Hyperthermia with photon radiotherapy is thermoradiobiologically analogous to neutrons for tumors without enhanced normal tissue toxicity

Hyperthermia: A Potential Game-Changer in the Management of Cancers in Low-Middle-Income Group Countries

Loco-regional hyperthermia at 40-44 °C is a multifaceted therapeutic modality with the distinct triple advantage of being a potent radiosensitizer, a chemosensitizer and an immunomodulator. Risk difference estimates from pairwise meta-analysis have shown that the local tumour control could be improved by 22.3% (p < 0.001), 22.1% (p < 0.001) and 25.5% (p < 0.001) in recurrent breast cancers, locally advanced cervix cancer (LACC) and locally advanced head and neck cancers, respectively by adding hyperthermia to radiotherapy over radiotherapy alone. Furthermore, thermochemoradiotherapy in LACC have shown to reduce the local failure rates by 10.1% (p = 0.03) and decrease deaths by 5.6% (95% CI: 0.6-11.8%) over chemoradiotherapy alone. As around one-third of the cancer cases in low-middle-income group countries belong to breast, cervix and head and neck regions, hyperthermia could be a potential game-changer and expected to augment the clinical outcomes of these patients in conjunction with radiotherapy and/or chemotherapy. Further, hyperthermia could also be a cost-effective therapeutic modality as the capital costs for setting up a hyperthermia facility is relatively low. Thus, the positive outcomes evident from various phase III randomized trials and meta-analysis with thermoradiotherapy or thermochemoradiotherapy justifies the integration of hyperthermia in the therapeutic armamentarium of clinical management of cancer, especially in low-middle-income group countries.

Mathematical model for the thermal enhancement of radiation response: thermodynamic approach

Radiotherapy can effectively kill malignant cells, but the doses required to cure cancer patients may inflict severe collateral damage to adjacent healthy tissues. Recent technological advances in the clinical application has revitalized hyperthermia treatment (HT) as an option to improve radiotherapy (RT) outcomes. Understanding the synergistic effect of simultaneous thermoradiotherapy via mathematical modelling is essential for treatment planning. We here propose a theoretical model in which the thermal enhancement ratio (TER) relates to the cell fraction being radiosensitised by the infliction of sublethal damage through HT. Further damage finally kills the cell or abrogates its proliferative capacity in a non-reversible process. We suggest the TER to be proportional to the energy invested in the sensitisation, which is modelled as a simple rate process. Assuming protein denaturation as the main driver of HT-induced sublethal damage and considering the temperature dependence of the heat capacity of cellular proteins, the sensitisation rates were found to depend exponentially on temperature; in agreement with previous empirical observations. Our findings point towards an improved definition of thermal dose in concordance with the thermodynamics of protein denaturation. Our predictions well reproduce experimental in vitro and in vivo data, explaining the thermal modulation of cellular radioresponse for simultaneous thermoradiotherapy.

Quantification of thermal dose in moderate clinical hyperthermia with radiotherapy: a relook using temperature-time area under the curve (AUC)

BACKGROUND

Thermal dose in clinical hyperthermia reported as cumulative equivalent minutes (CEM) at 43 °C (CEM43) and its variants are based on direct thermal cytotoxicity assuming Arrhenius 'break' at 43 °C. An alternative method centered on the actual time-temperature plot during each hyperthermia session and its prognostic feasibility is explored.

METHODS AND MATERIALS

Patients with bladder cancer treated with weekly deep hyperthermia followed by radiotherapy were evaluated. From intravesical temperature (T) recordings obtained every 10 secs, the area under the curve (AUC) was computed for each session for T > 37 °C (AUC > 37 °C) and T ≥ 39 °C (AUC ≥ 39 °C). These along with CEM43, CEM43(>37 °C), CEM43(≥39 °C), T_mean, T_min and T_max were evaluated for bladder tumor control.

RESULTS

Seventy-four hyperthermia sessions were delivered in 18 patients (median: 4 sessions/patient). Two patients failed in the bladder. For both individual and summated hyperthermia sessions, the T_mean, CEM43, CEM43(>37 °C), CEM43(≥39 °C), AUC > 37 °C and AUC ≥ 39 °C were significantly lower in patients who had a local relapse. Individual AUC ≥ 39 °C for patients with/without local bladder failure were 105.9 ± 58.3 °C-min and 177.9 ± 58.0 °C-min, respectively (p = 0.01). Corresponding summated AUC ≥ 39 °C were 423.7 ± 27.8 °C-min vs. 734.1 ± 194.6 °C-min (p < 0.001), respectively. The median AUC ≥ 39 °C for each hyperthermia session in patients with bladder tumor control was 190 °C-min.

CONCLUSION

AUC ≥ 39 °C for each hyperthermia session represents the cumulative time-temperature distribution at clinically defined moderate hyperthermia in the range of 39 °C to 45 °C. It is a simple, mathematically computable parameter without any prior assumptions and appears to predict treatment outcome as evident from this study. However, its predictive ability as a thermal dose parameter merits further evaluation in a larger patient cohort.

