Dose dependence of accelerated repopulation in head and neck cancer: Supporting evidence and clinical implications

HYpofractionated, dose-redistributed RAdiotherapy with protons and photons to combat radiation-induced immunosuppression in head and neck squamous cell carcinoma: study protocol of the phase I HYDRA trial

BACKGROUND

Radiotherapy (RT) is the standard of care for most advanced head and neck squamous cell carcinoma (HNSCC) and results in an unfavorable 5-year overall survival of 40%. Despite strong biological rationale, combining RT with immune checkpoint inhibitors does not result in a survival benefit. Our hypothesis is that the combination of these individually effective treatments fails because of radiation-induced immunosuppression and lymphodepletion. By integrating modern radiobiology and innovative radiotherapy concepts, the patient's immune system could be maximally retained by (1) increasing the dose per fraction so that the total dose and number of fractions can be reduced (HYpofractionation), (2) redistributing the radiation dose towards a higher peak dose within the tumor center and a lowered elective lymphatic field dose (Dose-redistribution), and (3) using RAdiotherapy with protons instead of photons (HYDRA).

METHODS

The primary aim of this multicenter study is to determine the safety of HYDRA proton- and photon radiotherapy by conducting two parallel phase I trials. Both HYDRA arms are randomized with the standard of care for longitudinal immune profiling. There will be a specific focus on actionable immune targets and their temporal patterns that can be tested in future hypofractionated immunoradiotherapy trials. The HYDRA dose prescriptions (in 20 fractions) are 40 Gy elective dose and 55 Gy simultaneous integrated boost on the clinical target volume with a 59 Gy focal boost on the tumor center. A total of 100 patients (25 per treatment group) will be recruited, and the final analysis will be performed one year after the last patient has been included.

DISCUSSION

In the context of HNSCC, hypofractionation has historically only been reserved for small tumors out of fear for late normal tissue toxicity. To date, hypofractionated radiotherapy may also be safe for larger tumors, as both the radiation dose and volume can be reduced by the combination of advanced imaging for better target definition, novel accelerated repopulation models and high-precision radiation treatment planning and dose delivery. HYDRA's expected immune-sparing effect may lead to improved outcomes by allowing for future effective combination treatment with immunotherapy.

TRIAL REGISTRATION

The trial is registered at ClinicalTrials.gov; NCT05364411 (registered on May 6th, 2022).

Clinical Radiobiology for Radiation Oncology

This chapter is focused on radiobiological aspects at the molecular, cellular, and tissue level which are relevant for the clinical use of ionizing radiation (IR) in cancer therapy. For radiation oncology, it is critical to find a balance, i.e., the therapeutic window, between the probability of tumor control and the probability of side effects caused by radiation injury to the healthy tissues and organs. An overview is given about modern precision radiotherapy (RT) techniques, which allow optimal sparing of healthy tissues. Biological factors determining the width of the therapeutic window are explained. The role of the six typical radiobiological phenomena determining the response of both malignant and normal tissues in the clinic, the 6R’s, which are Reoxygenation, Redistribution, Repopulation, Repair, Radiosensitivity, and Reactivation of the immune system, is discussed. Information is provided on tumor characteristics, for example, tumor type, growth kinetics, hypoxia, aberrant molecular signaling pathways, cancer stem cells and their impact on the response to RT. The role of the tumor microenvironment and microbiota is described and the effects of radiation on the immune system including the abscopal effect phenomenon are outlined. A summary is given on tumor diagnosis, response prediction via biomarkers, genetics, and radiomics, and ways to selectively enhance the RT response in tumors. Furthermore, we describe acute and late normal tissue reactions following exposure to radiation: cellular aspects, tissue kinetics, latency periods, permanent or transient injury, and histopathology. Details are also given on the differential effect on tumor and late responding healthy tissues following fractionated and low dose rate irradiation as well as the effect of whole-body exposure.

