External validation of a rectal cancer outcome prediction model with a cohort of patients treated with preoperative radiochemotherapy and deep regional hyperthermia

Feasibility of ultrasound tomography-guided localized mild hyperthermia using a ring transducer: Ex vivo and in silico studies

BACKGROUND

As of 2022, breast cancer continues to be the most diagnosed cancer worldwide. This problem persists within the United States as well, as the American Cancer Society has reported that ∼12.5% of women will be diagnosed with invasive breast cancer over the course of their lifetime. Therefore, a clinical need continues to exist to address this disease from a treatment and therapeutic perspective. Current treatments for breast cancer and cancers more broadly include surgery, radiation, and chemotherapy. Adjuncts to these methods have been developed to improve the clinical outcomes for patients. One such adjunctive treatment is mild hyperthermia therapy (MHTh), which has been shown to be successful in the treatment of cancers by increasing effectiveness and reduced dosage requirements for radiation and chemotherapies. MHTh-assisted treatments can be performed with invasive thermal devices, noninvasive microwave induction, heating and recirculation of extracted patient blood, or whole-body hyperthermia with hot blankets.

PURPOSE

One common method for inducing MHTh is by using microwave for heat induction and magnetic resonance imaging for temperature monitoring. However, this leads to a complex, expensive, and inaccessible therapy platform. Therefore, in this work we aim to show the feasibility of a novel all-acoustic MHTh system that uses focused ultrasound (US) to induce heating while also using US tomography (UST) to provide temperature estimates. Changes in sound speed (SS) have been shown to be strongly correlated with temperature changes and can therefore be used to indirectly monitor heating throughout the therapy. Additionally, these SS estimates allow for heterogeneous SS-corrected phase delays when heating complex and heterogeneous tissue structures.

METHODS

Feasibility to induce localized heat in tissue was investigated in silico with a simulated breast model, including an embedded tumor using continuous wave US. Here, both heterogenous acoustic and thermal properties were modeled in addition to blood perfusion. We further demonstrate, with ex vivo tissue phantoms, the feasibility of using ring-based UST to monitor temperature by tracking changes in SS. Two phantoms (lamb tissue and human abdominal fat) with latex tubes containing varied temperature flowing water were imaged. The measured SS of the water at each temperature were compared against values that are reported in literature.

RESULTS

Results from ex vivo tissue studies indicate successful tracking of temperature under various phantom configurations and ranges of water temperature. The results of in silico studies show that the proposed system can heat an acoustically and thermally heterogenous breast model to the clinically relevant temperature of 42°C while accounting for a reasonable time needed to image the current cross section (200 ms). Further, we have performed an initial in silico study demonstrating the feasibility of adjusting the transmit waveform frequency to modify the effective heating height at the focused region. Lastly, we have shown in a simpler 2D breast model that MHTh level temperatures can be maintained by adjusting the transmit pressure intensity of the US ring.

CONCLUSIONS

This work has demonstrated the feasibility of using a 256-element ring array transducer for temperature monitoring; however, future work will investigate minimizing the difference between measured SS and the values shown in literature. A hypothesis attributes this bias to potential volumetric average artifacts from the ray-based SS inversion algorithm that was used, and that moving to a waveform-based SS inversion algorithm will greatly improve the SS estimates. Additionally, we have shown that an all-acoustic MHTh system is feasible via in silico studies. These studies have indicated that the proposed system can heat a tumor within a heterogenous breast model to 42°C within a narrow time frame. This holds great promise for increasing the accessibility and reducing the complexity of a future all-acoustic MHTh system.

Long-Term Outcome in a Phase II Study of Regional Hyperthermia Added to Preoperative Radiochemotherapy in Locally Advanced and Recurrent Rectal Adenocarcinomas

