Peter Sminia

Clinical features, mechanisms, and management of pseudoprogression in malignant gliomas

Since the introduction of chemoradiotherapy with temozolomide as the new standard of care for patients with glioblastoma, there has been an increasing awareness of progressive and enhancing lesions on MRI, noted immediately after the end of treatment, which are not related to tumour progression, but which are a treatment effect. This so-called pseudoprogression can occur in up to 20% of patients who have been treated with temozolomide chemoradiotherapy, and can explain about half of all cases of increasing lesions after the end of this treatment. These lesions decrease in size or stabilise without additional treatments and often remain clinically asymptomatic. Additionally, there is evidence that treatment-related necrosis occurs more frequently and earlier after temozolomide chemotherapy than after radiotherapy alone. The mechanisms behind these events have not yet been fully elucidated, but the likelihood is that chemoradiotherapy causes a higher degree of (desired) tumour-cell and endothelial-cell killing. This increased cell kill might lead to secondary reactions, such as oedema and abnormal vessel permeability in the tumour area, mimicking tumour progression, in addition to subsequent early treatment-related necrosis in some patients and milder subacute radiotherapy reactions in others. In patients managed with temozolomide chemoradiotherapy who have clinically asymptomatic progressive lesions at the end of treatment, adjuvant temozolomide should be continued; in clinically symptomatic patients, surgery should be considered. If mainly necrosis is noted during surgery, continuation of adjuvant temozolomide is logical. Trials on the treatment of recurrent malignant glioma should exclude patients with progression within the first 3 months after temozolomide chemoradiotherapy unless histological confirmation of tumour recurrence is available. Further research is needed to establish reliable imaging parameters that distinguish between true tumour progression and pseudoprogression or treatment-related necrosis.

Angiogenesis-independent tumor growth mediated by stem-like cancer cells

In this work, highly infiltrative brain tumors with a stem-like phenotype were established by xenotransplantation of human brain tumors in immunodeficient nude rats. These tumors coopted the host vasculature and presented as an aggressive disease without signs of angiogenesis. The malignant cells expressed neural stem cell markers, showed a migratory behavior similar to normal human neural stem cells, and gave rise to tumors in vivo after regrafting. Serial passages in animals gradually transformed the tumors into an angiogenesis-dependent phenotype. This process was characterized by a reduction in stem cells markers. Gene expression profiling combined with high throughput immunoblotting analyses of the angiogenic and nonangiogenic tumors identified distinct signaling networks in the two phenotypes. Furthermore, proinvasive genes were up-regulated and angiogenesis signaling genes were down-regulated in the stem-like tumors. In contrast, proinvasive genes were down-regulated in the angiogenesis-dependent tumors derived from the stem-like tumors. The described angiogenesis-independent tumor growth and the uncoupling of invasion and angiogenesis, represented by the stem-like cancer cells and the cells derived from them, respectively, point at two completely independent mechanisms that drive tumor progression. This article underlines the need for developing therapies that specifically target the stem-like cell pools in tumors.

