Stereotactic Body Radiotherapy for Early-stage Non-small-cell Lung Cancer in Patients 80 Years and Older: A Multi-center Analysis

Stereotactic Ablative Radiotherapy in the Treatment of Early-Stage Lung Cancer - A Done Deal?

Stereotactic ablative radiotherapy (SABR) is an important curative-intent treatment option for early-stage non-small cell lung cancer. It offers good cancer control without invasive surgery and has become the standard of care for medically inoperable patients. The literature on SABR for early-stage non-small cell lung cancer is substantial and continues to grow. However, there remain areas of controversy where data are limited - notably the use of SABR in medically operable patients. Other areas of some debate include the treatment of central/ultra-central and large (>5 cm) lesions, as well as treatment with co-existing interstitial lung disease. This review article provides an overview of the current literature together with a discussion of future directions.

Initial treatment of early-stage small-sized non-small cell lung cancer for octogenarians: a population-based study

The objectives of this study is to figure out the appropriate initial treatment and criteria for clinical decision for early-stage small-sized non-small cell lung cancer (NSCLC) among octogenarians. Elderly patients (≥80 years) with stage I NSCLC (<3 cm) were identified between 2004 and 2015 in the Surveillance, Epidemiology, and End Results database. Patients were divided into four cohorts regarding treatment modalities, and overall survival and cancer-specific survival were evaluated via Kaplan-Meier analysis and Cox proportional hazard model. The propensity score matching method was introduced in the subgroup analysis stratified by four clinical characteristics to identify the preferable treatment. A total of 7861 patients were included with a median overall survival of 43 months (range 1-155 months). In younger patients (80-85 years), lobectomy was superior in improving the survival (versus segmentectomy, HR = 0.68, 95%CI 0.55-0.84; versus wedge resection, HR = 0.77; 95%CI 0.67-0.88). While in those over 85 years, lobectomy was superior to wedge resection (HR = 0.72; 95%CI 0.53-0.98), and all other treatments were comparable. As stratified by T stage in those over 85 years, lobectomy was superior to wedge resection (P = 0.023) for T1 disease, and the four treatments were all comparable in overall survival for T2 disease. In conclusions, the favored treatment of early stage NSCLC for octogenarians may be evaluated by age and T stage. Lobectomy might be preferred in patients between 80 and 85 years whenever possible. Among those over 85 years, radiotherapy might lead to a comparable prognosis and could be recommended as the prior treatment, while should surgery be recommended, lobectomy might be preferred for T1 disease and wedge resection for T2 disease.

Management of Metastatic Nonsmall Cell Lung Cancer in Elderly

There is limited data on management of metastatic nonsmall cell lung cancer (NSCLC) in the elderly population due to lack of representation of this subset in clinical trials. The projected representation of elderly population of patients globally is expected to rise significantly in the years to come. It is imperative to understand the specific challenges and opportunities in management of elderly with NSCLC. Even in the elderly, the medical management of advanced NSCLC begins with driver mutation testing on lung biopsy. Once the patient is classified as driver mutation positive or negative, they can either be treated with a single-agent-targeted therapy or with immunotherapy and chemotherapy or after programmed death ligand 1 (PDL-1) assessment, with immunotherapy alone. After starting the appropriate therapy, the disease needs to be monitored at every 3 months with reassessment scans. Treatment in elderly should be designed as per their functional and not chronological age, and geriatric assessment scales should be utilized wherever possible to understand the functional age of the patient.

The Role of Radiation Therapy in the Older Patient

PURPOSE OF REVIEW

Older patients represent a unique subgroup of the cancer patient population for which the role of radiation therapy (RT) requires special consideration. This review will discuss many of these considerations as well as various radiation treatment techniques in the context of a variety of disease sites.

