Re-irradiation with Moderate Hypo-Fractionation Using Intensity Modulated Photon or Proton Radiation Therapy in Locally Recurrent Squamous Cell Carcinoma of Nasopharynx

Radiation oncology for the rhinologist

PURPOSE OF REVIEW

This comprehensive review explores evolving treatment strategies for sinonasal and nasopharyngeal malignancies. It analyzes the role of adjuvant radiotherapy, the potential of intensity-modulated proton therapy (IMPT), and the relevance of de-escalation strategies nasopharyngeal carcinoma (NPC). Additionally, it discusses hyperfractionation in re-irradiation in NPC.

RECENT FINDINGS

Adjuvant radiotherapy remains pivotal for sinonasal tumors, improving locoregional control and survival, notably in squamous cell carcinomas, adenocarcinomas, and adenoid cystic carcinomas. IMPT promises enhanced outcomes by sparing healthy tissues, potentially improving patients' quality of life. For select stage II/T3N0 NPC, radiotherapy alone offers comparable outcomes to concurrent chemoradiotherapy, with fewer adverse events and improved quality of life. Selective neck irradiation in NPC patients with uninvolved necks maintains oncologic outcomes while reducing late toxicity. Hyperfractionation in re-irradiation shows promise in lowering late toxicities and improving overall survival, particularly in undifferentiated sinonasal carcinomas.

SUMMARY

This review underscores the significance of adjuvant radiotherapy and the potential of advanced radiation techniques in optimizing sinonasal and nasopharyngeal malignancy outcomes. It emphasizes evolving de-escalation methods and individualized, evidence-based approaches. Future research will further refine strategies for these challenging malignancies.

Low-dose radiotherapy effects the progression of anti-tumor response

The history of low-dose radiotherapy (LDRT or LDR) as a treatment modality for malignant tumors dates back to the 1920s. Even with the minimal total dose administered during treatment, LDRT can result in long-lasting remission. Autocrine and paracrine signaling are widely recognized for fostering the growth and development of tumor cells. LDRT exerts systemic anti-tumor effects through various mechanisms, such as enhancing the activity of immune cells and cytokines, shifting the immune response towards an anti-tumor phenotype, influencing gene expression, and blocking crucial immunosuppressive pathways. Additionally, LDRT has been demonstrated to enhance the infiltration of activated T cells and initiate a series of inflammatory processes while modulating the tumor microenvironment. In this context, the objective of receiving radiation is not to directly kill tumor cells but to reprogram the immune system. Enhancing anti-tumor immunity may be a critical mechanism by which LDRT plays a role in cancer suppression. Therefore, this review primarily focuses on the clinical and preclinical efficacy of LDRT in combination with other anti-cancer strategies, such as the interaction between LDRT and the tumor microenvironment, and the remodeling of the immune system.

Identifying the prognostic value of MRI-based tumor response and predicting the risk of radio-resistance in re-radiotherapy for locally recurrent nasopharyngeal carcinoma

OBJECTIVE

To investigate the prognostic value of tumor response (TR) for locoregionally recurrent nasopharyngeal carcinoma (lrNPC) patients at the end of re-radiotherapy (re-RT) and develop a risk score model to predict patient's radiosensitivity to re-RT.

MATERIALS AND METHODS

A total of 594 patients with lrNPC from 2010 to 2020 were retrospectively reviewed as the total cohort. Among these, 310 patients with complete first-line treatment data were reviewed as a secondary cohort. Overall survival (OS) was the primary endpoint. Locoregional control (LRC) was the secondary endpoint. Multivariate Cox analysis was performed to investigate the prognostic value of TR at the end of re-RT (rTR). A risk score model for predicting rTR was obtained by logistic regression analysis, and its effectiveness was compared using receiver operating characteristic (ROC) analysis.

RESULTS

Patients with complete response (CR) to rTR had higher 5-year OS and LRC rate than non-CR patients in both the total and secondary cohort. rTR was an independent prognostic factor for OS (P=0.002) and LRC (P=0.008). We developed a risk score model including four significant risk factors (relapse T stage, relapse gross tumor volume, time to recurrence, and initial TR). The area under the curve of the risk score model was 0.73 (95% CI: 0.678 to 0.780), which was significantly higher than that of each variable alone. Patients with the highest risk scores may be insensitive to re-RT and had a residual tumor risk of 89.9% after rRT.

CONCLUSION

rTR was an independent prognostic factor for OS and LRC in lrNPC patients. We developed a risk score model for predicting patients' sensitivity to re-RT to screen for radiosensitive patients. This can serve as a treatment decision-making tool for clinicians.

