[Current and future strategies in interdisciplinary treatment of medulloblastomas, supratentorial PNET (primitive neuroectodermal tumors) and intracranial germ cell tumors in childhood]

Impact of radiation technique, radiation fraction dose, and total cisplatin dose on hearing : Retrospective analysis of 29 medulloblastoma patients

PURPOSE

To analyze the incidence and degree of sensorineural hearing loss (SNHL) resulting from different radiation techniques, fractionation dose, mean cochlear radiation dose (D_mean), and total cisplatin dose.

MATERIAL AND METHODS

In all, 29 children with medulloblastoma (58 ears) with subclinical pretreatment hearing thresholds participated. Radiotherapy (RT) and cisplatin had been applied sequentially according to the HIT MED Guidance. Audiological outcomes up to the latest follow-up (median 2.6 years) were compared.

RESULTS

Bilateral high-frequency SNHL was observed in 26 patients (90%). No significant differences were found in mean hearing threshold between left and right ears at any frequency. A significantly better audiological outcome (p < 0.05) was found after tomotherapy at the 6 kHz bone-conduction threshold (BCT) and left-sided 8 kHz air-conduction threshold (ACT) than after a combined radiotherapy technique (CT). Fraction dose was not found to have any impact on the incidence, degree, and time-to-onset of SNHL. Patients treated with CT had a greater risk of SNHL at high frequencies than tomotherapy patients even though D_mean was similar. Increase in severity of SNHL was seen when the total cisplatin dose reached above 210 mg/m², with the highest abnormal level found 8-12 months after RT regardless of radiation technique or fraction dose.

CONCLUSION

The cochlear radiation dose should be kept as low as possible in patients who receive simultaneous cisplatin-based chemotherapy. The risk of clinically relevant HL was shown when D_mean exceeds 45 Gy independent of radiation technique or radiation regime. Cisplatin ototoxicity was shown to have a dose-dependent effect on bilateral SNHL, which was more pronounced in higher frequencies.

Primitive neuroectodermal tumor presenting with diffuse leptomeningeal involvement in a 55-year-old woman: a case report and brief summary of current diagnostic tests and treatment

Primitive neuroectodermal tumors (PNETs) are typically present as masses in children and adolescents, but rarely in adults. Diagnoses, management strategies, and prognostication factors are not well established in adult cases of PNETs. We describe the case of a central nervous system PNET diagnosed in a 55-year-old woman presenting with a sudden onset of symptoms consisting of increased intracranial pressure and findings of diffuse leptomeningeal enhancement and a small medullary lesion seen on MRI. Amongst the small database of PNETs diagnosed in adults, our case report stands out as one of few cases describing a primarily leptomeningeal PNET diagnosed on biopsy. We also review the literature on PNETs presenting with diffuse leptomeningeal disease and the treatment of PNETs in the adult population.

Current concepts and future strategies in the management of intracranial germinoma

Radiation therapy is the backbone in the management of intracranial germinoma. In localized disease chemotherapy followed by whole brain irradiation is the present standard providing cure rates in excess of 90%. Craniospinal irradiation alone in metastatic disease provides equally excellent outcome. Chemotherapy is able to convert macroscopic to microscopic disease permitting a dose reduction to the tumor site and possibly the ventricular system and is investigated in prospective trials. Chemotherapy alone cannot replace radiotherapy as sole treatment. Whole-ventricular radiotherapy followed by a boost to tumor site without chemotherapy might be feasible. New treatment technologies such as intensity-modulated radiotherapy or proton therapy permit a dose reduction to non-target brain. Data on functional outcome are conflicting and based on small heterogeneous series only mandating prospective investigations.

What's in a name? Intracranial peripheral primitive neuroectodermal tumors and CNS primitive neuroectodermal tumors are not the same

BACKGROUND

Intracranial peripheral primitive neuroectodermal tumors (P-PNET) are extremely rare. They can be easily misdiagnosed as central nervous system primitive neuroectodermal tumors (CNS-PNET) or meningiomas. Little is known about the optimal treatment and prognosis of these tumors.