RECENT FINDINGS

Several recent studies give insight into the management of older cancer patients considering their age, performance status, comorbid conditions, quality of life, genetics, cost, and individual goals. RT plays an evolving and pivotal role in providing optimal care for this population. Recent advances in RT technique allow for more precise treatment delivery and reduced toxicity. Studies evaluating the use of radiation therapy in breast, brain, lung, prostate, rectal, pancreatic, esophageal, and oligometastatic cancer are summarized and discussed in the context of treating the older patient population. Individual age, performance and functional status, comorbid conditions, and patients' objectives and goals should all be considered when presenting treatment options for older patients and age alone should not disqualify patients from curative intent treatments. When possible, hypofractionated courses should be utilized as outcomes are often equivalent and toxicities are reduced. In many cases, RT may be preferable to other treatment options due to decreased toxicity profile and acceptable disease control.

Stereotactic body radiation therapy for early-stage non-small-cell lung cancer in octogenarians and older: an alternative treatment

Surgery is the standard modality for early-stage I-II non-small-cell lung cancer (NSCLC). Generally, patients who are >80 years old tend to have more comorbidities and inferior physical status than younger patients. Stereotactic body radiation therapy (SBRT) may provide an alternative treatment for this group of patients. Here, we report our experience using SBRT to in the management of early-stage NSCLC in patients >80 years old. Patients aged ≥80 years old who were diagnosed with early-stage NSCLC and treated with definitive lung SBRT from January 2000 to January 2018 were retrospectively analysed. Local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), cancer-specific survival (CSS), progression-free survival (PFS), overall survival (OS) and treatment-related toxicities were analysed for patients >80 years old. A total of 153 patients were included, with a median age of 85 years (range, 80-94). The median follow-up period and OS was 39.8 months (range, 10-101 months) and 76 months, respectively. The 3-year OS, PFS, CSS, RRFS and LRFS were 65.3, 58.0, 75.7, 73.9 and 85.3%, respectively. Radiation pneumonitis grade 0-1, grade 2, grade 3 and grade 4 was observed in 135 (88.2%), 13 (8.5%), 4 (2.61%) and 1 (0.6%) patient(s), respectively. On multivariate analyses, tumor size, pretreatment C-reactive protein (CRP) value, histology and pretreatment physical state were significantly associated with OS. Definitive lung SBRT appears to have high LRFS and OS without causing high-grade radiation-related toxicities in early-stage NSCLC patients who were >80 years old.

Oncologic Outcomes of Surgery Versus SBRT for Non-Small-Cell Lung Carcinoma: A Systematic Review and Meta-analysis

BACKGROUND

The optimal treatment of stage I non-small-cell lung carcinoma is subject to debate. The aim of this study was to compare overall survival and oncologic outcomes of lobar resection (LR), sublobar resection (SR), and stereotactic body radiotherapy (SBRT).

METHODS

A systematic review and meta-analysis of oncologic outcomes of propensity matched comparative and noncomparative cohort studies was performed. Outcomes of interest were overall survival and disease-free survival. The inverse variance method and the random-effects method for meta-analysis were utilized to assess the pooled estimates.

RESULTS

A total of 100 studies with patients treated for clinical stage I non-small-cell lung carcinoma were included. Long-term overall and disease-free survival after LR was superior over SBRT in all comparisons, and for most comparisons, SR was superior to SBRT. Noncomparative studies showed superior long-term overall and disease-free survival for both LR and SR over SBRT. Although the papers were heterogeneous and of low quality, results remained essentially the same throughout a large number of stratifications and sensitivity analyses.

CONCLUSION

Results of this systematic review and meta-analysis showed that LR has superior outcomes compared to SBRT for cI non-small-cell lung carcinoma. New trials are underway evaluating long-term results of SBRT in potentially operable patients.

Development and external validation of a nomogram to predict overall survival following stereotactic body radiotherapy for early-stage lung cancer

BACKGROUND

Prognostication tools for early-stage non-small cell lung cancer (NSCLC) patients treated with stereotactic body radiotherapy (SBRT) are currently lacking. The purpose of this study was to develop and externally validate a nomogram to predict overall survival in individual patients with peripheral early-stage disease.

