Small lung tumors: long-scan-time CT for planning of hypofractionated stereotactic radiation therapy--initial findings

Feasibility of marker-less stereotactic body radiotherapy for hepatocellular carcinoma

BACKGROUND

The feasibility of marker-less stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) has not yet been established, and, thus, was examined in the present study.

MATERIAL AND METHODS

We retrospectively investigated patients who received marker-less SBRT for locally untreated HCC tumors between July 2005 and December 2018. Radiotherapy planning CT was performed under fixation with vacuum cushions and abdominal compression. The clinical target volume (CTV) was equivalent to the gross tumor volume (GTV). The internal target volume (ITV) margin to CTV was determined from calculations based on the motion of the diaphragm. The planning target volume (PTV) margin to ITV was 5-6 mm. In the set-up, radiotherapy planning CT and linac-integrated cone-beam CT performed in the same imaging and fixation settings were merged by referring to the anatomical components surrounding target tumors. The primary endpoint was the 3-year cumulative local tumor progression rate. The upper limit of the 95% confidence interval for the 3-year cumulative local tumor progression rate was less than 7.0%, which was interpreted as favorable local control and feasible for marker-less SBRT. Local tumor progression was assessed by mRECIST.

RESULTS

We reviewed 180 patients treated with 35-40 Gy/5 fractions. The median follow-up time for the local tumor progression of censored tumors was 32.3 months (range, 0.3-104). The 3-year cumulative local tumor progression rate was 3.0% (95% CI, 1.1-6.5%). The 3-year overall survival rate was 71.6% (95% CI, 63.5-78.2%). Regarding acute hematologic toxicities, grade 3 hypoalbuminemia and thrombocytopenia were detected in 1 (0.6%) and 5 (2.9%) patients, respectively. Treatment-related death from SBRT was not observed. SBRT was initiated within 7 days after radiotherapy planning CT for 84% (152/180) of patients.

CONCLUSIONS

Marker-less SBRT for HCC achieved favorable local control that fulfilled the threshold. This result suggests that marker-less SBRT with appropriate settings is a feasible treatment strategy.

Hypofractionated radiotherapy for hepatocellular carcinomas adjacent to the gastrointestinal tract

AIM

Decisions regarding therapeutic plans for inoperable patients with hepatocellular carcinoma (HCC) adjacent to the gastrointestinal (GI) tract are challenging because radiofrequency ablation has the potential risk of thermal injury. Moreover, the response rate of transcatheter arterial chemoembolization is relatively low and stereotactic body radiotherapy (SBRT) is believed to be too toxic. We have applied hypofractionated radiotherapy (HFRT) for such lesions. This study investigated the outcomes and toxicities of this treatment.

METHODS

Among consecutive HCC patients treated with radiotherapy with curative intent at our institution between 2015 and 2019, we retrospectively extracted those outside of the indication for SBRT due to exceeding the constraint of the GI tract and who were treated using HFRT with a prescription dose of 42 Gy in 14 fractions and prophylactic proton pump inhibitor administration for 6 months. The oncological outcomes and toxicities were investigated.

RESULTS

A total of 66 patients with 73 lesions were eligible. The median follow-up period was 24.0 months. The local recurrence, intrahepatic recurrence, liver-related death, and overall survival rates at 2 years were 11.3%, 50.6%, 15.9%, and 60.4%, respectively. Six (9.1%) patients experienced Child-Pugh score deterioration ≥2 within 6 months following treatment. Two and one patient developed grades 2 and 3 gastroduodenal bleeding, respectively.

CONCLUSIONS

HFRT can achieve good local control in patients with HCC adjacent to the GI tract, with low GI toxicity incidence. Our study demonstrated that HFRT can be a potentially curative treatment option for lesions.

Local control by salvage stereotactic body radiotherapy for recurrent/residual hepatocellular carcinoma after other local therapies

Background: To clarify local control by salvage stereotactic body radiotherapy (SBRT) for recurrent/residual hepatocellular carcinoma (HCC) compared with initial definitive SBRT for local treatment-naïve HCC.Material and methods: We retrospectively investigated HCC patients that received SBRT between July 2005 and December 2017. We classified HCC tumors as the initial definitive SBRT group (Arm-1; initial definitive SBRT, Arm-2; initial definitive planned SBRT following transarterial chemoembolization (TACE)) and salvage SBRT group (Arm-3; salvage SBRT for recurrent/residual tumors after TACE, Arm-4; salvage SBRT for recurrent/residual tumors after radiofrequency ablation (RFA), Arm-5; salvage SBRT for recurrent/residual other than Arm-3 or Arm-4). Local control was evaluated by mRECIST.Results: We reviewed 389 HCC tumors of 323 patients treated by 35-40 Gy/5 fr. The median follow-up time for local recurrence of tumors was 34.8 months (range, 6.5-99.2). The cumulative local recurrence rates at 3 years of Arm-1-5 were 1.4% (95% CI, 0.3-4.4%), 5.0% (95% CI, 1.6-11.5%), 12.4% (95% CI, 5.7-21.9%), 14.8% (95% CI, 3.3-34.3%) and 7.3% (95% CI, 1.9-18.0%), respectively. The cumulative local recurrence rates at 3 years of initial definitive treatment and salvage treatment groups were 2.8% (95% CI, 1.1-5.6%) and 11.1% (95% CI, 6.3-17.3%), respectively (p=.004). On multivariate analysis, salvage treatment and the tumor diameter were significant risk factors of local recurrence (p = .02, p < .001 respectively). Estimated overall survival at 3 years for all patients in initial definitive treatment and salvage treatment groups were 71.5% (95% CI, 63.4-78.1%) and 66.1% (95% CI, 56.4-74.2%), respectively (p = .20). No treatment-related death caused by SBRT was observed.Conclusions: This analysis showed local control of salvage SBRT for recurrent/residual HCC was significantly worse than that of initial definitive SBRT for local treatment-naïve HCC. However, local control of salvage SBRT was relatively good, and salvage SBRT is one of the favorable treatment options for recurrent/residual HCC.

