Accelerated Hypofractionated Radiotherapy Versus Stereotactic Body Radiotherapy for the Treatment of Stage I Nonsmall Cell Lung Cancer-A Single Institution Experience With Long-Term Follow-Up

Stereotactic ablative radiotherapy versus conventional fractionated radiotherapy for clinical early-stage non-small-cell lung cancer: a population-based study

INTRODUCTION

The use of stereotactic ablative radiotherapy (SABR) over conventional fractionated radiotherapy (CFRT) for early-stage non-small-cell lung cancer (NSCLC) has been advocated, but is also debated in the literature.

METHODS

In this retrospective cohort study, we adopted a target trial emulation framework to identify eligible patients diagnosed between 2011 and 2021 using the Taiwan Cancer Registry. In the primary analysis, the overall survival (OS) was the primary endpoint, whereas incidences of lung cancer mortality and radiation pulmonary toxicity were the secondary endpoints. Extensive supplementary analyses were also conducted.

RESULTS

We included 351 patients in the primary analysis and found that the OS was not significantly different between the SABR (n = 290) and CFRT (n = 61) groups. The propensity score weighting adjusted hazard ratio of death was 0.75 (95% confidence interval 0.53-1.07, p = 0.118). The secondary endpoints and supplementary analyses showed no significant differences.

CONCLUSIONS

The OS of patients with early-stage NSCLC treated with SABR was not significantly different from that of patients treated with CFRT alone. The results of the relevant ongoing clinical trials are eagerly awaited.

Histology-driven hypofractionated radiation therapy schemes for early-stage lung adenocarcinoma and squamous cell carcinoma

BACKGROUND AND PURPOSE

Histology was found to be an important prognostic factor for local tumor control probability (TCP) after stereotactic body radiotherapy (SBRT) of early-stage non-small-cell lung cancer (NSCLC). A histology-driven SBRT approach has not been explored in routine clinical practice and histology-dependent fractionation schemes remain unknown. Here, we analyzed pooled histologic TCP data as a function of biologically effective dose (BED) to determine histology-driven fractionation schemes for SBRT and hypofractionated radiotherapy of two predominant early-stage NSCLC histologic subtypes adenocarcinoma (ADC) and squamous cell carcinoma (SCC).

MATERIAL AND METHODS

The least-χ2 method was used to fit the collected histologic TCP data of 8510 early-stage NSCLC patients to determine parameters for a well-developed radiobiological model per the Hypofractionated Treatment Effects in the Clinic (HyTEC) initiative.

RESULTS

A fit to the histologic TCP data yielded independent radiobiological parameter sets for radiotherapy of early-stage lung ADC and SCC. TCP increases steeply with BED and reaches an asymptotic maximal plateau, allowing us to determine model-independent optimal fractionation schemes of least doses in 1-30 fractions to achieve maximal tumor control for early-stage lung ADC and SCC, e.g., 30, 44, 48, and 51 Gy for ADC, and 32, 48, 54, and 58 Gy for SCC in 1, 3, 4, and 5 fractions, respectively.

CONCLUSION

We presented the first determination of histology-dependent radiobiological parameters and model-independent histology-driven optimal SBRT and hypofractionated radiation therapy schemes for early-stage lung ADC and SCC. SCC requires substantially higher radiation doses to maximize tumor control than ADC, plausibly attributed to tumor genetic diversity and microenvironment. The determined optimal SBRT schemes agree well with clinical practice for early-stage lung ADC. These proposed optimal fractionation schemes provide first insights for histology-based personalized radiotherapy of two predominant early-stage NSCLC subtypes ADC and SCC, which require further validation with large-scale histologic TCP data.

Impact of Maximum Point Dose Within the Planning Target Volume on Local Control of Nonsmall Cell Lung Cancer Treated With Stereotactic Body Radiotherapy

BACKGROUND

No consensus exists on the maximum dose delivered to the planning target volume (PTV) in the delivery of stereotactic body radiotherapy (SBRT) for primary lung cancer. We investigated whether higher biologically effective doses (BED) within the PTV were associated with improved tumor control.

METHODS

We reviewed patients with early-stage, node-negative nonsmall cell lung cancer who received curative-intent SBRT between 2005 and 2018. We calculated the maximum BED (maxBED) within the PTV for all patients, analyzing outcomes using the cumulative incidence method and Fine-Gray test statistics to assess prognostic impact.

RESULTS

We analyzed 171 patients (median age, 70.2; range, 43 to 90 y) with 181 lung nodules. Median follow-up was 2.7 years (range, 0.1 to 12 y) for all patients and 4.2 years (range, 0.2 to 8.4 y) for living patients. Median maximum tumor diameter was 1.9 cm (range, 0.7 to 5.6 cm). Patients received a prescription of 48 or 50 Gy in 4 or 5 fractions, respectively, except for one who received 60 Gy in 5 fractions. Median maxBED was 120 Gy (range, 101 to 171 Gy). There was no difference in the 3-year local control (LC) rate among patients treated with a maxBED<120 Gy versus ≥120 Gy ( P =0.83).

