Local control dependence on consecutive vs. nonconsecutive fractionation in lung stereotactic body radiation therapy

Diagnostic and therapeutic challenges in a recurrent endometrial carcinoma in lung, 15 years after primary treatment

Endometrial carcinoma (EC) is the sixth most common cancer in females. Most ECs are detected in stage 1 and have a 5-year survival rate of more than 90%. Recurrence rates are highest within 5 years after treatment and are exceptionally rare after 10 years. Here, we describe a woman in her late 70s with endometrial cancer who was treated in 2008 and was diagnosed with a relapse in her left lung in 2023. Due to her advanced age and comorbidities, she was deemed inoperable. However, she received sequential chemotherapy and radiotherapy with a good partial response. She has now been started on hormonal therapy with an alternate megestrol and tamoxifen regime. There is a lack of follow-up imaging guidelines to detect late relapse, a dilemma in preferred treatment sequencing at relapse and an enigma in selecting chemotherapy or hormonal therapy.

Optimal Radiation Therapy Fractionation Regimens for Early-Stage Non-Small Cell Lung Cancer

PURPOSE

A series of radiobiological models were developed to study tumor control probability (TCP) for stereotactic body radiation therapy (SBRT) of early-stage non-small cell lung cancer (NSCLC) per the Hypofractionated Treatment Effects in the Clinic (HyTEC) working group. This study was conducted to further validate 3 representative models with the recent clinical TCP data ranging from conventional radiation therapy to SBRT of early-stage NSCLC and to determine systematic optimal fractionation regimens in 1 to 30 fractions for radiation therapy of early-stage NSCLC that were found to be model-independent.

METHODS AND MATERIALS

Recent clinical 1-, 2-, 3-, and 5-year actuarial or Kaplan-Meier TCP data of 9808 patients from 56 published papers were collected for radiation therapy of 2 to 4 Gy per fraction and SBRT of early-stage NSCLC. This data set nearly triples the original HyTEC sample, which was used to further validate the HyTEC model parameters determined from a fit to the clinical TCP data.

RESULTS

TCP data from the expanded data set are well described by the HyTEC models with α/β ratios of about 20 Gy. TCP increases sharply with biologically effective dose and reaches an asymptotic maximal plateau, which allows us to determine optimal fractionation schemes for radiation therapy of early-stage NSCLC.

CONCLUSIONS

The HyTEC radiobiological models with α/β ratios of about 20 Gy determined from the fits to the clinical TCP data for SBRT of early-stage NSCLC describe the recent TCP data well for both radiation therapy of 2 to 4 Gy per fraction and SBRT dose and fractionation schemes of early-stage NSCLC. A steep dose response exists between TCP and biologically effective dose, and TCP reaches an asymptotic maximum. This feature results in model-independent optimal fractionation regimens determined whenever safe for SBRT and hypofractionated radiation therapy of early-stage NSCLC in 1 to 30 fractions to achieve asymptotic maximal tumor control, and T2 tumors require slightly higher optimal doses than T1 tumors. The proposed optimal fractionation schemes are consistent with clinical practice for SBRT of early-stage NSCLC.

Five-Day Spacing of Two Fractionated Ablative Radiotherapies Enhances Antitumor Immunity

PURPOSE

This study aimed to enhance tumor control and abscopal effects by applying diverse stereotactic ablative radiation therapy (SABR) schedules.

METHODS AND MATERIALS

FSaII, CT-26, and 4T1 cells were used for tumor growth delay and lung metastases analysis after 1- or 5-day intervals radiation therapy (RT) with 40, 20, and 20 Gy, respectively. Immunodeficient BALB/c-nude, immunocompetent C3H, and BALB/c mouse models were used. For immune monitoring, FSaII tumors were analyzed using flow cytometry, immunofluorescence staining, and real-time quantitative reverse transcription polymerase chain reaction. The spleens were used for the ELISpot assay and flow cytometry to determine effector CD8 T cells. For abscopal effect analysis in CT-26 tumors, the volume of the nonirradiated secondary tumors was measured after primary tumors were irradiated with 1-day or 5-day intervals.