Hyperbaric Oxygen and Radiotherapy

Background:Hyperbaric oxygen (HBO) therapy is the inhalation of 100% oxygen at a pressure of at least 1.5 atmospheres absolute (150 kPa). It uses oxygen as a drug by dissolving it in the plasma and delivering it to the tissues independent of hemoglobin. For a variety of organ systems, HBO is known to promote new vessel growth into areas with reduced oxygen tension due to poor vascularity, and therewith promotes wound healing and recovery of radiation-injured tissue. Furthermore, tumors may be sensitized to irradiation by raising intratumoral oxygen tensions.Method:A network of hyperbaric facilities exists in Europe, and a number of clinical studies are ongoing. The intergovernmental framework COST B14 action “Hyperbaric Oxygen Therapy” started in 1999. The main goal of the Working Group Oncology is preparation and actual implementation of prospective study protocols in the field of HBO and radiation oncology in Europe.Results:In this paper a short overview on HBO is given and the following randomized clinical studies are presented:a) reirradiation of recurrent squamous cell carcinoma of the head and neck after HBO sensitization;b) role of HBO in enhancing radiosensitivity on glioblastoma multiforme;c) osseointegration in irradiated patients; adjunctive HBO to prevent implant failures;d) the role of HBO in the treatment of late irradiation sequelae in the pelvic region.The two radiosensitization protocols (a, b) allow a time interval between HBO and subsequent irradiation of 10–20 min.Conclusion:Recruitment of centers and patients is being strongly encouraged, detailed information is given on www.oxynet.org.Hintergrund:Unter „hyperbarer Sauerstofftherapie“, auch „hyperbare Oxygenation“ (HBO) genannt, versteht man die Atmung von 100% Sauerstoff bei einem Druck von mindestens 1,5 ATA (absolute Atmosphären; 150 kPa). Bei der HBO wird das Medikament Sauerstoff durch erhöhten Umgebungsdruck physikalisch im Plasma gelöst und unabhängig vom Hämoglobin in das Gewebe transportiert. Die HBO unterstützt in schlecht durchbluteten bestrahlten Geweben mit verringerter Sauerstoffspannung die Gefäßneubildung und trägt zur Wundheilung und Erholung des bestrahlten Gewebes bei. Andererseits kann Sauerstoff unter hyperbaren Bedingungen—während oder kurz vor der Strahlentherapie verabreicht—durch Erhöhung der intratumoralen Sauerstoffspannung als Radiosensitizer eingesetzt werden.Methodik:In Europa existiert ein Netzwerk von Druckkammern, an denen klinische Studien laufen. Im Jahr 1999 wurde das europäische Projekt COST B14 „Hyperbare Sauerstofftherapie“ gestartet. Das Hauptziel der Arbeitsgruppe „Onkologie“ ist die Vorbereitung und Implementierung klinischer Studienprotokolle, die sich mit dem Thema „HBO und Strahlentherapie“ beschäftigen.Ergebnisse:Die vorliegende Arbeit gibt einen kurzen Überblick über die Grundlagen und Wirkweise der HBO und stellt folgende zur Rekrutierung offenen randomisierten klinischen Studien vor:a) erneute Bestrahlung rezidivierter Plattenepithelkarzinome im Kopf-Hals-Bereich nach HBO-Sensibilisierung;b) HBO zur Erhöhung der Strahlensensibilität des Glioblastoma multiforme;c) Osseointegration nach Bestrahlung im Hopf-Hals-Bereich—adjuvante HBO zur Verhinderung der Implantatabstoßung;d) HBO bei radiogenen Spätfolgen im Beckenbereich.Die zwei Protokolle zur Strahlensensibilisierung (a, b) erlauben einen Zeitabstand zwischen HBO und nachfolgender Bestrahlung von 10–20 min.Schlussfolgerung:Interessierte Zentren werden eingeladen, sich aktiv an den Studien zu beteiligen (Details s. www.oxynet.org).

Absence of the MGMT protein as well as methylation of the MGMT promoter predict the sensitivity for temozolomide

Background:The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) can cause resistance to the alkylating drug temozolomide (TMZ). The purpose of this study was to determine the relationship between the MGMT status, determined by means of several techniques and methods, and the cytotoxic response to TMZ in 11 glioblastoma multiforme (GBM) cell lines and 5 human tumour cell lines of other origins.Methods:Cell survival was analysed by clonogenic assay. The MGMT protein levels were assessed by western blot analysis. The MGMT promoter methylation levels were determined using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and quantitative real-time methylation-specific PCR (qMSP). On the basis of the results of these techniques, six GBM cell lines were selected and subjected to bisulphite sequencing.Results:The MGMT protein was detected in all TMZ-resistant cell lines, whereas no MGMT protein could be detected in cell lines that were TMZ sensitive. The MS-MLPA results were able to predict TMZ sensitivity in 9 out of 16 cell lines (56%). The qMSP results matched well with TMZ sensitivity in 11 out of 12 (92%) glioma cell lines. In addition, methylation as detected by bisulphite sequencing seemed to be predictive of TMZ sensitivity in all six cell lines analysed (100%).Conclusion:The MGMT protein expression more than MGMT promoter methylation status predicts the response to TMZ in human tumour cell lines.

