction chemotherapy and radiation was 12 weeks. Two patients had a complete response to induction chemotherapy and two had stable disease. Twenty-six patients had a partial response to induction chemotherapy, with a median volume reduction of 66%. With a median follow-up of 4.0 years (range, 0.5-9.5 years), we observed 1 local failure 6 months following treatment in a patient who had a partial response to cyclosphophomide-based induction chemotherapy. The 5-year local control, progression-free survival, and overall survival rates were 97%, 97%, and 100%, respectively. Serious late toxicities included 18 patients with cataracts, 4 with exposure keratoconjunctivitis resulting in permanently reduced visual acuity, and 1 with chronic sinusitis. Conclusion: 45 GyRBE offers effective local control for most patients with group III orbital rhabdomyosarcoma. The delivery of proton therapy to the postinduction tumor volume plus a small margin can mitigate early- and intermediate-term toxicity, but side effects still occur and long-term data are needed to demonstrate the dosimetric advantage of proton therapy.

Outcome and Patterns of Relapse in Childhood Parameningeal Rhabdomyosarcoma Treated With Proton Beam Therapy

PURPOSE

The standard of care of childhood parameningeal rhabdomyosarcoma (pRMS) is chemotherapy and local radiation therapy. Protons are increasingly being used to decrease late effects. The aim of the present study is to analyze the pattern of relapse and the correlation with dosimetric factors in pRMS treated with proton therapy.

METHODS AND MATERIALS

This retrospective evaluation includes children treated in our institution for pRMS. Information on demographics, treatment, tumor characteristics, and toxicities and outcome was prospectively collected within the in-house registry. For patients presenting with local relapse, a fusion of the dosimetry with magnetic resonance imaging displaying site and geometry of recurrence was performed.

RESULTS

Median follow-up time was 2.9 years (0.5-4.7). Forty-six patients were identified in our institution between July 2013 and November 2017. Main characteristics of patients were as follows: 56.5% male, median age 5.1 years (1.3-17.5), 39.1% alveolar histology, 26.1%, 52.2%, 8.7%, and 13% patients with subgroup risk classification D, E/F/G, H, or metastatic, respectively, median total prescribed dose 55.8 Gy (50.4-56.4). Estimated 2-year local control, metastasis-free survival, event-free survival, and overall survival were 83.8%, 87.8%, 76.9%, and 88.9%, respectively. No acute or late local toxicity exceeding grade 3 was observed. Risk-group was identified as prognostic factor for metastasis-free survival in univariate analysis but not in multivariate analysis (trend: P = .09). In this cohort, dosimetric factors did not correlate with outcome. Isolated local failure happened in 5 of the 11 relapses. Local relapses were matched with dosimetry for 6 patients: 4 of them occurred in the high dose volume and 2 in the intermediate or low dose volume.

CONCLUSIONS

Proton therapy was effective and well feasible even in a critical cohort. Still, local relapse within the target volume of the radiation therapy remains an important issue in pRMS and new treatment strategies are needed.

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy: A safe treatment option for intraperitoneal rhabdomyosarcoma in children below 5 years of age

Advanced and relapsed intraperitoneal rhabdomyosarcomas in young children represent an oncological challenge and options for local tumor control are limited. Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is commonly used in advanced peritoneal tumors in adults. However, no studies are available regarding CRS and HIPEC in young children. We report our experiences treating six patients with intraperitoneal rhabdomyosarcoma with CRS and HIPEC using cisplatin and doxorubicin focusing on safety and outcomes. No procedure-associated mortalities occurred and no major short- or long-term toxicities were recorded. All patients showed no evidence of disease after 12-month median (7-41) follow-up.