The impact of technology on the changing practice of lung SBRT

Stereotactic body radiotherapy (SBRT) for lung tumours has been gaining wide acceptance in lung cancer. Here, we review the technological evolution of SBRT delivery in lung cancer, from the first treatments using the stereotactic body frame in the 1990's to modern developments in image guidance and motion management. Finally, we discuss the impact of current technological approaches on the requirements for quality assurance as well as future technological developments.

Comparison of gross tumor volume of primary oesophageal cancer based on contrast-enhanced three-dimensional, four-dimensional, and cone beam computed tomography

Background

To explore motion information included in 3DCT, 4DCT and CBCT by comparing volumetric and positional differences of GTV.

Results

Independent of tumor location, significant differences were observed among volumes [IGTV₁₀ > (IGTV_CBCT or IGTV_MIP) > (GTV_3D or GTV_4D50)]. The underestimations or overestimations between IGTV₁₀ and IGTV_CBCT were larger than those between IGTV₁₀ and IGTV_MIP (p < 0.001–0.011; p < 0.001–0.023). For upper oesophageal tumors, GTV_4D50/IGTV_CBCT negatively correlated with motion vector (r = –0.756, p = 0.011). In AP direction, the centroid coordinates of IGTV_CBCT differed from GTV_3D, GTV_4D50, IGTV_MIP and IGTV₁₀ (p = 0.006, 0.013, 0.038, and 0.010). For middle oesophageal tumors, IGTV₁₀/IGTV_CBCT positively correlated with motion vector (r = 0.695, p = 0.006). The centroid coordinates of IGTV_CBCT differed from those of IGTV₁₀ (p = 0.046) in AP direction. For distal oesophageal tumors, the centroid coordinates of IGTV_CBCT showed significant differences to those of IGTV_MIP (p = 0.042) in LR direction. For both middle and distal tumors, the degrees of associations of IGTV₁₀ outside IGTV_CBCT significantly correlated with the motion vector (r = 0.540, p = 0.046; r = 0.678, p = 0.031).

Materials and Methods

Thirty-four oesophageal cancer patients underwent 3DCT, 4DCT and CBCT. GTV_3D, GTV_4D50, internal GTV_MIP (IGTV_MIP) and IGTV_CBCT were delineated on 3DCT, 4DCT₅₀, 4DCT_MIP and CBCT. GTVs from 10 respiratory phases were combined to produce GTV₁₀. Differences in volume, position for different targets, correlation between volume ratio and motion vector were evaluated. The motion vector was the spatial moving of the target centroid position.

Conclusions

IGTV_CBCT encompasses more motion information than GTV_3D and GTV_4D50 for upper oesophageal tumors, but slightly less than IGTV₁₀ for middle and distal oesophageal tumors. IGTV_CBCT incorporated similar motion information to IGTV_MIP. However, motion information encompassed in CBCT and MIP cannot replace each other.

Stereotactic body radiotherapy for chronic obstructive pulmonary disease patients undergoing or eligible for long-term domiciliary oxygen therapy

A major cause of death in patients undergoing long-term domiciliary oxygen therapy (LTOT) is lung cancer progression. In our institution, we actively perform stereotactic body radiotherapy (SBRT) on patients with early-stage non-small-cell lung cancer undergoing LTOT. In this study, we retrospectively analyzed the treatment efficacy and safety of SBRT for patients with T1-3N0M0 non-small-cell lung cancer who had been prescribed LTOT for treatment of chronic obstructive pulmonary disease (COPD). A total of 24 patients were studied. Their median age was 74 years (range, 63-87 years). The median duration from the start of LTOT to SBRT was 23 months (range, 0-85 months). Four of the 24 patients underwent lobectomy due to lung cancer. The median follow-up duration was 29 months (range, 5-79 months). One patient had a local recurrence. The median survival time was 30 months. The 3-year overall survival was 49%. In 6 of the 24 patients (25%), COPD presented with interstitial pneumonia. The 3-year overall survival for patients with COPD without interstitial pneumonia was significantly better than that for patients with both COPD and interstitial pneumonia (67% and 0%, respectively; P < 0.0001). Grade 5 radiation pneumonitis occurred in one patient (4%) with COPD with interstitial pneumonia. SBRT was tolerated by patients with early-stage non-small-cell lung cancer undergoing LTOT. SBRT should be considered for patients undergoing LTOT. However, clinicians should consider the risk of severe radiation pneumonitis in patients with interstitial pneumonia.

