Re-irradiation for isolated neck recurrence in head and neck tumor: impact of rN category

Unresectable, isolated lymph node recurrence after radiotherapy is rare but a candidate for re-irradiation. However, severe toxicity is anticipated. Therefore, this study aimed to explore the efficacy and toxicity of re-irradiation in isolated lymph node recurrence of head and neck lesions. We analyzed 46 patients who received re-irradiation for lymph node recurrence without local progression. The primary tumor sites included the oral cavity in 17 patients, the hypopharynx in 12, the oropharynx in seven, the larynx in three, the nasopharynx in two, and other sites. During a median follow-up time of 10 months, the median survival time was 10.6 months, and the 1-year overall survival rate was 45.5%. The 1-year local control and progression-free survival rates were 49.8% and 39.3%, respectively. According to univariate analysis, age (≥ 65 years), the interval between treatment (≥ 12 months), rN category (rN1), and gross tumor volume (GTV < 25 cm3) were predisposing factors for better survival. In the multivariate analysis, the rN category and interval were identified as statistically significant predictors. Late toxicity grade ≥ 3 occurred in four patients (8.6%). These were all Grade 5 carotid blowout syndrome, which associated with tumor invasion of the carotid artery and/ or high doses administration for the carotid artery. Small-volume rN1 tumor that recur after a longer interval is a feasible candidate for re-irradiation. However, strict patient selection and meticulous care for the carotid are required.

The Dosimetric Analysis of Duodenal and Intestinal Toxicity After a Curative Dose Re-irradiation Using the Intensity-Modulated Radiotherapy for Abdominopelvic Lymph Node Lesions

INTRODUCTION

This study aimed to examine the influence of dosimetric factors on gastrointestinal toxicity after radical re-irradiation for lymph node recurrence in the abdominopelvic region using a composite plan.

METHODS

Between January 2008 and March 2017, 33 patients underwent radical re-irradiation for lymph node recurrence in the abdominopelvic region with a complete overlap with previous radiation therapy (RT) with the median prescription dose of the second RT of 71.7 Gy10. Re-irradiation planning protocol for target volume and organs at risk (OARs) (duodenum, small and large intestines) was decided as follows: more than equal to 97% of the prescription dose was administered to the D95 (percentage of the minimum dose that covered 95% of the target volume) of planning target volume (PTV); minimal dose to the maximally irradiated doses delivered to 1cc [D1 cc] and 5cc [D5 cc] of OARs was set below 70 Gy3 and 50 Gy3, respectively; and D1 cc and D5 cc in the cumulative plans to OARs were 120 Gy3 and 100 Gy3. Kaplan-Meier analyses were performed to evaluate overall survival (OS) and univariate log-rank and multivariate Cox proportional hazards model analyses were performed to explore predictive factors. Using dose summation of the first and re-irradiation plans, we conducted a dosimetric analysis for grade ≥ 3 toxicities of the duodenum and intestine.

RESULTS

With a median follow-up of 18 months, the two-year OS rate was 45.5%. The number of RT fields (localized or multiple) was a significant predisposing factor for OS rate with a hazard ratio of 0.23 (95% confidence interval 0.07-0.73). The two-year OS of the patients with a localized RT field was 63.6% and 9.1% for multiple RT fields (p= 0.00007). Four patients experienced grade ≥3 gastrointestinal toxicity related to re-irradiation (4/33=12.1%). We could not find any predisposing dosimetric value in the comparisons with and without toxicity.

CONCLUSIONS

The dose constraints presented in this study are relatively low rates of toxicity, which may be useful when planning re-irradiation. Especially, for the patients who could be treated with localized RT field, radical re-irradiation with a high curative dose is a good option. No dosimetric predisposing factor was found for radical re-irradiation of abdominopelvic lesions in the composite plan.

Intensity-Modulated Radiation Therapy for Bilateral Choroidal Metastases Involving Macula and Optic Disc

This case report discusses the case of a 76-year-old woman with choroidal metastasis from breast cancer who was treated with intensity-modulated radiation therapy (IMRT). Choroidal metastasis is a common ocular tumor, and the occurrence of this condition has increased due to improved diagnostic tools and longer survival of metastatic patients. IMRT is an innovative radiation therapy technique that reduces complications and improves the curative effect by concentrating radiation on the tumor while minimizing exposure to surrounding tissues. In this case, the patient had a history of breast cancer and was undergoing chemotherapy when she presented with vision loss and blurred vision. Imaging tests confirmed choroidal metastasis, and IMRT was performed under the guidance of a radiation oncologist. After treatment, the choroidal lesion dramatically reduced in size, and the patient's vision improved. The text concludes that radiation therapy, including IMRT, is becoming more common as a treatment for ocular metastasis to improve vision and preserve the eye. When choosing radiation therapy, it is essential to consider the size of the tumor and the impact on surrounding tissues. IMRT is an effective treatment that enables precise and concentrated irradiation of the tumor tissue while minimizing exposure to normal tissues.

Optimization of Fluence Map for CyberKnife Raster Scanning Intensity Modulated Radiotherapy

BACKGROUND/AIM

Stereotactic body radiotherapy for prostate cancer using CyberKnife with circular cone requires a long treatment time. Raster scanning intensity modulated radiotherapy (RS-IMRT) has a potential of improving treatment efficacy, introducing shorter treatment time, better target dose uniformity, and lower organ at risk (OAR) dose. The purpose of the study was to develop a fluence optimization system for RS-IMRT.

PATIENTS AND METHODS

RS-IMRT plans were created for five prostate cancer patients treated with the Novalis system and parameters were compared to the Novalis treatment plans. From 80 nodes available for the CyberKnife, twelve nodes were arbitrarily selected. On the beam's eye view of each beam, a 100×100 matrix of optimization points was created at the target center plane. The beam fluence map was optimized using the attraction-repulsion model (ARM). The beam fluence maps were converted to the scanning sequence using the ARM and a final dose calculation was performed.

RESULTS

For planning target volume (PTV), RS-IMRT plans showed higher dose covering 2% of the volume (D_2%) and lower D_98% compared to the Novalis plans. However, the homogeneity was within our Institutional clinical protocol. The RS-IMRT plans showed significantly lower OAR dose parameters including bladder volume receiving 100% of prescribed dose (V_100%) and dose delivered to 5 cm³ of rectum (D_{5 cc}).

CONCLUSION

We developed a fluence optimization system for RS-IMRT that performs the entire RS-IMRT treatment planning process, including scanning sequence optimization and final dose calculation. The RS-IMRT was capable of generating clinically acceptable plans.