CONCLUSIONS

No significant differences in LC were observed between patients with early-stage nonsmall cell lung cancer treated with SBRT in 4 or 5 fractions with a maxBED≥120 Gy. However, a higher maxBED trended toward improved LC rates, suggesting a maxBED threshold greater than 120 Gy may be needed to improve LC rates.

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.

Accelerated hypofractionated radiotherapy with 3 Gy per fraction for central/ultra-central lung tumors: toxicity to mediastinal organs

BACKGROUND

Accelerated hypofractionated radiotherapy with 3 Gy per fraction is routinely performed for central lung tumors in Japan. However, the tolerable doses to mediastinal organs at risk during this procedure are unclear. This study aimed to clarify the rate of toxicities and tolerable doses to mediastinal organs.

METHODS

Patients treated with accelerated hypofractionated radiotherapy using a total dose of 60-75 Gy, with 3 Gy per fraction, for central lung tumors (July 2009-April 2021) were retrospectively reviewed. We extracted patients who received ≥30 Gy irradiation to each mediastinal organ and analyzed dosimetric factors, including doses to 0.03, 0.5, 1, 4 and 10 mL of each organ, in relation to grade 3-5 toxicities, except for radiation pneumonitis.

RESULTS

In total, 251 organs in 91 (ultra-central, 24) lesions were analyzed, with a median follow-up duration of 26 months (range, 4-94). The prescribed doses were 75/72/69/66/63/60 Gy for 52/14/16/3/2/4 lesions, respectively. Grade 3 bronchopulmonary hemorrhage was confirmed in two (2.2%) patients, whose tumors were located ultra-centrally. The two patients with toxicity received up to 74.5 and 71.6 Gy to the bronchus. Among patients who received 70 Gy or more to the bronchus, the incidence rate was 7% (2/28 patients).

CONCLUSION

The rate of severe toxicities was low (2.2%). Although we did not identify the dose tolerance of the organs, because of the low incidence rate, we did note that doses of >70 Gy to the bronchus were likely to cause bronchopulmonary hemorrhage.

Dose-effect relationship of stereotactic body radiotherapy in non-small cell lung cancer patients

OBJECTIVE

To establish the dose effect relationship between the dose parameters of stereotactic body radiation therapy (SBRT) for early non-small cell lung cancer (NSCLC) and the local tumor control rate.

MATERIALS AND METHODS

A comprehensive literature search was conducted using PubMed, the Web of Science and the Cochrane databases to determine the articles treated with SBRT in early-stage NSCLC. Original studies with complete prescription dose information, tumor local control rate and other important parameters were screened and reported. Probit model in XLSTAT 2016 was used for regression analysis, and P < 0.05 was set as a statistically significant level.

RESULTS

After literature screening, 22 eligible studies were included in probit model regression analysis, involving 1861 patients. There is no significant dose effect relationship between nominal BED₁₀ and peripheral BED₁₀ versus 3 years local control probability. There were significant dose effect relationships between the center BED₁₀ and the average BED₁₀ versus the 3 years local control probability, with P values are 0.001 and < 0.0001, respectively. According to the results of this model, the 3 years local control rate of 90.5% (87.5-92.1%) and 89.5% (86.7-91.0%) can be expected at the center BED₁₀ of 180 Gy or the average BED₁₀ of 140 Gy, prospectively.

CONCLUSIONS

For NSCLC treated with SBRT, more attention should be paid to the central dose and average dose of PTV. A set of clear definition in the dose prescription should be established to ensure the effectiveness and comparability of treatment.

Stereotactic body radiation therapy for metastatic lung metastases

Although systemic therapy is standard management for patients with metastatic disease, several recent reports have indicated that an addition of local therapies including stereotactic body radiation therapy (SBRT) for patients with oligometastatic disease (OMD) could improve survival. The lung is the most common site of distant metastasis from many solid tumors, and the strategy of SBRT, such as dose-fraction schedules, timing, etc., would be different depending on the type of primary tumor, location, and patterns of OMD. This review describes the role of SBRT with curative-intent for patients with pulmonary OMD for each of these variables. First, differences according to the type of primary tumor, for which many studies suggest that SBRT-mediated local control (LC) for patients with pulmonary OMD from colorectal cancer (CRC) is less successful than for those from non-CRC tumors. In addition, higher dose-fraction schedules seemed to correlate with higher LC; hence, different SBRT treatment strategies may be needed for patients with pulmonary OMD from CRC relative to other tumors. Second, differences according to location, where the safety of SBRT for peripheral pulmonary tumors has been relatively well established, but safety for central pulmonary tumors including pulmonary OMD is still considered controversial. To determine the optimal dose-fraction schedules, further data from prospective studies are still needed. Third, differences according to the patterns of OMD, the number of metastases and the timing of SBRT whereby 1–5 lesions in most patients and patients with synchronous or metachronous OMD are considered good candidates for SBRT. We conclude that there are still several problems in defining suitable indications for local therapy including SBRT, and that further prospective studies are required to resolve these issues.