Stereotactic body radiotherapy for small lung tumors in the University of Tokyo Hospital

Our work on stereotactic body radiation therapy (SBRT) for primary and metastatic lung tumors will be described. The eligibility criteria for SBRT, our previous SBRT method, the definition of target volume, heterogeneity correction, the position adjustment using four-dimensional cone-beam computed tomography (4D CBCT) immediately before SBRT, volumetric modulated arc therapy (VMAT) method for SBRT, verifying of tumor position within internal target volume (ITV) using in-treatment 4D-CBCT during VMAT-SBRT, shortening of treatment time using flattening-filter-free (FFF) techniques, delivery of 4D dose calculation for lung-VMAT patients using in-treatment CBCT and LINAC log data with agility multileaf collimator, and SBRT method for centrally located lung tumors in our institution will be shown. In our institution, these efforts have been made with the goal of raising the local control rate and decreasing adverse effects after SBRT.

Stereotactic ablative body radiotherapy for previously untreated solitary hepatocellular carcinoma

BACKGROUND AND AIMS

Stereotactic ablative body radiotherapy (SABR) is a relatively new treatment for hepatocellular carcinoma (HCC). The outcomes of SABR for previously untreated solitary HCC unfit for ablation and surgical resection were evaluated.

METHODS

Untreated solitary HCC patients treated with SABR were retrospectively studied. Between 2005 and 2012, 221 HCC patients underwent SABR. Among them, patients with untreated solitary HCC, treated with only SABR or SABR preceded by transarterial chemoembolization, were eligible. Based on baseline liver function and liver volume receiving ≥ 20 Gy, 35-40 Gy in five fractions was prescribed to the planning target volume surface.

RESULTS

Sixty-three patients were eligible, with a median follow-up duration of 31.1 (range 12.0-88.1) months. No patients were lost to follow-up. Twenty patients were treated with only SABR. In 43 patients treated with SABR preceded by transarterial chemoembolization, accumulation of lipiodol in the tumor remained complete in five, a partial defect in 38 on pre-SABR computed tomography. The 1-, 2-, and 3-year local control rates were 100%, 95%, and 92%, respectively; the intrahepatic recurrence-free rates were 76%, 55%, and 36%, respectively; and the overall survival rates were 100%, 87%, and 73%, respectively. Grade 3 laboratory toxicities in the acute, subacute, and chronic phases were observed in 10, 9, and 13 patients, respectively, and ascites occurred in one patient.

CONCLUSIONS

Local control and overall survival after SABR for untreated solitary HCC were excellent despite the candidates being unfit for resection and ablation. SABR is safe and might be an alternative to resection and ablation.

High-dose stereotactic body radiotherapy correlates increased local control and overall survival in patients with inoperable hepatocellular carcinoma

BACKGROUND

Recent studies using stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) have reported high tumor response and local control. However, the optimal SBRT dose remains unknown, and it is still not clear whether a dose response relationship for local control (LC) and overall survival (OS) exist or not. We performed this study to determine whether a dose response relationship for LC and OS is observed in SBRT for inoperable HCC.

METHODS

Between 2003 and 2011, 108 patients with HCC were treated with SBRT. All patients were unsuitable for surgery or local ablation and had incomplete response to transarterial chemoembolization. Eighty-two patients with a longest tumor diameter (LD) less than or equal to 7.0 cm who were treated with 3-fraction SBRT and were analyzed. This cohort comprised 74 Child-Turcotte-Pugh (CTP) class A patients and 8 CTP class B7 patients. The median LD was 3.0 cm (range, 1.0-7.0 cm), and the median dose was 51 Gy (range, 33-60 Gy).

RESULTS

LC and OS rates at 2 years after SBRT were 87% and 63%, respectively, with a median follow-up duration of 30 months for all patients. The 2-year LC/OS rates for patients treated with doses of > 54, 45-54, and < 45 Gy were 100/71, 78/64, and 64%/30%, respectively (p = .009/p < .001). Multivariate analysis revealed that the SBRT dose (p = .005) and Barcelona Clinic Liver Cancer stage (p = .015) were significant prognostic factors for OS. Correlation analysis revealed a positive linear relationship between the SBRT dose and LC (p = .006, R = .899)/OS (p = .002, R = .940) at 2 years. Based on the tumor-control probability model, a dose of 54.8 Gy provides 2-year LC with a 90% probability. Five patients experienced grade 3 or higher gastrointestinal toxicity, and 6 had deteriorating of CTP score by greater than or equal to 2 within 3 months of SBRT.

CONCLUSIONS

This study demonstrated a dose response relationship for LC and OS with SBRT for HCC. Higher LC rates resulting from an increased dose may translate into survival benefits for patients with HCC.

Evaluation for local failure by 18F-FDG PET/CT in comparison with CT findings after stereotactic body radiotherapy (SBRT) for localized non-small-cell lung cancer

PURPOSE

Stereotactic body radiotherapy (SBRT) is the standard care for medically inoperable early non-small-cell lung cancer (NSCLC). However, it can be difficult to differentiate local recurrence from non-recurrence radiation-induced lung opacity. We retrospectively assessed (18)F-FDG PET/CT to detect local recurrence after SBRT for NSCLC.

METHODS

Between 2005 and 2011, 273 NSCLCs in 257 patients were treated with SBRT. Prescribed doses were 50Gy and 40Gy per 5 fractions for peripheral and central lesions, respectively. Tri-monthly follow-up CT scans were acquired. (18)F-FDG PET/CT scans were scheduled for screening at one year after SBRT or when recurrence was highly suspected. The dual-time-point maximum standardized uptake values (SUVmaxs) and their retention indexes (RIs) were obtained.