RESULTS

Contrary to the high-dose 1-day interval RT, the 5-day interval RT significantly delayed tumor growth in immunocompetent mice, which was not observed in immunodeficient mice. In addition, the 5-day interval RT significantly reduced the number of lung metastases in FSaII and CT-26 tumors. Five-day spacing was more effective than 1-day interval in enhancing the antitumor immunity via increasing the secretion of tumor-specific IFN-γ, activating the CD8 T cells, and suppressing the monocytic myeloid-derived suppressor cells. The 5-day spacing inhibited nonirradiated secondary tumor growth more effectively than did the 1-day interval.

CONCLUSIONS

Compared with the 1-day interval RT, the 5-day interval RT scheme demonstrated enhanced antitumor immunity of CD8 T cells associated with inhibition of myeloid-derived suppressor cells. Enhancing antitumor immunity leads to significant improvements in both primary tumor control and the abscopal effect.

Local control and survival after stereotactic body radiation therapy of early-stage lung cancer patients in Slovenia

BACKGROUND

Stereotactic body radiation therapy (SBRT) precisely and non-invasively delivers ablative radiation dose to tumors in early-stage lung cancer patients who are not candidates for surgery or refuse it. The aim of research was to evaluate local control, overall survival (OS), local progression free survival (LPFS), distant metastases free survival (DMFS), disease free survival (DFS) and toxicity in early-stage lung cancer patients treated with SBRT in a single tertiary cancer centre.

PATIENTS AND METHODS

We retrospectively evaluated medical records and radiation treatment plan parameters of 228 tumors irradiated in 206 early-stage lung cancer patients between 2016 and 2021 at the Institute of Oncology Ljubljana.

RESULTS

After 25 months of median follow up, 68 of 206 (33%) patients died. Median OS was 46 months (CI 36-56), 1-year, 2-year and 3-year OS were 87%, 74% and 62% and 5-year OS was 31%. A total of 45 disease progressions have been identified in 41 patients. Local progress only was noticed in 5 (2%) patients, systemic progress in 32 (16%) and combined systemic and local in 4 (2%) patients. Local control rate (LCR) at 1 year was 98%, at 2 and 3 years 96% and 95% at 5 years. The 1-, 2- and 3-year LPFS were 98%, 96% and 94%, respectively and 5-year LPFS was 82%. One, 2-, 3- and 5-year DFS were 89%, 81%, 72% and 49%, respectively. Among 28 toxicities recorded only one was Grade 4 (pneumonitis), all others were Grade 1 or 2. No differences in LCR, LPFS, DFS were found in univariate analysis comparing patient, tumor, and treatment characteristics. For OS the only statistically significant difference was found in patients with more than 3 comorbidities compared to those with less comorbidities.

CONCLUSIONS

Early lung cancer treated with SBRT at single tertiary cancer centre showed that LCR, LPFS, DFS, DMFS and OS were comparable to published studies. Patients with many comorbidities had significantly worse overall survival compared to those with less comorbidities. No other significant differences by patient, tumor, or treatment characteristics were found for DMFS, LPFS, and DFS. Toxicity data confirmed that treatment was well tolerated.

[Limits of dose constraint definition for organs at risk specific to stereotactic radiotherapy]

Stereotactic radiotherapy is a very hypofractionated radiotherapy (>7.5Gy per fraction), and therefore is more likely to induce late toxicities than conventional normofractionated irradiations. The present study examines four frequent and potentially serious late toxicities: brain radionecrosis, radiation pneumonitis, radiation myelitis, and radiation-induced pelvic toxicities. The critical review focuses on the toxicity scales, the definition of the dose constrained volume, the dosimetric parameters, and the non-dosimetric risk factors. The most commonly used toxicity scales remain: RTOG/EORTC or common terminology criteria for adverse events (CTCAE). The definition of organ-at-risk volume requiring protection is often controversial, which limits the comparability of studies and the possibility of accurate dose constraints. Nevertheless, for the brain, whatever the indication (arteriovenous malformation, benign tumor, metastasis of solid tumors...), the association between the volume of brain receiving 12Gy (V12Gy) and the risk of cerebral radionecrosis is well established for both single and multi-fraction stereotactic irradiation. For the lung, the average dose received by both lungs and the V20 seem to correlate well with the risk of radiation-induced pneumonitis. For the spinal cord, the maximum dose is the most consensual parameter. Clinical trial protocols are useful for nonconsensual dose constraints. Non-dosimetric risk factors should be considered when validating the treatment plan.

