Definition of stereotactic body radiotherapy: principles and practice for the treatment of stage I non-small cell lung cancer

SBRT in operable early stage lung cancer patients

Since decades the gold standard for treatment of early stage non-small cell lung cancer (NSCLC) is surgical lobectomy plus mediastinal lymph node dissection. Patients in worse health status are treated with sublobar resection or radiation treatment. With development of stereotactic-body-radiotherapy (SBRT), outcome of patients treated with radiation was substantially improved. Comparison of SBRT and surgical techniques is difficult due to the lack of randomized trials. However, all available evidence in form of case control studies of population based studies show equivalence between sublobar resection and SBRT indicating that SBRT-when performed by a trained and experienced team-should be offered to all high-risk surgical patients. For patients not willing to take the risk of lobectomy and therefore refusing surgery, SBRT is an excellent treatment option.

Stereotactic body radiotherapy in operable patients with stage I NSCLC: where is the evidence?

This review summarizes the evidence of stereotactic body radiotherapy (SBRT) as an alternative to surgery (lobectomy and sublobar resection) for stage I NSCLC. Three randomized trials comparing SBRT and surgery were initiated but all three were stopped early due to poor accrual. As the next level of evidence, results from matched-pair analyses performed in single-institutional (n = 4), multi-institutional (n = 3) and population-based (n = 3) settings are available. There was close agreement between all studies that SBRT is at least equivalent to sublobar resection making it the preferred treatment for a high-risk population. SBRT was equivalent to lobectomy in the endpoints of loco-regional control and cancer-specific survival. Disease-free survival and overall survival were inferior after SBRT compared with lobectomy in one and two studies, respectively, and not significantly different in all other studies. Consequently, for patients without relevant comorbidities, who are accepting the risk of a surgical procedure, lobectomy remains the standard of care.

Validation of Tuba1a as appropriate internal control for normalization of gene expression analysis during mouse lung development

The expression ratio between the analysed gene and an internal control gene is the most widely used normalization method for quantitative RT-PCR (qRT-PCR) expression analysis. The ideal reference gene for a specific experiment is the one whose expression is not affected by the different experimental conditions tested. In this study, we validate the applicability of five commonly used reference genes during different stages of mouse lung development. The stability of expression of five different reference genes (Tuba1a, Actb Gapdh, Rn18S and Hist4h4) was calculated within five experimental groups using the statistical algorithm of geNorm software. Overall, Tuba1a showed the least variability in expression among the different stages of lung development, while Hist4h4 and Rn18S showed the maximum variability in their expression. Expression analysis of two lung specific markers, surfactant protein C (SftpC) and Clara cell-specific 10 kDA protein (Scgb1a1), normalized to each of the five reference genes tested here, confirmed our results and showed that incorrect reference gene choice can lead to artefacts. Moreover, a combination of two internal controls for normalization of expression analysis during lung development will increase the accuracy and reliability of results.

Quantification of an external motion surrogate for quality assurance in lung cancer radiation therapy

The purpose of this work was to validate the stability of the end exhale position in deep expiration breath hold (DEBH) technique for quality assurance in stereotactic lung tumor radiation therapy. Furthermore, a motion analysis was performed for 20 patients to evaluate breathing periods and baseline drifts based on an external surrogate. This trajectory was detected using stereo infrared (IR) cameras and reflective body markers. The respiratory waveform showed large interpatient differences in the end exhale position during irradiation up to 18.8 mm compared to the global minimum. This position depends significantly on the tumor volume. Also the baseline drifts, which occur mostly in posterior direction, are affected by the tumor size. Breathing periods, which depend mostly on the patient age, were in a range between 2.4 s and 7.0 s. Fifteen out of 20 patients, who showed a reproducible end exhale position with a deviation of less than 5 mm, might benefit from DEBH due to smaller planning target volumes (PTV) compared to free breathing irradiation and hence sparing of healthy tissue. Patients with larger uncertainties should be treated with more complex motion compensation techniques.