RESULTS

A total of 214 (18)F-FDG PET/CT scans were obtained for 164 localized NSCLC tumors in 154 patients. The median follow-up period was 24.9 months (range: 6.3-72.1). Among these, 21 scans of 17 tumors were diagnosed as local recurrence. The median SUVmaxs on early and late images of recurrence and their RI were 5.0 (range: 3.2-10.7), 6.3 (range: 4.2-13.4), and 0.20 (range; 0-0.41), respectively. These were significantly higher than the respective values of non-recurrence images of 1.8 (range: 0.5-4.6), 1.7 (range: 0.5-6.1), and 0.00 (range: -0.37-0.41) (all p<0.05). For SUVmaxs on early and late images, optimal thresholds were identified as 3.2 and 4.2. Using each threshold, the sensitivity and specificity were 100% and 96-98%, respectively. CT findings were classified into ground-glass opacity (N=9), scar or fibrotic change (N=96), consolidation with air-bronchogram (N=34), consolidation only (N=22), and nodule (N=17); the respective numbers of recurrence were 0, 0, 1, 3, and 17.

CONCLUSION

SUVmaxs of (18)F-FDG PET/CT could detect local recurrence after SBRT for localized NSCLC. In contrast, CT scan results had a limited ability to diagnose local recurrence.

Prognostic factors for local control of stage I non-small cell lung cancer in stereotactic radiotherapy: a retrospective analysis

Background

The purpose of this study is to investigate the prognostic factors of stereotactic radiotherapy for stage I NSCLC to improve outcomes.

Methods

Stage I non-small cell lung cancer patients who were treated with stereotactic radiotherapy between 2005 and 2009 at our hospital were enrolled in this study. The primary endpoint was local control rate. Survival estimates were calculated from the completion date of radiotherapy using the Kaplan-Meier method. The prognostic factors including patients’ characteristics and dose-volume histogram parameters were evaluated using Cox’s proportional hazard regression model.

Results

Eighty patients (81 lesions) treated with 3 dose levels, 48 Gy/4 fractions, 60 Gy/8 fractions and 60 Gy/15 fractions, were enrolled in this study. Median follow-up was 30.4 months (range, 0.3 – 78.5 months). A Cox regression model showed T factor (p = 0.013), biological effective dose calculated from prescribed dose (BED₁₀) (p = 0.048), and minimum dose for PTV (p = 0.013) to be prognostic factors for local control. Three-year overall survival rate and local control rate were 89.9% (T1: 86.8%, T2: 100%) and 89.0% (T1: 97.9%; T2: 64.8%), respectively. When the 3-year local control rates were examined by prescribed doses, they were 100% for the dose per fraction of 48 Gy /4 fractions (105.6 Gy BED₁₀), 82.1% for 60 Gy/8 fractions (105 Gy BED₁₀), and 57.1% for 60 Gy/15 fractions (84 Gy BED₁₀). The median value of the minimum dose for PTV (%) was 89.88 (%), and the 3-year local control rates were 100% in those with the minimum dose for PTV (%) ≥ 89.88% and 79.2% in those with the minimum dose for PTV (%) < 89.88%.

Conclusions

Our results suggest that T factor, BED₁₀, and minimum dose for PTV influence the local control rate. Local control rate can be improved by securing the minimum dose for PTV.

Four dimensional CT imaging: a review of current technologies and modalities

Organ motion is a substantial concern in the treatment of thoracic tumours using radiotherapy. A number of technologies have evolved in order to address this both during computed tomography (CT) imaging and radiation delivery. This review paper investigates the various technologies which have been developed in the field of CT scanning as well as their accuracy, cost and the implications of their clinical implementation. The scanning modalities covered include: slow CT, breath hold CT, gated CT and retrospectively correlated CT (4DCT). It was found that there are advantages and drawbacks to each of the mentioned techniques relating to patient dose, scan time, extra equipment and workload. Also some scanning techniques are only compatible with certain treatment modalities which would further influence the decision as to which technologies to implement.

Stereotactic body radiotherapy (SBRT) for oligometastatic lung tumors from colorectal cancer and other primary cancers in comparison with primary lung cancer

PURPOSE

To analyze local control of oligometastatic lung tumors (OLTs) compared with that of primary lung cancer after stereotactic body radiotherapy (SBRT).

MATERIALS AND METHODS

Retrospective record review of patients with OLTs who received SBRT with 50Gy in 5 fractions. Local control rates (LCRs), toxicities, and factors of prognostic significance were assessed.

RESULTS

Twenty-one colorectal OLTs, 23 OLTs from other origins, and 188 primary lung cancers were included. Multivariate analysis revealed only tumor origin was prognostically significant (p<0.05). The 1-year/2-year LCRs in colorectal OLTs and OLTs from other origins were 80%/72% and 94%/94%, respectively. The LCR in colorectal OLTs was significantly worse than that in OLTs from the other origins and primary lung cancers with pathological and clinical diagnosis (p<0.05, p<0.0001 and p<0.005). Among 44 OLT patients, Grades 2 and 3 radiation pneumonitis were identified in 2 and 1 patients, respectively. No other toxicities of more than Grade 3 occurred.

CONCLUSION

SBRT for OLTs is tolerable. The LCR for OLTs from origins other than colorectal cancer is excellent. However, LCR for colorectal OLTs is worse than that from other origins. Therefore dose escalation should be considered to achieve good local control for colorectal OLTs.

Evaluation of heterogeneity dose distributions for Stereotactic Radiotherapy (SRT): comparison of commercially available Monte Carlo dose calculation with other algorithms

Background

The purpose of this study was to compare dose distributions from three different algorithms with the x-ray Voxel Monte Carlo (XVMC) calculations, in actual computed tomography (CT) scans for use in stereotactic radiotherapy (SRT) of small lung cancers.

