Role of 4D Stereotactic Radiotherapy with the CyberKnife® System in the Treatment of Lung Cancer

European Oncology & Haematology, 2012;April:[ePub Ahead of Print]

Abstract:

Lung cancer remains in 2012 the leading cause of cancer-related deaths within the European Union. Although surgery still constitutes the standard treatment for lung cancer, it is not feasible for a large number of patients. Treatment of lung tumours thus requires an innovative treatment solution. The ability of the CyberKnife® stereotactic radiotherapy system to track and automatically correct for respiratory motion allows an increase of the radiation dose, and thus gives the opportunity to improve the efficacy of the treatment. In this article, an overview of this technology and its clinical benefits is provided and shows that it can offer an effective and safe option in the treatment of lung tumours, whether they are primary and early-stage, recurrent or secondary, as well as peripheral or central.
Keywords: Lung cancer, stereotactic body radiation therapy (SBRT), CyberKnife® system, mobile targets, Synchrony® tracking system, early-stage lung cancer, peripheral lung tumour, central lung tumour, re-irradiation
Disclosure: The authors have no conflicts of interest to declare.
Received: April 13, 2012 Accepted April 20, 2012
Correspondence: Joost J Nuyttens, Erasmus MC-Daniel den Hoed Cancer Center, Department of Radiation Oncology, Postbus 2040–3000 CA, Rotterdam, The Netherlands.
Support: The publication of this article was funded by Accuray®. The views and opinions expressed are those of the authors and not necessarily those of Accuray®.

Lung cancer has been the world’s most frequent cancer, as well as the world’s leading cause of cancer-related deaths, for several decades.1 It remains today the leading cancer in males2 and, even if incidence rates are generally lower, it represents among females the fourth most frequent cancer and the second most common cause of death from cancer.1 Furthermore, the distribution of histological subtypes has considerably changed over the recent decades, with an increasing frequency of adenocarcinoma compared with squamous cell carcinoma.3 In the European Union, in 2008, lung cancer represented an incidence of 391,000, making it the third most frequent cancer after colorectal and breast cancer.4 However, with an estimated 342,000 related deaths in 2008, it is the number one killer cancer.4 Although the mortality rate in men has been decreasing for more than 20 years, the mortality rate in women has been increasing in many European countries2 and rose from 12.6/100,000 in 2007 to 13.1/100,000 in 2011.5 As a consequence, it tends to approach and sometimes exceed the mortality rate of breast cancer, as was the case in the UK and Poland, where lung cancer was the leading cause of cancer-related deaths in women from 2007 to 2008. The lung cancer epidemic in women is still expanding.6 Predictions for the year 2012 show a 7 % increase of lung cancer in European females.5

Treatments for Patients with Lung Cancer and Their Side Effects
Clinical management and prognosis of lung cancer depend on the histological type of cancer, its stage and the general state of health of the patient. Non-small-cell lung cancer (NSCLC, 75–80 % of lung cancers) is primarily treated with surgery, while limited small-cell lung cancer (SCLC, 20–25 % of lung cancers) is usually treated with chemotherapy and radiotherapy.

The extent of surgery depends on the size and location of the tumour. The death rate following surgery is about 4.4 %, depending in particular on the condition of the patient’s lungs.7 The overall five-year survival rate for these patients varies, depending on the stage of the disease, from 61 % (stage IA) to 1 % (stage IV).8,9 In most cases of open lobectomy, numerous post-operative complications are noted, such as prolonged chest-tube placement, atrial arrhythmias and lobar atelectasis, as well as infections. Patients’ physical and social quality of life also deteriorates and pain can persist. Some patients do not completely recover, even at 24 months after surgery.10,11

Although surgery is the standard treatment for early primary lung cancer, it is not feasible for many patients. In that case, if the tumour remains located in the thorax, conventional radiotherapy (≈30 fractions/session) is indicated, but the total dose delivered remains limited because of the risk of complications (radiation-induced pneumonia, poor pulmonary tolerance in the case of peripheral tumours, poor mediastinal tolerance in the case of central tumours), especially in patients with an impaired respiratory capacity. Furthermore, radiotherapy can cause a number of side effects that appear gradually over the sessions, which are generally spread out over five to eight weeks, including unusual fatigue, painful swallowing, a dry cough and skin reactions. It can be combined with chemotherapy.

When the tumour has invaded other organs and gives rise to metastases, treatment is based primarily on chemotherapy, and sometimes on symptomatic radiotherapy. Patients under chemotherapy may experience side effects such as reduced resistance to infections, loss of appetite, altered taste, nausea and vomiting, stomatitis and alopecia. All these side effects decrease or cease upon discontinuation of treatment.

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Keywords: Lung cancer, stereotactic body radiation therapy (SBRT), CyberKnife® system, mobile targets, Synchrony® tracking system, early-stage lung cancer, peripheral lung tumour, central lung tumour, re-irradiation