Dosimetric comparison of intensity modulated and volumetric arc radiation therapy for gastric cancer

Optimal tumor coverage with different beam energies by IMRT, VMAT and TOMO: Effects on patients with proximal gastric cancer

To compare the effects of different photon energies on radiation planning by intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and helical tomotherapy (TOMO) for proximal gastric cancer (PGC). Network analysis with microarray procession and gene ontology were used to identify the effect of radiotherapy (RT) on PGC. Then, we retrospectively analyzed 8 PGC patients after receiving irradiation with a prescribed dose of 50.4 Gy. The Pinnacle treatment planning system (TPS, V9.8) was used to generate IMRT and VMAT plans by using 6 or 10 MV. TOMO plans were calculated on the Tomotherapy Planning Station Hi-Art Version 4.2.3 workstation (Tomotherapy Incorporated, Madison, WI, USA). PGC is associated with high DNA repair ability. TOMO plan results in higher tumor coverage and a better conformity index than IMRT and VMAT. 10-MV VMAT yields better dosimetric quality of the gradient index than 6-MV VMAT (P = .012). TOMO was associated with a lower irradiation dose in the mean dose to the right kidney (P = .049), left kidney and heart than 6-MV IMRT and 6-MV VMAT. 6-MV IMRT plan presented a higher dose of lung Dmean (P = .017) than 10-MV IMRT. Additionally, VMAT, using a planning energy of 6 MV, was associated with a significantly higher left kidney Dmean (P = .018) and V10 (P = .036) than a planning energy of 10 MV. TOMO is a better RT plan not only for tumor coverage but also for sparing organs at risk. IMRT and VMAT plans with 10 MV beams are more suitable than 6 MV beams for PGC treatment.

Tomotherapy as an adjuvant treatment for gastroesophageal junction and stomach cancer may reduce bowel and bone marrow toxicity compared to intensity-modulated radiotherapy and volumetric-modulated arc therapy

Purpose

To compare dosimetric parameters of intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and tomotherapy (TOMO) in the adjuvant treatment of gastroesophageal junction (GEJ)/stomach cancer. The planning goal was to maintain high target coverage while keeping the dose to the bowel and bone marrow (BM) as low as possible.

Materials and Methods

After curative surgery, 16 patients with GEJ/stomach cancer were re-planned by coplanar IMRT (five fixed beam), VMAT (double-arc), and TOMO. The dose to the planning target volume (PTV) was 45 Gy in 25 fractions. The target parameters, including the homogeneity index (HI) and conformity index (CI), and doses to the organs at risk (OARs) were analyzed.

Results

Dosimetric parameters for PTV and OARs were comparable among the three techniques. However, TOMO provided improved conformity (CI = 0.92±0.03) and homogeneity (HI = 1.07±0.02) than IMRT (CI = 0.87±0.03; HI = 1.09±0.02; p < 0.05) and VMAT (CI = 0.86±0.03; HI = 1.09±0.02; p < 0.01). TOMO also improved dose sparing of the bowel (percentage of the volume receiving a dose of ≥ 30 Gy [V30] = 23.24±9.85) and BM (V30 = 71.66±6.15) compared with IMRT (bowel V30 = 30.02±11.74; BM V30 = 83.74±8.42; p < 0.01) and VMAT (bowel V30 = 31.88±11.59; BM V30 = 79.51±9.07; p < 0.01).

Conclusions

TOMO is a good option for adjuvant treatment of GEJ/stomach cancer in patients undergoing radical surgery due to its superior bowel and BM dose sparing, dose conformity and dose homogeneity; however, future studies are required to validate its clinical efficacy.

Automated VMAT planning for postoperative adjuvant treatment of advanced gastric cancer

Background

Postoperative/adjuvant radiotherapy of advanced gastric cancer involves a large planning target volume (PTV) with multi-concave shapes which presents a challenge for volumetric modulated arc therapy (VMAT) planning. This study investigates the advantages of automated VMAT planning for this site compared to manual VMAT planning by expert planners.