METHODS

A total of 587 NSCLC patients treated with biologically effective dose > 100 Gy₁₀ were eligible. A Cox proportional hazards model was used to build a nomogram to predict 6-month, 1-year, 3-year and 5-year overall survival. Internal validation was performed using bootstrap sampling. External validation was performed in a separate cohort of 124 NSCLC patients with central tumors treated with SBRT. Discriminatory ability was measured by the concordance index (C-index) while predictive accuracy was assessed with calibration slope and plots.

RESULTS

The resulting nomogram was based on six prognostic factors: age, sex, Karnofsky Performance Status, operability, Charlson Comorbidity Index, and tumor diameter. The slope of the calibration curve for nomogram-predicted versus Kaplan-Meier-estimated overall survival was 0.77. The C-index of the nomogram (corrected for optimism) was moderate at 0.64. In the external validation cohort, the model yielded a C-index of 0.62.

CONCLUSIONS

We established and validated a nomogram which can provide individual survival predictions for patients with early stage lung cancer treated with SBRT. The nomogram may assist patients and clinicians with treatment decision-making.

Survival after stereotactic radiotherapy in patients with early-stage non-small cell lung cancer

Introduction: Stereotactic radiotherapy (SBRT) is the treatment of choice for inoperable early stage non-small cell lung cancer (NSCLC). We report analyses of the influence of age on survival after SBRT. Methods and material: From 2005 to 2017, 544 previously un-irradiated patients with early stage NSCLC had SBRT. The data were analyzed in four age groups: A: -69 (176 pts), B: 70-74 (115 pts), C: 75-79 (131 pts) and D: 80 years or older (122 pts). Two SBRT dose regimes were used: 45 Gy/3F (N = 103) and 66 Gy/3F (N = 441). Results: All patients had a follow up (time to censoring, FU) of at least 16 months, the median FU being 48.0 months. The median age was 74.4 years. The overall survival (OS) was associated with age. The median OS was 50.7, 45.9, 45.4 and 33.0 months, and the 5-year OS was 45%, 32%, 33% and 18% in groups A, B, C and D, respectively. No difference was found between groups B and C, while OS in group A was significantly better than remaining groups, and the OS in group D significantly poorer. In multivariable analyses, OS was heavily influenced by age, Charlson's comorbidity index (CCI) and performance status (PS). For lung cancer-specific survival (LCSS), only increasing tumor diameter and PS were associated with poor survival. Conclusions: The OS was influenced by age, but the study suggests that a cut point of 75 year is inappropriate in evaluating the effect of old age on survival. Poor PS was associated with poor OS. CCI influenced OS, but not LCSS, which was only affected by PS and tumor size.

Prognostic value of two geriatric screening tools in a cohort of older patients with early stage Non-Small Cell Lung Cancer treated with hypofractionated stereotactic radiotherapy

OBJECTIVES

To investigate whether assessment with two geriatric screening tools shows a correlation with clinical outcomes of patients aged 65 years or more, with early-stage Non-Small Cell Lung Cancer (es-NSCLC) treated with hypofractionated stereotactic radiotherapy.

METHODS

From March 2014 to June 2018 we retrospectively evaluated 42 patients with stage I and II lung tumors. Patients were assessed with Charlson Comorbidity Index (CCI) and G8 screening tool. Median age was 74 years (range, 65-91). Stereotactic radiotherapy was performed with Helical Tomotherapy delivering 50-70 Gray (Gy) in 8-10 fractions. Toxicity was evaluated using Common Terminology Criteria for Adverse Events v4.0 criteria.

