[Indications and results for protontherapy in cancer treatments]

Inhalation anesthesia without any intravenous management for pediatric proton beam therapy

INTRODUCTION

Proton beam therapy is an oncological treatment, argued to be an appropriate tumor irradiation technique for childhood solid tumors. Due to its duration and the need for immobility, many children require anesthesia for proton therapy sessions. As not many centers in the world provide this therapy, there is little published research about pediatric anesthesia for these cases, and the available data suggest a preference for intravenous anesthesia or combined intravenous and inhalation anesthesia. We conducted this study with the aim of describing and analyzing the inhalation anesthetic management of children undergoing proton therapy at our medical center, comparing our results with studies that have followed different anesthetic protocols.

METHODS

We reviewed two major databases (Web of Science and Scopus) to find papers that had addressed, to date, anesthesia for pediatric proton therapy. To describe our anesthetic management, we included all pediatric patients treated with proton therapy under anesthesia in our center between June 2020 and August 2021. The characteristics of the patients, their diagnoses, treatments, airway management, drugs administered, duration of induction, and recovery from anesthesia, and adverse effects where all recorded. All anesthesiologists followed a strict anesthetic protocol based only on inhalational anesthesia with sevoflurane delivered via laryngeal mask airway.

RESULTS

Of the total of 1082 papers found in Web of Science and Scopus on pediatric proton therapy, 11 have addressed its anesthetic management, using intravenous or combined intravenous and inhalation anesthesia. Between June 2020 and August 2021, 31 children were anesthetized in our center to receive proton therapy under inhalational anesthesia (total number of sessions: 873). The mean anesthesia induction time was 4.1 min (SD = 0.7, 95% CI [3.9, 4.4]). The mean anesthesia recovery time was 13.8 min (SD = 4.1, 95% CI [12.3, 15.3]). The percentage of non-serious adverse effects was 0.7% (Clopper-Pearson 95% CI [0.3, 1.5]). The percentage of serious adverse effects was 0.1% (Clopper-Pearson 95% CI [0, 0.6]), without statistically significant difference with other published works with different anesthetic approaches.

CONCLUSION

Inhalation anesthesia without any intravenous management for pediatric proton therapy is, in our experience, an effective technique with a complication rate similar to other anesthetic approaches.

[High energy proton therapy for extraocular tumors, neurotrophic keratitis and functional consequence: A series of 3 cases]

INTRODUCTION

High energy proton therapy (HEP) is a form of radiation therapy using protons for extraocular tumors. Its ballistic properties are theoretically advantageous, but the real impact on the surrounding ocular tissues during cerebral and ENT irradiation is poorly documented. We describe three consecutive patients with corneal damage following such irradiation.

MATERIALS/METHODS

Post-proton therapy neurotrophic keratitis (NK) is defined as corneal hypo/anesthesia responsible for an alteration of corneal trophicity and graded according to the Mackie classification, in terms of a prospective ophthalmological follow-up protocol for all patients with extraocular tumors treated with HEP.

RESULTS

Among 193 patients treated with HEP between 2018 and 2021 for extraocular tumors, three patients developed severe neurotrophic keratitis, i.e. 1.6% of treated patients. According to the Mackie classification, the three patients showed grade 3 NK less than one year after the conclusion of their HEP. These three patients underwent amniotic membrane grafting. They were placed on autologous serum eye drops. Two of the three patients had to be eviscerated. The dose to the cornea was greater than 50 Gray (Gy)_Relative biological effectiveness (RBE) in the three cases.

DISCUSSION

The diagnosis and etiological origin of neurotrophic keratitis are often difficult to establish. In these cases, the imputability of radiation therapy, proton therapy in our cases, in the development of neurotrophic keratitis was plausible based on the dosimetry of the patients, all of whom had anterior tumors with a poor prognosis requiring high tumoricidal doses.

CONCLUSION

Further studies to establish the impact of proton therapy on corneal sensitivity are necessary. However, this feedback and the multidisciplinary management of tumors can help to limit the risk of some complications of radiation therapy. Early diagnosis allows for appropriate management and could possibly minimize the anatomical and functional ocular complications of neurotrophic keratitis.

[Radiotherapy of rare head and neck tumors]

Management of head and neck tumors is complex because of multiple anatomical locations and histologies possibilities. Rare tumors must be managed in a specialized center and be registered in the French network of expertise on ENT Cancers (Refcor). Despite heterogeneous levels of evidence, radiotherapy plays an essential role in their treatment. Radiation therapy is generally indicated in the adjuvant setting, or in case of non-operability. Dose and target volumes depend on histology, location and extensions of the tumor, and the quality of the excision if applicable. We present here a review of the literature and available guidelines for the management by radiotherapy of rare upper aerodigestive tract tumors.

