Response: Commentary: The Impact of the Time Interval Between Radiation and Hyperthermia on Clinical Outcome in Patients With Locally Advanced Cervical Cancer

Radiosensitization by Hyperthermia Critically Depends on the Time Interval

PURPOSE

Hyperthermia is a potent sensitizer of radiation therapy that improves both tumor control and survival in women with locally advanced cervical cancer (LACC). The optimal sequence and interval between hyperthermia and radiation therapy are still under debate.

METHODS AND MATERIALS

We investigated the interval and sequence in vitro in cervical cancer cell lines, patient-derived organoids, and SiHa cervical cancer hind leg xenografts in athymic nude mice and compared the results with retrospective results from 58 women with LACC treated with thermoradiotherapy.

RESULTS

All 3 approaches confirmed that shortening the interval between hyperthermia and radiation therapy enhanced hyperthermic radiosensitization by 2 to 8 times more DNA double-strand breaks and apoptosis and 10 to 100 times lower cell survival, delayed tumor growth in mice, and increased the 5-year survival rate of women with LACC from 22% (interval ≥80 minutes) to 54% (interval <80 minutes). In vitro and in vivo results showed that the sequence of hyperthermia and radiation therapy did not affect the outcome.

CONCLUSIONS

Shortening the interval between hyperthermia and radiation therapy significantly improves treatment outcomes. The sequence of hyperthermia and radiation therapy (before or after) does not seem to matter.

The Relevance of High Temperatures and Short Time Intervals Between Radiation Therapy and Hyperthermia: Insights in Terms of Predicted Equivalent Enhanced Radiation Dose

PURPOSE

The radiosensitization effect of hyperthermia can be considered and quantified as an enhanced equivalent radiation dose (EQD_RT), that is, the dose needed to achieve the same effect without hyperthermia. EQD_RT can be predicted using an extended linear quadratic model, with temperature-dependent parameters. Clinical data show that both the achieved temperature and time interval between radiation therapy and hyperthermia correlate with clinical outcome, but their effect on expected EQD_RT is unknown and was therefore evaluated in this study.

METHODS AND MATERIALS

Biological modeling was performed using our in-house developed software (X-Term), considering a 23- × 2-Gy external beam radiation scheme, as applied for patients with locally advanced cervical cancer. First, the EQD_RT was calculated for homogeneous temperature levels, evaluating time intervals between 0 and 4 hours. Next, realistic heterogeneous hyperthermia treatment plans were combined with radiation therapy plans and the EQD_RT was calculated for 10 patients. Furthermore, the effect of achieving 0.5°C to 1°C lower or higher temperatures was evaluated.

RESULTS

EQD_RT increases substantially with both increasing temperature and decreasing time interval. The effect of the time interval is most pronounced at higher temperatures (>41°C). At a typical hyperthermic temperature level of 41.5°C, an enhancement of ∼10 Gy can be realized with a 0-hour time interval, which is decreased to only ∼4 Gy enhancement with a 4-hour time interval. Most enhancement is already lost after 1 hour. Evaluation in patients predicted an average additional EQD_RT (D95%) of 2.2 and 6.3 Gy for 4- and 0-hour time intervals, respectively. The effect of 0.5°C to 1°C lower or higher temperatures is most pronounced at high temperature levels and short time intervals. The additional EQD_RT (D95%) ranged between 1.5 and 3.3 Gy and between 4.5 and 8.5 Gy for 4- and 0-hour time intervals, respectively.

CONCLUSIONS

Biological modeling provides relevant insight into the relationship between treatment parameters and expected EQD_RT. Both high temperatures and short time intervals are essential to maximize EQD_RT.

Hyperthermia as a Potential Cornerstone of Effective Multimodality Treatment with Radiotherapy, Cisplatin and PARP Inhibitor in IDH1-Mutated Cancer Cells