RESULTS

Median CCI and G8 scores were 6 (4-11) and 14 (12-17), respectively. With a median follow-up of 14 months (3-37), we observed: 3 cases of acute Grade 2 (G2) radiation pneumonitis, 1 late G2 non-cardiac chest pain, 1 late G2 dysphagia and 1 case of late G2 radiation pneumonitis. At statistical analysis, G8 scores ≤14 were significantly associated with late toxicity rates (p = .0073). Local failure was predictive of disease free survival and Overall Survival (p < .001 and p = .001). Death occurred in 12 patients, 6 for non-cancer related causes, with 1- and 2-yrs cancer specific survival rates of 94.8% and 90%, 1- and 2-yrs OS rates of 93% and 80%, respectively.

CONCLUSIONS

Our experience shows a correlation between G8 scores and late toxicity in older patients treated with stereotactic radiotherapy for lung cancer, suggesting the need for prospective studies evaluating its use for the identification of patients at higher risk of adverse events.

Prediction of early mortality following stereotactic body radiotherapy for peripheral early-stage lung cancer

BACKGROUND/PURPOSE

To investigate prognostic factors for death within 6 months of stereotactic body radiotherapy (SBRT) for patients with peripheral early-stage non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

This analysis included 586 NSCLC patients with peripheral tumors treated with SBRT. Potential patient and tumor prognostic factors, including the Charlson Comorbidity Index (CCI) and Cumulative Illness Rating Scale (CIRS), were analyzed by logistic regression analysis for association with early mortality (death <6 months after SBRT). Additionally, CCI and CIRS were compared with respect to their predictive ability for early mortality by comparing multivariate models with each comorbidity index, and assessing their respective discriminatory abilities (C-index).

RESULTS

A total of 36 patients (6.1%) died within 6 months of the start of SBRT. With a median follow-up of 25 months, 3-year overall survival was 54%. CIRS and tumor diameter were significant predictors of early mortality on multivariate analysis (p = .001). Patients with a CIRS score of 8 or higher and a tumor diameter over 3 cm had a 6-month survival of 70% versus 97% for those lacking these two features (p < .001). CCI was not predictive for early mortality on univariate nor multivariate analysis; the model containing CCI had a C-index of 0.65 versus 0.70 for the model containing CIRS.

CONCLUSION

CIRS and tumor diameter predict for early-mortality in peripheral early-stage NSCLC treated with SBRT. CIRS may be a more useful comorbidity index than CCI in this population when assessing short-term life expectancy.

Stereotactic body radiation therapy in early-stage NSCLC: historical review, contemporary evidence and future implications

Clinical use of stereotactic body radiation therapy (SBRT) has increased dramatically over the last 2 decades and is the current standard-of-care in cases of inoperable early stage non-small-cell lung cancer. While surgical resection remains the standard-of-care for operable patients, several ongoing clinical trials are investigating the role of SBRT in these operative candidates as well. Taking into consideration the expanding role and utility of SBRT, this paper will: review the historical basis of SBRT; examine landmark trials establishing the framework for the current body of evidence; discuss areas of active and future research; and identify epidemiological trends that are likely to further increase the use of SBRT.

Treatment completion, treatment compliance and outcomes of old and very old patients treated by dose adapted stereotactic ablative radiotherapy (SABR) for T1-T3N0M0 non-small cell lung cancer

AIM

This is a retrospective single-institution review of the treatment completion and clinical outcomes of patients aged 75 and older, treated with stereotactic ablative body radiotherapy (SABR) for T1-T3 N0 M0 non-small cell lung cancer (NSCLC).

MATERIAL

METHODS

From April 2008 to September 2015, 200 patients, aged 75-93, received respiratory-managed, intensity-modulated-based SABR. Dose fractionation was risk-adapted and delivered in 2-3 weekly treatments. Treatment completion, local control, overall survival and treatment-related toxicities were evaluated.

