Re-irradiation is Now a Real Option – But How Do We Take it Forward?

Re-irradiation for recurrent/progressive pediatric brain tumors: from radiobiology to clinical outcomes

INTRODUCTION

Brain tumors are the most common solid tumors in children. Neurosurgical excision, radiotherapy, and/or chemotherapy represent the standard of care in most histopathological types of pediatric central nervous system (CNS) tumors. Even though the successful cure rate is reasonable, some patients may develop recurrence locally or within the neuroaxis.

AREA COVERED

The management of these recurrences is not easy; however, significant advances in neurosurgery, radiation techniques, radiobiology, and the introduction of newer biological therapies, have improved the results of their salvage treatment. In many cases, salvage re-irradiation is feasible and has achieved encouraging results. The results of re-irradiation depend upon several factors. These factors include tumor type, extent of the second surgery, tumor volume, location of the recurrence, time that elapses between the initial treatment, the combination with other treatment agents, relapse, and the initial response to radiotherapy.

EXPERT OPINION

Reviewing the radiobiological basis and clinical outcome of pediatric brain re-irradiation revealed that re-irradiation is safe, feasible, and indicated for recurrent/progressive different tumor types such as; ependymoma, medulloblastoma, diffuse intrinsic pontine glioma (DIPG) and glioblastoma. It is now considered part of the treatment armamentarium for these patients. The challenges and clinical results in treating recurrent pediatric brain tumors were highly documented.

An international Delphi consensus for pelvic stereotactic ablative radiotherapy re-irradiation

INTRODUCTION

Stereotactic Ablative Radiotherapy (SABR) is increasingly used to treat metastatic oligorecurrence and locoregional recurrences but limited evidence/guidance exists in the setting of pelvic re-irradiation. An international Delphi study was performed to develop statements to guide practice regarding patient selection, pre-treatment investigations, treatment planning, delivery and cumulative organs at risk (OARs) constraints.

MATERIALS AND METHODS

Forty-one radiation oncologists were invited to participate in three online surveys. In Round 1, information and opinion was sought regarding participants' practice. Guidance statements were developed using this information and in Round 2 participants were asked to indicate their level of agreement with each statement. Consensus was defined as ≥75% agreement. In Round 3, any statements without consensus were re-presented unmodified, alongside a summary of comments from Round 2.

RESULTS

Twenty-three radiation oncologists participated in Round 1 and, of these, 21 (91%) and 22 (96%) completed Rounds 2 and 3 respectively. Twenty-nine of 44 statements (66%) achieved consensus in Round 2. The remaining 15 statements (34%) did not achieve further consensus in Round 3. Consensus was achieved for 10 of 17 statements (59%) regarding patient selection/pre-treatment investigations; 12 of 13 statements (92%) concerning treatment planning and delivery; and 7 of 14 statements (50%) relating to OARs. Lack of agreement remained regarding the minimum time interval between irradiation courses, the number/size of pelvic lesions that can be treated and the most appropriate cumulative OAR constraints.

CONCLUSIONS

This study has established consensus, where possible, in areas of patient selection, pre-treatment investigations, treatment planning and delivery for pelvic SABR re-irradiation for metastatic oligorecurrence and locoregional recurrences. Further research into this technique is required, especially regarding aspects of practice where consensus was not achieved.

Further development of spinal cord retreatment dose estimation: including radiotherapy with protons and light ions

PURPOSE

A graphical user interface (GUI) was developed to aid in the assessment of changes in the radiation tolerance of spinal cord/similar central nervous system tissues with time between two individual treatment courses.

METHODS

The GUI allows any combination of photons, protons (or ions) to be used as the initial, or retreatment, radiotherapy courses. Allowances for clinical circumstances, of reduced tolerance, can also be made. The radiobiological model was published previously and has been incorporated with additional checks and safety features, to be as safe to use as possible. The proton option includes use of a fixed RBE of 1.1 (set as the default), or a variable RBE, the latter depending on the proton linear energy transfer (LET) for organs at risk. This second LET-based approach can also be used for ions, by changing the LET parameters.

RESULTS

GUI screenshots are used to show the input and output parameters for different clinical situations used in worked examples. The results from the GUI are in agreement with manual calculations, but the results are now rapidly available without tedious and error-prone manual computations. The software outputs provide a maximum dose limit boundary, which should not be exceeded. Clinicians may also choose to further lower the number of treatment fractions, whilst using the same dose per fraction (or conversely a lower dose per fraction but with the same number of fractions) in order to achieve the intended clinical benefit as safely as possible.

CONCLUSIONS

The new GUI will allow scientific-based estimations of time related radiation tolerance changes in the spinal cord and similar central nervous tissues (optic chiasm, brainstem), which can be used to guide the choice of retreatment dose fractionation schedules, with either photons, protons or ions.

Paget's disease of scrotum and penis case report of a re-irradiation and review of the literature

Extramammary Paget's disease (EMPD) is a rare cutaneous adenocarcinoma generally arising in the anogenital region. Surgery is still considered the treatment of choice for patients with EMPD, while Radiotherapy is a common alternative for inoperable cases and it's necessary in case of lack of surgical radicality. In this article, we described our experience and a review of the literature, with a particular focus on radiation-induced toxicity and on the feasibility of re-irradiation. A 70-year-old patient with EPMD underwent adjuvant radiotherapy in 2015. After 28 months for recurrence another radiant treatment was performed. No G3 (CTCAE v4) toxicity were recorded. In the last follow-up visit at 18 months, no signs of relapse were reported. A search strategy of the bibliographic database PubMed was performed. The inclusion criteria for the articles were case report, clinical prospective, or retrospective studies with histological confirmation of EMPD of scrotum and penis; studies with patients undergoing RT; studies in the past 30 years. In most of the 14 reported studies, RT was overall well tolerated. The major observed toxicity was G3 skin toxicity in one study. To our knowledge, there are no other cases of EPMD re-irradiation in literature. Our patient showed an excellent response and tolerated very well the high doses of both the radiation treatments. This suggests that the tolerance of skin to re-irradiation following a long period between the two treatments may be comparable to the normal constraints.