Reirradiation for Rare Head and Neck Cancers: Orbit, Auditory Organ, and Salivary Glands

We analyzed the efficacy and toxicity following reirradiation for locoregional recurrence of rare head and neck tumors. We retrospectively analyzed 17 patients who had received reirradiation for rare head and neck tumors. Primary tumor sites included nine ears (auditory organ), four salivary glands, and four orbits. The median follow-up time was 13.2 months for surviving patients. The median survival time was 12.6 months with one- and two-year survival rates of 53.1% and 44.3%, respectively. Nine out of 17 patients experienced local failure. The one- and two-year local control rates were 42.4% and 31.8%, respectively. The median survival times were 12.6, 5.3, and 11.0 months for orbit, auditory organ, and salivary glands, respectively. Three patients experienced grade 3 toxicity, including meningitis, brain necrosis, and facial nerve disorders. No grade ≥4 toxicities were observed. Reirradiation of rare head and neck tumors is feasible, with acceptable toxicity.

Development of raster scanning IMRT using a robotic radiosurgery system

Treatment time with the CyberKnife frameless radiosurgery system is prolonged due to the motion of the robotic arm. We have developed a novel scanning irradiation method to reduce treatment time. We generated treatment plans mimicking eight-field intensity-modulated radiotherapy (IMRT) plans generated for the Novalis radiosurgery system. 2D dose planes were generated with multiple static beam spots collimated by a fixed circular cone. The weights of the uniformly distributed beam spots in each dose plane were optimized using the attraction-repulsion model. The beam spots were converted to the scanning speed to generate the raster scanning plan. To shorten treatment time, we also developed a hybrid scanning method which combines static beams with larger cone sizes and the raster scanning method. Differences between the Novalis and the scanning plan's dose planes were evaluated with the criterion of a 5% dose difference. The mean passing rates of three cases were > 85% for cone sizes ≤ 12.5 mm. Although the total monitor units (MU) increased for smaller cone sizes in an inverse-square manner, the hybrid scanning method greatly reduced the total MU, while maintaining dose distributions comparable to those with the Novalis plan. The estimated treatment time of the hybrid scanning with a 12.5 mm cone size was on average 22% shorter than that of the sequential plans. This technique will be useful in allowing the CyberKnife with conventional circular cones to achieve excellent dose distribution with a shortened treatment time.

Metastasis-Directed Radiotherapy for Oligoprogressive Castration-Resistant Prostate Cancer Recurrence Revealed by Choline PET/CT

We report a 49-year-old male with castration-resistant prostate cancer (CRPC) with oligometastasis diagnosed by ¹¹C-choline positron emission tomography-computed tomography (PET/CT) and treated with target radiotherapy. In the diagnosis of CRPC (serum prostate-specific antigen [PSA] level of 6.53 ng/mL after maximum androgen blockade (MAB) therapy, high-dose brachytherapy, and external beam radiotherapy), ¹¹C-choline PET/CT detected one tiny obturator lymph node metastasis which fluorodeoxyglucose PET/CT could not detect. He underwent intensity-modulated radiation therapy and MAB was restarted. The PSA value decreased and reached nadir (0.091 ng/mL) after 6 months. The time to PSA progression was 10 months. The choline PET/CT finding and the corresponding local treatment could play an important role in the management sequence of oligoprogressive CRPC.

Analyses of local control and survival after stereotactic body radiotherapy for pulmonary oligometastases from colorectal adenocarcinoma

This study is a subset analysis of a retrospective multicenter study performed in Japan and its purpose was to investigate the effectiveness of stereotactic body radiotherapy (SBRT) for pulmonary oligometastases from colorectal cancer. Local control (LC), freedom from further metastases, relapse-free survival and overall survival (OS) after SBRT were retrospectively analyzed. The Kaplan-Meier method was used to estimate lifetime data and the log-rank test was performed as univariate analyses. The Cox proportional hazards model was applied in multivariate analyses. Data for 330 patients with 371 tumors were used for analyses. The median follow-up period was 25.0 months. The 3-year LC, freedom from further metastases, relapse-free survival and OS rates were 64.9, 34.9, 24.9 and 63.4%, respectively. The results of multivariate analyses showed that a higher LC rate was associated with no history of local therapy for oligometastases (P = 0.01), SBRT without concurrent chemotherapy (P < 0.01), type B calculation algorithm (P < 0.01) and higher biological effective radiation doses (≥115 Gy, P = 0.04). A longer OS was associated with no history of local therapy for oligometastases (P = 0.04), a more recent period of SBRT (2010-15, P = 0.02), tumor located in the upper or middle lobe (P < 0.01) and higher biological effective radiation doses (≥115 Gy, P = 0.01). In conclusion, OS after SBRT was good, but LC rate was relatively low. The use of high biological effective radiation doses can improve both LC and OS outcomes.

Analyses of the local control of pulmonary Oligometastases after stereotactic body radiotherapy and the impact of local control on survival

Background

Successful local therapy for oligometastases may lead to longer survival. The purpose of this multicentre retrospective study was to investigate factors affecting the local control (LC) of pulmonary oligometastases treated by stereotactic body radiotherapy (SBRT) and to investigate the impact of LC on survival.

Methods

The inclusion criteria included 1 to 5 metastases, the primary lesion and other extrathoracic metastases were controlled before SBRT, and the biological effective dose (BED₁₀) of the SBRT was 75 Gy or more. The Cox proportional hazards model was used for analyses.

Results

Data of 1378 patients with 1547 tumours from 68 institutions were analysed. The median follow-up period was 24.2 months. The one-year, 3-year and 5-year LC rates were 92.1, 81.3 and 78.6%, respectively, and the 1-year, 3-year and 5-year overall survival rates were 90.1, 60.3 and 45.5%, respectively. Multivariate analysis for LC showed that increased maximum tumour diameter (p = 0.011), type A dose calculation algorithm (p = 0.005), shorter overall treatment time of SBRT (p = 0.035) and colorectal primary origin (p < 0.001 excluding oesophagus origin) were significantly associated with a lower LC rate. In the survival analysis, local failure (p < 0.001), worse performance status (1 vs. 0, p = 0.013; 2–3 vs. 0, p < 0.001), oesophageal primary origin (vs. colorectal origin, p = 0.038), squamous cell carcinoma (vs. adenocarcinoma, p = 0.006) and increased maximum tumour diameter (p < 0.001) showed significant relationships with shorter survival.

Conclusions

Several factors of oligometastases and SBRT affected LC. LC of pulmonary oligometastases by SBRT showed a significant survival benefit compared to patients with local failure.