The Role of Hypofractionation in Proton Therapy

Hypofractionated radiotherapy is an attractive approach for minimizing patient burden and treatment cost. Technological advancements in external beam radiotherapy (EBRT) delivery and image guidance have resulted in improved targeting and conformality of the absorbed dose to the disease and a reduction in dose to healthy tissue. These advances in EBRT have led to an increasing adoption and interest in hypofractionation. Furthermore, for many treatment sites, proton beam therapy (PBT) provides an improved absorbed dose distribution compared to X-ray (photon) EBRT. In the past 10 years there has been a notable increase in reported clinical data involving hypofractionation with PBT, reflecting the interest in this treatment approach. This review will discuss the reported clinical data and radiobiology of hypofractionated PBT. Over 50 published manuscripts reporting clinical results involving hypofractionation and PBT were included in this review, ~90% of which were published since 2010. The most common treatment regions reported were prostate, lung and liver, making over 70% of the reported results. Many of the reported clinical data indicate that hypofractionated PBT can be well tolerated, however future clinical trials are still needed to determine the optimal fractionation regime.

Toxicity Profiles and Survival Outcomes Among Patients With Nonmetastatic Nasopharyngeal Carcinoma Treated With Intensity-Modulated Proton Therapy vs Intensity-Modulated Radiation Therapy

IMPORTANCE

Patients with nonmetastatic nasopharyngeal carcinoma (NPC) are primarily treated by radiotherapy with curative intent with or without chemotherapy and often experience substantial treatment-related toxic effects even with modern radiation techniques, such as intensity-modulated radiation therapy (IMRT). Intensity-modulated proton therapy (IMPT) may improve the toxicity profile; however, there is a paucity of data given the limited availability of IMPT in regions with endemic NPC.

OBJECTIVE

To compare toxic effects and oncologic outcomes among patients with newly diagnosed nonmetastatic NPC when treated with IMPT vs IMRT with or without chemotherapy.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study included 77 patients with newly diagnosed nonmetastatic NPC who received curative-intent radiotherapy with IMPT or IMRT at a tertiary academic cancer center from January 1, 2016, to December 31, 2019. Forty-eight patients with Epstein-Barr virus (EBV)-positive tumors were included in a 1:1 propensity score-matched analysis for survival outcomes. The end of the follow-up period was March 31, 2021.

EXPOSURES

IMPT vs IMRT with or without chemotherapy.

MAIN OUTCOMES AND MEASURES

The main outcomes were the incidence of acute and chronic treatment-related adverse events (AEs) and oncologic outcomes, including locoregional failure-free survival (LRFS), progression-free survival (PFS), and overall survival (OS).

RESULTS

We identified 77 patients (25 [32.5%] women; 52 [67.5%] men; median [interquartile range] age, 48.7 [42.2-60.3] years), among whom 28 (36.4%) were treated with IMPT and 49 (63.6%) were treated with IMRT. Median (interquartile range) follow-up was 30.3 (17.9-41.5) months. On multivariable logistic regression analyses, IMPT was associated with lower likelihood of developing grade 2 or higher acute AEs compared with IMRT (odds ratio [OR], 0.15; 95% CI, 0.03-0.60; P = .01). Only 1 case (3.8%) of a chronic grade 3 or higher AE occurred in the IMPT group compared with 8 cases (16.3%) in the IMRT group (OR, 0.21; 95% CI, 0.01-1.21; P = .15). Propensity score matching generated a balanced cohort of 48 patients (24 IMPT vs 24 IMRT) and found similar PFS in the IMPT and IMRT groups (2-year PFS, 95.7% [95% CI, 87.7%-100%] vs 76.7% [95% CI, 60.7%-97.0%]; hazard ratio [HR], 0.31; 95% CI, 0.07-1.47; P = .14). No locoregional recurrence or death was observed in the IMPT group from the matched cohort. Two-year LRFS was 100% (95% CI, 100%-100%) in the IMPT group and 86.2% (95% CI, 72.8%-100%) in the IMRT group (P = .08). Three-year OS was 100% (95% CI, 100%-100%) in the IMPT group and 94.1% (95% CI, 83.6%-100%) in the IMRT group (P = .42). Smoking history was the only clinical factor significantly associated with both poor LRFS (HR, 63.37; 95% CI, 3.25-1236.13; P = .006) and poor PFS (HR, 6.33; 95% CI, 1.16-34.57; P = .03) on multivariable analyses.

CONCLUSIONS AND RELEVANCE

In this study, curative-intent radiotherapy with IMPT for nonmetastatic NPC was associated with significantly reduced acute toxicity burden in comparison with IMRT, with rare late complications and excellent oncologic outcomes, including 100% locoregional control at 2 years. Prospective trials are warranted to direct the optimal patient selection for IMPT as the primary radiotherapy modality for nonmetastatic NPC.