RESULTS

All patients completed the prescribed SABR course. However, 29 patients required interruption of at least one fraction of SABR and optimization of pain control before continuation of the fraction. Median follow-up was 20.9 months. The median OS was 31.6 months with 1-,3-year survival rates of 80.7%, and 44.4% respectively. Local control at 1- and 3- years were 97.6%, 83.5% respectively. Treatment was well-tolerated. However, there were two (1%) G5 (fatal) toxicities: one acute sudden dyspnoea of unknown cause and one late SABR-related haemoptysis. No statistically significant differences in outcomes/toxicities were observed between old (75-84 years old) and very old patients (>85 years old).

CONCLUSIONS

Old and very old patients can successfully complete SABR for NSCLC, with good local control, survival and acceptable toxicity. Old patients might require increased supportive care for successful treatment delivery.

Feasibility of radiotherapy in nonagenarian patients: a retrospective study

PURPOSE

Specific information about radiation therapy in nonagenarians is limited. In order to shed more light on the feasibility of radiotherapy in this challenging subgroup, a retrospective study was performed.

METHODS

The data of 93 consecutive patients receiving irradiation treatment at the Department of Radiation Oncology, Ordensklinikum Linz Barmherzige Schwestern between June 2005 and December 2016 were analyzed. Patient- and treatment-related factors were extracted from the patient records. Overall survival (OS) was defined as time from irradiation to death or last follow-up. The survival rates were analyzed using the Kaplan-Meier method and log-rank test.

RESULTS

The study population of 93 patients was between 90 and 99 years old (median 91 years). It included 59 women (63%) and 34 men (37%). Of these, 38 (41%) received definitive radiotherapy, 14 (15%) received neoadjuvant or adjuvant radiotherapy, whereas a palliative regimen was prescribed in 44% of the cases (n = 41). In all, 79 patients (85%) were able to complete their prescribed course of radiotherapy. While 16 (17%) patients reported grade 2 toxicities or higher, 4 had ≥grade 3 side effects (4%). The median survival was significantly higher in patients treated with adjuvant, neoadjuvant or definitive radiotherapy (13.8 months) compared to patients treated with palliative radiotherapy (3.6 months; p < 0.001).

CONCLUSION

Even in patients managed without preradiotherapy comprehensive geriatric assessment, carefully planned fractionated radiotherapy was feasible and resulted in acceptable rates of acute toxicities.

Real-world treatment patterns for patients 80 years and older with early lung cancer: a nationwide claims study

Background

Old age is an important factor that could affect the treatment of early-stage lung cancer. In this study, we evaluated the treatment patterns and outcomes of patients over the age of 80 years who had been diagnosed with early-stage lung cancer in real-world practice.

Methods

Elderly patients who were diagnosed with early-stage lung cancer between 2008 and 2016 were identified using claims data provided by the Health Insurance Review and Assessment Service. The proportion of patients who underwent surgical resection or stereotactic body radiation therapy (SBRT), practice pattern trends, and overall survival (OS) were analyzed from the population-based data.

Results

Over 9 years, 1,684 patients underwent surgical resection (74.9%) or SBRT (25.1%) as a localized treatment. From 2008 to 2016, the treatment modality changed: the percentage of patients who underwent surgical resection decreased from 90.6 to 71.4%, and those who underwent SBRT increased from 9.4 to 28.6%. The percentage of patients treated with SBRT increased over time (p < 0.001). The median OS was 56.4 months in the surgery group and 35.5 months in the SBRT group. The SBRT group showed worse OS compared with the surgery group (Adjusted hazard ratio, 1.44; 95% confidence interval, 1.21–1.72; p < 0.001).

Conclusion

Changes in local treatment patterns in elderly lung cancer patients were observed and SBRT increased its role in this population. Surgical resection or SBRT should be considered the treatment of choice in elderly patients with localized lung cancer. Further prospective studies are required to elucidate the benefits of surgery and SBRT.

Practice-changing radiation therapy trials for the treatment of cancer: where are we 150 years after the birth of Marie Curie?

