Intensity-Modulated Radiotherapy with Regional Hyperthermia for High-Risk Localized Prostate Carcinoma

Background: The purpose of this study was to evaluate the efficacy and toxicity of adding regional hyperthermia to intensity-modulated radiotherapy (IMRT) plus neoadjuvant androgen deprivation therapy (ADT) for high-risk localized prostate carcinoma. Methods: Data from 121 consecutive patients with high-risk prostate carcinoma who were treated with IMRT were retrospectively analyzed. The total planned dose of IMRT was 76 Gy in 38 fractions for all patients; hyperthermia was used in 70 of 121 patients. Intra-rectal temperatures at the prostate level were measured to evaluate thermal dose. Results: Median number of heating sessions was five and the median total thermal dose of CEM43T90 was 7.5 min. Median follow-up duration was 64 months. Addition of hyperthermia to IMRT predicted better clinical relapse-free survival. Higher thermal dose with CEM43T90 (>7 min) predicted improved biochemical disease-free survival. The occurrence of acute and delayed toxicity ≥Grade 2 was not significantly different between patients with or without hyperthermia. Conclusions: IMRT plus regional hyperthermia represents a promising approach with acceptable toxicity for high-risk localized prostate carcinoma. Further studies are needed to verify the efficacy of this combined treatment.

Bronchoskopische Thermoablation beim Lungenkarzinom: Ermutigende Daten eines experimentellen Verfahrens

<b>Background:</b> Bronchoscopic thermal vapour ablation (BTVA) is an established and approved modality for minimally invasive lung volume reduction in severe emphysema. Preclinical data suggest potential for BTVA in minimally invasive ablation of lung cancer lesions. <b>Objectives:</b> The objective of this study is to establish the safety, feasibility, and ablative efficacy of BTVA for minimally invasive ablation of lung cancers. <b>Methods:</b> Single arm treat-and-resect clinical feasibility study of patients with biopsy-confirmed lung cancer. A novel BTVA for lung cancer (BTVA-C) system for minimally invasive treatment of peripheral pulmonary tumours was used to deliver 330 Cal thermal vapour energy via bronchoscopy to target lesion. Patients underwent planned lobectomy to complete oncologic care. Pre-surgical CT chest and post-resection histologic analysis were performed to evaluate ablative efficacy. <b>Results:</b> Six patients underwent BTVA-C, and 5 progressed to planned lobectomy. Median procedure duration was 12 min. No major procedure-related complications occurred. All 5 resected lesions were part-solid lung adenocarcinomas with median solid component size 1.32 ± 0.36 cm. Large uniform ablation zones were seen in 4 patients where thermal dose exceeded 3 Cal/mL, with complete/near-complete necrosis of target lesions seen in 2 patients. Tumour positioned within ablation zones demonstrated necrosis in &#x3e;99% of cross-sectional area examined. <b>Conclusion:</b> BTVA of lung tumours is feasible and well tolerated, with preliminary evidence suggesting high potential for effective ablation of tumours. Thermal injury is well demarcated, and uniform tissue necrosis is observed within ablation zones receiving sufficient thermal dose per volume of lung. Treatment of smaller volumes and ensuring adequate thermal dose may be important for ablative efficacy.

Inverse planning for radiofrequency ablation in cancer therapy using multiple damage models

Radiofrequency ablation (RFA) offers localized and minimally invasive treatment of small-to-medium sized inoperable tumors. In RFA, tissue is ablated with high temperatures obtained from electrodes (needles) inserted percutaneously or via an open surgery into the target. RFA treatments are generally not planned in a systematic way, and do not account for nearby organs-at-risk (OARs), potentially leading to sub-optimal treatments and inconsistent treatment quality. We therefore develop a mathematical framework to design RFA treatment plans that provide complete ablation while minimizing healthy tissue damage. Borrowing techniques from radiosurgery inverse planning, we design a two-stage approach where we first identify needle positions and orientations, called needle orientation optimization, and then compute the treatment time for optimal thermal dose delivery, called thermal dose optimization. Several different damage models are used to determine both target and OAR damage. We present numerical results on three clinical case studies. Our findings indicate a need for high source voltage for short tip length (conducting portion of the needle) or fewer needles, and low source voltage for long tip length or more needles to achieve full coverage. Further, more needles yields a larger ablation volume and consequently more OAR damage. Finally, the choice of damage model impacts the source voltage, tip length, and needle quantity.

A new CEM₄₃ thermal dose model based on Vogel-Tammann-Fulcher behaviour in thermal damage processes

Thermal dose models are metrics that quantify thermal damage in tissues based on the temperature and the time of exposure. The validity and accuracy of one of the commonly used models (CEM₄₃) for high temperature thermal therapy applications (50-90 degree Celcius) is questionable. It was found to over-estimate the accumulation of thermal damage for high-temperature applications. A new CEM₄₃ dose model based on Arrhenius type Vogel-Tammann-Fulcher equation using published data is introduced in this work. The new dose values for the same damage threshold that was produced at different in-vivo skin experiments were in the same order of magnitude, while the current dose values were 2 orders of magnitude different. The new dose values for same damage threshold in 6 lessions in ex-vivo liver experiments were more consistent than the current dose values. Computer simulations of laser interstitial thermal therapy showed that the current model usually predicts bigger volume than the new model does. The deviation in damaged volume prediction can be significant. The contribution of this work is introducing methods that can lead to more robust thermal dosimetry which will result in improved therapy modelling, monitoring and control.