Cell survival and radiosensitisation: modulation of the linear and quadratic parameters of the LQ model (Review).

The linear-quadratic model (LQ model) provides a biologically plausible and experimentally established method to quantitatively describe the dose-response to irradiation in terms of clonogenic survival. In the basic LQ formula, the clonogenic surviving fraction Sd/S₀ following a radiation dose d (Gy) is described by an inverse exponential approximation: Sd/S₀ = e-(αd+βd²), wherein α and β are experimentally derived parameters for the linear and quadratic terms, respectively. Radiation is often combined with other agents to achieve radiosensitisation. In this study, we reviewed radiation enhancement ratios of hyperthermia (HT), halogenated pyrimidines (HPs), various cytostatic drugs and poly(ADP-ribose) polymerase‑1 (PARP1) inhibitors expressed in the parameters α and β derived from cell survival curves of various mammalian cell cultures. A significant change in the α/β ratio is of direct clinical interest for the selection of optimal fractionation schedules in radiation oncology, influencing the dose per fraction, dose fractionation and dose rate in combined treatments. The α/β ratio may increase by a mutually independent increase of α or decrease of β. The results demonstrated that the different agents increased the values of both α and β. However, depending on culture conditions, both parameters can also be separately influenced. Moreover, it appeared that radiosensitisation was more effective in radioresistant cell lines than in radiosensitive cell lines. Furthermore, radiosensitisation is also dependent on the cell cycle stage, such as the plateau or exponentially growing phase, as well as on post-treatment plating conditions. The LQ model provides a useful tool in the quantification of the effects of radiosensitising agents. These insights will help optimize fractionation schedules in multimodality treatments.

Radiosensitization of human glioma cells by cyclooxygenase-2 (COX-2) inhibition: Independent on COX-2 expression and dependent on the COX-2 inhibitor and sequence of administration

Purpose: Patients with a malignant glioma have a very poor prognosis. Cyclooxygenase-2 (COX-2) protein is regularly upregulated in gliomas and might be a potential therapeutic target. The effects of three selective COX-2 inhibitors were studied on three human glioma cell lines. Materials and methods: The selective COX-2 inhibitors NS-398, Celecoxib and Meloxicam and three human glioma cell lines (D384, U251 and U87) were used. Cell growth was assessed by a proliferation assay, the interaction with radiation (0 – 6 Gy) was studied using the clonogenic assay and cell cycle distribution was determined by FACS (fluorescence-activated cell sorting) analysis. Results: All COX-2 inhibitors reduced proliferation of the glioma cell lines irrespective of their COX-2 expression level. Incubation with 200 μM NS-398 24 h before radiation enhanced radiation-induced cell death of D384 cells and 750 μM Meloxicam resulted in radiosensitization of D384 and U87 cells. No radiosensitization was observed with COX-2 inhibitor administration after radiotherapy. Treatment of D384 with NS-398 (200 μM) or Celecoxib (50 μM) and U87 with NS-398 (200 μM) after radiation resulted even in radioprotection. Conclusions: Effectiveness of COX-2 inhibitors on cell proliferation and radio-enhancement was independent of COX-2 protein expression. The sequence of COX-2 inhibitor addition and irradiation is very important.