Radiotherapy of salivary gland tumours

Primary tumours of the salivary glands account for about 5 to 10% of tumours of the head and neck. These tumours represent a multitude of situations and histologies, where surgery is the mainstay of treatment and radiotherapy is frequently needed for malignant tumours (in case of stage T3-T4, nodal involvement, extraparotid invasion, positive or close resection margins, histological high-grade tumour, lymphovascular or perineural invasion, bone involvement postoperatively, or unresectable tumours). The diagnosis relies on anatomic and functional MRI and ultrasound-guided fine-needle aspiration for the diagnostic of benign or malignant tumors. In addition to patient characteristics, the determination of primary and nodal target volumes depends on tumor extensions and stage, histology and grade. Therefore, radiotherapy of salivary gland tumors requires a certain degree of personalization, which has been codified in the recommendations of the French multidisciplinary network of expertise for rare ENT cancers (Refcor) and may justify a specialised multidisciplinary discussion. Although radiotherapy is usually recommended for malignant tumours only, recurrent pleomorphic adenomas may sometimes require radiotherapy based on multidisciplinary discussion. An update of indications and recommendations for radiotherapy for salivary gland tumours in terms of techniques, doses, target volumes and dose constraints to organs at risk of the French society for radiotherapy and oncology (SFRO) was reported in this article.

Biological Effects of Scattered Versus Scanned Proton Beams on Normal Tissues in Total Body Irradiated Mice: Survival, Genotoxicity, Oxidative Stress and Inflammation

Side effects of proton therapy are poorly studied. Moreover, the differences in the method of dose delivery on normal tissues are not taken into account when proton beams are scanned instead of being scattered. We proposed here to study the effects of both modalities of proton beam delivery on blood; skin; lung and heart in a murine model. In that purpose; C57BL/6 mice were total body irradiated by 190.6 MeV proton beams either by Double Scattering (DS) or by Pencil Beam Scanning (PBS) in the plateau phase before the Bragg Peak. Mouse survival was evaluated. Blood and organs were removed three months after irradiation. Biomarkers of genotoxicity; oxidative stress and inflammation were measured. Proton irradiation was shown to increase lymphocyte micronucleus frequency; lung superoxide dismutase activity; erythrocyte and skin glutathione peroxidase activity; erythrocyte catalase activity; lung; heart and skin oxidized glutathione level; erythrocyte and lung lipid peroxidation and erythrocyte protein carbonylation even 3 months post-irradiation. When comparing both methods of proton beam delivery; mouse survival was not different. However, PBS significantly increased lymphocyte micronucleus frequency; erythrocyte glutathione peroxidase activity and heart oxidized glutathione level compared to DS. These results point out the necessity to take into account the way of delivering dose in PT as it could influence late side effects.

Mixed-beam approach in locally advanced nasopharyngeal carcinoma: IMRT followed by proton therapy boost versus IMRT-only. Evaluation of toxicity and efficacy

Objective: To compare radiation-induced toxicity and dosimetry parameters in patients with locally advanced nasopharyngeal cancer (LANPC) treated with a mixed-beam (MB) approach (IMRT followed by proton therapy boost) with an historic cohort of patients treated with a full course of IMRT-only.Material and methods: Twenty-seven patients with LANPC treated with the MB approach were compared to a similar cohort of 17 patients treated with IMRT-only. The MB approach consisted in a first phase of IMRT up to 54-60 Gy followed by a second phase delivered with a proton therapy boost up to 70-74 Gy (RBE). The total dose for patients treated with IMRT-only was 69.96 Gy. Induction chemotherapy was administrated to 59 and 88% and concurrent chemoradiotherapy to 88 and 100% of the MB and IMRT-only patients, respectively. The worst toxicity occurring during the entire course of treatment (acute toxicity) and early-late toxicity were registered according to the Common Terminology Criteria Adverse Events V4.03.Results: The two cohorts were comparable. Patients treated with MB received a significantly higher median total dose to target volumes (p = .02). Acute grade 3 mucositis was found in 11 and 76% (p = .0002) of patients treated with MB and IMRT-only approach, respectively, while grade 2 xerostomia was found in 7 and 35% (p = .02) of patients treated with MB and IMRT-only, respectively. There was no statistical difference in late toxicity. Local progression-free survival (PFS) and progression-free survival curves were similar between the two cohorts of patients (p = .17 and p = .40, respectively). Local control rate was 96% and 81% for patients treated with MB approach and IMRT-only, respectively.Conclusions: Sequential MB approach for LANPC patients provides a significantly lower acute toxicity profile compared to full course of IMRT. There were no differences in early-late morbidities and disease-related outcomes (censored at two-years) but a longer follow-up is required to achieve conclusive results.

[Proton therapy for head and neck cancers]

The absence of exit dose and the sharp lateral penumbra are key assets for proton therapy, which are responsible for its dosimetric superiority over advanced photon radiotherapy. Dosimetric comparisons have consistently shown a reduction of the integral dose and the dose to organs at risk favouring intensity-modulated proton therapy (IMPT) over intensity-modulated radiotherapy (IMRT). The structures that benefit the most of these dosimetric improvements in head and neck cancers are the anterior oral cavity, the posterior fossa, the visual apparatus and swallowing structures. A number of publications have concluded that these dosimetric differences actually translate into reduced toxicities with IMPT, for example with regards to reduced weight loss or need for feeding tube. Patient survival is usually similar to IMRT series, except in base of skull or sinonasal malignancies, where a survival advantage of IMPT could exist. The goals of the present review is to describe the major characteristics of proton therapy, to analyse the clinical data with regards to head and neck cancer patients, and to highlight the issue of patient selection and physical and biological uncertainties.