Local Control Correlates with Overall Survival in Radiotherapy for Early-stage Non-small Cell Lung Cancer: A Systematic Review

PURPOSE

Local control (LC) is an important outcome of local cancer therapy, besides overall survival (OS). We conducted a comprehensive literature search to investigate whether a high LC rate contributes to good OS in radiotherapy for early-stage non-small cell lung cancer (ES-NSCLC).

MATERIALS AND METHODS

Studies in patients receiving radiotherapy for peripheral ES-NSCLC, mainly staged as T1-2N0M0 were included for a systematic review. Relevant information was collected including, dose fractionation, T stage, median age, 3-year LC, cancer-specific survival (CSS), disease-free survival (DFS), distant metastasis-free survival (DMFS), and OS. Correlations between outcomes and clinical variables were evaluated.

RESULTS

After screening, 101 data points from 87 studies including 13,435 patients were selected for the quantitative synthesis. Univariate meta-regression analysis revealed that the coefficients between the 3-year LC and 3-year DFS, DMFS, CSS, and OS were 0.753 (95% confidence interval (CI): 0.307-1.199; p<0.001), 0.360 (95% CI: 0.128-0.593; p=0.002), 0.766 (95% CI: 0.489-1.044; p<0.001), and 0.574 (95% CI: 0.275-0.822; p<0.001), respectively. Multivariate analysis revealed that the 3-year LC (coefficient, 0.561; 95% CI: 0.254-0.830; p<0.001) and T1 proportion (coefficient, 0.207; 95% CI: 0.030-0.385; p=0.012) were significantly associated with the 3-year OS and CSS (coefficient for 3-year LC, 0.720; 95% CI: 0.468-0.972; p<0.001 and T1 proportion, 0.002; 95% CI: 0.000-0.003; p=0.012). Toxicities ≥grade 3 were low (3.4%).

CONCLUSIONS

Three-year LC was correlated with three-year OS in patients receiving radiotherapy for ES-NSCLC. A 5% increase in 3-year LC is expected to improve the 3-year CSS and OS rates by 3.8% and 2.8%, respectively.

Analysis of tumour dose-response data from animal experiments via two TCP models accounting for tumor hypoxia and resensitization

To treat animal dose-response data exhibiting inverse dose-response behavior with two tumor control probability (TCP) models accounting for tumor hypoxia and re-oxygenation leading to resensitization of the tumor. One of the tested TCP models uses a modified linear-quadratic (LQ) model of cell survival where both α and β radiosensitivities increase in time during the treatment due to re-oxygenation of the hypoxic tumor sub-population. The other TCP model deals with two types of hypoxia-chronic and acute-and accounts for tumor re-sensitization via oxygenation of the chronically hypoxic and fluctuating oxygenation of the acutely hypoxic sub-populations. The two models are fit using the maximum likelihood method to the data of Fowler et al. on mice mammary tumors irradiated to different doses using different fractionated schedules. These data are chosen since as many as five of the dose-response curves show an inverse dose behavior, which is interpreted as due to re-sensitization. The p-values of the fits of both models to the data render them statistically acceptable. A performed comparison test shows that both models describe the data equally well. It is also demonstrated that the most sensitive (oxic) tumor component has no impact on the treatment outcome. The ability of the tested models to predict and describe the impact of re-sensitization on the treatment outcome is thus proven. It is also demonstrated that prolonged treatment schedules can be more beneficial than shorter ones. However, this may be true only for schedules with small number of fractions, i.e. for hypo-fractionated treatments only.