PATIENTS AND METHODS

We evaluated the treatment and outcome of 17 patients with intracranial, nonmetastatic, genetically confirmed P-PNET. Three patients were treated at our institutions. Thirteen other cases providing sufficient treatment and follow-up information were extracted from the literature.

RESULTS

The median age at diagnosis was 17 years. All patients underwent initial surgery. Complete resection was achieved in 9 of the 17 cases (53 %). Combined adjuvant treatment consisting of radiotherapy (focal, n = 10; craniospinal, n = 1) and chemotherapy was administered to 11 of the 17 patients (59 %). The median follow-up time was 1.4 years. In 8 of the 17 patients (47 %), the disease progressed; 4 of the 17 patients (24 %) died. The 2-year progression-free and overall survival rates were 64 % and 76 %, respectively.

CONCLUSION

The differential diagnosis for intracranial, meningeal-based, small, round-cell tumors should include P-PNET. It is highly probable that complete resection has a positive impact on survival--as previously reported for extracranial P-PNET--but this cannot be shown by our data. Intensive adjuvant treatment consisting of radiotherapy and chemotherapy seems to be essential. A statistically grounded recommendation for the appropriate target volume and radiation dose is not yet possible. However, in most case reports of primary intracranial P-PNET published to date, patients were treated with focal irradiation. The optimal chemotherapy regimen has yet to be established, with both the Ewing tumor and CNS-PNET protocols being promising candidates for effective treatment.

Curative treatment for central nervous system medulloepithelioma despite residual disease after resection. Report of two cases treated according to the GPHO Protocol HIT 2000 and review of the literature

Medulloepithelioma of the central nervous system (CNS) is an uncommon primitive neuroectodermal tumor (PNET) usually occurring in early childhood. It is characterized by highly malignant behavior with a propensity for progression, recurrence, and dissemination despite intensive therapy. Due to its rarity, the optimal management is still unknown. However, gross total resection (GTR) has been considered crucial to achieve cure. In this article, the authors report on 2 cases of CNS medulloepithelioma in which long-term survival (more than 6 years) could be achieved despite evidence of, or suspected postoperative residual disease with an otherwise dismal prognosis.The patients were treated according to different strata of the protocol for primitive neuroectodermal tumors (PNET) of the German-Austrian multicenter trial of the German Society for Pediatric Oncology and Hematology (GPOH) for childhood brain tumors (HIT 2000). Treatment included postoperative hyperfractionated radiotherapy of the craniospinal axis followed by a boost to the tumor site in combination with chemotherapy. A review of the 2 reported and 37 previously published cases confirmed GTR and older age as positive prognostic factors.

Carboplatin and ototoxicity: hearing loss rates among survivors of childhood medulloblastoma

PURPOSE

Patients with medulloblastoma are exposed to ototoxic treatments including radiation therapy and platinum chemotherapy. The favorable toxicity profile of carboplatin led us to substitute this chemotherapeutic agent for cisplatin in the HIT-1991, HIT-MED-1999, and HIT-2000 chemotherapy protocols. We retrospectively investigated its consequences in terms of overall survival and ototoxicity rates.

METHODS

Twenty-four medulloblastoma patients were treated according to HIT protocols with carboplatin substitution between April 1999 and June 2006. Nineteen (79%) patients had adequate baseline and post-treatment audiological data. Mean age at diagnosis was 9.3 (range 3.5-18.9) years with a mean follow-up time of 30.8 (8.1-111.3) months. Patients received a mean carboplatin cumulative dose of 2,131 (830-4312) mg/m(2).

RESULTS

Twenty-three patients were alive at the time of assessment. Hearing loss greater than 20 dB was observed in two (10.5%) of 19 patients. Both had grade 2 ototoxicity according to Brock's scale. There were no significant differences between the patients' baseline and post-treatment audiograms at any frequency. The observed hearing loss was significantly correlated to younger age at diagnosis and cumulative carboplatin dose (p<0.05).

CONCLUSIONS

The encouraging overall survival and low hearing loss rates in this medulloblastoma patient cohort suggest that protocols containing carboplatin may offer a viable alternative to standard cisplatin protocols and warrant further investigation.