Mutations in the isocitrate dehydrogenase 1 (IDH1MUT) gene occur in various types of malignancies, including ~60% of chondrosarcomas, ~30% of intrahepatic cholangiocarcinomas and >80% of low-grade gliomas. IDH1MUT are causal in the development and progression of these types of cancer due to neomorphic production of the oncometabolite D-2-hydroxyglutarate (D-2HG). Intracellular accumulation of D-2HG has been implicated in suppressing homologous recombination and renders IDH1MUT cancer cells sensitive to DNA-repair-inhibiting agents, such as poly-(adenosine 5′-diphosphate−ribose) polymerase inhibitors (PARPi). Hyperthermia increases the efficacy of DNA-damaging therapies such as radiotherapy and platinum-based chemotherapy, mainly by inhibition of DNA repair. In the current study, we investigated the additional effects of hyperthermia (42 °C for 1 h) in the treatment of IDH1MUT HCT116 colon cancer cells and hyperthermia1080 chondrosarcoma cancer cells in combination with radiation, cisplatin and/or a PARPi on clonogenic cell survival, cell cycle distribution and the induction and repair of DNA double-strand breaks. We found that hyperthermia in combination with radiation or cisplatin induces an increase in double-strand breaks and cell death, up to 10-fold in IDH1MUT cancer cells compared to IDH1 wild-type cells. This vulnerability was abolished by the IDH1MUT inhibitor AGI-5198 and was further increased by the PARPi. In conclusion, our study shows that IDH1MUT cancer cells are sensitized to hyperthermia in combination with irradiation or cisplatin and a PARPi. Therefore, hyperthermia may be an efficacious sensitizer to cytotoxic therapies in tumors where the clinical application of hyperthermia is feasible, such as IDH1MUT chondrosarcoma of the extremities.

Biological modeling in thermoradiotherapy: present status and ongoing developments toward routine clinical use

Biological modeling for anti-cancer treatments using mathematical models can be very supportive in gaining more insight into dynamic processes responsible for cellular response to treatment, and predicting, evaluating and optimizing therapeutic effects of treatment. This review presents an overview of the current status of biological modeling for hyperthermia in combination with radiotherapy (thermoradiotherapy). Various distinct models have been proposed in the literature, with varying complexity; initially aiming to model the effect of hyperthermia alone, and later on to predict the effect of the combined thermoradiotherapy treatment. Most commonly used models are based on an extension of the linear-quadratic (LQ)-model enabling an easy translation to radiotherapy where the LQ model is widely used. Basic predictions of cell survival have further progressed toward 3 D equivalent dose predictions, i.e., the radiation dose that would be needed without hyperthermia to achieve the same biological effect as the combined thermoradiotherapy treatment. This approach, with the use of temperature-dependent model parameters, allows theoretical evaluation of the effectiveness of different treatment strategies in individual patients, as well as in patient cohorts. This review discusses the significant progress that has been made in biological modeling for hyperthermia combined with radiotherapy. In the future, when adequate temperature-dependent LQ-parameters will be available for a large number of tumor sites and normal tissues, biological modeling can be expected to be of great clinical importance to further optimize combined treatments, optimize clinical protocols and guide further clinical studies.

The Effect of Hyperthermia and Radiotherapy Sequence on Cancer Cell Death and the Immune Phenotype of Breast Cancer Cells

Simple Summary

Hyperthermia (HT) is a cancer treatment which locally heats the tumor to supraphysiological temperature, and it is an effective sensitizer for radiotherapy (RT) and chemotherapy. HT is further capable of modulating the immune system. Thus, a better understanding of its effect on the immune phenotype of tumor cells, and particularly when combined with RT, would help to optimize combined anti-cancer treatments. Since in clinics, no standards about the sequence of RT and HT exist, we analyzed whether this differently affects the cell death and immunological phenotype of human breast cancer cells. We revealed that the sequence of HT and RT does not strongly matter from the immunological point of view, however, when HT is combined with RT, it changes the immunophenotype of breast cancer cells and also upregulates immune suppressive immune checkpoint molecules. Thus, the additional application of immune checkpoint inhibitors with RT and HT should be beneficial in clinics.

Abstract

Hyperthermia (HT) is an accepted treatment for recurrent breast cancer which locally heats the tumor to 39–44 °C, and it is a very potent sensitizer for radiotherapy (RT) and chemotherapy. However, currently little is known about how HT with a distinct temperature, and particularly, how the sequence of HT and RT changes the immune phenotype of breast cancer cells. Therefore, human MDA-MB-231 and MCF-7 breast cancer cells were treated with HT of different temperatures (39, 41 and 44 °C), alone and in combination with RT (2 × 5 Gy) in different sequences, with either RT or HT first, followed by the other. Tumor cell death forms and the expression of immune checkpoint molecules (ICMs) were analyzed by multicolor flow cytometry. Human monocyte-derived dendritic cells (moDCs) were differentiated and co-cultured with the treated cancer cells. In both cell lines, RT was the main stressor for cell death induction, with apoptosis being the prominent cell death form in MCF-7 cells and both apoptosis and necrosis in MDA-MB-231 cells. Here, the sequence of the combined treatments, either RT or HT, did not have a significant impact on the final outcome. The expression of all of the three examined immune suppressive ICMs, namely PD-L1, PD-L2 and HVEM, was significantly increased on MCF-7 cells 120 h after the treatment of RT with HT of any temperature. Of special interest for MDA-MB-231 cells is that only combinations of RT with HT of both 41 and 44 °C induced a significantly increased expression of PD-L2 at all examined time points (24, 48, 72, and 120 h). Generally, high dynamics of ICM expression can be observed after combined RT and HT treatments. There was no significant difference between the different sequences of treatments (either HT + RT or RT + HT) in case of the upregulation of ICMs. Furthermore, the co-culture of moDCs with tumor cells of any treatment had no impact on the expression of activation markers. We conclude that the sequence of HT and RT does not strongly affect the immune phenotype of breast cancer cells. However, when HT is combined with RT, it results in an increased expression of distinct immune suppressive ICMs that should be considered by including immune checkpoint inhibitors in multimodal tumor treatments with RT and HT. Further, combined RT and HT affects the immune system in the effector phase rather than in the priming phase.