The Impact of Different Timing Schedules on Prostate HDR-Mono-Brachytherapy. A TCP Modeling Investigation

Simple Summary

Reported clinical data on high dose rate mono brachytherapy of prostate cancer carried out using two different treatment regimens are analyzed in this study. The analysis is based on a mechanistic tumor control probability model, which accounts for a possible increase in the tumor radio-sensitivity during treatment. The aim of the study was to verify a hypothesis that the clinically observed better performance of the longer treatment regimen (28 days vs. 14 days) might be due to a state of initial hypoxia and its ensued overcoming by re-oxygenation and, hence, re-sensitization of the prostate cancer. The performed investigation confirmed the assumption of initially hypoxic stage of the tumor followed by its re-sensitization, thus providing a foundation for the use of prolonged schedules for low- to intermediate-risk prostate cancer treatment.

Abstract

Background: Mechanistic TCP (tumor control probability) models exist that account for possible re-sensitization of an initially hypoxic tumor during treatment. This phenomenon potentially explains the better outcome of a 28-day vs 14-day treatment schedule of HDR (high dose rate) brachytherapy of low- to intermediate-risk prostate cancer as recently reported. Methods: A TCP model accounting for tumor re-sensitization developed earlier is used to analyze the reported clinical data. In order to analyze clinical data using individual TCP model, TCP distributions are constructed assuming inter-individual spread in radio-sensitivity. Results: Population radio-sensitivity parameter values are found that result in TCP population values which are close to the reported ones. Using the estimated population parameters, two hypothetical regimens are investigated that are shorter than the ones used clinically. The impact of the re-sensitization rate on the calculated treatment outcome is also investigated as is the anti-hypothesis that there is no re-sensitization during treatment. Conclusions: The carried out investigation shows that the observed clinical data cannot be described without assuming an initially hypoxic state of the tumor followed by re-oxygenation and, hence, re-sensitization. This phenomenon explains the better outcome of the prolonged treatment schedule compared to shorter regimens based on the fact that prostate cancer is a slowly repopulating tumor.

Prolonged overall treatment time negatively affects the outcomes of stereotactic body radiotherapy for early-stage non-small-cell lung cancer: A propensity score-weighted, single-center analysis

Previous studies have reported conflicting results for the effect of overall treatment time with stereotactic body radiotherapy on tumor control in early-stage non-small-cell lung cancer. To examine this effect, we conducted a propensity score-weighted, retrospective, observational study at a single institution. We analyzed the data of 200 patients with early-stage non-small-cell lung cancer who underwent stereotactic body radiotherapy (48 Gy in 4 fractions) at our institution between January 2007 and October 2013. Patients were grouped into consecutive (overall treatment time = 4–5 days, n = 116) or non-consecutive treatment groups (overall treatment time = 6–10 days, n = 84). The outcomes of interest were local control and overall survival. The Cox regression model was used with propensity score and inverse probability of treatment weighting. The median overall treatment times in the consecutive and non-consecutive groups were 4 and 6 days, respectively. The 5-year local control and overall survival rates in the consecutive vs. the non-consecutive group were 86.3 vs. 77.2% and 55.5 vs. 51.8%, respectively. After propensity score weighting, consecutive stereotactic body radiotherapy was associated with positive local control (adjusted hazard ratio 0.30, 95% confidence interval 0.14–0.65; p = 0.002) and overall survival (adjusted hazard ratio 0.56, 95% confidence interval 0.34–0.91; p = 0.019) benefits. The prolonged overall treatment time of stereotactic body radiotherapy treatment negatively affected the outcomes of patients with early-stage non-small-cell lung cancer. To our knowledge, this is the first study to show that in patients with early-stage non-small-cell lung cancer treated with the same dose-fractionation regimen, consecutive stereotactic body radiotherapy has a more beneficial effect on tumor control than non-consecutive stereotactic body radiotherapy.

Theoretical investigation of the impact of different timing schemes in hypofractionated radiotherapy

PURPOSE

This study compares the effectiveness of three fractionation schemes of equal fraction size, comprising five fractions of SBRT over 5 days, 10 days, or 15 days, respectively.