Methods

Slow CT scan of 20 patients was performed and the internal target volume (ITV) was delineated on Pinnacle³. All plans were first calculated with a scatter homogeneous mode (SHM) which is compatible with Clarkson algorithm using Pinnacle³ treatment planning system (TPS). The planned dose was 48 Gy in 4 fractions. In a second step, the CT images, structures and beam data were exported to other treatment planning systems (TPSs). Collapsed cone convolution (CCC) from Pinnacle³, superposition (SP) from XiO, and XVMC from Monaco were used for recalculating. The dose distributions and the Dose Volume Histograms (DVHs) were compared with each other.

Results

The phantom test revealed that all algorithms could reproduce the measured data within 1% except for the SHM with inhomogeneous phantom. For the patient study, the SHM greatly overestimated the isocenter (IC) doses and the minimal dose received by 95% of the PTV (PTV95) compared to XVMC. The differences in mean doses were 2.96 Gy (6.17%) for IC and 5.02 Gy (11.18%) for PTV95. The DVH's and dose distributions with CCC and SP were in agreement with those obtained by XVMC. The average differences in IC doses between CCC and XVMC, and SP and XVMC were -1.14% (p = 0.17), and -2.67% (p = 0.0036), respectively.

Conclusions

Our work clearly confirms that the actual practice of relying solely on a Clarkson algorithm may be inappropriate for SRT planning. Meanwhile, CCC and SP were close to XVMC simulations and actual dose distributions obtained in lung SRT.

Stereotactic body radiotherapy (SBRT) for solitary pulmonary nodules clinically diagnosed as lung cancer with no pathological confirmation: comparison with non-small-cell lung cancer

INTRODUCTION

In non-surgical candidates with solitary pulmonary nodules (SPNs) and no histological confirmation, optimal management remains uncertain.

METHODS

Between February 2005 and February 2011 we treated 298 lung cancers with stereotactic body radiotherapy (SBRT), including SPNs clinically diagnosed as lung cancer (CDLC). Among them, we extracted patients treated with a total dose of 40-50 Gy per 5 fractions and followed up more than 6 months. Patients who had a history of previously treated lung cancer, or were diagnosed pathologically, or suspected as having small-cell lung cancer or large cell neuroendcrine cancer were excluded from this study. The remaining patients were divided into two groups; CDLC and non-small-cell lung cancer (NSCLC) patients and their outcomes were assessed and compared.

RESULTS

Fifty-eight CDLC and 115 NSCLC patients were included in this study. The proportions of female and inoperable cases were significantly higher in the CDLC group. Other characteristics, including T stage and standard uptake value, were well balanced. Median follow-up durations were 20.2 (range, 6.0-58.8) and 21.2 (range, 6-63.7) months, respectively. The 3-year local control, regional-free, metastasis-free, progression-free, cause-specific survival, and overall survival rates were 80% and 87% (p = 0.73), 88% and 91% (p = 0.72), 70% and 74% (p = 0.57), 64% and 67% (p = 0.45), 74% and 71% (p = 0.17), 54% and 57% (p = 0.48), respectively.

CONCLUSION

These results indicate that the treatment outcome of CDLC group was almost identical to that of NSCLC and that few benign lesions seemed to be included. We advocate that SBRT can be legitimately applied to CDLC, provided that they are carefully diagnosed by integrating various clinical findings.

Comparison of clinical, tumour-related and dosimetric factors in grade 0-1, grade 2 and grade 3 radiation pneumonitis after stereotactic body radiotherapy for lung tumours

OBJECTIVE

The aim of this study was to investigate significant clinical, tumour-related and dosimetric factors among patients with grade 0-1, grade 2 and grade 3 radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT) for lung tumours.

METHODS

Patients (n=128) with a total of 133 lung tumours treated with SBRT of 50 Gy in 5 fractions were analysed. RP was graded according to the Common Terminology Criteria for Adverse Events v.3.0. Significant factors were identified by univariate and multivariate analyses. Threshold dose-volume histograms (DVHs) were constructed to identify the incidence of RP.

RESULTS

The median follow-up period was 12 months (range, 6-45 months). In univariate analyses, gender, operability, forced expiratory volume in 1 s (FEV1), internal target volume, lung volumes treated with doses >5-30 Gy (V5-30) and mean lung dose were significant factors differentiating between grade 0-1 and grade 2 RP, and V15-30 were significant factors differentiating between grade 2 and grade 3. However, no factors were significant between grade 0-1 and grade 3 RP. Multivariate analysis showed that female gender, high FEV1 and high V15 were significant factors differentiating between grade 0-1 and grade 2 RP. Threshold DVH curves were created based on ≤5% and ≤15% risk of grade 2 RP among patients with grade 0-2 RP.

CONCLUSIONS

Grade 0-2 RP was dose-volume dependent, and female gender and high FEV1 were significant predictive clinical factors for grade 2 RP among patients with grade 0-2 RP. However, incidences of V15-30 in grade 3 RP were significantly lower than those in grade 2 RP, and no significant clinical or tumour-related factors were found. Further studies are needed to identify the mechanism underlying the development of grade 3 RP after SBRT for lung tumours.