Factors related to primary cancer death and non-primary cancer death in patients treated with stereotactic body radiotherapy for pulmonary oligometastases

Cancer‐specific death (CSD) and non‐cancer‐specific death (non‐CSD) after stereotactic body radiotherapy (SBRT) for pulmonary oligometastases have not been studied in detail. The aim of this study was to determine the cumulative incidences of CSD and non‐CSD and to reveal prognostic factors. Data from a large survey of SBRT for pulmonary oligometastases were used for analyses, and patients with unknown cause of death were excluded from current analyses. CSD was primary cancer death and non‐CSD was non‐primary cancer death including a series of cancer treatment‐related deaths. Cumulative incidences were calculated using the Kaplan‐Meier method and a stratified Cox regression model was used for multivariate analyses (MVA). Fifty‐two patients with an unknown death were excluded and a total of 1326 patients was selected. CSD and non‐CSD occurred in 375 and 109 patients, respectively. The median OS period was 53.2 months and the cumulative incidences of 1‐, 3‐, and 5‐year CSD vs. non‐CSD rates were 6.5% vs. 2.3%, 29.5% vs. 8.6%, and 41.2% vs. 11.0%, respectively. In MVA, the incidence of CSD was related to performance status (1 vs. 0; p < 0.001, 2–3 vs. 0; p = 0.011), oligometastatic state (sync‐oligometastases vs. oligo‐recurrence, p = 0.026) and maximum tumor diameter (p = 0.009), and the incidence of non‐CSD was related to age (p = 0.001), sex (p = 0.030), performance status (2–3 vs. 0; p = 0.002), and irradiated tumor‐located lung lobe (left lower lobe vs. other lobes, p = 0.036). CSD was main cause of death, but non‐CSD was not rare after SBRT. Prognostic factors for CSD and non‐CSD were different, and an understanding of the factors would help in treatment.

Stereotactic Body Radiotherapy for Pulmonary Oligometastases from Esophageal Cancer: Results and Prognostic Factors

BACKGROUND/AIM

The aim of this multi-center retrospective study was to investigate the results of stereotactic body radiotherapy (SBRT) for pulmonary oligometastases from esophageal cancer.

PATIENTS AND METHODS

Oligometastases from the esophagus were identified from a dataset of a Japanese survey. The Kaplan-Meier method and Cox regression were applied to perform analyses.

RESULTS

A total of 114 patients with 132 pulmonary oligometastases were collected. The 3-year local control rate, freedom from further metastasis (FFFM) rate and overall survival (OS) rate were 70.2%, 25.3% and 37.5%, respectively. Performance status (PS) (PS 1 vs. PS 0, p<0.01), disease-free interval (p=0.03) and history of local therapy for metastasis (p=0.01) had significant relationships with FFFM and only PS was an independent prognostic factor for OS (PS 1 vs. PS 0, p=0.02; PS 2-3 vs. PS 0, p=0.04).

CONCLUSION

SBRT for pulmonary oligometastases from esophageal cancer provided good local control and survival.

Pulmonary Oligometastases Treated by Stereotactic Body Radiation Therapy: A Nationwide Survey of 1,378 Patients

AIM

This study was performed to confirm the superior overall survival (OS) after pulmonary oligo-recurrence compared to pulmonary sync-oligometastases in a large nationwide study.

PATIENTS AND METHODS

Patients that met the following criteria were included: 1 to 5 lung-only metastases at the beginning of stereotactic body radiation therapy (SBRT) was performed between January 2004 and June 2015, and the biological effective dose (BED) of SBRT was 75 Gy or more. The parameters included in the analyses were age, gender, ECOG PS, primary lesion, pathology, oligoetastatic state, SBRT date, chemotherapy before SBRT, chemotherapy concurrent SBRT, chemotherapy after SBRT, maximum tumor diameter, number of metastases, field coplanarity, dose prescription, BED₁₀, OTT of SBRT.

RESULTS

In total, 1,378 patients with 1,547 tumors were enrolled. Oligo-recurrence occurred in 1,016 patients, sync-oligometastases in 118, and unclassified oligometastases in 121. The three-year OS was 64.0% for oligo-recurrence and 47.5% for sync-oligometastasis (p<0.001). In the multivariate analysis, the hazard ratio (HR) for sync-oligometastases versus oligo-recurrence was 1.601 (p=0.014). Adverse events of Grade 5 were occurred in 3 patients.

CONCLUSION

This is the first nationwide to indicate that the OS of patients with pulmonary oligo-recurrence is better than that of patients with sync-oligometastases.

An effective method to reduce the interplay effects between respiratory motion and a uniform scanning proton beam irradiation for liver tumors: A case study

Purpose

For scanning particle beam therapy, interference between scanning patterns and interfield organ motion may result in suboptimal dose within target volume. In this study, we developed a simple offline correction technique for uniform scanning proton beam (USPB) delivery to compensate for the interplay between scanning patterns and respiratory motion and demonstrate the effectiveness of our technique in treating liver cancer.

Methods

The computed tomography (CT) and respiration data of two patients who had received stereotactic body radiotherapy for hepatocellular carcinoma were used. In the simulation, the relative beam weight delivered to each respiratory phase is calculated for each beam layer after treatment of each fraction. Respiratory phases with beam weights higher than 50% of the largest weight are considered “skipped phases” for the next fraction. For the following fraction, the beam trigger is regulated to prevent beam layers from starting irradiation in skipped phases by extending the interval between each layer. To calculate dose‐volume histogram (DVH), the dose of the target volume at end‐exhale (50% phase) was calculated as the sum of each energy layer, with consideration of displacement due to respiratory motion and relative beam weight delivered per respiratory phase.

Results

For a single fraction, D_1%, D_99%, and V_100% were 114%, 88%, and 32%, respectively, when 8 Gy/min of dose rate was simulated. Although these parameters were improved with multiple fractions, dosimetric inhomogeneity without motion management remained even at 30 fractions, with V_100% 86.9% at 30 fractions. In contrast, the V_100% values with adaptation were 96% and 98% at 20 and 30 fractions, respectively. We developed an offline correction technique for USPB therapy to compensate for the interplay effects between respiratory organ motion and USPB beam delivery.

Conclusions

For liver tumor, this adaptive therapy technique showed significant improvement in dose uniformity even with fewer treatment fractions than normal USPB therapy.

Definitive re-irradiation using intensity-modulated radiation therapy in cancers of the head and neck, focusing on rare tumors

PURPOSE

To analyze the outcomes following re-irradiation for local recurrence of rare head and neck tumors.

MATERIAL AND METHODS

We retrospectively analyzed 11 patients who had received intensity-modulated radiation therapy (IMRT) for recurrent tumors in the head and neck except for laryngopharynx.

