Séquelles radio-induites et tests prédictifs

The Normal, the Radiosensitive, and the Ataxic in the Era of Precision Radiotherapy: A Narrative Review

(1) Background: radiotherapy is a cornerstone of cancer treatment. When delivering a tumoricidal dose, the risk of severe late toxicities is usually kept below 5% using dose-volume constraints. However, individual radiation sensitivity (iRS) is responsible (with other technical factors) for unexpected toxicities after exposure to a dose that induces no toxicity in the general population. Diagnosing iRS before radiotherapy could avoid unnecessary toxicities in patients with a grossly normal phenotype. Thus, we reviewed iRS diagnostic data and their impact on decision-making processes and the RT workflow; (2) Methods: following a description of radiation toxicities, we conducted a critical review of the current state of the knowledge on individual determinants of cellular/tissue radiation; (3) Results: tremendous advances in technology now allow minimally-invasive genomic, epigenetic and functional testing and a better understanding of iRS. Ongoing large translational studies implement various tests and enriched NTCP models designed to improve the prediction of toxicities. iRS testing could better support informed radiotherapy decisions for individuals with a normal phenotype who experience unusual toxicities. Ethics of medical decisions with an accurate prediction of personalized radiotherapy's risk/benefits and its health economics impact are at stake; (4) Conclusions: iRS testing represents a critical unmet need to design personalized radiotherapy protocols relying on extended NTCP models integrating iRS.

Improving Patients’ Life Quality after Radiotherapy Treatment by Predicting Late Toxicities

Simple Summary

Over 50% of patients with cancer will receive radiotherapy treatment. Five to ten percent of patients who received radiotherapy will develop side effects. Identifying these patients before treatment start would allow for treatment modification to minimize these effects and improve the life quality of these patients. Our team developed a test, which allows predicting these secondary effects before starting the treatment. This will help in proposing personalized treatments to improve the outcome. This review presents how this test is performed, its results, as well as its modification in order to be used in hospitals.

Abstract

Personalized treatment and precision medicine have become the new standard of care in oncology and radiotherapy. Because treatment outcomes have considerably improved over the last few years, permanent side-effects are becoming an increasingly significant issue for cancer survivors. Five to ten percent of patients will develop severe late toxicity after radiotherapy. Identifying these patients before treatment start would allow for treatment adaptation to minimize definitive side effects that could impair their long-term quality of life. Over the last decades, several tests and biomarkers have been developed to identify these patients. However, out of these, only the Radiation-Induced Lymphocyte Apoptosis (RILA) assay has been prospectively validated in multi-center cohorts. This test, based on a simple blood draught, has been shown to be correlated with late radiation-induced toxicity in breast, prostate, cervical and head and neck cancer. It could therefore greatly improve decision making in precision radiation oncology. This literature review summarizes the development and bases of this assay, as well as its clinical results and compares its results to the other available assays.

Tumour and normal tissue radiosensitivity

The place of personalized treatments is highly increasing in medical and radiation oncology. During the last decades, a huge number of assays have been developed to predict responses of normal tissues and tumours. These tests have not yet been included into daily clinical practice but the recent developments of radiation oncology are paving the way of personalized strategies including the risk of tumour recurrence and normal tissue reactions. Concerning tumor radiosensitivity prediction, no test are currently used, even if the radiosensitivity index and the genome-based model for adjusting radiotherapy dose assays seem the most promising with level II of evidence. Commercial developments are under progress. Concerning normal tissue radiosensitivity prediction, single nucleotide polymorphims of prostate cancer patients and radiation-induced CD8 T-lymphocyte apoptosis breast and prostate assays are of level I of evidence. They can be proposed before the beginning of radiotherapy in order to propose personalized treatments according to both risks of tumour and normal tissue radiosensitivity. Commercial developments are also under way.

Association between single nucleotide polymorphisms in the XRCC1 and RAD51 genes and clinical radiosensitivity in head and neck cancer

PURPOSE

Individual variability in radiosensitivity is large in cancer patients. Single nucleotide polymorphisms (SNPs) in genes involved in DNA repair and in protection against reactive oxygen species (ROS) could be responsible for such cases of radiosensitivity. We investigated the association between the occurrence of acute reactions in 101 patients with squamous cell carcinoma of the head and neck (SCCHN) after radiotherapy (RT) and five genetic polymorphisms: XRCC1 c.1196A>G, XRCC3 c.722C>T, RAD51 (c.-3429G>C, c.-3392G>T), and GSTP1 c.313A>G.

MATERIALS AND METHODS

Genetic polymorphisms were detected by high resolution melting analysis (HRMA). The development of acute reactions (oral mucositis, skin erythema and dysphagia) associated with genetic polymorphisms was modeled using Cox proportional hazards, accounting for biologically effective dose (BED).

RESULTS

Development of grade ≥2 mucositis was increased in all patients (chemo-radiotherapy and radiotherapy alone) with XRCC1-399Gln allele (HR=1.72). The likelihood of developing grade ≥2 dysphagia was higher in carriers of RAD51 c.-3429 CC/GC genotypes (HR=4.00). The presence of at least one SNP or the co-presence of both SNPs in XRCC1 p.Gln399Arg /RAD51 c.-3429 G>C status were associated to higher likelihood of occurrence of acute toxicities (HR=2.03).

CONCLUSIONS

Our findings showed an association between genetic polymorphisms, XRCC1 c.1196A>G and RAD51 c.-3429 G>C, and the development of radiation-induced toxicities in SCCHN patients.

[Late neurotoxicity after nasopharyngeal carcinoma treatment]

PURPOSE

A retrospective analysis of risk factors for late neurological toxicity after nasopharyngeal carcinoma radiotherapy.

PATIENTS AND METHODS

Between 1993 and 2004, 239 patients with non metastatic nasopharyngeal carcinoma were treated by radiotherapy associated or not to chemotherapy. Radiotherapy was delivered with two modalities: hyperfractionated for 82 patients and conventional fractionation for 157 patients. We evaluated the impact of tumour stage, age, gender, radiotherapy schedule and chemotherapy on neurological toxicity.

RESULTS

After a mean follow-up of 107 months (35-176 months), 21 patients (8.8%) developed neurological complications, such as temporal necrosis in nine cases, brain stem necrosis in five cases, optics nerve atrophy in two cases and myelitis in one case. Five- and ten-year free of toxicity survival was 95 and 84% respectively. Young patients had greater risk of temporal necrosis, and hyperfractionated radiotherapy was associated with a significantly higher risk of neurological complications (14.6% vs 5.7%, p=0.02). On multivariate analysis, hyperfractionation and age were insignificant.

CONCLUSION

Late neurological toxicity after radiotherapy for nasopharyngeal carcinoma was rare. Younger age and hyperfractionation were considered as risk factors of neurological toxicity in our study.