Excessive Treatment Failures in Patients With Parameningeal Rhabdomyosarcoma With Reduced-dose Cyclophosphamide and Delayed Radiotherapy

Pediatric patients with parameningeal rhabdomyosarcoma and high-risk features are recommended to receive radiotherapy at initiation of protocol therapy due to concerns about the increased risk of local and leptomeningeal failure from treatment delay. We report our early experience on a multi-institutional prospective trial incorporating delayed primary site radiation and reduced dose cyclophosphamide in all patients with parameningeal tumors. We observed an excessive number of locoregional treatment failures following this approach and have subsequently amended our trial to move radiation therapy upfront for those patients with high-risk features. We suggest that investigators should be vigilant for treatment failure given our early prospective experience with delayed radiotherapy and reduced dose cyclophosphamide.

Adherence to Treatment, Response and Patterns of Failure in Pediatric Parameningeal Rhabdomyosarcoma: Experience From a Tertiary Cancer Care Center From India

The study was aimed at evaluating adherence to treatment protocol and outcome in pediatric parameningeal rhabdomyosarcoma (PM-RMS). We analyzed the characteristics, treatment administered, outcomes and patterns of failure of pediatric PM-RMS, who were treated with multimodality therapy between January 2005 and December 2013.Univariate and multivariate analysis (MVA) was completed to evaluate the impact of various prognostic factors. Thirty-seven patients were treated at our institution. Majority of them had the primary disease in paranasal sinuses (n=13). Majority of the patients belonged to group III (n=30) and stage III (n=24). The overall response rate to treatment was 52.5% (n=21). At a mean follow-up of 19.1 months, 23 patients developed disease progression. The actuarial rates of failure-free survival and overall survival (OS) at 2 years were 40% and 67.5%, respectively. Patients who received >20 weeks of intended chemotherapy schedule (P=0.02) and had complete response to first-line treatment (P=0.0004) were found to have superior failure-free survival on MVA. Complete response was the lone determinant of superior OS on MVA (P=0.006). Majority of patients with PM-RMS present with advanced stage disease. Response to first-line treatment is a significant predictor of superior progression-free survival and OS in these patients.

Stage 1 embryonal rhabdomyosarcoma of the female genital tract: a retrospective clinical study of nine cases

Background

The aim of the study is to investigate the clinical features, treatments, and prognosis of stage 1 embryonal rhabdomyosarcoma of the female genital tract.

Methods

A retrospective analysis was performed on nine cases of stage 1 embryonal rhabdomyosarcoma of the female genital tract. Clinical characteristics, treatments, recurrence, and prognosis were analyzed.

Results

Of the nine patients with embryonal rhabdomyosarcoma, three originated from the vagina and six from the cervix. For the eight patients who initially received surgery, the median survival time was 88 months. As for the six patients that received adjuvant chemotherapy, five of them who received six or more cycles of treatment achieved tumor-free survival and the survival time ranged from 9 to 228 months. The remaining patient, who declined further treatment after two cycles of chemotherapy, relapsed 11 months following the surgery and died 3 months later. Out of the nine patients, only one was initially treated with chemotherapy, and achieved complete remission, but relapsed 21 months later. After a combination of surgery and chemotherapy, this patient remained tumor-free for total of 117 months.

Conclusions

Patients with early stage embryonal rhabdomyosarcoma of the female genital tract have good prognosis, and the combination of surgery and chemotherapy can lead to better outcomes.

Current standards of care in bladder and prostate rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue tumor in children, and 15% to 20% arise from the genitourinary tract. Multicenter collaborative studies have improved survival substantially, and in addition to excellent oncologic control, current treatment focuses on organ preservation and minimization of late treatment effects. The multiple modalities needed to treat RMS dictate that treating physicians must be familiar with the disease as well as the goals and possible sequelae of treatment with chemotherapy, radiotherapy, and surgery. This article discusses the current standards of care for bladder and prostate RMS.

