Tomas Drizdal

Reirradiation combined with hyperthermia in breast cancer recurrences: overview of experience in Erasmus MC.

For superficial hyperthermia a custom-built multi-applicator multi-amplifier superficial hyperthermia system operating at 433 MHz is utilised. Up to 6 Lucite Cone applicators can be used simultaneously to treat an area of 600 cm2. Temperatures are measured continuously with fibre optic multi-sensor probes. For patients with non-standard clinical problems, hyperthermia treatment planning is used to support decision making with regard to treatment strategy. In 74% of our patients with recurrent breast cancer treated with a reirradiation scheme of 8 fractions of 4 Gy in 4 weeks, combined with 4 or 8 hyperthermia treatments, a complete response is achieved, approximately twice as high as the CR rate following the same reirradation alone. The CR rate in tumours smaller than 30 mm is 80–90%, for larger tumours it is 65%. Hyperthermia appears beneficial for patients with microscopic residual tumour as well. To achieve high CR rates it is important to heat the whole radiotherapy field, and to use an adequate heating technique.

Procedure for creating a three-dimensional (3D) model for superficial hyperthermia treatment planning

PurposeTo make a patient- and treatment-specific computed tomography (CT) scan and to create a three-dimensional (3D) patient model for superficial hyperthermia treatment planning (SHTP).Patients, Materials, and MethodsPatients with recurrent breast adenocarcinoma in previously irradiated areas referred for radiotherapy (RT) and hyperthermia (HT) treatment and giving informed consent were included. After insertion of the thermometry catheters in the treatment area, a CT scan in the treatment position was made.ResultsA total of 26 patients have been, thus far, included in the study. During the study period, five types of adjustments were made to the procedure: (1) marking the RT field with radioopaque markers, (2) making the CT scan after the first HT treatment instead of before, (3) using an air- and foam-filled (dummy) water bolus, (4) a change to radiolucent catheters for which radioopaque markers were needed, and (5) marking the visible/palpable extent of the tumor with radioopaque markers, if necessary. With these adjustments, all necessary information is visible on the CT scan. Each CT slice was automatically segmented into muscle, fat, bone, and air. RT field, catheters, applicators, and tumor lesions, if indicated, were outlined manually using the segmentation program iSeg. Next the model was imported into SEMCAD X, a 3D electromagnetic field simulator.ConclusionUsing the final procedure to obtain a patient- and treatment-specific CT scan, it is possible to create a 3D model for SHTP.ZusammenfassungZielErstellen eines patienten- und behandlungsspezifischen CT zur Therapieplanung von Oberflächenhyperthermiebehandlungen und eines 3D-Patientenmodell für die Planung der Hyperthermiebehandlung.Patientengut und MethodePatientinnen mit Brustwandrezidiven eines Mammakarzinoms in vorbestrahlten Regionen, die zur Strahlentherapie und Hyperthermie (HT) zugewiesen wurden, wurden nach entsprechender Aufklärung und Einwilligung in die Studie aufgenommen. Nach dem Einsetzen der Thermometrie-Katheter in die Therapieregion wurde ein CT in Behandlungsposition durchgeführt.Ergebnisse26 Patienten wurden bis jetzt in die Studie eingeschlossen. Im Verlauf der Studiendauer wurden fünf Arten von Anpassungen im Verfahren vorgenommen: (1) Markierung des Bestrahlungsfeldes mit röntgendichten Markern; (2) das CT wurde nach der ersten HT Behandlung gemacht statt voher; (3) dabei wurde ein mit Luft und Schaum gefüllter Wasserbolus (Dummy) verwendet; (4) ein Wechsel zu strahlendurchlässigen Kathetern, für die röntgendichte Marker benötigt wurden; (5) Markierung des sichtbaren und tastbaren Tumors mit röntgendichten Markern, wenn nötig. Mit diesen Anpassungen werden all notwendigen Informationen auf dem CT-Scan sichtbar. Jeder CT-Schnitt wurde automatisch segmentiert in Muskel, Fett, Knochen und Luft. Das Strahlenfeld, der Thermometrie-Katheter, Applikator und Tumor wurden, wenn angegeben, manuell mit dem Segmentierungsprogramm iSEG segmentiert. Dann wurde das Modell in SEMCAD X, einem 3D-Simulator für elektromagnetische Felder, importiert.SchlussfolgerungMit dem endgültigen Verfahren für ein patienten- und behandlungsspezifisches CT ist ein 3D-Modell für lokale Oberflächenhyperthermie-Bestrahlungsplanung (OHBP) möglich und in der Praxis realisierbar.