Chorioallantoic membrane tumor models highlight the effects of cisplatin compounds in oral carcinoma treatment

The European Society for Medical Oncology (ESMO) suggests the use of chemotherapy as neoadjuvant, adjuvant, and concomitant to surgery and radiotherapy for the treatment of oral carcinoma by depending on the cancer stage. The usual drug of choice belongs to the platinum compounds. In this context, the evaluation of the cancer behavior associated with the administration of standard or emerging cisplatin compounds supports the establishment of optimal cancer management. Here, we have assessed and compared the performance of cisplatin alone and contained in biodegradable nanocapsules on standardized chorioallantoic membrane (CAM) tumor models. The vascularized environment and optimized grafting procedure allowed the establishment of solid tumors. The treatments showed antitumor and anti-angiogenic activities together with deregulation of pivotal genes responsible of treatment resistance and tumor aggressiveness. This study further supports the significance of CAM tumor models in oncological research for the comprehension of the molecular mechanisms involved in tumor treatment response.

177Lu-PSMA-RLT of metastatic castration-resistant prostate cancer: limitations and improvements

The prevalence of metastatic castration-resistant prostate cancer (mCRPC) is increasing, and its prognosis is often poor. As a highly expressed target in mCRPC, prostate-specific membrane antigen (PSMA) is very attractive for its diagnosis and treatment. When the efficacy of chemical therapy is limited, radioligand therapy (RLT)-based on Lutetium-177 (177Lu)-PSMA has received more research as an emerging treatment. To date, most published related studies have proven this method is effective and safe. However, about 1/3 of mCRPC patients have not benefited from 177Lu-PSMA-RLT. The underlying mechanism of this phenomenon remains unclear. So based on the comprehensive research in recent years, this article proposes the possible reasons, including tumor lesions, PSMA heterogeneity, differences in DNA repair defects, and accelerated repopulation. Combining with the existing experience to give suggestions to improve the treatment efficacy, benefit more mCRPC patients.

Development of transient radioresistance during fractionated irradiation in vitro

BACKGROUND AND PURPOSE

Effective combination treatments with fractionated radiotherapy rely on a proper understanding of the dynamic responses that occur during treatment. We explored the effect of clinical fractionated radiotherapy on the development and timing of radioresistance in tumor cells.

METHODS AND MATERIALS

Different colon (HT29/HCT116/COLO320/SW480/RKO) and high-grade astrocytoma (D384/U-251MG) cancer cell lines were treated for 6 weeks with daily fractions of 2 Gy, 5 days per week. Clonogenic survival was determined throughout the treatment period. In addition, the radiosensitivity of irradiated and non-irradiated was compared. Finally, the effect of different dose fractions on the development of radioresistance was determined.

RESULTS

All cell lines developed radioresistance within 2-3 weeks during fractionated radiotherapy. This was characterized by the occurrence of a steady state phase of clonogenic survival. In U-251MG cells this was accompanied by increased cell senescence and stemness. After recovering from six weeks of treatment, the radiosensitivity of fractionally irradiated and non-irradiated cells was similar. Including transient radioresistance, described as (α/β)^-(d+1), as a factor in the classic LQ model resulted in a perfect fit with the experimental data observed during fractionated radiotherapy. This was confirmed when different dose fractions were applied.

CONCLUSIONS

Fractionated irradiation of cancer cells in vitro following clinical radiation schedules induces a reversible radioresistance response. This adaptive response can be included in the LQ model as a function of the dose fraction and the alpha/beta-ratio of a given cell line. These findings warrant further investigation of the mechanisms and clinical relevance of adaptive radioresistance.

Impact of primary tumor-specific growth rate on treatment failure for nonoropharyngeal head and neck cancers

OBJECTIVES

To investigate the prognostic impact of primary tumor-specific growth rate (TSGR) on treatment outcomes after definitive radiation therapy (RT) for nonoropharyngeal squamous cell carcinoma (non-OPSCC).

METHODS

The diagnostic tumor and nodal volumes of 39 non-OPSCC patients were contoured and compared to corresponding RT planning scan volumes to determine TSGR. Overall survival (OS), disease-free survival (DFS), and local recurrence-free survival were evaluated according to the Kaplan-Meier method; and hazard ratios (HR) were estimated using Cox regression. Based on the 75th percentile TSGR of 2.18%, we stratified patients into a high TSGR group (≥ 2.18% per day) and low TSGR group (< 2.18% per day).