Methods

For 20 gastric cancer patients in the postoperative/adjuvant setting, dual-arc VMAT plans were generated using fully automated multi-criterial treatment planning (autoVMAT), and compared to manually generated VMAT plans (manVMAT). Both automated and manual plans were created to deliver a median dose of 45 Gy to the PTV using identical planning and segmentation parameters. Plans were evaluated by two expert radiation oncologists for clinical acceptability. AutoVMAT and manVMAT plans were also compared based on dose-volume histogram (DVH) and predicted normal tissue complication probability (NTCP) analysis.

Results

Both manVMAT and autoVMAT plans were considered clinically acceptable. Target coverage was similar (manVMAT: 96.6 ± 1.6%, autoVMAT: 97.4 ± 1.0%, p = 0.085). With autoVMAT, median kidney dose was reduced on average by > 25%; (for left kidney from 11.3 ± 2.1 Gy to 8.9 ± 3.5 Gy (p = 0.002); for right kidney from 9.2 ± 2.2 Gy to 6.1 ± 1.3 Gy (p <  0.001)). Median dose to the liver was lower as well (18.8 ± 2.3 Gy vs. 17.1 ± 3.6 Gy, p = 0.048). In addition, Dmax of the spinal cord was significantly reduced (38.3 ± 3.7 Gy vs. 31.6 ± 2.6 Gy, p <  0.001). Substantial improvements in dose conformity and integral dose were achieved with autoVMAT plans (4.2% and 9.1%, respectively; p <  0.001). Due to the better OAR sparing in the autoVMAT plans compared to manVMAT plans, the predicted NTCPs for the left and right kidney and the liver-PTV were significantly reduced by 11.3%, 12.8%, 7%, respectively (p ≤ 0.001). Delivery time and total number of monitor units were increased in autoVMAT plans (from 168 ± 19 s to 207 ± 26 s, p = 0.006) and (from 781 ± 168 MU to 1001 ± 134 MU, p = 0.003), respectively.

Conclusions

For postoperative/adjuvant radiotherapy of advanced gastric cancer, involving a complex target shape, automated VMAT planning is feasible and can substantially reduce the dose to the kidneys and the liver, without compromising the target dose delivery.

Electronic supplementary material

The online version of this article (10.1186/s13014-018-1032-z) contains supplementary material, which is available to authorized users.

Integrated microRNA and mRNA expression profile analysis of tumor-associated macrophages after exposure to single-dose irradiation

BACKGROUND

Radiotherapy (RT) is a common approach that accounts for nearly 50% of cancer patient treatment and has the potential for long-term tumor control. Recently, we published a research article on gene expression profiling of tumor-associated macrophages (TAM) that were exposed to ionizing radiation (IR). Single-dose irradiation of tumors could initiate differentially expressed genes in TAM as a time series from irradiated tumors that are associated with the immune response. It is also well known that human cancers are associated with microRNA (miRNA) alterations that are involved in cancer progression. However, the role of miRNA on TAM after exposure to irradiation remains unclear.

RESULTS

In this study, miRNA expression profiles from microarrays were used to identify the key miRNAs and correlating pathways involved in the role of TAMs in tumor progression and recurrence after RT. Using a mouse tumor model, we identified miRNA pattern changes over time in response to irradiation. Based on our results, we hypothesize that miRNA expression in the irradiated tumor may be used as a distinguishing marker to indicate the best time for therapeutic intervention to prevent tumor recurrence after RT.

CONCLUSIONS

We established a murine model irradiated with a single dose of 25 Gy that could initiate temporal changes in the expression of miRNAs associated with cell proliferation and the immune response, as evidenced by macrophages directly extracted from irradiated tumors after two weeks of IR. Statistical analyses were conducted by comparing the miRNA expression in macrophages from non-irradiated versus irradiated tumors. Thus, our study could lead to a better understanding of the function of miRNA expressions, which changed temporally in an irradiated tumor microenvironment.

Volumetric-modulated arc therapy versus intensity-modulated radiotherapy for large volume retroperitoneal sarcomas: A comparative analysis of dosimetric and treatment delivery parameters

Purpose

To compare dosimetric and treatment delivery parameter differences between volumetric‐modulated arc radiotherapy (VMAT) and intensity‐modulated radiotherapy (IMRT) for large volume retroperitoneal sarcomas (RPS).