Accurate Three-Dimensional Thermal Dosimetry and Assessment of Physiologic Response Are Essential for Optimizing Thermoradiotherapy

Numerous randomized trials have revealed that hyperthermia (HT) + radiotherapy or chemotherapy improves local tumor control, progression free and overall survival vs. radiotherapy or chemotherapy alone. Despite these successes, however, some individuals fail combination therapy; not every patient will obtain maximal benefit from HT. There are many potential reasons for failure. In this paper, we focus on how HT influences tumor hypoxia, since hypoxia negatively influences radiotherapy and chemotherapy response as well as immune surveillance. Pre-clinically, it is well established that reoxygenation of tumors in response to HT is related to the time and temperature of exposure. In most pre-clinical studies, reoxygenation occurs only during or shortly after a HT treatment. If this were the case clinically, then it would be challenging to take advantage of HT induced reoxygenation. An important question, therefore, is whether HT induced reoxygenation occurs in the clinic that is of radiobiological significance. In this review, we will discuss the influence of thermal history on reoxygenation in both human and canine cancers treated with thermoradiotherapy. Results of several clinical series show that reoxygenation is observed and persists for 24-48 h after HT. Further, reoxygenation is associated with treatment outcome in thermoradiotherapy trials as assessed by: (1) a doubling of pathologic complete response (pCR) in human soft tissue sarcomas, (2) a 14 mmHg increase in pO2 of locally advanced breast cancers achieving a clinical response vs. a 9 mmHg decrease in pO2 of locally advanced breast cancers that did not respond and (3) a significant correlation between extent of reoxygenation (as assessed by pO2 probes and hypoxia marker drug immunohistochemistry) and duration of local tumor control in canine soft tissue sarcomas. The persistence of reoxygenation out to 24-48 h post HT is distinctly different from most reported rodent studies. In these clinical series, comparison of thermal data with physiologic response shows that within the same tumor, temperatures at the higher end of the temperature distribution likely kill cells, resulting in reduced oxygen consumption rate, while lower temperatures in the same tumor improve perfusion. However, reoxygenation does not occur in all subjects, leading to significant uncertainty about the thermal-physiologic relationship. This uncertainty stems from limited knowledge about the spatiotemporal characteristics of temperature and physiologic response. We conclude with recommendations for future research with emphasis on retrieving co-registered thermal and physiologic data before and after HT in order to begin to unravel complex thermophysiologic interactions that appear to occur with thermoradiotherapy.

Present Practice of Radiative Deep Hyperthermia in Combination with Radiotherapy in Switzerland

BACKGROUND

Moderate hyperthermia is a potent and evidence-based radiosensitizer. Several indications are reimbursed for the combination of deep hyperthermia with radiotherapy (dHT+RT). We evaluated the current practice of dHT+RT in Switzerland.

METHODS

All indications presented to the national hyperthermia tumor board for dHT between January 2017 and June 2021 were evaluated and treatment schedules were analyzed using descriptive statistics.

RESULTS

Of 183 patients presented at the hyperthermia tumor board, 71.6% were accepted and 54.1% (99/183) finally received dHT. The most commonly reimbursed dHT indications were "local recurrence and compression" (20%), rectal (14.7%) and bladder (13.7%) cancer, respectively. For 25.3% of patients, an individual request for insurance cover was necessary. 47.4% of patients were treated with curative intent; 36.8% were in-house patients and 63.2% were referred from other hospitals.

CONCLUSIONS

Approximately two thirds of patients were referred for dHT+RT from external hospitals, indicating a general demand for dHT in Switzerland. The patterns of care were diverse with respect to treatment indication. To the best of our knowledge, this study shows for the first time the pattern of care in a national cohort treated with dHT+RT. This insight will serve as the basis for a national strategy to evaluate and expand the evidence for dHT.