RESULTS

Primary tumor sites included the maxillary sinus, nasal cavity, and external ear canal in six, three, and two patients, respectively. The median follow-up times were 13 (range, 3-54) months. The median survival time was 17 months with 1- and 2-year survival rates of 63.64 and 39.77%, respectively. Among 11 patients, five experienced local failure in the follow-up period. The 1- and 2-year local control rates were 58 and 47%, respectively. Patients who had received a radiation dose of ≥3 Gy per fraction showed significantly better local control than those receiving less (p = .0419). One patient experienced Grade 3 facial pain as acute toxicity. Late toxicities included radiographic findings of partial central nervous system necrosis in three patients and Grade 3 osteonecrosis and Grade 3 facial nerve disorder in one patient.

CONCLUSIONS

Re-irradiation of rare head and neck tumors using IMRT for loco-regional recurrence may be an acceptable treatment option.

Long-term Outcomes of Radiotherapy Regimen of 72 Gy in 30 Fractions for Prostate Cancer

BACKGROUND/AIM

The long-term efficacy and safety of moderately hypofractionated intensity-modulated radiation therapy (MH-IMRT) in prostate cancer remains uncertain. This study aimed to evaluate MH-IMRT regimen of 72 Gy in 30 fractions in patients with prostate cancer.

PATIENTS AND METHODS

The outcomes of 412 consecutive prostate cancer patients, who received MH-IMRT between May 2007 and December 2012, were retrospectively reviewed. The median patient age was 70.9 (range=50-84) years. Late gastrointestinal (GI) and genitourinary (GU) toxicity rates were evaluated according to the CTCAE ver. 3.0. The overall survival, biochemical relapse-free survival rate (bRFS), late GI toxicity, and GU toxicity rates were analyzed with the Kaplan-Meier method.

RESULTS

The median follow-up was 71.5 (range, 1.4-124.8) months. The 5-year bRFS rate was 93.2%. The 5-year grade ≥2 late GI and GU toxicity rates were 3.3% and 4.5%, respectively.

CONCLUSION

MH-IMRT regimen of 72 Gy in 30 fractions was effective and safe for prostate cancer patients.

Lower urinary tract symptoms in patients with prostate cancer under and after intensity-modulated radiation therapy

OBJECTIVE

The aim of the present study was to collect data on the characteristics, degree, and natural course of urinary complications, as well as self-care for such complications, in patients during and after prostate intensity-modulated radiation therapy (IMRT).

METHODS

Quality of life data were collected retrospectively for all eligible patients who underwent IMRT. In all eligible patients, urinary symptoms were evaluated using questionnaires and face-to-face interview. Participants were asked to respond to a self-administered questionnaire concerning the core lower urinary tract symptom score during the course of IMRT and up to 12 months after the completion of IMRT.

RESULTS

In all, 29 eligible patients were included in the study. The frequency of urinary symptoms increased over of the course of IMRT, decreased at ≥3 months after completion of IMRT, and disappeared 6 months after IMRT. Responses to the questionnaire revealed a variety of approaches to self-care and adaptations by patients to manage urinary symptoms.

CONCLUSIONS

During and after IMRT for localized prostate cancer, patients often developed more frequent urination and urgency than at the start of IMRT, and recovered 3-6 months after the completion of IMRT. Based on the present study, clinicians and nurses could help convey this information to patients and thus offer better support.

[Radiofrequency Ablation under Computed Tomography during Arterial Portography for Hypovascular Liver Metastases from Advanced Pancreatic Cancer]

A 70's man had been treated with gemcitabine(GEM)and nab-paclitaxel(nabPTX)combination for advanced pancreatic tail cancer with splenic invasion and liver metastases. However, the primary lesion was not controlled, then intensity-modulat- ed radiation therapy(76.5 Gy/17 Fr)was performed for primary lesion. Three grown hypovascular liver metastases were detected by follow-up EOB-MRI and PET-computed tomography(CT)imaging with 18F-FDG. Unfortunately, these lesions were not detected by intravenous injection of contrast media with CT nor ultrasonography. Radiofrequency ablation(RFA) under computed tomography during arterial portography(CTAP)guidance was performed. The patient has been alive for 1 year after RFA with no recurrence. CTAP could be a feasible image guidance for the treatment of hypovascular liver metastases with RFA.

Clinical Assessment of Micro-residual Tumors during Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma

BACKGROUND

This study aimed to assess the need to consider microscopic invasion in terms of treatment planning in stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma and elucidate the appropriate clinical target volume (CTV) margin.

PATIENTS AND METHODS

A total of 121 patients (with 146 liver tumors) who underwent SBRT between July 2007 and August 2016 were analyzed, regarding overall survival and local control (LC).

RESULTS

The 2- and 5-year LC rates were 91.5% and 89.8%, respectively. Planning target volume (PTV) margin <8 mm was associated with poor LC. Of the 77 patients with PTV margin of <8 mm, age <75 years was associated with poor LC, while alpha-fetoprotein (AFP) ≤20 ng/ml was associated with good LC.

CONCLUSION

In patients with high AFP levels, there is a possibility of microscopic invasion around the tumor, suggesting that LC may be improved by adding an additional clinical target volume margin to the gross tumor volume.

Effect of primary tumor location and tumor size on the response to radiotherapy for liver metastases from colorectal cancer

Metastatic liver tumors (MLTs) from colorectal cancer (CRC) are often treated with stereotactic body radiation therapy (SBRT). The present study aimed to examine the predictive factors for response of MLTs to SBRT. A total of 39 MLTs from 24 patients with CRC were retrospectively analyzed. Radiotherapy for MLT was typically performed with a prescribed dose equivalent to a biologically effective dose (BED)10 of 100 Gy. The median follow-up period was 16 months (range, 5-64 months). The median prescribed dose and total BED10 were 56 Gy (range, 45-72 Gy) and 97.5 Gy (range, 71.7-115.5 Gy), respectively, in a median of 8 fractions (range, 4-33 fractions). The 1- and 2-year local control rates were 67.2 and 35.9%, respectively. For patients with MLT treated with ablative SBRT (BED10 ≥100 Gy in ≤5 fractions), the 1- and 2-year local control rates were 83.3 and 62.5%, respectively. Univariate analysis showed that primary tumor location (left-sided colon), maximum tumor diameter (≤30 mm) and ablative SBRT (BED10 ≥100 Gy in ≤5 fractions) were significantly associated with improved local control (P=0.0058, P=0.0059 and P=0.0268, respectively). Multivariate analysis showed that tumor diameter was significantly associated with improved local control (P=0.0314). In addition, patients who received ablative SBRT had significantly prolonged overall survival times compared with those treated with non-ablative SBRT (P=0.0261). To conclude, tumors ≤30 mm that can be treated with ablative SBRT are associated with good local control rates. The primary tumor location may affect the radiosensitivity of MLTs.