Dose volume histogram analysis of focal liver reaction in follow-up multiphasic CT following stereotactic body radiotherapy for small hepatocellular carcinoma

PURPOSE

To investigate threshold dose (TD) of focal liver reaction (FLR) following stereotactic body radiotherapy (SBRT) for patients with hepatocellular carcinoma (HCC) and liver cirrhosis.

MATERIALS AND METHODS

In consecutive 50 patients receiving SBRT for small HCC, 38 patients receiving SBRT and follow up >6 months, FLR on follow-up CT had been previously studied. Patients with good concordance between FLR and highly irradiated area were eligible. Dose volume histogram (DVH) was used to identify TDs for FLR. Clinical factors were analyzed for correlation with TDs.

RESULTS

Of 24 eligible patients, 23 had Child-Pugh score A and 1 scored B. Presence of FLR peaked at a median of 6 (range; 3-12) months. The median and 95% confidential intervals of TDs of pre-contrast and portal-venous phase CT were 32.4 Gy (30.3-35.4) and 34.4 Gy (31.9-36.0), respectively. Each median coefficient representing the concordance was 74.9% (range; 55.8-98.0%) and 80.5% (range; 70.8-92.4%), respectively. No clinical factors significantly correlated with the TDs.

CONCLUSION

We proposed 30 Gy/5 fractions as TD of FLRs following SBRT for patients with HCC and liver cirrhosis. This TD will enable us to predict injured liver volume and to avoid complication beforehand from toxicity. Further pathological and clinical studies, in addition to more practical and precise data of DVH, are needed to clarify the significance of FLRs.

The maximum standardized uptake value (SUVmax) on FDG-PET is a strong predictor of local recurrence for localized non-small-cell lung cancer after stereotactic body radiotherapy (SBRT)

BACKGROUND

The maximum standardized uptake value (SUVmax) of FDG-PET may predict local recurrence for localized non-small-cell lung cancer (NSCLC) after stereotactic body radiotherapy (SBRT).

METHODS

Among 195 localized NSCLCs that were treated with total doses of either 40Gy or 50Gy in 5 SBRT fractions, we reviewed those patients who underwent pre-treatment FDG-PET using a single scanner for staging. Local control rates (LCRs) were obtained by the Kaplan-Meier method and a log-rank test. Prognostic significance was assessed by univariate and multivariate analyses.

RESULTS

A total of 95 patients with 97 lesions were eligible. Median follow-up was 16.0months (range: 6.0-46.3months). Local recurrences occurred in 9 lesions. By multivariate analysis, only the SUVmax of a primary tumor was a significant predictor (p=0.002). Two years LCRs for lower SUVmax (<6.0; n=78) and higher SUVmax (⩾6; n=19) were 93% and 42%, respectively. In subgroups with T1b and T2, LCRs were significantly better for lower SUVmax than for higher SUVmax (p<0.0005 and p<0.01). In both subgroups that received 40Gy and 50Gy, LCRs were also significantly better for lower SUVmax than for higher SUVmax (p<0.001 and p<0.01).

CONCLUSIONS

SUVmax was the strongest predictor for local recurrence. A high SUVmax may be considered for dose escalation to improve local control. Additional follow-up is needed to determine if SUVmax is correlated with regional recurrence, distant metastasis, and survival.

Analysis of suitable prescribed isodose line fitting to planning target volume in stereotactic body radiotherapy using dynamic conformal multiple arc therapy

PURPOSE

To assess the most suitable value of a relative prescribed dose in clinical treatment plans of stereotactic body radiotherapy (SBRT) using dynamic conformal multiple arc therapy to treat lung tumors.

METHODS AND MATERIALS

We retrospectively generated alternative SBRT plans for typical examples of 8 patients who had been treated with SBRT for a lung tumor with a prescribed dose of 50 Gy in 5 fractions. The prescribed dose had been defined as 80% of the maximal dose in the planning target volume (PTV) ("the 80% isodose plan"). Alternative 20%-90% isodose plans at 10% intervals were generated (64 plans; 8 plans for each of the 8 patients), and factors related to leaf margins, target volume, normal lung volume, and monitor units were compared using dose-volume histogram analysis.

RESULTS

We could generate all the 64 plans. Compared with the 80% isodose plan, the V20 and mean lung dose (MLD) were both lower in the 60% plan; the V20 was approximately 19% lower (4.72% vs 3.84%) and the MLD was 13% lower (4.0 Gy vs 3.5 Gy). Mean PTV and ITV doses were higher in the lower percentage isodose plans. Compared with the 80% isodose plan, in the 60% isodose plan the mean PTV was 19% higher (56.1 Gy vs 66.8 Gy) and the mean ITV was 30% higher (59.6 Gy vs 77.4 Gy). The mean total monitor units increased more steeply than did the mean homogeneity index. The mean conformity index values in the 60% and 70% isodose plans were less than 1.15.

CONCLUSIONS

The 60% isodose plan was considered the best plan in this analysis because of the lower comparative dosimetric factors in normal lung tissue (including V20 and MLD) and the higher comparative mean PTV and internal target volume doses achieved, along with good conformity index values. In clinical use, accurate estimation and commissioning should be performed for the dose distribution prior to selecting a plan. Further investigation is warranted to determine whether the calculated dosimetric advantages result in improved outcomes.