RESULTS

The median follow-up was 22 months (range: 1-86 months) and median time between diagnostic and simulation computed tomography scans was 22 days (range: 7-170 days). Median RT dose was 70 Gy (range: 60-79.2 Gy). Based on the 75th percentile TSGR, OS at median follow-up was 50.0% for the high TSGR group compared to 92.5% for the low TSGR group (HR [95% confidence interval (CI)] = 2.12[1.16-11.42], P = 0.018). There was a trend toward worse DFS at median follow-up for the high versus low TSGR groups, at 55.6% and 82.3%, respectively (HR [95% CI] = 2.29[0.82-6.38], P = 0.103).

CONCLUSION

Our study contributes to growing literature on TSGR as a temporal biomarker in patients with non-OPSCC. Patients with high TSGR ≥2.18% per day have significantly worse OS compared to those with TSGR below this threshold. Efforts to address treatment initiation delays may benefit patients with particularly aggressive and rapidly growing tumors.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:2378-2384, 2020.

Characterization of a prognostic four‑gene methylation signature associated with radiotherapy for head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) remains one of the most common malignancies associated with poor prognosis. DNA methylation has emerged as an important mechanism underlying the radio-resistance of tumors. Prognostic biomarkers based on radiotherapy-related aberrant DNA methylation are limited. Methylation profiles of 388 patients with HNSCC were acquired from The Cancer Genome Atlas (TCGA) portal. Genes with differentially methylated CpG sites (DMGs) were screened between patients with a favorable and poor prognosis with or without radiotherapy. A weight gene co-methylation network was constructed using a Weighted Gene Co-expression Network Analysis (WGCNA) package. A lasso Cox-PH model was used to identify the optimal panel of genes with the ability to predict survival in these patients. Prognostic performance of the multi-gene methylation signature was assessed in a training set and confirmed in a validation set. A total of 976 DMGs were observed between favorable and poor prognostic samples. Four DMG-enriched co-methylation modules were identified. A four-gene methylation signature was determined by the lasso Cox-PH model that consisted of ZNF10, TMPRSS12, ERGIC2, and RNF215. The risk score based on the four-gene signature was able to divide the training or validation set into two risk groups with significantly different overall survival. Thus, the present study revealed a radiotherapy-related four-gene methylation signature to predict survival outcomes of patients with HNSCC, providing candidate therapeutic targets for novel therapy against HNSCC. However, substantial validation experiments are required.

DNA Repair Deficient Chinese Hamster Ovary Cells Exhibiting Differential Sensitivity to Charged Particle Radiation under Aerobic and Hypoxic Conditions

It has been well established that hypoxia significantly increases both cellular and tumor resistance to ionizing radiation. Hypoxia associated radiation resistance has been known for some time but there has been limited success in sensitizing cells to radiation under hypoxic conditions. These studies show that, when irradiated with low linear energy transfer (LET) gamma-rays, poly (ADP-ribose), polymerase (PARP), Fanconi Anemia (FANC), and mutant Chinese Hamster Ovary (CHO) cells respond similarly to the non-homologous end joining (NHEJ) and the homologous recombination (HR) repair mutant CHO cells. Comparable results were observed in cells exposed to 13 keV/μm carbon ions. However, when irradiated with higher LET spread out Bragg peak (SOBP) carbon ions, we observed a decrease in the oxygen enhancement ratio (OER) in all the DNA of repair mutant cell lines. Interestingly, PARP mutant cells were observed as having the largest decrease in OER. Finally, these studies show a significant increase in the relative biological effectiveness (RBE) of high LET SOBP carbon and iron ions in HR and PARP mutants. There was also an increase in the RBE of NHEJ mutants when irradiated to SOBP carbon and iron ions. However, this increase was lower than in other mutant cell lines. These findings indicate that high LET radiation produces unique types of DNA damage under hypoxic conditions and PARP and HR repair pathways play a role in repairing this damage.