Paclitaxel as a radiosensitizer combined with fractionated stereotactic radiotherapy in the treatment of recurrent medulloblastoma

Progress from clinical trials and emerging non-conventional therapies for the treatment of Medulloblastomas

Medulloblastomas are highly aggressive tumors of the cerebellum with an embryonal origin. Despite current treatment modalities which include a combination of surgery, chemotherapy and/or radiation, challenges still exist to effectively treat some patients, especially those within the younger age group. In an effort to find improved therapies, ongoing research led by world-wide teams have explored non-conventional therapeutic strategies, as well as examined the efficacy of several drugs in clinical trials among patients with Medulloblastomas. We outline in this article, recent advances on the efficacy and toxicity of numerous therapeutic agents including those that are DNA damaging agents, microtubules binding compounds, and those that are inhibitors of Topoisomerase and of the Notch and Hedgehog signaling pathway, which were assessed in recent Phase I and II clinical trials. Among these clinical trials, it is unfortunate that the outcomes were dismal with the majority of the patients with Medulloblastomas still succumbing to relapse after conventional therapies. Furthermore, it is yet to be established clearly the clinical efficacy of non-conventional therapies such as immunotherapy and gene therapy. Moreover, there is growing interest in proton therapy as a potential replacement for photon therapy, while high dose chemotherapy and autologous stem cell rescue may improve therapeutic efficacies. However, further research is needed to resolve the inherent toxicity from these novel therapeutic methods. In conclusion, novel therapies based on a better understanding of the biology of Medulloblastomas are pivotal in improving non-conventional therapies in the treatment of this deadly disease.

[Radiosurgery as adjuvant treatment of a recurrent adult medulloblastoma. Ultra-early response]

The role of radiosurgery after multimodality treatment of recurrent desmoplastic adult medulloblastoma is analyzed. The ultra-early clinical and pathological response of this tumor to adjunctive radiosurgery is stressed.

Stereotactic Radiosurgery: Adjacent Tissue Injury and Response after High-Dose Single Fraction Radiation—Part II: Strategies for Therapeutic Enhancement, Brain Injury Mitigation, and Brain Injury Repair

IN THE FIRST part of this series, we reviewed the histological, radiographic, and molecular data gathered regarding the brain parenchymal response to radiosurgery and suggested future studies that could enhance our understanding of the topic. With this article, we begin by addressing methods of potentiating the effect of radiosurgery on target lesions of the central nervous system. Much of the work on potentiating the effects of cranial radiation has been performed in the field of whole-brain radiotherapy. Data from Phase III trials evaluating the efficacy of various agents as radiosensitizers or radioenhancers in whole-brain radiotherapy are reviewed, and trials for investigating certain agents as enhancers of radiosurgery are suggested. The roles of gene therapy and nanotechnology in enhancing the therapeutic efficacy of radiosurgery are then addressed. Focus is then shifted to a discussion of strategies of protecting healthy tissue from the potentially deleterious aspects of the brain's response to radiosurgery that were presented in the first article of this series. Finally, comments are made regarding the role of neural progenitor or stem cells in the repair of radiation-induced brain injury after radiosurgery. The importance of both the role of the extracellular matrix and properly directed axonal regrowth leading to appropriate target reinnervation is highlighted.

Stereotactic radiation therapy with chemotherapy in the management of recurrent medulloblastomas

Medulloblastomas are highly lethal tumors when they recur. Very few patients survive with conventional treatment. This report documents the preliminary study results of a treatment for recurrent medulloblastomas consisting of stereotactic radiation therapy (SRT) with chemotherapy. Four patients had local recurrence without apparent metastases and 8 patients had metastases with or without local recurrence. Twelve patients with 18 lesions underwent SRT as a single session (n=8) or in a hypofractionated manner (n=10) using a gamma knife or modified linear accelerator. All patients then received systemic chemotherapy. Five patients were treated with one to two sequential courses of high-dose chemotherapy with peripheral blood stem cell transplantation. The reduction in tumor size after SRT was often remarkable. Fourteen of 18 lesions treated disappeared 1-6 months after SRT. Two of 4 patients who had local recurrences without apparent metastasis at the time of SRT are alive without evidence of disease 70 and 72 months after SRT, respectively. In contrast, all 8 patients with metastasis had new lesions either in the spinal canal or on the surface of the brain outside the target area of SRT. Median progression-free survival and overall survival from the time of SRT were 9 and 19 months, respectively. The Kaplan-Meier estimates of PFS and overall survival at 3 years were 17 and 25%, respectively. One patient had brainstem edema after SRT causing bulbar palsy and quadriparesis. One patient died of toxicity of chemotherapy. Our experience suggests that local recurrence can be controlled by SRT with chemotherapy but survival of patients with metastases can not be improved effectively by SRT in conjunction with aggressive chemotherapy.

What have we learnt from previous phase II trials to help in the management of childhood brain tumours?

Contrary to major advances in cure rates observed for almost all childhood cancers, progress in reducing brain tumour survival rates remains very limited. Although new drug development in oncology is founded on principles outlined in the organised methodology of phase I, II, and III trials, based on rigorous study design using standardised criteria, this approach has been applied very slowly in the field of neuro-oncology. There are multiple explanations for the paucity of well-conducted prospective clinical trials, such as the rarity and the heterogeneity of these tumours, and the reluctance of some investigators to enroll their patients in constraining trials. Data from the past two decades shows that several methodological problems preclude the drawing of any definite conclusions for the majority of drugs assessed. Among them, the necessity of a central neuropathological and neuroradiological review has been highlighted in, at least, two multicentric studies. Changes in histological diagnosis and grade have been reported in a proportion as high as 20%, and changes in response rate in 14% of the cases. This review of phase II trials for brain tumours reveals a wide array of sometimes arbitrary response definitions, that is if response is defined at all, and most series have enrolled small numbers of patients. We report on the different problems encountered in childhood brain tumours in these phase II trials, and their impact on phase III trials.

Taxanes in combined modality therapy for solid tumors

The taxanes, paclitaxel and docetaxel, are novel antimitotic agents that are under extensive investigation in clinical trials. Both taxanes have demonstrated significant activity against many solid tumors as single agents and in combination with other chemotherapeutic agents. In addition, taxanes arrest cells at the G2/M phase of the cell cycle, which is the most radiosensitive phase. These properties are exploited in clinical trials combining this taxane with radiation therapy. Most studies included patients with non-small cell lung cancer (NSCLC) and cancers of the head and neck and there are a few studies with concurrent taxane/RT in esophageal, gastric, pancreatic, brain and breast cancer. Information concerning the tolerability and possible utility of docetaxel is also becoming available. This manuscript will review some of the more prominent trials of the taxanes in combination with radiation therapy for solid tumors.