Rhabdomyosarcoma

A malignant tumor of striated muscle origin, rhabdomyosarcoma (RMS) is a childhood tumor that has benefited from nearly 30 years of multimodality therapy, culminating in a >70% overall 5-year survival. Prognosis for RMS is dependent on primary tumor site, age, completeness of resection, presence and number of metastatic sites, histology, and biology of the tumor cells. Multimodality treatment is based on risk stratification according to pre-treatment stage, postoperative group, histology, and site. Unique to RMS is the concept of postoperative clinical grouping that assesses the completeness of disease resection and takes into account lymph node evaluation at both the regional and metastatic basins. At all sites, if complete operative resection of disease is accomplished, including microscopic disease, survival is improved. Therefore, the surgeon plays a vital role in determining risk stratification for treatment, local control of the primary tumor and overall outcome for the patient with RMS.

Patterns of Failure in Pediatric Rhabdomyosarcoma After Proton Therapy

PURPOSE

To report on the patterns of failure in children with rhabdomyosarcoma treated with proton therapy.

PATIENTS AND METHODS

Between February 2007 and November 2013, 66 children with a median age of 4.1 years (range, 0.6-15.3 years) diagnosed with nonmetastatic rhabdomyosarcoma were treated with proton therapy. Clinical target volume 1 was defined as the prechemotherapy tumor plus a 1-cm anatomically constrained margin. Clinical target volume 2 was defined as the postchemotherapy tumor (or tumor bed) plus a 0.5-cm anatomically constrained margin, further expanded to encompass potential pathways of spread, including soft tissue infiltrated with tumor at diagnosis.

RESULTS

Of the 66 children, 11 developed locally progressive disease at a median of 16 months (range, 14-32 months), for an actuarial 2-year local control rate of 88%. Among the children who progressed, median age and tumor size at diagnosis were 6.7 years (range, 0.6-16 years) and 6 cm (range, 2-8 cm), respectively. Of the recurrences, 64% and 36% were embryonal and alveolar, respectively. Disease progression was observed in 7 (64%) parameningeal, 2 (18%) head and neck (other), and 2 (18%) bladder/prostate subsites. At diagnosis, 8 of 11 patients who developed a recurrence were Intergroup Rhabdomyosarcoma Study stage 3, and all 11 were group III. Of the relapses, 100% (11 of 11) were confirmed as in-field within the composite 95% isodose line. One of the 11 patients (9%) developed a new simultaneous regional nodal recurrence outside of the previously treated radiation field.

CONCLUSION

Early data suggest that the sharp dosimetric gradient associated with proton therapy is not associated with an increased risk of marginal failure. Routine use of a 0.5- to 1-cm clinical target volume 1/2 margin with highly conformal proton therapy does not compromise local control in children diagnosed with rhabdomyosarcoma with unfavorable risk features.

Tumour volume reduction after neoadjuvant chemotherapy impacts outcome in localised embryonal rhabdomyosarcoma

BACKGROUND

Response (tumour volume reduction) to induction chemotherapy has been used to stratify secondary local and systemic treatment of Intergroup Rhabdomyosarcoma Study Group III (IRSG-III) embryonal rhabdomyosarcoma (RME) in consecutive CWS-trials. To evaluate its actual impact we studied response-related treatment and outcomes.

PROCEDURE

Patients with IRSG-III RME <21 years and non-response (NR, <33% volume reduction) in five consecutive CWS-trials were analysed and compared with partial responders (PAR, ≥ 33% reduction). The NR was reviewed and sub-classified as Objective Response (OR, <0%-33% reduction) or Stable/Progressive Disease (SPD).

RESULTS

Fifty-nine of 529 patients had NR (n = 34 OR, n = 25 SPD). Primary risk-factors including age, tumour size, and TN-classification did not differ between NR and PAR groups but NR had more patients with unfavourable sites comparatively (P = 0.04). There were no differences in primary risk-factors between OR and SPD. Significant factors associated with poor outcome in multivariate analysis were NR, TN-classification, age >10 years, tumour size >5 cm and therapy in older trials. After response assessment n = 24 NR continued to receive induction chemotherapy, n = 32 received other combinations and n = 3 no further chemotherapy. Forty-two non-responders were irradiated, and the tumours were completely resected in n = 20. After a median follow-up of 8 years, 34 NR are alive. Seventeen of 21 failures leading to disease-related deaths were locoregional. The five-year overall survival rate (OS) was 76 ± 4% for PAR, 79 ± 14% for OR, but only 40 ± 19% for SPD (P < 0.001).