CT evaluations of focal liver reactions following stereotactic body radiotherapy for small hepatocellular carcinoma with cirrhosis: relationship between imaging appearance and baseline liver function

This study aimed to assess the imaging appearances of focal liver reactions following stereotactic body radiotherapy (SBRT) for small hepatocellular carcinoma (HCC) and to examine relationships between imaging appearance and baseline liver function. We retrospectively studied 50 lesions in 47 patients treated with SBRT (30-40 Gy in 5 fractions) for HCC, who were followed up for more than 6 months. After SBRT, all patients underwent regular follow-ups with blood tests and dynamic CT scans. At a median follow-up of 18.1 months (range 6.2-43.7 months), all lesions but one were controlled. 3 density patterns describing focal normal liver reactions around HCC tumours were identified in pre-contrast, arterial and portal-venous phase scans: iso/iso/iso in 4 patients (Type A), low/iso/iso in 8 patients (Type B) and low/iso (or high)/high in 38 patients (Type C). Imaging changes in the normal liver surrounding the treated HCC began at a median of 3 months after SBRT, peaked at a median of 6 months and disappeared 9 months later. Liver function, as assessed by the Child-Pugh classification, was the only factor that differed significantly between reactions to treatment showing "non-enhanced" (Type A and B) and "enhanced" (Type C) appearances in CT. Hence, liver tissue with preserved function is more likely to be well enhanced in the delayed phase of a dynamic contrast-enhanced CT scan. The CT appearances of normal liver seen in reaction to the treatment of an HCC by SBRT were therefore related to background liver function and should not be misread as recurrence of HCC.

Dose distribution analysis in stereotactic body radiotherapy using dynamic conformal multiple arc therapy

PURPOSE

We have used dynamic conformal multiple arc therapy (DCMAT) for stereotactic body radiotherapy (SBRT) since 2001. We investigated the consistency of DCMAT for SBRT using dose-volume histogram analysis.

METHODS AND MATERIALS

A total of 50 patients with peripheral lung tumors underwent SBRT. The median tumor diameter was 2.4 cm (range, 0.9-5.9). Treatment planning was performed using a superposition algorithm. The prescribed 50 Gy dose was divided into five fractions. The prescribed dose was defined as 80% of the maximal dose in the planning target volume (PTV), and the leaf margins were modified to ensure the PTV was included in the 80% isodose surface. The dose-volume histogram analysis was used to assess the PTV and normal lung volume.

RESULTS

The median dose covering 95% of the PTV was 50.27 Gy (range, 46.14-52.67), essentially consistent with the prescribed dose. The median homogeneity and conformity index was 1.41 (range, 1.31-1.53) and 1.73 (range, 1.41-2.21), respectively. The median volume of lung receiving > or =20 Gy (V(20)) was 4.2% (range, 1.4-10.2%). A linear correlation was found between the tumor diameter and V(20), and an even stronger correlation was found between the PTV/(normal lung volume) and V(20). The estimated V(20) was 7.1% (range, 3.9-10.4%) for a 5-cm-diameter tumor, assumed to be the maximal size limitation for SBRT.

CONCLUSION

SBRT with DCMAT achieved high conformity and delivered adequate doses within the PTV. The median dose covering 95% of the PTV was consistent with the prescribed dose. V(20) can be estimated using the tumor diameter and normal lung volume. DCMAT was thus both a feasible and a reproducible method of SBRT delivery.

[Discrepancy between the intended isocenter and that from orthogonal linacgrams in the treatment of CT-guided stereotactic body radiotherapy(SBRT)]

PURPOSE

In our institution a CT scanner was installed in the same room as the linear accelerator. In stereotactic body radiotherapy (SBRT) we confirmed the isocenter position by serial thin-slice and long-scan-time CT images before every treatment as well as in planning. In planning we constructed digitally reconstructed radiography (DRR) of both the anterior and lateral views. At the first treatment we also checked the isocenter with linacgraphy. Then we compared the isocenter positions obtained from the DRR and linacgraphy.

MATERIALS AND METHODS

Between Feb. 2005 and Oct. 2006, we treated 75 lung and liver tumors with SBRT in this way. Based on bony structures, we measured the differences between in-isocenter positions for SI, LR, and AP directions between DRR and linacgraphy.

RESULTS

The median (min-max) of the differences in-isocenter positions for SI, LR, and AP directions between DRR and linacgraphy were 0.0 mm (0-6.0), 0.0 mm (0-10.0), and 0.0 mm (0-10.0), respectively, as well as 3.2 mm (0-12.3) for 3-dimensional distance. In 28 tumors (37%) the differences exceeded 5 mm in three-dimensional distance. The frequency of differences exceeding 5 mm in upper lung lesions tended to be more than that in liver lesions, and that in left pulmonary lesions was significantly more than that in right ones.

CONCLUSION

This result suggests that the relative position of the target volume to the bony structure differ in planning and in every treatment. It was recommended to verify isocenter accuracy in institutions where isocenter position is checked only by orthogonal linacgraphy in SBRT.

Possible Misinterpretation of Demarcated Solid Patterns of Radiation Fibrosis on CT Scans as Tumor Recurrence in Patients Receiving Hypofractionated Stereotactic Radiotherapy for Lung Cancer

PURPOSE

To retrospectively analyze opacity changes near primary lung cancer tumors irradiated by using hypofractionated stereotactic radiotherapy (HSRT) to determine the presence or absence of tumor recurrence.

METHODS AND MATERIALS

After review-board approval for a retrospective study, we examined data from 50 patients treated with curative intent for proven or highly suspected localized peripheral-lung cancer and followed up for at least 12 months. All patients had received 50 Gy in five fractions (80% isodose) and were followed up monthly with chest X-ray until clinical and X-ray findings stabilized. Follow-up computed tomography scans were performed 1 and 3 months after HSRT and thereafter at 3-month intervals during the first 2 years.