Additive effects of 5-aza-2'-deoxycytidine and irradiation on clonogenic survival of human medulloblastoma cell lines

BACKGROUND AND PURPOSE

In recent years, epigenetic modulators were introduced into tumor therapy. Here, the authors investigated the antitumor effect of 5-aza-2'-deoxycytidine-(5-aza-dC-)induced demethylation combined with irradiation on human medulloblastoma (MB) cells, which form the most common malignant brain tumor in children.

MATERIAL AND METHODS

Three MB cell lines were treated with 5-aza-dC in a low-dose (0.1 microM, 6 days) or high-dose (3/5 microM, 3 days) setting and irradiated with 2, 4, 6, or 8 Gy single dose on an X-ray unit. Methylation status and mRNA expression of three candidate genes were analyzed by methylation-specific PCR (polymerase chain reaction) and quantitative real-time RT-PCR. Cell survival and mortality were determined by trypan blue exclusion test. Proliferation was analyzed by BrdU incorporation assay, and long-term cell survival was assessed by clonogenic assay.

RESULTS

5-aza-dC treatment resulted in partial promoter demethylation and increased expression of hypermethylated candidate genes. A significant decrease of vital cell count, proliferation inhibition and increase of mortality was observed in 5-aza-dC-treated as well as in irradiated MB cells, whereby combination of both treatments led to additive effects. Although high-dose 5-aza-dC treatment was more effective in terms of demethylation, clonogenic assay revealed no differences between high- and low-dose settings indicating no relevance of 5-aza-dC-induced demethylation for decreased cell survival. MB cells pretreated with 5-aza-dC showed significantly lower plating efficiencies than untreated cells at all irradiation doses investigated. Analysis of surviving curves in irradiated MB cells, however, revealed no significant differences of alpha-, beta-values and 2-Gy surviving fraction with or without 5-aza-dC treatment.

CONCLUSION

5-aza-dC did not enhance radiation sensitivity of MB cells but significantly reduced the clonogenicity versus irradiation alone, which merits further investigation of its potential clinical application in MB possibly by combination with other chemotherapeutic agents.

Adult neuroectodermal tumors of posterior fossa (medulloblastoma) and of supratentorial sites (stPNET)

Medulloblastoma and supratentorial primitive neuroectodermal tumors are rare diseases in adults. Due to this rarity, few prospective clinical trials have been conducted on medulloblastoma in adults, investigations being based exclusively on retrospective studies; the populations considered in literature are small, and the different treatments given span decades, during which diagnostic procedures, neurosurgical skills and radiotherapy techniques have changed. Unlike pediatric patients, adult medulloblastoma patients have been treated according to risk-adapted therapeutic strategies in only a few series and despite risk-tailored treatments, 20-30% of patients experience recurrence. Although patients could respond to second line treatments, the prognosis of relapsed patients remains dismal. An important challenge for the future will be the biological characterization of medulloblastoma, with the identification of specific genetic patterns of patients with a better or a worse prognosis.

Primitive neuroectodermal tumor (PNET) in the differential diagnosis of malignant kidney tumors

Primitive neuroectodermal tumors (PNETs) of the kidney, a rare neoplastic disease of high malignancy with a tendency towards early metastasis, affect young adults (26-30 years) irrespective of the gender. Differential diagnosis from other renal tumors is very important for an effective therapy. Herein, we report on a 24-year-old male patient with a renal tumor consisting of small, round cells, and summarize the diagnostic procedures that establish the diagnosis of PNET. Light microscopy revealed not only areas containing small, round cells forming rosettes and pseudorosettes, but also areas containing spindle cells. Expression of CD 99 in combination with neural markers, such as NSE, was detected by immunohistochemistry, and further evidence of neural differentiation was provided by electron microscopy. Image cytometry revealed a peridiploid DNA-stemline. A reciprocal translocation of the chromosomes 11 and 22 [t(11;22)(q24;q12)] with expression of a EWS/FLI-1 fusion transcript was demonstrated by molecular pathology. Using these methods, the diagnosis of PNET was firmly established, and the tumor was treated by surgical resection and subsequent adjuvant chemotherapy. Eighteen months after therapy, the patient is in excellent health condition without any evidence of tumor recurrence.