Benefit of Optimizing the Dose to the Carotid in Hypofractionated Stereotactic Body Reirradiation?

Modern radiotherapy for head and neck cancer

Radiation therapy (RT) plays a key role in curative-intent treatments for head and neck cancers. Its use is indicated as a sole therapy in early stage tumors or in combination with surgery or concurrent chemotherapy in advanced stages. Recent technologic advances have resulted in both improved oncologic results and expansion of the indications for RT in clinical practice. Despite this, RT administered to the head and neck region is still burdened by a high rate of acute and late side effects. Moreover, about 50% of patients with high-risk disease experience loco-regional recurrence within 3 years of follow-up. Therefore, in recent decades, efforts have been dedicated to optimize the cost/benefit ratio of RT in this subset of patients. The aim of the present review was to highlight modern concepts of RT for head and neck cancers considering both the technological advances that have been achieved and recent knowledge that has informed the biological interaction between radiation and both tumor and healthy tissues.

[Re-irradiation of head and neck cancers: Target volumes, technical evolutions and prospects]

Malignant tumors of the head and neck have a predominantly regional recurrence pattern, with most deaths resulting from this progression. Optimization of re-radiation in recurrence setting is a major objective for these patients. Extensive research has been carried out with the PubMed search engine to find publications dealing with this topic. The first attempts to reirradiate the ORL sphere date back to the 1980s and the first to be performed by intensity modulation conformational radiotherapy (IMRT) date back to the late 1990s. Compared to 3 dimensional conformal radiotherapy, IMRT improves clinical outcomes and reduces toxicity. In IMRT series, associated or not with concomitant chemotherapy, the locoregional control obtained at 2 years was of the order of 45 to 65% and the overall survival of 15 to 60%, depending on predictive factors. Grade 3 acute toxicity occurred on the order of 10 to 30% and late-grade 3 toxicity on the order of 15 to 50%. In a selected population with low volumes tumors, stereotactic re-irradiation at a minimum dose of 35Gy obtained outcome comparable to IMRT. Re-irradiation of head and neck tumors by proton therapy is rare. The toxicity rate appears to be lower than that usually seen after photon therapy. However, we do not have a long follow-up. This technique therefore remains reserved for search protocols and represents a future perspective in these situations.

Risk of carotid blowout after reirradiation with particle therapy

Purpose

Carotid blowout (CB) is a serious complication in retreatment of neoplasms in the head and neck (H&N) region. Rates seem to increase in hypofractionated or accelerated hyperfractionated regimens. In this study, we investigate the CB rate and the cumulative doses received by the carotid artery (CA) in a cohort of patients who were reirradiated at CNAO with particle therapy in the H&N region.

Methods and materials

The dosimetric information, medical records, and tumor characteristics of 96 patients were analyzed. For 49 of these patients, the quality of dosimetric information was sufficient to calculate the cumulative doses to the CA. The corresponding biological equivalent dose in 2 Gy fractions (EQD2) was calculated with an α/β-ratio of 3.

Results

In the final reirradiation at CNAO, 17 patients (18%) had been treated with protons and 79 (82%) with carbon ions. Two patients experienced profuse oronasal bleeding, of which one case was confirmed to be caused by CB. If attributing both cases to CB, we found an actuarial CB rate of 2.7%. Interestingly, there were no CB cases in the carbon ion group even though this was the large majority of patients and they generally were treated more aggressively in terms of larger fraction doses and higher cumulative EQD2.

Conclusions

The current practice of particle reirradiation at CNAO for recurrent neoplasms in the H&N region results in acceptable rates of CB.

Stereotactic body radiotherapy for head and neck cancer: an addition to the armamentarium against head and neck cancer

In the recent years, stereotactic body radiation therapy (SBRT) has emerged as a potential therapy for head and neck malignancies. Although early results appear to be promising, serious acute and late effects have been observed, mainly in patients who have had prior external beam radiotherapy. This review will discuss the radiobiology of SBRT, clinical rationale and outcomes for SBRT in head and neck cancers and focus on the benefits and potential limitations in both de novo and re-irradiation settings.

Carotid blowout syndrome in pharyngeal cancer patients treated by hypofractionated stereotactic re-irradiation using CyberKnife: A multi-institutional matched-cohort analysis

BACKGROUND AND PURPOSE

Although reirradiation has attracted attention as a potential therapy for recurrent head and neck tumors with the advent of modern radiotherapy, severe rate toxicity such as carotid blowout syndrome (CBOS) limits its potential. The aim of this study was to identify the risk factors of CBOS after hypofractionated stereotactic radiotherapy (SBRT).

METHODS AND PATIENTS

We conducted a matched-pair design examination of pharyngeal cancer patients treated by CyberKnife reirradiation in four institutes. Twelve cases with CBOS were observed per 60 cases without CBOS cases. Prognostic factors for CBOS were analyzed and a risk classification model was constructed.

RESULTS

The median prescribed radiation dose was 30 Gy in 5 fractions with CyberKnife SBRT after 60 Gy/30 fractions of previous radiotherapy. The median duration between reirradiation and CBOS onset was 5 months (range, 0-69 months). CBOS cases showed a median survival time of 5.5 months compared to 22.8 months for non-CBOS cases (1-year survival rate, 36% vs.72%; p=0.003). Univariate analysis identified an angle of carotid invasion of >180°, the presence of ulceration, planning treatment volume, and irradiation to lymph node areas as statistically significant predisposing factors for CBOS. Only patients with carotid invasion of >180° developed CBOS (12/50, 24%), whereas no patient with tumor involvement less than a half semicircle around the carotid artery developed CBOS (0/22, 0%, p=0.03). Multivariate Cox hazard model analysis revealed that the presence of ulceration and irradiation to lymph nodes were statistically significant predisposing factors. Thus, we constructed a CBOS risk classification system: CBOS index=(summation of risk factors; carotid invasion >180°, presence of ulceration, lymph node area irradiation). This system sufficiently separated the risk groups.

CONCLUSION

The presence of ulceration and lymph node irradiation are risk factors of CBOS. The CBOS index, including carotid invasion of >180°, is useful in classifying the risk factors and determining the indications for reirradiation.