Materials and Methods

Both VMAT and IMRT planning were performed on CT datasets of 10 patients with RPS who had been previously treated with preoperative radiotherapy. Plans were optimized to deliver ≥95% dose to the PTV and were evaluated for conformity and homogeneity. Dose to the organs at risk (OARs) (kidney, liver, spinal cord, and bowel space), unspecified tissue, and dose evaluation volumes (DEVs) at 1, 2, and 5 cm from PTV were calculated and compared. Monitor units (MUs) and treatment delivery times were recorded and compared between the two techniques. The deliverability of the large volume RPS VMAT plans was verified by portal dosimetry on a Truebeam™ linac.

Results

VMAT and IMRT plans were equivalent for PTV coverage and homogeneity (P > 0.05); however, VMAT plans had slightly better conformity index, CI (P < 0.001). Doses to the OARs were not significantly different between VMAT and IMRT plans (P > 0.05). Mean doses to the unspecified tissue as well as at 1, 2, and 5 cm DEVs were lower with VMAT compared with IMRT, P = 0.04 and P < 0.01, respectively. MUs and average beam‐on times were both significantly lower in the VMAT vs IMRT plans, P < 0.001 and P = 0.001, respectively. All VMAT plans passed portal dosimetry delivery verification with an average gamma passing rate of 99.6 ± 0.4%.

Conclusions

VMAT planning for large volume RPS improved CI, and achieved comparable OAR sparing, as compared with IMRT. As treatment delivery time was lower, the use of VMAT for RPS may translate into improved treatment delivery efficiency.

Dosimetric comparison of 3-dimensional conformal radiotherapy, volumetric modulated arc therapy, and helical tomotherapy for postoperative gastric cancer patients

PURPOSE

To compare dosimetric data for the planning target volume (PTV) and organs at risk (OARs) between 3-dimensional conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy [1].

MATERIALS AND METHODS

The dosimetric data for 15 gastric cancer patients treated with 3DCRT, VMAT, or HT techniques were used. Cumulative dosimetric parameters, homogeneity index (HI), and conformal index (CI) were compared for the PTV and OARs.

RESULTS

The average maximum doses of PTV were significantly higher in VMAT plans than in 3DCRT (p = 0.04) and HT (p = 0.02) plans, whereas minimum dose values were significantly lower in 3DCRT plans compared with VMAT (p < 0.001) and HT (p = 0.02) plans. Liver mean dose (D _mean) and D _mean values for both kidneys were significantly lower in HT plans than in 3DCRT and VMAT plans. The doses in high dose regions (V30-V45) using 3DCRT plans were significantly higher compared to both VMAT and HT plans. The bowel V5-V30 and V45 was significantly less in HT plans compared to VMAT plans. There were no significant differences in dose sparing of the spinal cord.

CONCLUSIONS

The HT plans reduced the maximum dose applied to the target and improved the conformality and homogeneity of radiation, while providing sufficient PTV coverage.

Chemoradiation for gastric cancer: controversies, updates and novel techniques

The INT0116 trial established the role of adjuvant chemoradiation (CRT) in the multidisciplinary approach to the management of locally advanced gastric cancer. However, whether adjuvant CRT is indispensable for patients undergoing D2 dissection remains undefined. The adjuvant chemoradiation therapy in stomach cancer (ARTIST) trial, which was designed to compare adjuvant chemotherapy to CRT, failed to demonstrate differences in disease-free and overall survival in the whole study group; however, subgroup analysis indicated that patients with lymph node metastasis may benefit from additional radiation. A follow-up ARTIST II trial is currently under way. The efficacy of adjuvant CRT remains controversial because of variation among studies in the inclusion criteria and treatment delivery methods; however, the identification of patients who would benefit from CRT is critical. Advanced radiotherapy techniques such as intensity-modulated radiotherapy protect normal tissues via motion management and decreased radiation-induced toxicity and contribute to plan optimization. Further studies integrating clinical and molecular factors as well as neoadjuvant CRT are warranted.