Clinical outcome of patients treated with re-irradiation for spine or pelvic bone metastasis: A multi-institutional analysis of 98 patients

The present study aimed to describe the clinical results of re-irradiation (Re-RT) for spine or pelvic bone metastasis at the same initial irradiated area. Between April 2010 and March 2014, cases involving 98 patients with spine or pelvic bone metastasis who had undergone Re-RT at five institutions were reviewed. The clinical outcomes following Re-RT were evaluated, including overall survival (OS) and severe adverse events. The median time interval from initial radiation therapy (RT) to Re-RT was 439 days (range, 23–4,993 days), and the median duration of patient follow-up was 256 days (range, 11–2,284 days). The median biological effective dose for the Re-RT was 150 Gy₂ (range, 17–240 Gy₂; α/β = 2). Severe late adverse events occurred in two patients who underwent three-dimensional conformal radiotherapy for lumbar spine or pelvic bone metastases, which may be associated with tumor progression. The median survival time following Re-RT was 255 days, and the actuarial OS rate at 1 year was 36%. The interval between initial RT and Re-RT, and their performance statuses (PS) were significant independent prognostic factors for OS rates in multivariate analysis. Re-RT for spine or pelvic bone metastases is a relatively acceptable option with low risk of anticipated severe adverse events, particularly for patients with good PS following a long disease-free interval.

Validation of the liver mean dose in terms of the biological effective dose for the prevention of radiation-induced liver damage

AIM

The purpose of this study was to determine the optimal mean liver biologically effective dose (BED) to prevent radiation-induced liver disease (RILD) in stereotactic body radiation therapy (SBRT).

BACKGROUND

The actual mean doses appropriate for liver irradiation in modern radiotherapy techniques have not been adequately investigated, although SBRT is sometimes alternatively performed using fractionated regimens.

MATERIALS AND METHODS

SBRT treatment plans for liver tumors in 50 patients were analyzed. All distributions of the physical doses were transformed to BED₂ using the linear-quadratic model. The relationship between physical doses and the BED₂ for the liver were then analyzed, as was the relationship between the mean BED₂ for the liver and the planning target volume (PTV).

RESULTS

A significantly positive correlation was observed between the mean physical dose for the background liver and the mean BED₂ for the whole liver (P < 0.0001, r = 0.9558). Using the LQ model, a mean BED₂ of 73 and 16 Gy for the whole liver corresponded to the hepatic tolerable mean physical dose of 21 and 6 Gy for Child-Pugh A- and B-classified patients, respectively. Additionally, the PTV values were positively correlated with the BEDs for the whole liver (P < 0.0001, r = 0.8600), and the background liver (P < 0.0001, r = 0.7854).

CONCLUSION

A mean BED₂ of 73 and 16 Gy for the whole liver appeared appropriate to prevent RILD in patients with Child-Pugh classes A and B, respectively. The mean BED₂ for the liver correlated well with the PTV.

Feasibility study of a non-invasive eye fixation and monitoring device using a right-angle prism mirror for intensity-modulated radiotherapy for choroidal melanoma

We aimed to describe the feasibility and efficacy of a novel non-invasive fixation and monitoring (F-M) device for the eyeballs (which uses a right-angle prism mirror as the optic axis guide) in three consecutive patients with choroidal melanoma who were treated with intensity-modulated radiotherapy (IMRT). The device consists of an immobilization shell, a right-angle prism mirror, a high magnification optical zoom video camera, a guide lamp, a digital voice recorder, a personal computer, and a National Television System Committee standard analog video cable. Using the right-angle prism mirror, the antero-posterior axis was determined coincident with the optic axis connecting the centers of the cornea and pupil. The axis was then connected to the guide light and video camera installed on the couch top on the distal side. Repositioning accuracy improved using this method. Furthermore, the positional error of the lens was markedly reduced from ±1.16, ±1.68 and ±1.11 mm to ±0.23, ±0.58 and ±0.26 mm in the horizontal direction, and from ±1.50, ±1.03 and ±0.48 mm to ±0.29, ±0.30 and ±0.24 mm in the vertical direction (Patient #1, #2 and #3, respectively). Accordingly, the F-M device method decreased the planning target volume size and improved the dose-volume histogram parameters of the organ-at-risk via IMRT inverse planning. Importantly, the treatment method was well tolerated.

Threshold doses and prediction of visually apparent liver dysfunction after stereotactic body radiation therapy in cirrhotic and normal livers using magnetic resonance imaging

The purpose of the present study was to investigate the threshold dose for focal liver damage after stereotactic body radiation therapy (SBRT) in cirrhotic and normal livers using magnetic resonance imaging (MRI). A total of 64 patients who underwent SBRT for liver tumors, including 54 cirrhotic patients with hepatocellular carcinoma (HCC) and 10 non-cirrhotic patients with liver metastases, were analyzed. MRI was performed 3-6 months after SBRT, using gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced T1-weighted sequences. All MRI datasets were merged with 3D dosimetry data. All dose distributions were corrected to the biologically effective dose using the linear-quadratic model with an assumed α/β ratio of 2 Gy. The development of liver dysfunction was validly correlated with isodose distribution. The median biologically effective dose (BED2) that provoked liver dysfunction was 57.3 (30.0-227.9) and 114.0 (70.4-244.9) Gy in cirrhotic and normal livers, respectively (P = 0.0002). The BED2 associated with a >5% risk of liver dysfunction was 38.5 in cirrhotic livers and 70.4 Gy in normal livers. The threshold BED2 for liver dysfunction was not significantly different between Child-Pugh A and B patients (P = 0.0719). Moreover, the fractionation schedule was not significantly correlated with threshold BED2 for liver dysfunction in the cirrhotic liver (P = 0.1019). In the cirrhotic liver, fractionation regimen and Child-Pugh classification did not significantly influence the threshold BED2 for focal liver damage after SBRT. We suggest that the threshold BED2 for liver dysfunction after SBRT is 40 and 70 Gy in the cirrhotic and normal liver, respectively.