The addition of deep hyperthermia to gemcitabine-based chemoradiation may achieve enhanced survival in unresectable locally advanced adenocarcinoma of the pancreas

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Intensification of chemoradiation with hyperthermia was feasible in nine patients with LAPC.

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Only one grade three toxicity was reported and two tumours became resectable.

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The 24 months median OS and 100% 1 year OS are superior to historical series.

Introduction

Driven by the current unsatisfactory outcomes for patients with locally advanced pancreatic cancer (LAPC), a biologically intensified clinical protocol was developed to explore the feasibility and efficacy of FOLFORINOX chemotherapy followed by deep hyperthermia concomitant with chemoradiation and subsequent FOLFORINOX chemotherapy in patients with LAPC.

Methods

Nine patients with LAPC were treated according to the HEATPAC Phase II trial protocol which consists of 4 cycles of FOLFORINOX chemotherapy followed by gemcitabine-based chemoradiation to 56 Gy combined with weekly deep hyperthermia and then a further 8 cycles of FOLFORINOX chemotherapy.

Results

One grade three related toxicity was reported and two tumours became resectable. The median overall survival was 24 months and 1 year overall survival was 100%.

Conclusions

Intensification of chemoradiation with deep hyperthermia was feasible in nine consecutive patients with LAPC.

Integrating Loco-Regional Hyperthermia Into the Current Oncology Practice: SWOT and TOWS Analyses

Moderate hyperthermia at temperatures between 40 and 44°C is a multifaceted therapeutic modality. It is a potent radiosensitizer, interacts favorably with a host of chemotherapeutic agents, and, in combination with radiotherapy, enforces immunomodulation akin to “in situ tumor vaccination.” By sensitizing hypoxic tumor cells and inhibiting repair of radiotherapy-induced DNA damage, the properties of hyperthermia delivered together with photons might provide a tumor-selective therapeutic advantage analogous to high linear energy transfer (LET) neutrons, but with less normal tissue toxicity. Furthermore, the high LET attributes of hyperthermia thermoradiobiologically are likely to enhance low LET protons; thus, proton thermoradiotherapy would mimic ¹²C ion therapy. Hyperthermia with radiotherapy and/or chemotherapy substantially improves therapeutic outcomes without enhancing normal tissue morbidities, yielding level I evidence reported in several randomized clinical trials, systematic reviews, and meta-analyses for various tumor sites. Technological advancements in hyperthermia delivery, advancements in hyperthermia treatment planning, online invasive and non-invasive MR-guided thermometry, and adherence to quality assurance guidelines have ensured safe and effective delivery of hyperthermia to the target region. Novel biological modeling permits integration of hyperthermia and radiotherapy treatment plans. Further, hyperthermia along with immune checkpoint inhibitors and DNA damage repair inhibitors could further augment the therapeutic efficacy resulting in synthetic lethality. Additionally, hyperthermia induced by magnetic nanoparticles coupled to selective payloads, namely, tumor-specific radiotheranostics (for both tumor imaging and radionuclide therapy), chemotherapeutic drugs, immunotherapeutic agents, and gene silencing, could provide a comprehensive tumor-specific theranostic modality akin to “magic (nano)bullets.” To get a realistic overview of the strength (S), weakness (W), opportunities (O), and threats (T) of hyperthermia, a SWOT analysis has been undertaken. Additionally, a TOWS analysis categorizes future strategies to facilitate further integration of hyperthermia with the current treatment modalities. These could gainfully accomplish a safe, versatile, and cost-effective enhancement of the existing therapeutic armamentarium to improve outcomes in clinical oncology.

Knockdown GTSE1 enhances radiosensitivity in non-small-cell lung cancer through DNA damage repair pathway

Radiotherapy is an important strategy for NSCLC. However, although a variety of comprehensive radiotherapy-based treatments have dominated the treatment of NSCLC, it cannot be avoided to overcome the growing radioresistance during radiotherapy. The purpose of this study was to elucidate the radiosensitizing effects of NSCLC via knockdown GTSE1 expression and its mechanism. Experiments were performed by using multiple NSCLC cells such as A549, H460 and H1299. Firstly, we found GTSE1 conferred to radioresistance via clonogenic assay and apoptosis assay. Then, we detected the level of DNA damage through comet assay and γH2AX foci, which we could clearly observe knockdown GTSE1 enhance DNA damage after IR. Furthermore, through using laser assay and detecting DNA damage repair early protein expression, we found radiation could induce GTSE1 recruited to DSB site and initiate DNA damage response. Our finding demonstrated that knockdown GTSE1 enhances radiosensitivity in NSCLC through DNA damage repair pathway. This novel observation may have therapeutic implications to improve therapeutic efficacy of radiation.