Relationship between Dose Prescription Methods and Local Control Rate in Stereotactic Body Radiotherapy for Early Stage Non-Small-Cell Lung Cancer: Systematic Review and Meta-Analysis

Variations in dose prescription methods in stereotactic body radiotherapy (SBRT) for early stage non-small-cell lung cancer (ES-NSCLC) make it difficult to properly compare the outcomes of published studies. We conducted a comprehensive search of the published literature to summarize the outcomes by discerning the relationship between local control (LC) and dose prescription sites. We systematically searched PubMed to identify observational studies reporting LC after SBRT for peripheral ES-NSCLC. The correlations between LC and four types of biologically effective doses (BED) were evaluated, which were calculated from nominal, central, and peripheral prescription points and, from those, the average BED. To evaluate information on SBRT for peripheral ES-NSCLC, 188 studies were analyzed. The number of relevant articles increased over time. The use of an inhomogeneity correction was mentioned in less than half of the articles, even among the most recent. To evaluate the relationship between the four BEDs and LC, 33 studies were analyzed. Univariate meta-regression revealed that only the central BED significantly correlated with the 3-year LC of SBRT for ES-NSCLC (p = 0.03). As a limitation, tumor volume, which might affect the results of this study, could not be considered due to a lack of data. In conclusion, the central dose prescription is appropriate for evaluating the correlation between the dose and LC of SBRT for ES-NSCLC. The standardization of SBRT dose prescriptions is desirable.

Comparison of stereotactic body radiotherapy and radiofrequency ablation for early-stage non-small cell lung cancer: a systematic review and meta-analysis

Background

Stereotactic body radiation therapy (SBRT) and radiofrequency ablation (RFA) are recommended for patients with inoperable early-stage non-small cell lung cancer (NSCLC), with both offering promising results. However, it is largely unknown which of these two treatment modalities provides superior benefits for patients. Therefore, this systematic review and meta-analysis compared clinical outcomes and safety between SBRT and RFA in patients with inoperable early-stage NSCLC.

Methods

Eligible studies published between 2001 and 2020 were obtained through a comprehensive search of the PubMed, Medline, Embase, and Cochrane Library databases. Original English-language studies on the treatment of early-stage NSCLC with SBRT or RFA were included. Local control (LC) rates, overall survival (OS) rates, and adverse events were obtained by pooled analyses.

Results

Eighty-seven SBRT studies (12,811 patients) and 18 RFA studies (1,535 patients) met the eligibility criteria. For SBRT, the LC rates (with 95% confidence intervals) at 1, 2, 3, and 5 years were 98% (97-98%), 95% (95-96%), 92% (91-93%), and 92% (91-93%), respectively, which were significantly higher than those for RFA [75% (69-82%), 31% (22-39%), 67% (58-76%), and 41% (30-52%), respectively] (P<0.01). There were no significant differences in short-term OS between SBRT and RFA [1-year OS rate: 87% (86-88%) versus 89% (88-91%), P=0.07; 2-year OS rate: 71% (69-72%) versus 69% (64-74%), P=0.42]. Regarding long-term OS, the 3- and 5-year OS rates for SBRT were 58% (56-59%) and 39% (37-40%), respectively, which were significantly (P<0.01) superior to those for RFA [48% (45-51%) and 21% (19-23%), respectively]. The most common complication of SBRT was radiation pneumonitis (grade ≥2), making up 9.1% of patients treated with SBRT, while pneumothorax was the most common complication of RFA, making up 27.2% of patients treated with RFA.

Discussion

Compared with RFA, SBRT has superior LC and long-term OS rates but similar short-term OS rates. Prospective randomized trials with large sample sizes comparing the efficacy of SBRT and RFA are warranted.