Differential Evolution Optimization of the SAR Distribution for Head and Neck Hyperthermia

Hyperthermia is an emerging cancer treatment modality, which involves applying heat to the malignant tumor. The heating can be delivered using electromagnetic (EM) energy, mostly in the radiofrequency (RF) or microwave range. Accurate patient-specific hyperthermia treatment planning (HTP) is essential for effective and safe treatments, in particular, for deep and loco-regional hyperthermia. An important aspect of HTP is the ability to focus microwave energy into the tumor and reduce the occurrence of hot spots in healthy tissue. This paper presents a method for optimizing the specific absorption rate (SAR) distribution for the head and neck cancer hyperthermia treatment. The SAR quantifies the rate at which localized RF or microwave energy is absorbed by the biological tissue when exposed to an EM field. A differential evolution (DE) optimization algorithm is proposed in order to improve the SAR coverage of the target region. The efficacy of the proposed algorithm is demonstrated by testing with the Erasmus MC patient dataset. DE is compared to the particle swarm optimization (PSO) method, in terms of average performance and standard deviation and across various clinical metrics, such as the hot-spot-tumor SAR quotient (HTQ), treatment quantifiers, and temperature parameters. While hot spots in the SAR distribution remain a problem with current approaches, DE enhances focusing microwave energy absorption to the target region during hyperthermia treatment. In particular, DE offers improved performance compared to the PSO algorithm currently deployed in the clinic, reporting a range of improvement of HTQ standard deviation of between 40.1–96.8% across six patients.

Impact of silicone and metal port-a-cath implants on superficial hyperthermia treatment quality.

Abstract Purpose: A port-a-cath is a device implanted under the skin for continuous drug administration. It is composed of a catheter and a silicone or metal reservoir. A simulation study was done to assess the impact of a port-a-cath implant on the quality of superficial hyperthermia treatments applied using the Lucite cone applicator (LCA). Methods: Specific absorption rate (SAR) and temperature distributions were predicted using SEMCAD-X (version 14.8). We simulated 72 arrangements: two LCA-implant set-ups (central port-a-cath or at an edge below the LCA footprint), six translations of the LCA per set-up, two LCA orientations (Parallel or perpendicular electric field direction) per set-up, two implant materials (silicon or metal) and a control without port-a-cath. Treatment quality was quantified by the average 1 g SAR coverage (CV25%), i.e. volume within the 25% iso-SAR surface, and the volume within the 40 °C iso-temperature surface (CV40 °C). Results: CV25% reduced with a silicon port-a-cath located below the LCA footprint. In the worst scenario, only 64% of the CV25% of the control set-up was achieved. For a metal port-a-cath below the LCA aperture, dramatic reductions of CV25% were predicted: worst scenario down to 12.1% of the control CV25%. For the CV40 °C the worst case values were 74.5% and 6.5%, for silicon and metal implants, respectively. Conclusions: A silicone port-a-cath below the LCA had a smaller effect on treatment quality than a metal implant. Based on this study we recommend verifying heating quality by 3D patient-specific treatment planning when a port-a-cath is located below the footprint of the applicator.

Hyperthermia treatment planning guided applicator selection for sub-superficial head and neck tumors heating

Abstract Purpose: In this study, we investigated the differences in hyperthermia treatment (HT) quality between treatments applied with different hyperthermia systems for sub-superficial tumours in the head and neck (H&N) region. Materials and methods: In 24 patients, with a clinical target volume (CTV) extending up to 6 cm from the surface, we retrospectively analysed the predicted HT quality achievable by two planar applicator arrays or one phased-array hyperthermia system. Hereto, we calculated and compared the specific absorption rate (SAR) and temperature distribution coverage of the CTV and gross tumour volume (GTV) for the Lucite cone applicator (LCA: planar), current sheet applicator (CSA: planar) and the HYPERcollar (phased-array). Results: The HYPERcollar provides better SAR coverage than planar applicators if the target region is fully enclosed by its applicator frame. For targets extending outside the HYPERcollar frame, sufficient SAR coverage (25% target coverage, i.e. TC25 ≥ 75%) can still be achieved using the LCA when the target is fully under the LCA aperture and not deeper than 50 mm from the patient surface. Conclusion: Simulations predict that the HYPERcollar (hence also its successor the HYPERcollar3D) is to be preferred over planar applicators such as LCA and current sheet applicator in sub-superficial tumours in the H&N region when used within specifications.

Hyperthermia and the need to monitor temperature

Extensive biologic research has shown that adjuvant thermal therapy, i.e. heating tumors to 40-43°C, is a promising approach to increase the efficacy of existing radio- and chemotherapy protocols. The fact that in clinical trials, hyperthermia has shown not to increase toxicity is a major drive to invest in developing innovative devices and applicators to deliver thermal therapies. Moreover, the recent demonstrated ability of hyperthermia to decrease the repair of DNA double strand breaks provides a gateway to new treatments strategies involving hyperthermia and in combination with temperature sensitive drug carriers hyperthermia can be used for triggered local drug delivery. A point of concern, however, is that the quality of hyperthermia, i.e. the height of the achieved tumor temperature is closely related to its effectiveness, whereas in clinical practice application of hyperthermia is hampered by a low ability to control energy deposition and poor quality of temperature monitoring. In the light of our quest to control and prescribe hyperthermia quality the progress with regard to non-invasive thermometry and hyperthermia treatment planning should be considered to provide the gate-way to next generation of hyperthermia systems. Hybrid systems combining simultaneous heating and noninvasive thermometry are excellent to verify the temperature distribution. However, non-invasive thermometry cannot provide a prospectively evaluation of the potential quality of the hyperthermia treatment. For this purpose accurate hyperthermia treatment planning holds a pivotal position, as hyperthermia treatment planning is the only tool that has the potential to evaluate a priori the thermal dose to be delivered and to perform on-line optimization of the thermal dose.