As we mark 150 years since the birth of Marie Curie, we reflect on the global advances made in radiation oncology and the current status of radiation therapy (RT) research. Large-scale international RT clinical trials have been fundamental in driving evidence-based change and have served to improve cancer management and to reduce side effects. Radiation therapy trials have also improved practice by increasing quality assurance and consistency in treatment protocols across multiple centres. This review summarises some of the key RT practice-changing clinical trials over the last two decades, in four common cancer sites for which RT is a crucial component of curative treatment: breast, lung, urological and lower gastro-intestinal cancer. We highlight the global inequality in access to RT, and the work of international organisations, such as the International Atomic Energy Agency (IAEA), the European SocieTy for Radiotherapy and Oncology (ESTRO), and the United Kingdom National Cancer Research Institute Clinical and Translational Radiotherapy Research Working Group (CTRad), that aim to improve access to RT and facilitate radiation research. We discuss some emerging RT technologies including proton beam therapy and magnetic resonance linear accelerators and predict likely future directions in clinical RT research.

Stereotactic body radiation therapy for lung, spine and oligometastatic disease: current evidence and future directions

Stereotactic body radiation therapy (SBRT) also referred to as stereotactic ablative radiotherapy (SABR), is a technique which has emerged over the past two decades due to improvements in radiation technology. Unlike conventional external beam radiotherapy (cEBRT) which traditionally delivers radiation in small doses [approximately 2 Gray (Gy) per fraction] over several weeks, SBRT, typically delivered in one to eight fractions, is a technique whereby potentially ablative doses of radiotherapy (usually 7.5-20 Gy per fraction) can be delivered with steeper dose gradients and sub millimetre precision, minimising risk to surrounding normal tissues. The potential benefits of excellent tumor control with low toxicity has led to the increasing use of SBRT in a number of clinical situations. Due to compelling evidence, SBRT is now the treatment of choice for medically inoperable patients with peripherally located stage I non-small cell lung cancer (NSCLC). Controversy remains however as to its efficacy and safety for central or ultra-central lung tumors. The evidence base supporting the use of SBRT as a novel treatment for spinal metastases and oligometastases is rapidly expanding but challenges remain in these difficult patient populations. In an era where targeted therapy and improved systemic treatments for stage IV cancer have resulted in increased disease-free survival, and our knowledge of the oligometastatic state is ever expanding, using SBRT to treat metastatic disease and gain durable local control is increasingly desirable. Several randomized trials are currently underway and are sure to provide valuable information on the benefit and utility of SBRT across many tumor sites including early-stage NSCLC, spinal metastases and oligometastatic disease. Recognizing the evolving role of SBRT in clinical practice, this paper provides a critical review of recent developments in each of these areas particularly highlighting the challenges facing clinicians and discusses potential areas for future research.

Stereotactic body radiation therapy (SBRT) for early-stage lung cancer in the elderly

Early-stage non-small cell lung cancer (NSCLC) is on the rise due to the implementation of screening guidelines for patients at risk for developing lung cancer. It is anticipated that as the US population continues to age, there will be a higher percentage of medically inoperable early-stage lung cancer patients. For this reason, noninvasive ablative therapies are necessary. Stereotactic body radiation therapy (SBRT) is an effective modality in addressing early-stage NSCLC. SBRT consists of high-dose radiation delivered over 3-5 treatments. Several randomized trials comparing surgery to SBRT in early-stage operable patients have unfortunately closed early due to poor accrual. However, a recent pooled analysis from 2 randomized trials (StereoTActic Radiotherapy and Radiosurgery Or Surgery for operable Early-stage non-small cell Lung cancer) comparing surgery to SBRT did show comparable local control and overall survival rates between surgery and SBRT, offering a very effective, noninvasive modality for older adult patients with early-stage NSCLC. In this review, we summarize the role of SBRT in early-stage NSCLC, in particularly applied to the older adult population.

