Evidence-based radiation oncology in head and neck squamous cell carcinoma

Abstract

Background and purpose: Historically, radiation therapy (RT) has been an available treatment option for patients with early resectable head and neck squamous cell carcinoma (HNSCC) and the sole therapy for those with unresectable or inoperable disease. Recently, four noteworthy strategies have emerged for the improvement of therapeutic outcome in the curative treatment of HNSCC: they include the development of altered fractionation radiotherapy, integration of chemotherapy with radiotherapy, incorporation of intensity-modulated radiotherapy and the introduction of targeted biological therapy. These strategies are briefly reviewed in an effort to help interpret evidence-based data and to facilitate clinical-decision making in a clinical context.

Materials and methods: For patients with early stage HNSCC no level 1 study exists in which radiation therapy is compared with conservative surgery for the evaluation of local control or survival. Only evidence from prospective and retrospective cohort studies is available to evaluate the role external radiotherapy and/or brachytherapy currently play in limited disease. For patients with locally advanced HNSCC the recommendations to address the questions about better treatment in resectable and unresectable tumors are based on more than 100 randomized Phase III trials included in six meta-analyses on chemo-radiotherapy and/or altered fractionation. Data from phase II trials and cohort studies help interpret the advances in intensity-modulated radiotherapy.

Results: External radiotherapy and/or brachytherapy are crucial treatment options in patients with early stage HNSCC. For patients with locally advanced HNSCC, where outcome with conventional radiotherapy is poor, meta-analyses and collective data showed that loco-regional control may be improved at high level of evidence by altered fractionation radiotherapy, chemo-radiotherapy with concomitant approach or association of selected hypoxic cell radiosensitizer with radiotherapy. For these patients, overall survival may be improved at high level of evidence by concomitant chemo-radiotherapy or hyperfractionated RT delivered with increased total dose. Also EGFR-inhibitors (cetuximab)-radiotherapy strategy offers at a lower level of evidence better loco-regional control and overall survival than radiotherapy alone. Chemo-radiotherapy programs can achieve an improved larynx-function preservation program without the risk of overall survival reduction, for patients with larynx or hypopharynx tumors who are candidates to radical surgery followed by radiotherapy. Recently, strong evidence for an improved outcome for high-risk resected patients has been shown by the use of adjuvant concomitant chemo-radiotherapy. Despite improved results, a higher severe toxicity has been largely evidenced with concomitant chemo-radiotherapy by reducing the gain in the therapeutic index with new treatment strategies. Three-dimensional conformal radiotherapy is the minimal standard of technique in HNSCC: however, as advances are promising, intensity-modulated radiotherapy should be largely implemented.

Conclusions: Stepwise improvements in HNSCC non-surgical therapy have shown favorable impact on loco-regional control and overall survival. However, despite hundreds of clinical trials in patients with advanced disease, there is no absolute consensus about patient selection for altered fractionation regimens, type of chemo-radiotherapy association, radiation or chemotherapy dose schedule. Nevertheless, many well-conducted clinical studies have expanded therapy options besides standard radiotherapy and have contributed to defining the evolving standard of care for patients with HNSCC.