Outcomes and toxicity of radiotherapy for refractory bone and soft tissue sarcomas

Surgical resection is a well-established treatment option for sarcoma. However, anatomical barriers often hamper radical surgical procedures. The treatment of unresectable sarcoma, including local or distant failures following initial treatment, is challenging. The aim of the present study was to analyze the outcome of radiotherapy (RT) for refractory sarcoma, including unresectable, metastatic and recurrent disease, following radical treatment. We retrospectively reviewed a total of 67 tumors in 28 patients who were treated with RT between 2007 and 2014. Clinical target volume (CTV) was generally not defined in a preventive manner; therefore, in the majority of the cases, CTV equaled the gross tumor volume. The total delivered dose, number of fractions and biological equivalent dose were 52 (range, 40-69), 10 (range, 4-24) and 92.2 (range, 56-119.6) Gy, respectively. Only 1 patient developed local failure, with a median follow-up of 11 months (range, 1-59 months). Therefore, the 12-month progression-free survival rate for 67 sites was 96.8%. The overall survival rates at 12 and 36 months were 75.8 and 30.2%, respectively. A total of 2 patients developed grade >2 toxicities, including grade 3 mucositis and grade 4 pericardial effusion. Our results demonstrated that radical RT using modern techniques is highly feasible, achieves excellent local control, and may be an effective treatment option for refractory sarcoma.

Evaluation of potential internal target volume of liver tumors using cine-MRI

PURPOSE

Four-dimensional computed tomography (4DCT) is widely used for evaluating moving tumors, including lung and liver cancers. For patients with unstable respiration, however, the 4DCT may not visualize tumor motion properly. High-speed magnetic resonance imaging (MRI) sequences (cine-MRI) permit direct visualization of respiratory motion of liver tumors without considering radiation dose exposure to patients. Here, the authors demonstrated a technique for evaluating internal target volume (ITV) with consideration of respiratory variation using cine-MRI.

METHODS

The authors retrospectively evaluated six patients who received stereotactic body radiotherapy (SBRT) to hepatocellular carcinoma. Before acquiring planning CT, sagittal and coronal cine-MRI images were acquired for 30 s with a frame rate of 2 frames/s. The patient immobilization was conducted under the same condition as SBRT. Planning CT images were then acquired within 15 min from cine-MRI image acquisitions, followed by a 4DCT scan. To calculate tumor motion, the motion vectors between two continuous frames of cine-MRI images were calculated for each frame using the pyramidal Lucas-Kanade method. The target contour was delineated on one frame, and each vertex of the contour was shifted and copied onto the following frame using neighboring motion vectors. 3D trajectory data were generated with the centroid of the contours on sagittal and coronal images. To evaluate the accuracy of the tracking method, the motion of clearly visible blood vessel was analyzed with the motion tracking and manual detection techniques. The target volume delineated on the 50% (end-exhale) phase of 4DCT was translated with the trajectory data, and the distribution of the occupancy probability of target volume was calculated as potential ITV (ITV Potential). The concordance between ITV Potential and ITV estimated with 4DCT (ITV 4DCT) was evaluated using the Dice's similarity coefficient (DSC).

RESULTS

The distance between blood vessel positions determined with motion tracking and manual detection was analyzed. The mean and SD of the distance were less than 0.80 and 0.52 mm, respectively. The maximum ranges of tumor motion on cine-MRI were 2.4 ± 1.4 mm (range, 1.0-5.0 mm), 4.4 ± 3.3 mm (range, 0.8-9.4 mm), and 14.7 ± 5.9 mm (range, 7.4-23.4 mm) in lateral, anterior-posterior, and superior-inferior directions, respectively. The ranges in the superior-inferior direction were larger than those estimated with 4DCT images for all patients. The volume of ITV Potential was 160.3% ± 13.5% (range, 142.0%-179.2%) of the ITV 4DCT. The maximum DSC values were observed when the cutoff value of 24.7% ± 4.0% (range, 20%-29%) was applied.

CONCLUSIONS

The authors demonstrated a novel method of calculating 3D motion and ITV Potential of liver cancer using orthogonal cine-MRI. Their method achieved accurate calculation of the respiratory motion of moving structures. Individual evaluation of the ITV Potential will aid in improving respiration management and treatment planning.

Stereotactic body radiotherapy for Stage I lung cancer with chronic obstructive pulmonary disease: special reference to survival and radiation-induced pneumonitis

This retrospective study aimed to evaluate radiation-induced pneumonitis (RIP) and a related condition that we define in this report--prolonged minimal RIP (pmRIP)--after stereotactic body radiotherapy (SBRT) for Stage I primary lung cancer in patients with chronic obstructive pulmonary disease (COPD). We assessed 136 Stage I lung cancer patients with COPD who underwent SBRT. Airflow limitation on spirometry was classified into four Global Initiative for Chronic Obstructive Lung Disease (GOLD) grades, with minor modifications: GOLD 1 (mild), GOLD 2 (moderate), GOLD 3 (severe) and GOLD 4 (very severe). On this basis, we defined two subgroups: COPD-free (COPD -) and COPD-positive (COPD +). There was no significant difference in overall survival or cause-specific-survival between these groups. Of the 136 patients, 44 (32%) had pmRIP. Multivariate analysis showed that COPD and the Brinkman index were statistically significant risk factors for the development of pmRIP. COPD and the Brinkman index were predictive factors for pmRIP, although our findings also indicate that SBRT can be tolerated in early lung cancer patients with COPD.

Differences in rates of radiation-induced true and false rib fractures after stereotactic body radiation therapy for Stage I primary lung cancer

The purpose of this study was to analyze the dosimetry and investigate the clinical outcomes of radiation-induced rib fractures (RIRFs) after stereotactic body radiotherapy (SBRT). A total of 126 patients with Stage I primary lung cancer treated with SBRT, who had undergone follow-up computed tomography (CT) at least 12 months after SBRT and who had no previous overlapping radiation exposure were included in the study. We used the Mantel-Haenszel method and multiple logistic regression analysis to compare risk factors. We analyzed D(0.5 cm(3)) (minimum absolute dose received by a 0.5-cm(3) volume) and identified each rib that received a biologically effective dose (BED) (BED3, using the linear-quadratic (LQ) formulation assuming an α/β = 3) of at least 50 Gy. Of the 126 patients, 46 (37%) suffered a total of 77 RIRFs. The median interval from SBRT to RIRF detection was 15 months (range, 3-56 months). The 3-year cumulative probabilities were 45% (95% CI, 34-56%) and 3% (95% CI, 0-6%), for Grades 1 and 2 RIRFs, respectively. Multivariate analysis showed that tumor location was a statistically significant risk factor for the development of Grade 1 RIRFs. Of the 77 RIRFs, 71 (92%) developed in the true ribs (ribs 1-7), and the remaining six developed in the false ribs (ribs 8-12). The BED3 associated with 10% and 50% probabilities of RIRF were 55 and 210 Gy to the true ribs and 240 and 260 Gy to the false ribs. We conclude that RIRFs develop more frequently in true ribs than in false ribs.