RESULTS

Median follow-up was 30.4 months (range, 12.0-73.8 months). Abnormal opacities that were suspicious for recurrent tumor appeared in 20 patients at a median of 20.7 months (range, 5.9-61.4 months). Only 3 patients were finally found to have recurrence; 14 were recurrence free but were suspected to have fibrosis, and findings for the other 3 patients were considered equivocal because of a short follow-up period (<or=6 months).

CONCLUSION

Radiation fibrosis, which may occur 1 year or longer after completion of HSRT, is difficult to distinguish from tumor recurrence. Even when opacities increase on follow-up radiologic scans, recurrence cannot be diagnosed conclusively based on image findings; biopsy occasionally is warranted.

Hypofractionated stereotactic radiotherapy with and without transarterial chemoembolization for small hepatocellular carcinoma not eligible for other ablation therapies: Preliminary results for efficacy and toxicity

AIM

To investigate the efficacy and toxicity of hypofractionated stereotactic radiotherapy for the treatment of patients presenting with hepatocellular carcinoma (HCC) in a single institutional setting.

METHODS

Sixteen patients who presented with solitary HCC, including two patients with a tumor thrombus of the portal veins, were treated with stereotactic radiotherapy with or without transarterial chemoembolization. The criteria for stereotactic radiotherapy were existence of technical difficulties for other ablation therapies, inoperable disease or refusal to undergo surgery, tumor staged as Grade A or B according to the Child-Pugh classification, and solitary tumor distant from the gastrointestinal tract and kidney with a tumor volume <100 cm(3). In 14 of 16 patients, a total dose of 35- 50 Gy was delivered in 5-7 fractions over 5-9 days.

RESULTS

At the end of a mean follow-up of 612 days (median 611 days; range 244-994 days), all patients were alive. Eight of 16 patients had complete responses and seven others were judged as stable with lipiodol accumulation. In one patient, local recurrence developed after 489 days. Intrahepatic recurrences developed outside the treated volume in six patients and no extrahepatic metastases developed during follow-up. No serious treatment-related toxic manifestations developed.

CONCLUSIONS

Stereotactic radiotherapy for HCC with or without transarterial chemoembolization is feasible therapy and provides good local control with a short treatment period. Stereotactic radiotherapy may be of clinical benefit in patients who are inoperable or for whom there are difficulties in other ablation therapies.

Respiratory biofeedback during CT-guided procedures

PURPOSE

Respiratory motion can be a complicating factor during image-guided interventions. The ability to reproduce breath-holds may facilitate safer needle-based procedures. The purpose of this study was to evaluate if respiratory biofeedback decreased variability among breath-holds and if the signals from the respiratory bellows belt can be used to measure target motion.

MATERIALS AND METHODS

In phase 1 of the study, a respiratory bellows belt was applied to patients before image-guided interventional procedures. Belt stretch from respiratory motion was converted into voltage readings and displayed on a monitor as biofeedback. Patients were asked to perform inspiratory, expiratory, and midcycle breath-holds with and without the biofeedback. The variability in voltage readings between breath-holds with and without biofeedback was compared. In phase 2, the respiratory bellows belt was used during computed tomography (CT)-guided procedures with the patients blinded to the biofeedback. Voltage readings and CT series numbers were recorded as patients were asked to hold their breath during scans. The variability of CT z-axis targets was compared with the variability of voltage readings.

RESULTS

A significant decrease in variability was found during expiratory breath-holds (P = .0083) with trends toward significance with midcycle and inspiratory breath-holds. A positive correlation (Kendall tau = 0.5; P = .024) was shown between CT z-axis and belt stretch variability in subjects who received smaller doses of moderate sedation compared with those who received larger doses or general anesthesia.

CONCLUSIONS

Biofeedback may help the patient to have a more consistent breath-hold. The belt could decrease the error and unpredictability from craniocaudal motion of targets during image-guided interventions.

Interinstitutional variations in planning for stereotactic body radiation therapy for lung cancer

PURPOSE

The aim of this study was to assess interinstitutional variations in planning for stereotactic body radiation therapy (SBRT) for lung cancer before the start of the Japan Clinical Oncology Group (JCOG) 0403 trial.

METHODS AND MATERIALS

Eleven institutions created virtual plans for four cases of solitary lung cancer. The created plans should satisfy the target definitions and the dose constraints for the JCOG 0403 protocol.

RESULTS

FOCUS/XiO (CMS) was used in six institutions, Eclipse (Varian) in 3, Cadplan (Varian) in one, and Pinnacle3 (Philips/ADAC) in one. Dose calculation algorithms of Clarkson with effective path length correction and superposition were used in FOCUS/XiO; pencil beam convolution with Batho power law correction was used in Eclipse and Cadplan; and collapsed cone convolution superposition was used in Pinnacle3. For the target volumes, the overall coefficient of variation was 16.6%, and the interinstitutional variations were not significant. For maximal dose, minimal dose, D95, and the homogeneity index of the planning target volume, the interinstitutional variations were significant. The dose calculation algorithm was a significant factor in these variations. No violation of the dose constraints for the protocol was observed.

CONCLUSION

There can be notable interinstitutional variations in planning for SBRT, including both interobserver variations in the estimate of target volumes as well as dose calculation effects related to the use of different dose calculation algorithms.