Hyperthermia was added to standard preoperative chemoradiation for rectal adenocarcinomas in a phase II study. Patients with T3-4 N0-2 M0 rectal cancer or local recurrences were included. Radiation dose was 54 Gy combined with capecitabine 825 mg/m2 × 2 daily and once weekly oxaliplatin 55 mg/m2. Regional hyperthermia aimed at 41.5–42.5 °C for 60 min combined with oxaliplatin infusion. Radical surgery with total or extended TME technique, was scheduled at 6–8 weeks after radiation. From April 2003 to April 2008, a total of 49 eligible patients were recruited. Median number of hyperthermia sessions were 5.4. A total of 47 out of 49 patients (96%) had the scheduled surgery, which was clinically radical in 44 patients. Complete tumour regression occurred in 29.8% of the patients who also exhibited statistically significantly better RFS and CSS. Rate of local recurrence alone at 10 years was 9.1%, distant metastases alone occurred in 25.6%, including local recurrences 40.4%. RFS for all patients was 54.8% after 5 years and CSS was 73.5%. Patients with T50 temperatures in tumours above median 39.9 °C had better RFS, 66.7% vs. 31.3%, p = 0.047, indicating a role of hyperthermia. Toxicity was acceptable.

A Narrative Review of Regional Hyperthermia: Updates From 2010 to 2019

The role of hyperthermia (HT) in cancer therapy and palliative care has been discussed for years in the literature. There are plenty of articles that show good feasibility of HT and its efficacy in terms of tumor response and survival improvements. Nevertheless, HT has never gained enough interest among oncologists to become a standard therapy in clinical practice. The main advantage of HT is the enhancement of chemotherapy (CHT), radiotherapy (RT), chemoradiotherapy (CRT), and immunotherapy benefits. This effect has been confirmed in several types of tumors: esophageal, gastrointestinal, pancreas, breast, cervix, head and neck, and bladder cancers, and soft tissue sarcoma. HT effects include oxygenation and perfusion changes, DNA repair inhibition and immune system activation as a consequence of new antigen exposure. The literature shows a wide variety of randomized, nonrandomized, and observational studies and both prospective and retrospective data to confirm the advantage of HT association to CHT and RT. There are still many ongoing trials on this subject. This article summarizes the available literature on HT in order to update the current knowledge on HT use in association with RT and/or CHT from 2010 up to 2019.

Deep regional hyperthermia with preoperative radiochemotherapy in locally advanced rectal cancer, a prospective phase II trial

PURPOSE

The goal of the present study was to investigate the effect of deep regional hyperthermia on early and long-term oncological outcomes in the context of preoperative radiochemotherapy in rectal cancer.

METHODS

In this prospective phase II trial, patients with locally advanced rectal cancer were treated with 5-fluorouracil based preoperative radiochemotherapy with 50.4 Gy in 28 fractions. Deep regional hyperthermia was scheduled twice weekly. Pathological tumor regression was scored according to the Dworak regression system. The primary endpoint was pathological complete response (pCR). Further endpoints were local control (LC), distant control (DC), disease-free survival (DFS) and overall survival (OS). Hyperthermia was defined as feasible if 70% of patients received at least eight treatments. Quality of life was assessed at follow-up by the EORTC-QLQ-C30 and QLQ-CR29 questionnaires. Time to event data was analyzed according to Kaplan-Meier based on first-events. The study was registered on clinicaltrials.gov (NCT02353858).

RESULTS

From 2012 until 2017, 78 patients were recruited. Median follow-up was 54 months. Based on magnetic resonance imaging, the mesorectal fascia was involved or threatened in 60% of the patients. Compliance with radiotherapy was 99%, 91% received both cycles of chemotherapy and 77% had eight or more hyperthermia treatments. Median time from the end of radiotherapy to surgery was 6.7 weeks. A pathological complete response was reported in 14% of the patients, 50% had either Dworak 4 (complete regression) or Dworak 3 regression (scattered tumor cells only). Three year estimates for OS, DFS, LC and DC were 94%, 81%, 96% and 87%. Patients with higher hyperthermia related cumulative temperatures showed stronger tumor regression. Global health status based on EORTC-QLQ-C30 was comparable with data from the general population.

CONCLUSION

Deep regional hyperthermia was feasible, did not compromise standard treatments and resulted in promising long-term oncological outcomes and QoL.

It's Getting Hot in Here: Targeting Cancer Stem-like Cells with Hyperthermia

Cancer stem-like cells (CSCs) are a subset of cancer cells that are resistant to conventional radiotherapy and chemotherapy. As such, CSCs have been recognized as playing a large role in tumor initiation and recurrence. Although hyperthermia is broadly used in cancer treatment either alone or in combination with radio- or chemo-therapy, its potential to target CSCs is not well understood. In this review, we discuss different types of hyperthermia and potential mechanisms of action in cancer treatment, particularly in regards to killing CSCs.