METHOD

This comparative study is based on two tumor-control-probability (TCP) models that take into account tumor cell re-sensitization and repopulation during treatment; the Zaider-Minerbo-Stavreva (ZMS) and the Ruggieri-Nahum (RN) models. The ZMS model is further modified to include also re-sensitization according to the β mechanism of the linear-quadratic (LQ) model of cell killing. The modified version of the ZMS model is verified through fitting to the experimental data set of Fisher and Moulder. The study applies an idea used in a plan ranking methodology developed for the case when the specific values of the model parameters are not known.

RESULTS

The TCPs of the compared regimens are calculated for various values of the model parameters and for two different values of the dose per fraction. The TCPs are presented as 2-D functions of two of the model parameters for each model correspondingly. The differences between the TCPs of each of the prolonged regimens and the TCP of the every week day regimen are also calculated for each model.

CONCLUSIONS

Both models predict that the prolonged regimens are superior in terms of TCP to the every week-day one for most of the studied cases; however this is shown to exist to a different degree by the two models. It is shown again to a different degree that reversed situations where the every week day schedule is better than the prolonged regimens are also possible. It is concluded that a 30% TCP difference observed in a clinical study in favor of the fifteen-day regimen is theoretically possible. However, the fifteen-day regimen is outperformed in terms of TCP by the every week day regimen in more cases than the regimen lasting ten days. Therefore the choice of a prolongation in time must be made with care.

Discontinuous stereotactic body radiotherapy schedule increases overall survival in early-stage non-small cell lung cancer

OBJECTIVES

The duration of stereotactic body radiotherapy (SBRT) for early-stage non-small cell lung cancer (NSCLC) may affect patient outcomes. We aimed to determine the impact of a continuous versus discontinuous SBRT schedule on local control (LC) and overall survival (OS) in NSCLC patients.

MATERIALS AND METHODS

Consecutive NSCLC stage I patients (475) treated with SBRT in four centers were retrospectively analyzed. The delivered dose ranged from 48 to 75 Gy in 3-10 fractions. Based on the ratio between the treatment duration (TD) and number of fractions (n), patients were divided into two groups: continuous schedule (CS) (TD ≤ 1.6n; 239 patients) and discontinuous schedule (DS) (TD > 1.6n; 236 patients). LC and OS were compared using Cox regression analyses after propensity score matching (216 pairs).

RESULTS

The median follow-up period was 41 months. Multivariate analysis showed that the DS (hazard ratio (HR): 0.42; 95 % confidence interval (CI): 0.22-0.78) and number of fractions (HR: 1.24; 95 % CI: 1.07-1.43) were significantly associated with LC. The DS (HR: 0.67; 95 % CI: 0.51-0.89), age (HR: 1.02; 95 % CI: 1-1.03), WHO performance status (HR: 2.27; 95 % CI: 1.39-3.7), and T stage (HR: 1.4; 95 % CI: 1.03-1.87) were significantly associated with OS. The 3-year LC and OS were 92 % and 64 % and 81 % and 53 % for DS and CS treatments, respectively (p < 0.01). Cox analysis confirmed that the discontinuous SBRT schedule significantly increased LC and OS.

CONCLUSION

DS is associated with significantly improved LC and OS in early-stage NSCLC patients treated with SBRT.

Chest wall toxicity after stereotactic radiation in early lung cancer: a systematic review

Background

Radiation-induced chest wall pain (cwp) and rib fracture (rf) are late adverse effects after stereotactic body radiation therapy (sbrt) for stage i non-small-cell lung cancer (nsclc); however, the literature about their incidence and risk factors shows variability. We performed a systematic review to determine the pooled incidence of cwp and rf in the relevant population.

Methods

A literature search using the prisma (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines considered English publications in medline and embase from January 1996 to August 2017. Abstracts were screened, followed by full-text review and data extraction.

Results

The database searches identified 547 records. Twenty-eight publications comprising 3892 patients met the inclusion criteria. Median reported ages and follow-up durations fell into the ranges 67-82 years and 12-84 months. Prescriptions fell into the range of 40-70 Gy in 3-10 fractions. Despite study heterogeneity, the pooled incidences of cwp and rf were estimated to be 8.94% and 5.27% respectively. Nineteen studies reported cwp grade: 58 of 308 patients (18.8%) experienced grades 3-4 cwp (no grade 5 events reported). Thirteen studies reported rf grade: grades 3-4 rf were observed in 9 of 113 patients (7.96%). A high chest wall V30 was an important predictor of cwp and rf.