CONCLUSION

Response to induction chemotherapy appears to be an important surrogate marker of poor outcome in patients with SPD largely due to ineffective local control.

Preliminary results of a phase II trial of proton radiotherapy for pediatric rhabdomyosarcoma

PURPOSE

This prospective phase II study was designed to assess disease control and to describe acute and late adverse effects of treatment with proton radiotherapy in children with rhabdomyosarcoma (RMS).

PATIENTS AND METHODS

Fifty-seven patients with localized RMS (age 21 years or younger) or metastatic embryonal RMS (age 2 to 10 years) were enrolled between February 2005 and August 2012. All patients were treated with chemotherapy based on either vincristine, actinomycin, and cyclophosphamide or vincristine, actinomycin, and ifosfamide-based chemotherapy and proton radiation. Surgical resection was based on tumor site and accessibility. Common Terminology Criteria for Adverse Events, Version 3.0, was used to assess and grade adverse effects of treatment. Concurrent enrollment onto Children's Oncology Group or European Pediatric Sarcoma Study Group protocols was allowed. All pathology and imaging were reviewed at the treating institution.

RESULTS

Median follow-up was 47 months (range, 14 to 102 months) for survivors. Five-year event-free survival (EFS), overall survival (OS), and local control (LC) were 69%, 78%, and 81%, respectively, for the entire cohort. The 5-year LC by risk group was 93% for low-risk and 77% for intermediate-risk disease. There were 13 patients with grade 3 acute toxicity and three patients with grade 3 late toxicity. There were no acute or late toxicities higher than grade 3.

CONCLUSION

Five-year LC, EFS, and OS rates were similar to those observed in comparable trials that used photon radiation. Acute and late toxicity rates were favorable. Proton radiation appears to represent a safe and effective radiation modality for pediatric RMS.

Rhabdomyosarcoma in adolescent and young adult patients: current perspectives

Rhabdomyosarcoma (RMS), a malignant tumor of mesenchymal origin, is the third most common extracranial malignant solid tumor in children and adolescents. However, in adults, RMS represents <1% of all solid tumor malignancies. The embryonal and alveolar histologic variants are more commonly seen in pediatric patients, while the pleomorphic variant is rare in children and seen more often in adults. Advances in the research of the embryonal and alveolar variants have improved our understanding of certain genes and biologic pathways that are involved in RMS, but much less is known for the other variants. Multimodality therapy that includes surgery and chemotherapy with or without radiation therapy is the mainstay of treatment for RMS. Improvements in the risk stratification of the pediatric patients based on presurgical (primary tumor site, tumor size, regional lymph node involvement, presence of metastasis) and postsurgical parameters (completeness of resection or presence of residual disease or metastasis) has allowed for the treatment assignment of patients in different studies and therapeutic trials, leading to increases in 5-year survival from 25%–70% over the past 40 years. However, for adult patients, in great part due to rarity of the disease and the lack of consensus on optimal treatment, clinical outcome is still poor. Many factors have been implicated for the differing outcomes between pediatric RMS versus adult RMS, such as the lack of standardized treatment protocols for adult RMS patients and the increased prevalence of advanced presentations. Now that there are increased numbers of survivors, we can appreciate the sequelae from therapy in these patients, such as bone growth abnormalities, endocrinopathies, and infertility. Improvements in risk stratification have led to clinical trials using lower doses of chemotherapy or radiation therapy with the intention of decreasing the incidence of side effects without compromising survival outcome.