Clinical introduction of Monte Carlo treatment planning for lung stereotactic body radiotherapy

The purpose of this study was to investigate the impact of Monte Carlo (MC) calculations and optimized dose definitions in stereotactic body radiotherapy (SBRT) for lung cancer patients. We used a retrospective patient review and basic virtual phantom to determine dose prescriptions. Fifty-three patients underwent SBRT. A basic virtual phantom had a gross tumor volume (GTV) of 10.0 mm with equivalent water density of 1.0 g/cm3, which was surrounded by equivalent lung surrounding the GTV of 0.25 g/cm3. D95 of the planning target volume (PTV) and D99 of the GTV were evaluated with different GTV sizes (5.0 to 30.0 mm) and different lung densities (0.05 to 0.45 g/cm3). Prescribed dose was defined as 95% of the PTV should receive 100% of the dose (48 Gy/4 fractions) using pencil beam (PB) calculation and recalculated using MC calculation. In the patient study, average doses to the D95 of the PTV and D99 of the GTV using the MC calculation plan were 19.9% and 10.2% lower than those by the PB calculation plan, respectively. In the phantom study, decreased doses to the D95 of the PTV and D99 of the GTV using the MC calculation plan were accompanied with changes GTV size from 30.0to 5.0 mm, which was decreased from 8.4% to 19.6% for the PTV and from 17.4%to 27.5% for the GTV. Similar results were seen with changes in lung density from 0.45 to 0.05 g/cm3, with doses to the D95 of the PTV and D99 of the GTV were decreased from 12.8% to 59.0% and from 7.6% to 44.8%, respectively. The decrease in dose to the PTV with MC calculation was strongly dependent on lung density. We suggest that dose definition to the GTV for lung cancer SBRT be optimized using MC calculation. Our current clinical protocol for lung SBRT is based on a prescribed dose of 44 Gy in 4 fractions to the GTV using MC calculation.

Approach to dose definition to the gross tumor volume for lung cancer with respiratory tumor motion

The purpose of this study was to validate the dose prescription defined to the gross tumor volume (GTV) 3D and 4D dose distributions of stereotactic radiotherapy for lung cancer. Treatment plans for 94 patients were generated based on computed tomography (CT) under free breathing. A uniform margin of 8 mm was added to the internal target volume (ITV) to generate the planning target volume (PTV). A leaf margin of 2 mm was added to the PTV. The prescription dose was defined such that 99% of the GTV should receive 100% of the dose using the Monte Carlo calculation (iPlan RT Dose(TM)) for 6-MV photon beams. The 3D dose distribution was determined using CT under free breathing. The 4D dose distribution plan was recalculated to investigate the effect of tumor motion using the same monitor units as those used for the 3D dose distribution plan. D99 (99% of the GTV) in the 4D plan was defined as the average D99 in each of the four breathing phases (0%, 25%, 50% and 75%). The dose difference between maximum and minimum at D99 of the GTV in 4D calculations was 0.6 ± 1.0% (range 0.2-4.6%). The average D99 of the GTV from 4D calculations in most patients was almost 100% (99.8 ± 1.0%). No significant difference was found in dose to the GTV between 3D and 4D dose calculations (P = 0.67). This study supports the clinical acceptability of treatment planning based on the dose prescription defined to the GTV.

Reirradiation of paraaortic lymph node metastasis by brachytherapy with hyaluronate injection via paravertebral approach: With DVH comparison to IMRT

PURPOSE/INTRODUCTION: To safely irradiate retroperitoneal targets as paraaortic lymph node by separating abdominal at-risk organs from the target during irradiation, we created a percutaneous paravertebral approach of high-dose-rate brachytherapy with hyaluronate gel injection (HGI). We report a case treated with this technique.

METHODS AND MATERIALS

We encountered a patient with symptomatic regrowth of paraaortic lymph node metastasis from prostatic cancer. He had previously received 58.4Gy of radiotherapy to the same region 12 months prior. Brachytherapy needles and a HGI needle were deployed via the paravertebral approach under local anesthesia at our outpatient clinic.

RESULTS

A single dose of 22.5Gy (equivalent to 60.94Gy in 2Gy per fraction schedule calculated at α/β=10) was delivered to the target, with preservation of the surrounding small intestine by HGI with D(2cc) (minimum dose to the most irradiated volume of 2mL) of 5.05Gy. Therapeutic ratio was 3.64 times higher for this brachytherapy plan compared with an intensity-modulated radiation therapy plan. At followup at 1 year after brachytherapy, the symptoms had disappeared, tumor size had reduced with no fluorodeoxyglucose accumulation, and prostate-specific antigen level had decreased.

CONCLUSION

We consider that high-dose-rate brachytherapy with the HGI procedure offers effective treatment even in this type of reirradiation situation.

High-dose-rate brachytherapy without external beam irradiation for locally advanced prostate cancer

BACKGROUND AND PURPOSE

High-dose-rate brachytherapy (HDR-BT) had been used only in combination with external beam irradiation (EBI) until our previously reported first trial of HDR-BT alone without EBI. The purpose of the current report is to evaluate the feasibility, toxicity and efficacy of this regimen, with more patient accrual and longer follow-up.

MATERIAL AND METHODS

From 1995 through 2004, 111 patients with localized prostate cancer were treated with HDR-BT without EBI. Fifteen patients were considered as low-risk, 28 as intermediate-risk, and 68 as high-risk. The prescribed dose was 48 Gy/8 fractions/5 days or 54 Gy/9 fractions/5 days. Median follow-up time was 27 months (range 5-119).

RESULTS

All the patients completed the treatment regimen. The 3- and 5-year PSA failure-free rates were 83% and 70%, and the local control rates 100% and 97%. The maximum toxicities observed were Grade 3 by CTCAE v3.0 (6 acute, 1 chronic).

CONCLUSIONS

HDR-BT without EBI was feasible and its toxicity acceptable. Short-term tumor control was promising, even for locally advanced cases. More patient accrual and longer follow-up are needed to confirm the efficacy of this novel approach.

Intracavitary brachytherapy for carcinoma of the uterine cervix—Comparison of HDR (Ir-192) and MDR (Cs-137)—

PURPOSE

To compare the results of high dose rate (HDR) (Ir-192) and medium dose rate (MDR) (Cs-137) intracavitary brachytherapy (ICRT) for carcinoma of the uterine cervix.

MATERIALS AND METHODS

Between May 1991 and March 2001, a total of 206 patients with Stage I-IVA previously untreated cervical cancer were treated with ICRT combined with external beam radiotherapy (EBRT). HDR was administered to a total of 135 patients: 22 patients in Stage I, 49 in Stage II, 56 in Stage III, and eight in Stage IVA. MDR was administered to a total of 71 patients: six patients in Stage I, 27 in Stage II, 33 in Stage III, and five in Stage IVA. The MDR at point A was 30 Gy/hour for HDR and 1.7 Gy/hour for MDR treatment, and the corresponding median follow-up periods for survivors were 55 and 68 months.