Significance of stereotactic body radiotherapy in older patients with early stage non-small cell lung cancer

OBJECTIVES

Our aim was to investigate long-term treatment outcomes in older patients with early stage non-small cell lung cancer (NSCLC) and the presence or absence of therapeutic benefits, using the G8 screening tool.

METHODS

We retrospectively studied 43 older patients (median age 78 years, range 65-89 years) with stage I lung tumors (T1 and T2 tumors in 34 and 9 patients, respectively), who underwent stereotactic body radiotherapy (SBRT). This study assessed outcomes in a cohort of patients who received geriatric assessments, performed between 2004 and 2011, before the start of their SBRT regimen. Any questions asked to patients before undergoing treatment were applied to the G8 screening tool.

RESULTS

G8 scores ranged from 8 to 16 (median, 12) in all patients (n = 43), while G8 scores in the T1 and T2 groups ranged from 9 to 16 (median, 13) and 8 to 15 (median, 12), respectively. In patients with G8 scores ≤12, the 2-year and 5-year survival rates were 56.1% and 28% respectively, while the rates were 94.1% and 68.4%, respectively, in patients with G8 scores ≥13 (P = 0.0014). During long-term follow-up, 25.9% of the patients (n = 43) died of the primary disease, NSCLC, and 34.9% of patients died of other diseases or other types of cancer.

CONCLUSION

SBRT may be effective, even in older adults. Regardless of age, SBRT improved the long-term survival of patients only with G8 scores ≥13. The G8 screening tool may aid in determining whether older patients with comorbidities would benefit from SBRT.

Acquired resistance to tyrosine kinase inhibitors may be linked with the decreased sensitivity to X-ray irradiation

Acquired resistance to chemotherapy and radiation therapy is one of the major obstacles decreasing efficiency of treatment of the oncologic diseases. In this study, on the two cell lines (ovarian carcinoma SKOV-3 and neuroblastoma NGP-127), we modeled acquired resistance to five target anticancer drugs. The cells were grown on gradually increasing concentrations of the clinically relevant tyrosine kinase inhibitors (TKIs) Sorafenib, Pazopanib and Sunitinib, and rapalogs Everolimus and Temsirolimus, for 20 weeks. After 20 weeks of culturing, the half-inhibitory concentrations (IC₅₀) increased by 25 – 186% for the particular combinations of the drugs and cell types. We next subjected cells to 10 Gy irradiation, a dose frequently used in clinical radiation therapy. For the SKOV-3, but not NGP-127 cells, for the TKIs Sorafenib, Pazopanib and Sunitinib, we noticed statistically significant increase in capacity to repair radiation-induced DNA double strand breaks compared to naïve control cells not previously treated with TKIs. These peculiarities were linked with the increased activation of ATM DNA repair pathway in the TKI-treated SKOV-3, but not NGP-127 cells. Our results provide a new cell culture model for studying anti-cancer therapy efficiency and evidence that there may be a tissue-specific radioresistance emerging as a side effect of treatment with TKIs.

Elucidation of radiation-resistant clones by a serial study of intratumor heterogeneity before and after stereotactic radiotherapy in lung cancer

Stereotactic radiotherapy (SRT) for inoperable stage I non-small cell lung cancer has shown promising results and is now an alternative therapy for this disease. Several reports have detailed changes in mutation profiles after treatment with chemotherapy; however, such changes after SRT for lung cancer have not been reported. A patient who received SRT for lung cancer developed local recurrence 9 months after treatment and underwent surgery in our department. Using bronchoscopically biopsied and surgically resected specimens, we performed targeted sequencing of 53 lung cancer-related genes and compared the tumor mutation profiles before and after SRT. Identical mutations were detected from tumor specimens collected before and after SRT, and the specimens were confirmed to be clonal. However, the number of mutations decreased after SRT, suggesting that it induced mutation selection. Analyses of the statistical inference of clonal population structure showed that this evolving heterogeneous genomic landscape may be caused by heterogeneous responsiveness to SRT.