Dosimetric Effects of Differences in Multi-Leaf Collimator Speed on SBRT-VMAT for Central Lung Cancer Patients

Purpose: We aimed to investigate the effects of different multi-leaf collimator (MLC) speed constraints in volumetric modulated radiotherapy (VMAT) on the robustness of treatment plans for central lung cancer patients. Method and Materials: Twenty patients with central lung tumor who underwent stereotactic body radiotherapy (SBRT) with the VMAT technique at our hospital were included in this retrospective study. The reference plans were created with 3 different MLC speed constraints (Plan A: 0.1 cm/deg., Plan B: 0.3 cm/deg., and Plan C: 0.5 cm/deg.) with a 50-Gy/8Fr, planning target volume (PTV) D_95% prescription. In each of these plans, setup errors from 1 to 5 mm were intentionally added in the direction of the central organ at 1-mm intervals (300 plans [20 cases × 3 MLC speeds × 5 error plans] were created in total). Each plan was then calculated by the same beam conditions as each reference plan. The actual average MLC speed and dose difference between the reference plan and the error-added plan were then calculated and compared among the 3 MLC speeds. Results: In the reference plans, the actual average MLC speeds were 0.25 ± 0.04, 0.34 ± 0.07, and 0.39 ± 0.12 cm/deg. for Plan A, Plan B, and Plan C, respectively (P < .05). For PTV and OARs, many dose indices tended to improve as the MLC speed increased, while no significant differences were observed among the 3 MLC speed constraints. However, in assessments of robustness, no significant differences in dose difference were observed among the 3 MLC speed constraints for most of the indices. Conclusions: When necessary, increasing the MLC speed constraint with a priority on improving the quality of the dose distribution is an acceptable approach for central lung cancer patients.

A meta-analysis comparing stereotactic body radiotherapy vs conventional radiotherapy in inoperable stage I non-small cell lung cancer

BACKGROUND

Stereotactic body radiotherapy (SBRT) superseded conventional radiotherapy (CRT) for the treatment of patients with inoperable early stage non-small cell lung cancer (NSCLC) over a decade ago. However, the direct comparisons of the outcomes of SBRT and CRT remain controversial. This meta-analysis was performed to compare the survival and safety of SBRT and CRT in patients with inoperable stage I NSCLC.

METHODS

We systematically searched the Cochrane Library, Embase, PubMed, Web of Science, Ovid MEDLINE, ScienceDirect, Scopus and Google Scholar for relevant articles. Overall survival (OS), progression-free survival (PFS), lung cancer-specific survival (LCSS), local control rate (LCR) and adverse effects (AEs) were the primary outcomes.

RESULTS

We identified 11,110 articles, 17 of which were eventually included in this study; these 17 articles had 17,973 patients (SBRT: 7395; CRT: 10,578). Compared to CRT for the treatment of inoperable stage I NSCLC, SBRT had superior survival in terms of OS (hazard ratio [HR]: 0.66, 95% confidence interval [CI]: 0.62-0.70, P < .00001), LCSS (HR: 0.42 [0.35-0.50], P < .00001), and PFS (HR: 0.34 [0.25-0.48], P < .00001). The 4-year OS rate (OSR); 4-year LCSS rate (LCSSR); 3-year local control rate (LCR); 5-year PFS rate (PFSR) with SBRT were all higher than those with CRT. With regard to all-grade AEs, the SBRT group had a significantly lower rate of dyspnea, esophagitis and radiation pneumonitis; no significant difference was found in grade 3-5 AEs (risk ratio [RR]: 0.68 [0.30-1.53], P = .35).

CONCLUSIONS

With better survival and a lower rate of dyspnea, esophagitis and radiation pneumonitis than CRT, SBRT appears to be more suitable for patients with inoperable stage I NSCLC.

Hypofractionated carbon-ion radiotherapy for stage I peripheral nonsmall cell lung cancer (GUNMA0701): Prospective phase II study

This phase II study's aim was to confirm the efficacy and safety of hypofractionated carbon-ion radiotherapy in patients with stage I peripheral nonsmall cell lung cancer (NSCLC). The study encompassed 37 patients with histologically proven peripheral stage I NSCLC in the period June 2010-March 2015. All underwent the planned full dose of carbon-ion radiotherapy, administered with relative biological effectiveness of 52.8 Gy and 60 Gy (divided into four fractions over 1 week) for T1 and T2a tumors, respectively. The 2-year local control rate was set as the primary endpoint, while overall survival, progression-free survival, and the incidence rates of acute and late adverse events were secondary endpoints. The patients were followed up for 56.3 months overall and 62.2 months in the surviving patients, respectively. The actuarial local control rates were 91.2% after 2 years, and 88.1% after 5 years. No differences were found between the T1 and T2a tumors in the 5-year local control rate (90.9% vs 86.7%, P = .75). The actuarial overall survival rates achieved 91.9% for 2-year and 74.9% for 5-year period. T1 tumors showed actuarial 5-year overall survival rates of 80%, compared to 66.7% in T2a tumors. Two patients with T2a tumors and either severe emphysema or bronchiectasis experienced lung toxicity ≥ grade 2, in contrast to T1 patients who only experienced mild toxicities (lower than grade 2). The findings suggest that carbon-ion radiotherapy is effective and safe for peripheral stage I NSCLC; however, further clinical evaluations are needed to confirm its therapeutic efficacy. Trial registration: UMIN000003797. Registered 21 June 2010, prospectively registered.