Conclusions

In patients with stage i nsclc, rates of cwp and rf after sbrt are low; however, tumour location, accurate toxicity reporting, and dose-fractionation schemes might alter those rates. Prospective correlation with dosimetry and quality of life assessment will further improve the understanding of cwp and rf after sbrt.

[Prognosis factors after lung stereotactic body radiotherapy for non-small cell lung carcinoma]

Lung cancer is the fourth most common cancer in France with a prevalence of 30,000 new cases per year. Lobectomy surgery with dissection is the gold standard treatment for T1-T2 localized non-small cell lung carcinoma. A segmentectomy may be proposed to operable patients but fragile from a respiratory point of view. For inoperable patients or patients with unsatisfactory pulmonary function tests, local treatment with stereotactic radiotherapy may be proposed to achieve local control rates ranging from 85 to 95% at 3-5 years. Several studies have examined prognostic factors after stereotaxic pulmonary radiotherapy. We conducted a general review of the literature to identify factors affecting local control.

Organs at Risk Considerations for Thoracic Stereotactic Body Radiation Therapy: What Is Safe for Lung Parenchyma?

PURPOSE

Stereotactic body radiation therapy (SBRT) has become the standard of care for inoperable early-stage non-small cell lung cancer and is often used for recurrent lung cancer and pulmonary metastases. Radiation-induced lung toxicity (RILT), including radiation pneumonitis and pulmonary fibrosis, is a major concern for which it is important to understand dosimetric and clinical predictors.

METHODS AND MATERIALS

This study was undertaken through the American Association of Physicists in Medicine's Working Group on Biological Effects of Stereotactic Body Radiotherapy. Data from studies of lung SBRT published through the summer of 2016 that provided detailed information about RILT were analyzed.

RESULTS

Ninety-seven studies were ultimately considered. Definitions of the risk organ and complication endpoints as well as dose-volume information presented varied among studies. The risk of RILT, including radiation pneumonitis and pulmonary fibrosis, was reported to be associated with the size and location of the tumor. Patients with interstitial lung disease appear to be especially susceptible to severe RILT. A variety of dosimetric parameters were reported to be associated with RILT. There was no apparent threshold "tolerance dose-volume" level. However, most studies noted safe treatment with a rate of symptomatic RILT of <10% to 15% after lung SBRT with a mean lung dose (MLD) of the combined lungs ≤8 Gy in 3 to 5 fractions and the percent of total lung volume receiving more than 20 Gy (V₂₀) <10% to 15%.

CONCLUSIONS

To allow more rigorous analysis of this complication, future studies should standardize reporting by including standardized endpoint and volume definitions and providing dose-volume information for all patients, with and without RILT.

High Single Doses of Radiation May Induce Elevated Levels of Hypoxia in Early-Stage Non-Small Cell Lung Cancer Tumors

PURPOSE

Tumor hypoxia correlates with treatment failure in patients undergoing conventional radiation therapy. However, no published studies have investigated tumor hypoxia in patients undergoing stereotactic body radiation therapy (SBRT). We aimed to noninvasively quantify the tumor hypoxic volume (HV) in non-small cell lung cancer (NSCLC) tumors to elucidate the potential role of tumor vascular response and reoxygenation at high single doses.

METHODS AND MATERIALS

Six SBRT-eligible patients with NSCLC tumors >1 cm were prospectively enrolled in an institutional review board-approved study. Dynamic positron emission tomography images were acquired at 0 to 120 minutes, 150 to 180 minutes, and 210 to 240 minutes after injection of 18F-fluoromisonidazole. Serial imaging was performed prior to delivery of 18 Gy and at approximately 48 hours and approximately 96 hours after SBRT. Tumor HVs were quantified using the tumor-to-blood ratio (>1.2) and rate of tracer influx (>0.0015 mL·min·cm-3).