Re-Irradiation of the Human Spinal Cord

Purpose: Experimental animal data give evidence of long-term recovery of the spinal cord after irradiation. By extrapolation of these data, re-irradiation regimens were designed for eight patients who required palliative radiotherapy. As a consequence of re-irradiation, their spinal cords were exposed to cumulative doses exceeding the tolerance dose. Radiobiological and clinical data are presented. Patients and Method: Eight patients were re-irradiated on the cervical (n=1), thoracic (n=5) and lumbar (n=2) spinal cord. The time interval between the initial and re-treatment ranged from 4 months to 12.7 years (median: 2.5 years). (Re-)treatment schemes were designed and analyzed on basis of the biologically effective dose (BED) according to the linear-quadratic model. The repair capacity (α/β ratio) for the cervico-thoracic and lumbar spinal cord was assumed to be 2 Gy and 4 Gy, with a BEDtolerance of 100 Gy and 84 Gy, respectively. Results: The cumulative irradiation dose applied to the spinal cord varied between 125 and 172% of the BEDtolerance. During follow-up, ranging from 33 days to >4.5 years (median: 370 days) none of the patients developed neurological complications. Seven patients died from tumor progression, and one patient is still alive. Conclusion: Long-term recovery of the spinal cord from radiation injury, which has been demonstrated in rodents and primates, may also occur in humans.Gegenstand: Tierversuchsdaten belegen eine Langzeiterholung des Rückenmarks nach Bestrahlung. Nach Extrapolation dieser Daten wurden Wiederbestrahlungsregimes für acht Patienten, die eine palliative Radiotherapie benötigten, entworfen. Als Konsequenz wurde das Rückenmark dieser Patienten einer kumulativen Dosis ausgesetzt, die die Rückenmarkstoleranzdosis überschritt. Radiobiologische und klinische Daten werden präsentiert. Patienten und Methodik: Bei acht Patienten wurde das zervikale (n=1), thorakale (n=5) und das lumbale (n=2) Rückenmark erneut bestrahlt. Der Zeitintervall zwischen Erst- und Wiederbehandlung lag bei 4 Monaten bis 12,7 Jahren (Median = 2,5 Jahre). (Wieder-)Behandlungsschemata wurden auf der Basis der biologisch effektiven Dosis (BED) anhand des linearquadratischen Modells entworfen und analysiert. Als Reparaturkapazität (α/β-Wert) wurden für das zervikothorakale Rückenmark 2 Gy und für das lumbale Rückenmark 4 Gy mit einer BED von 100 Gy bzw. 84 Gy angenommen. Ergebnisse: Die kumulative Bestrahlungsdosis im Rückenmark variierte zwischen 125% und 172% der BEDToleranz. Während der Nachbeobachtungsperiode (zwischen 33 Tagen und bis zu 4,5 Jahren, Median = 370 Tage) entwickelte kein Patient neurologische Komplikationen. Sieben Patienten verstarben infolge einer Tumorprogression, ein Patient ist noch am Leben. Schlussfolgerung: Langzeiterholungsphänomene des Rückenmarks nach Bestrahlung – bei Nagetieren und Primaten belegt – sind auch beim Menschen als wahrscheinlich anzunehmen.