Post-operative re-irradiation with hyperthermia in locoregional breast cancer recurrence: Temperature matters

PURPOSE

To investigate the impact of hyperthermia thermal dose (TD) on locoregional control (LRC), overall survival (OS) and toxicity in locoregional recurrent breast cancer patients treated with postoperative re-irradiation and hyperthermia.

METHODS

In this retrospective study, 112 women with resected locoregional recurrent breast cancer treated in 2010-2017 with postoperative re-irradiation 8frx4Gy (n = 34) or 23frx2Gy (n = 78), combined with 4-5 weekly hyperthermia sessions guided by invasive thermometry, were subdivided into 'low' (n = 56) and 'high' TD (n = 56) groups by the best session with highest median cumulative equivalent minutes at 43 °C (Best CEM43T50) < 7.2 min and ≥7.2 min, respectively. Actuarial LRC, OS and late toxicity incidence were analyzed. Backward multivariable Cox regression and inverse probability weighting (IPW) analysis were performed.

RESULTS

TD subgroups showed no significant differences in patient/treatment characteristics. Median follow-up was 43 months (range 1-107 months). High vs. low TD was associated with LRC (p = 0.0013), but not with OS (p = 0.29) or late toxicity (p = 0.58). Three-year LRC was 74.0% vs. 92.3% in the low and high TD group, respectively (p = 0.008). After three years, 25.0% and 0.9% of the patients had late toxicity grade 3 and 4, respectively. Multivariable analysis showed that distant metastasis (HR 17.6; 95%CI 5.2-60.2), lymph node involvement (HR 2.9; 95%CI 1.2-7.2), recurrence site (chest wall vs. breast; HR 4.6; 95%CI 1.8-11.6) and TD (low vs. high; HR 4.1; 95%CI 1.4-11.5) were associated with LRC. TD was associated with LRC in IPW analysis (p = 0.0018).

CONCLUSIONS

High thermal dose (best CEM43T50 ≥ 7.2 min) was associated with significantly higher LRC for patients with locoregional recurrent breast cancer treated with postoperative re-irradiation and hyperthermia, without augmenting toxicity.

Clinical Evidence for Thermometric Parameters to Guide Hyperthermia Treatment

Hyperthermia (HT) is a cancer treatment modality which targets malignant tissues by heating to 40-43 °C. In addition to its direct antitumor effects, HT potently sensitizes the tumor to radiotherapy (RT) and chemotherapy (CT), thereby enabling complete eradication of some tumor entities as shown in randomized clinical trials. Despite the proven efficacy of HT in combination with classic cancer treatments, there are limited international standards for the delivery of HT in the clinical setting. Consequently, there is a large variability in reported data on thermometric parameters, including the temperature obtained from multiple reference points, heating duration, thermal dose, time interval, and sequence between HT and other treatment modalities. Evidence from some clinical trials indicates that thermal dose, which correlates with heating time and temperature achieved, could be used as a predictive marker for treatment efficacy in future studies. Similarly, other thermometric parameters when chosen optimally are associated with increased antitumor efficacy. This review summarizes the existing clinical evidence for the prognostic and predictive role of the most important thermometric parameters to guide the combined treatment of RT and CT with HT. In conclusion, we call for the standardization of thermometric parameters and stress the importance for their validation in future prospective clinical studies.

The role of hyperthermia in the treatment of locally advanced cervical cancer: a comprehensive review

Radiotherapy with cisplatin (chemoradiation) is the standard treatment for women with locally advanced cervical cancer. Radiotherapy with deep hyperthermia (thermoradiation) is a well established alternative, but is rarely offered as an alternative to chemoradiation, particularly for patients in whom cisplatin is contraindicated. The scope of this review is to provide an overview of the biological rationale of hyperthermia treatment delivery, including patient workflow, and the clinical effectiveness of hyperthermia as a radiosensitizer in the treatment of cervical cancer. Hyperthermia is especially effective in hypoxic and nutrient deprived areas of the tumor where radiotherapy is less effective. Its radiosensitizing effectiveness depends on the temperature level, duration of treatment, and the time interval between radiotherapy and hyperthermia. High quality hyperthermia treatment requires an experienced team, adequate online adaptive treatment planning, and is preferably performed using a phased array radiative locoregional hyperthermia device to achieve the optimal thermal dose effect. Hyperthermia is well tolerated and generally leads to only mild toxicity, such as patient discomfort. Patients in whom cisplatin is contraindicated should therefore be referred to a hyperthermia center for thermoradiation.