RESULTS

An elevated and in some cases persistent level of tumor hypoxia was observed in 3 of 6 patients. Two patients exhibited no detectable baseline tumor hypoxia, and 1 patient with high baseline hypoxia only completed 1 imaging session. On the basis of the tumor-to-blood ratio, in the remaining 3 patients, tumor HVs increased on day 2 after 18 Gy and then showed variable responses on day 4. In the 3 of 6 patients with detectable hypoxia at baseline, baseline tumor HVs ranged between 17% and 24% (mean, 21%), and HVs on days 2 and 4 ranged between 33% and 45% (mean, 40%) and between 18% and 42% (mean, 28%), respectively.

CONCLUSIONS

High single doses of radiation delivered as part of SBRT may induce an elevated and in some cases persistent state of tumor hypoxia in NSCLC tumors. Hypoxia imaging with 18F-fluoromisonidazole positron emission tomography should be used in a larger cohort of NSCLC patients to determine whether elevated tumor hypoxia is predictive of treatment failure in SBRT.

Stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC): contemporary insights and advances

The standard-of-care treatment for early-stage non-small cell lung cancer (NSCLC) continues to be surgery in the form of lobectomy or pneumonectomy. Stereotactic body radiation therapy (SBRT) has evolved as a viable alternative to surgery for medically inoperable patients, achieving excellent local control (LC) with relatively minimal toxicity in standard-risk patients. Nevertheless, the maturation of SBRT has fostered debate regarding its use, technique, dose, and fractionation, particularly in the context of patient- and disease-specific characteristics such as tumor size and location. This review will cover the recent trends and future directions of SBRT as it becomes an increasingly individualized modality in the treatment of early-stage NSCLC.

Local control for clinical stage I non-small cell lung cancer treated with 5-fraction stereotactic body radiation therapy is not associated with treatment schedule

PURPOSE

Clinical concern remains regarding the relationship between consecutive (QD) versus nonconsecutive (QoD) lung stereotactic body radiation therapy (SBRT) treatment schedules and outcomes for clinical stage I non-small cell lung cancer (NSCLC). We examined a multi-institutional series of patients receiving 5-fraction lung SBRT to compare the local failure rates and overall survival between patients receiving QD versus QoD treatment.

METHODS AND MATERIALS

Lung SBRT databases from 2 high-volume institutions were combined, and patients receiving 5-fraction SBRT for a solitary stage I NSCLC were identified. QD treatment was defined as completing SBRT in ≤7 days, whereas QoD treatment was defined as completing treatment in >7 days. To control for patient characteristics between the 2 institutions, a 1:1 propensity-matched analysis was performed. Multivariable logistic regression was performed to identify variables independently associated with local failure, and Cox proportional hazards modeling to identify variables independently associated with increased mortality.

RESULTS

From 2005 through 2016, 245 clinical stage I NSCLC patients receiving 5-fraction SBRT were identified. A total of 117 (47.8%) patients received QD treatment and 128 (52.2%) patients received QoD treatment. On propensity-matched analysis, no association was seen between QD treatment and local failure (odds ratio [OR] for QD treatment, 0.48; 95% confidence interval [CI], 0.12-1.99; P = .5). On multivariable logistic regression, central tumors were independently associated with increased likelihood of local recurrence (OR, 5.2; 95% CI, 1.11-24.2; P = .04). Kaplan-Meier analysis identified no difference in median overall survival between QD versus QoD treatments (38.0 vs 38.0 months, log-rank P = .7), respectively. QD treatment was not associated with an increased mortality hazard (hazard ratio, 1.08; 95% CI, 0.67-1.75; P = .75).

CONCLUSIONS

This analysis demonstrated no association between QD versus QoD treatment scheduling and local control or overall survival for early-stage NSCLC.