Lymphatic fistulas: obliteration by low-dose radiotherapy

Background:Lymphatic drainage from the surgical wound is an uncommon but challenging complication of surgical intervention. Protracted lymphorrhea contributes to morbidity, favors infections and results in a prolonged hospital stay. Treatment options include surgical ligation and, more conservatively, leg elevation, continuous local pressure, subatmospheric pressure dressings, and low-dose radiotherapy. This study examines the efficacy of low-dose radiotherapy.Patients and Methods:17 patients (19 fistulas) with lymphorrhea following vena saphena harvesting (n = 7), femoropopliteal bypass (n = 3), varicose vein surgery (n = 2), hip arthroplasty (n = 3; five fistulas), shunt surgery (n = 1), and piercing (n = 1) were referred for external radiotherapy. Depending on the depth of the fistula, orthovoltage (n = 12), electrons (4–11 MeV; n = 2) or photons (8 MV; n = 3) were used. Fractions between 0.3 Gy and 2 Gy were applied; the individual total dose depended on the success of the radiotherapy, i. e., the obliteration of the lymph fistula, and varied from 1 to 12 Gy.Results:In 13 out of 17 patients complete obliteration of the fistula was achieved. Interestingly, this was achieved in nine of the ten patients irradiated with total doses of ≤3 Gy and with fraction sizes ranging from 0.3 to 0.5 Gy. In one patient with hip arthroplasty, only two out of three fistulas disappeared after 12 Gy and in a further three cases no distinct benefit was observed after 2.4 Gy, 8 Gy, and 10.5 Gy, respectively. No treatment-related side effects occurred.Conclusion:Radiotherapy represents an efficacious and economical treatment option in cases of persistent lymphorrhea and is able to reduce the risk of secondary infection, to decrease the duration of hospitalization, and to reduce overall costs for the individual patient. Daily scoring of treatment efficacy is recommended, because radiotherapy can be terminated as soon as lymphorrhea has stopped. Very low total doses with 0.3–0.5 Gy fraction size are recommended up to a maximum of 10–12 Gy in nonresponders.Hintergrund:Persistierende sezernierende Lymphfisteln stellen eine seltene, aber für den Patienten belastende Komplikation chirurgischer Eingriffe dar. Sie können aufsteigende Infektionen unterstützen und den Krankenhausaufenthalt deutlich verlängern. Als mögliche Behandlungsoptionen werden neben chirurgischen Reinterventionen auch konservative Maßnahmen wie Bettruhe, Hochlagerung, Druckverbände bzw. niedrigdosierte Strahlentherapie diskutiert.Patienten und Methodik:17 Patienten (13 Männer, vier Frauen) mit insgesamt 19 klinisch symptomatischen Lymphfisteln wurden zur externen Strahlentherapie zugewiesen. Auslösende Ursachen für die Fistelbildung waren: Entnahme der Vena saphena magna (n = 7), Anlegen eines femoropoplitealen Bypass (n = 3), erneuter Wechsel einer Totalendoprothese (TEP) der Hüfte (n = 3; fünf Fisteln), Varizenoperation (n = 2), Anlegen eines Dialyseshunts (n = 1) bzw. Piercing (n = 1). Je nach Tiefenausdehnung der Fistel wurden die Patienten mit Orthovolttherapie (n = 12), Elektronen (4–11 MeV; n = 2) oder Photonen (8 MV; n = 3) bestrahlt. Die Einzeldosen schwankten zwischen 0,3 Gy und 2 Gy, die individuelle Gesamtdosis hing vom Erfolg der Strahlentherapie, d. h. der Obliteration der Lymphfistel, ab und schwankte zwischen 1 und 12 Gy.Ergebnisse:Bei 13 von 17 Patienten kam es zu einem vollständigen Verschluss der Lymphfistel. Es fiel auf, dass bei neun von zehn Patienten, die mit sehr niedrigen Einzeldosen (0,3–0,5 Gy) und Gesamtdosen von ≤3 Gy bestrahlt wurden, eine komplette Obliteration der Lymphfistel beobachtet werden konnte. Bei einem Patienten nach Hüftoperation schlossen sich zwei von drei Fisteln nach 12 Gy. Bei weiteren drei Patienten wurde kein eindeutiger Nutzen nach Gesamtdosen von 2,4 Gy, 8 Gy bzw. 10,5 Gy beobachtet. Bestrahlungsinduzierte Nebenwirkungen traten nicht auf.Schlussfolgerung:Die Strahlentherapie stellt eine wirksame und kosteneffektive Behandlungsoption klinisch symptomatischer sezernierender Lymphfisteln dar. Die tägliche Kontrolle des Behandlungsergebnisses ist anzuraten, da die Strahlentherapie sofort nach Sistieren des Lymphflusses beendet werden kann. Empfehlenswert scheint die Anwendung kleiner Einzeldosen (0,3–0,5 Gy) bis zu einer maximalen Gesamtdosis von 10–12 Gy.

The optimal fraction size in high-dose-rate brachytherapy: dependency on tissue repair kinetics and low-dose rate.