RESULTS

For the HDR group, 5-year cause-specific survival rates were 90%, 78%, 53% and 33% for Stages I, II, III, and IVA, respectively. For the MDR group, the corresponding rates were 100%, 76%, 51%, and 40%. In the HDR group, 19 patients (14%) developed Grade 2 or higher late complications, and, in the MDR group, four patients (6%) did.

CONCLUSIONS

There was no statistically significant difference in cause-specific survivals between the results of HDR and MDR brachytherapy for cervical cancer. The incidence of late complications tended to be higher for the HDR group than for the MDR group, but did not show a statistically significant difference (p=0.07).

High-dose-rate brachytherapy combined with long-term hormonal therapy for high-risk prostate cancer: Results of a retrospective analysis

PURPOSE

High-dose-rate (HDR) brachytherapy combined with hormonal therapy (HTx), without the addition of external beam radiation therapy (EBRT) for high-risk prostate cancer was evaluated retrospectively.

MATERIALS AND METHODS

Between May 1995 and April 2002, 35 patients with prostate cancer [Stage > or = T2b (UICC 1997) or tumor grading=3 or prostate-specific antigen (PSA) level > or = 20 ng/mL] were treated with HDR brachytherapy combined with HTx. Most patients (74%) had two or more of these factors. All patients received Iridium-192 HDR brachytherapy with a total dose of 54 Gy/9 fractions/5 days (48 Gy/8 fractions/5 days for the first 6 cases) in one implant session. The median neoadjuvant HTx [luteinizing hormone-releasing hormone (LH-RH) agonist and antiandrogen] period was 7 months. The median adjuvant HTx (ATH) (LH-RH agonist) period was 40 months, and median follow-up was 57 months (range, 23-117 months).

RESULTS

The 5-year actuarial biochemical control, local control, and disease-free rates were 62%, 96%, and 76% respectively. No patients experienced local and/or regional relapse without distant progression. The 5-year actuarial cause-specific survival and overall survival rates were 89% and 87%, respectively. The acute and late toxicity were moderate and well tolerated.

CONCLUSION

HDR brachytherapy plus long-term HTx is at least as effective as conventional EBRT plus long-term HTx.

An optimization algorithm of dose distribution using attraction-repulsion model (application to low-dose-rate interstitial brachytherapy)

PURPOSE

To optimize dose distribution for prostate cancer in low-dose-rate interstitial brachytherapy, we have developed a new algorithm named the Attraction-Repulsion Model. The purpose was to find the optimal source configuration.

METHODS AND MATERIALS

The Attraction-Repulsion Model is used to optimize the dose distribution by finding the best seed configuration. We arranged grids at intervals of a certain space inside and established target and critical organs as areas of interest. We can make an attribute for grids, and the grids show attraction or repulsion depending on dose delivered from source. Source position is changed by the forces that the grids impose to the sources. A calculation was done repeatedly until the attraction and repulsion forces reached a balance. The optimal configuration was established when the sources reached a stable distribution in time. To evaluate the optimization plan, dose-volume histograms were used.

RESULTS

Source configuration can be optimized automatically. The calculation time was approximately 5 min. The V100, V150, V200, and D90 of the target were 95%, 39%, 9%, and 157 Gy, respectively. V150 of the urethra and V80 of the rectum were 2% and 0%, respectively.

CONCLUSION

This method can optimize the dose distribution objectively.

Prospective study of HDR (192Ir) versus MDR (137Cs) intracavitary brachytherapy for carcinoma of the uterine cervix

PURPOSE

The aim of this study was to compare the results of high-dose rate (HDR) and medium-dose rate (MDR) intracavitary brachytherapy for carcinoma of the uterine cervix on the basis of a prospective study and to determine the dose rate conversion factor (DRCF) from low-dose rate (LDR) to MDR via HDR, because a DRCF of 0.54 from LDR to HDR has been widely accepted.

MATERIALS AND METHODS

Between August 1991 and July 1999, 104 patients were entered into this trial to compare results between HDR (n=54) and MDR (n=50). Three patients were excluded from this study, leaving 54 HDR patients and 47 MDR patients eligible. Method and dose of external beam radiotherapy were the same for both groups. For HDR intracavitary brachytherapy, point A dose was adjusted to 32 Gy/4 fractions for stages I and II, to 30 Gy/4 fractions for stage III, and to 22.5 Gy/3 fractions for stage IV. The corresponding values for MDR were 35.6 Gy/4 fractions, 34 Gy/4 fractions, and 25.5 Gy/3 fractions. The average dose rate at point A was 30 Gy/hour (9.0-65.2) for HDR and 1.7 Gy/hour (1.3-2.2) for MDR. We assumed a DRCF of 0.9 from MDR to HDR.

RESULTS

The 3-year cause-specific survival rates for HDR were 85%, 83%, 75%, and 0% for stages I, II, III, and IV, respectively. The corresponding figures for MDR were 100%, 82%, 58%, and 40%. Six of the HDR patients (11%) and 2 of the MDR patients (4%) developed Kottmeier's grade 2 or 3 late complications. A DRCF of 0.6 from LDR to MDR could be derived from a DRCF of 0.9 from MDR to HDR and one of 0.54 from LDR to HDR.

CONCLUSIONS

There were no statistically significant differences in cause-specific survival and incidence of late complications between HDR and MDR. A DRCF of 0.6 from LDR to MDR could be determined. However, because the results of this trial were preliminary, a further study is needed.

Quantitative evaluation of changes in irradiated lung fields after stereotactic irradiation by the Polygon Method

PURPOSE

To evaluate areas of change in lung after thoracic stereotactic irradiation (STI).

MATERIALS AND METHODS

We developed a method of evaluation named the Polygon Method, to measure the irradiated lung fields of 12 lung tumors treated by STI. Before treatment, each targeted field was divided into several circular zones of 2 cm in width centered at the tumor on high resolution computed tomography, and the areas of each zone before and after treatment were compared.

RESULTS

Six months after treatment, the areas of the zone within 2 cm from the tumor decreased, and the mean ratio of areas after and before STI was 0.849 (range, 0.515 to 1.052, p=0.0254). By contrast, the areas of zones located at 4 to 6, 6 to 8, 8 to 10, and more than 10 cm from the tumor tended to increase, with mean ratios of 1.059, 1.058, 1.089 (p=0.0374), and 1.084, respectively.

CONCLUSION

After thoracic STI, volume loss in the lung is limited to the field in close proximity to the tumor, while compensatory expansion of the lung occurs in fields distant from the tumor.