Stereotactic body radiation therapy (SBRT) in the management of non-small-cell lung cancer: Clinical impact and patient perspectives

Stereotactic body radiation therapy (SBRT) has emerged as a new technology in radiotherapy delivery, allowing for potentially curative treatment in many patients previously felt not to be candidates for radical surgical resection of stage I non-small-cell lung cancer (NSCLC). Several studies have demonstrated very high local control rates using SBRT, and more recent data have suggested overall survival may approach that of surgery in operable patients. However, SBRT is not without unique toxicities, and the balance of toxicity, and effect on patient-reported quality of life need to be considered with respect to oncologic outcomes. We therefore aim to review SBRT in the context of important patient-related factors, including quality of life in several domains (and in comparison to other therapies such as conventional radiation, surgery, or no treatment). We will also describe scenarios in which SBRT may be reasonably offered (i.e. elderly patients and those with severe COPD), and where it may need to be approached with some caution due to increased risks of toxicity (i.e. tumor location, patients with interstitial lung disease). In total, we hope to characterize the physical, emotional, and functional consequences of SBRT, in relation to other management strategies, in order to aid the clinician in deciding whether SBRT is the optimal treatment choice for each patient with early stage NSCLC.

Influence of Fractionation Scheme and Tumor Location on Toxicities After Stereotactic Body Radiation Therapy for Large (≥5 cm) Non-Small Cell Lung Cancer: A Multi-institutional Analysis

PURPOSE

To describe the impact of fractionation scheme and tumor location on toxicities in stereotactic body radiation therapy (SBRT) for ≥5-cm non-small cell lung cancer (NSCLC), as part of a multi-institutional analysis.

METHODS

Patients with primary ≥5-cm N0 M0 NSCLC who underwent ≤5-fraction SBRT were examined across multiple high-volume SBRT centers. Collected data included clinical/treatment parameters; toxicities were prospectively assessed at each institution according to the Common Terminology Criteria for Adverse Events. Patients treated daily were compared with those treated every other day (QOD)/other nondaily regimens. Stratification between central and peripheral tumors was also performed.

RESULTS

Ninety-two patients from 12 institutions were evaluated (2004-2016), with median follow-up of 12 months. In total there were 23 (25%) and 6 (7%) grade ≥2 and grade ≥3 toxicities, respectively. Grades 2 and 3 pulmonary toxicities occurred in 9% and 4%, respectively; 1 patient treated daily experienced grade 5 radiation pneumonitis. Of the entire cohort, 46 patients underwent daily SBRT, and 46 received QOD (n=40)/other nondaily (n=6) regimens. Clinical/treatment parameters were similar between groups; the QOD/other group was more likely to receive 3-/4-fraction schemas. Patients treated QOD/other experienced significantly fewer grade ≥2 toxicities as compared with daily treatment (7% vs 43%, P<.001). Patients treated daily also had higher rates of grade ≥2 pulmonary toxicities (P=.014). Patients with peripheral tumors (n=66) were more likely to receive 3-/4-fraction regimens than those with central tumors (n=26). No significant differences in grade ≥2 toxicities were identified according to tumor location (P>.05).

CONCLUSIONS

From this multi-institutional study, toxicity of SBRT for ≥5-cm lesions is acceptable, and daily treatment was associated with a higher rate of toxicities.

Comparative Analysis of Local Control Prediction Using Different Biophysical Models for Non-Small Cell Lung Cancer Patients Undergoing Stereotactic Body Radiotherapy

PURPOSE

The consistency for predicting local control (LC) data using biophysical models for stereotactic body radiotherapy (SBRT) treatment of lung cancer is unclear. This study aims to compare the results calculated from different models using the treatment planning data.

MATERIALS AND METHODS

Treatment plans were designed for 17 patients diagnosed with primary non-small cell lung cancer (NSCLC) using 5 different fraction schemes. The Martel model, Ohri model, and the Tai model were used to predict the 2-year LC value. The Gucken model, Santiago model, and the Tai model were employed to estimate the 3-year LC data.

RESULTS

We found that the employed models resulted in completely different LC prediction except for the Gucken and the Santiago models which exhibited quite similar 3-year LC data. The predicted 2-year and 3-year LC values in different models were not only associated with the dose normalization but also associated with the employed fraction schemes. The greatest difference predicted by different models was up to 15.0%.

CONCLUSIONS

Our results show that different biophysical models influence the LC prediction and the difference is not only correlated to the dose normalization but also correlated to the employed fraction schemes.