BACKGROUND AND PURPOSE Indications of the existence of long repair half-times on the order of 2-4 h for late-responding human normal tissues have been obtained from continuous hyperfractionated accelerated radiotherapy (CHART). Recently, these data were used to explain, on the basis of the biologically effective dose (BED), the potential superiority of fractionated high-dose rate (HDR) with large fraction sizes of 5-7 Gy over continuous low-dose rate (LDR) irradiation at 0.5 Gy/h in cervical carcinoma. We investigated the optimal fraction size in HDR brachytherapy and its dependency on treatment choices (overall treatment time, number of HDR fractions, and time interval between fractions) and treatment conditions (reference low-dose rate, tissue repair characteristics). METHODS AND MATERIALS Radiobiologic model calculations were performed using the linear-quadratic model for incomplete mono-exponential repair. An irradiation dose of 20 Gy was assumed to be applied either with HDR in 2-12 fractions or continuously with LDR for a range of dose rates. HDR and LDR treatment regimens were compared on the basis of the BED and BED ratio of normal tissue and tumor, assuming repair half-times between 1 h and 4 h. RESULTS With the assumption that the repair half-time of normal tissue was three times longer than that of the tumor, hypofractionation in HDR relative to LDR could result in relative normal tissue sparing if the optimum fraction size is selected. By dose reduction while keeping the tumor BED constant, absolute normal tissue sparing might therefore be achieved. This optimum HDR fraction size was found to be largely dependent on the LDR dose rate. On the basis of the BED(NT/TUM) ratio of HDR over LDR, 3 x 6.7 Gy would be the optimal HDR fractionation scheme for replacement of an LDR scheme of 20 Gy in 10-30 h (dose rate 2-0.67 Gy/h), while at a lower dose rate of 0.5 Gy/h, four fractions of 5 Gy would be preferential, still assuming large differences between tumor and normal tissue repair half-times and equal overall treatment time. For the same fraction size, an even larger normal tissue sparing can be obtained by prolongation of the HDR overall treatment time. CONCLUSION Radiobiologic model calculations presented here aim to demonstrate that hypofractionation in HDR might have its opportunities for widening the therapeutic window, but definitely has its limits. For each specific combination of the parameters, a theoretical optimal HDR fraction size with regard to relative or absolute normal tissue sparing can be estimated, but because of uncertainty in the biologic parameters, these hypofractionation schemes cannot be generalized for all HDR brachytherapy indications.

Hyperthermia, radiation carcinogenesis and the protective potential of vitamin A and N-acetylcysteine

The in vivo carcinogenic risk of hyperthermia, alone or in combination with irradiation, and the anti-carcinogenic potential of vitamin A andN-acetylcysteine (AcCys) were investigated. Starting 1 month before treatment, 160 rats were divided into four diet groups: no additives, vitamin A-enriched diet, AcCys and the combination vitamin A+AcCys. In 10 animals per diet group, the hind leg was treated with either X-irradiation alone (16 Gy), hyperthermia alone (60 min at 43°C), hyperthermia 5 h prior to irradiation or hyperthermia 5 h after irradiation. Animals were observed for 2 years after treatment with regard to the development of tumours either inside or outside the treated volume. After 16 Gy alone 12±5% of the animals developed a tumour. Tumour incidence increased to 37±9% (borderline significanceP=0.07 versus treatment with X-rays alone) when hyperthermia was applied prior to X-rays, and to 24±8% (NS) with hyperthermia after irradiation. The relative risk ratio (RRR) for tumour induction was increased to 2.4 by hyperthermia if combined with X-irradiation. Pathological characterization of induced tumours showed that these were of the fibrosarcoma, osteosarcoma and carcinoma type. Vitamin A alone or in combination with AcCys slightly protected against the induction of tumours by X-rays without or with hyperthermia (RRR of 0.4). However, morphological changes such as lipid accumulation in hepatocytes and damage to the parenchyma were noticed in livers from all animals that were given a vitamin-A-enriched diet (P<0.0001). Data from the present and past reports show that hyperthermia alone is not carcinogenic, but that it may increase radiation carcinogenesis. Treatment temperature and time of exposure to heat in addition to the radiation dose applied are important factors in the carcinogenic process. The enhancement of radiation carcinogenesis seems to occur independently of the sequence and time interval between irradiation and hyperthermia. However, not all data are consistent with this interpretation.