乳腺癌保乳术后常规、三维适形及两种调强放疗技术剂量学评估(英文)

Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.     

光子束和电子束在早期乳腺癌患者放疗瘤床加量计划的剂量学研究

Objective

The aim of our study was to assess and compare the potential dosimetric advantages and drawbacks of photon beams and electron beams as a boost for the tumor bed in superficial and deep seated early-stage breast cancer.

Methods

We planned CTs of 10 women with early breast cancer underwent breast conservative surgery were selected. Tumor bed was defined as superficial and deep with a cut of point 4 cm, those with less than 4 cm were defined as superficial tumors representing 4 patients and those with depth of 4 cm or more were classified as deep tumors representing 6 patients. The clinical target volume (CTV) was defined as the area of architectural distortion surrounded by surgical clips. The planning target volume (PTV) was the CTV plus margin 1 cm. A dose of 10 Gy in 2 Gy fractions was given concurrently at the last week of treatment. Organs at risk (OARs) were heart, lungs, contra-lateral breast and a 5 mm thick skin segment of the breast surface. Dose volume histograms were defined to quantify the quality of concurrent treatment plans assessing target coverage and sparing OARs. The following treatment techniques were assessed: photon beam with 3D-conformal technique and a single electron beam.

Results

For superficial tumors better coverage for CTV and PTV with good homogeneity with better CI was found for the 3D conformal radiotherapy (3DCRT) but with no significant planning objectives over electron beam. For deep tumors, the 3DCRT met the planning objectives for CTV, PTV with better coverage and fewer hot spots with better homogeneity and CI. For superficial tumors, OARs were spared by both techniques with better sparing for the electron beam where as for deep tumors also OARs were well spared by both techniques.

Conclusion

Boosting the tumor bed in earlystage breast cancer with optimized photon may be preferred to electron beam for both superficial and deep tumors. The OARs dose sparing effect may allow for a potential long-term toxicity risk reduction and better cosmesis.     

局部晚期宫颈癌调强和适形放疗的剂量学对比研究(英文)

Objective:This study was to compare 5 field conformal technique to the intensity modulated radiotherapy (IMRT) 8 fields technique in boosting locally advanced cancer cervix cases after external beam radiotherapy with respect to target volume coverage and dose to normal tissues. Methods:We conducted a single institutional comparative dosimetric analysis of 10 patients with cancer cervix who was presented to radiotherapy department in National Cancer Institute, Cairo in period between June 2012 to September 2012 and received a CRT boost in the place of planned brachytherapy after large field pelvic radiotherapy (PRT) with concurrent chemotherapy were retrospectively identified. All tumors were situated in the low central pelvis. Two plans were done for every patient; one using the 8 fields IMRT and the second one using 5 fields’ 3DCRT the two techniques were then compared using dose volume histogram (DVH) analysis for the PTV, bladder, rectum and both femoral heads. Results:Comparing different DVHs, it was found that the planning target volume (PTV) was adequately covered in both plans while it was demonstrates that the 8 fields IMRT technique carried less doses reaching OARs (rectum, bladder, both femoral heads). Conclusion:From the present study, it is concluded that IMRT technique spared more efficiently OARs than CRT technique but both techniques covered the PTV adequately so whenever possible IMRT technique should be used.     

Pilot study of feasibility and dosimetric comparison of prone versus supine breast radiotherapy

Purpose

The aim of this study was to demonstrate feasibility and analyze dosimetric differences in prone and supine position breast cancer radiotherapy in women with large or pendulous breast.

Methods

Ten post-lumpectomy breast cancer patients underwent supine and prone computed tomography-based treatment plan. On each data set, the whole breast, the ipsilateral lung and the heart were outlined. Multisegment tangential-fields plans were generated for each position. Target coverage, homogeneity, overdosage outside breast and organ at risk sparing were analyzed and compared for supine and prone position.

Results

Coverage and dose homogeneity of the PTV measured by D ₉₀ and V _95 % were similar for both plans although breast maximum dose was higher in the supine plan (p = 0.017). Prone position reduced the percentage of ipsilateral lung receiving 20 Gy (V _20Gy) from 26.5 to 2.9 % (p = 0.007), medium lung dose, as well as the percentage of the heart receiving 35 Gy heart (V _35Gy) from 3.4 to 1.2 % (p = 0.038). Overdosage of areas outside breast PTV was also consistently reduced with prone position (p = 0.012). In addition, average number of segments and monitor units needed was reduced in prone position.

Conclusions

Prone position in large breast women appears to favor normal tissue sparing in breast radiotherapy as compared to supine position, without diminishing the target coverage.     

Accelerated intensity-modulated radiotherapy plus temozolomide in patients with glioblastoma: a phase I dose-escalation study (ISIDE-BT-1)

Background

We performed a dose-escalation trial to determine the maximum tolerated dose (MTD) of intensity-modulated radiotherapy (IMRT) with standard concurrent and sequential-dose temozolomide (TMZ) in patients with glioblastoma multiforme.

Methods

Histologically proven glioblastoma patients underwent IMRT dose escalation. IMRT was delivered over 5 weeks with the simultaneous integrated boost (SIB) technique to the two planning target volumes (PTVs) defined by adding 5-mm margin to the respective clinical target volumes (CTVs). CTV1 was the tumor bed plus the enhancing lesion with 10-mm margin; CTV2 was the area of perifocal edema with 20-mm margin. Only the PTV1 dose was escalated (planned dose escalation: 60, 62.5, 65, 67.5, 70 Gy) while the PTV2 dose remained the same (45 Gy).

Results

Forty consecutive glioblastoma patients were treated. While no dose-limiting toxicity (DLT) was recorded during the dose escalation up to 67.5/2.7 Gy, two out of the first six consecutively enrolled patients on the highest dose level (70/2.8 Gy) experienced a DLT, and therefore a cohort expansion was required. 3/14 patients experienced a DLT on the highest planned dose level, and therefore the MTD was not exceeded. After a median follow-up time of 25 months no grade >2 late neurological toxicity was recorded.

Conclusions

By using a SIB IMRT technique, a radiation dose of 70 Gy in 25 fractions (biological effective dose—BED—of 92.8 Gy) can be delivered with concurrent and sequential standard dose TMZ, without unacceptable acute toxicity in patients with glioblastoma.     

Dosimetric Benefits and Practical Pitfalls of Daily Online Adaptive MRI-Guided Stereotactic Radiation Therapy for Pancreatic Cancer

Purpose

Magnetic resonance imaging guided (MRI-g) radiation therapy provides visualization of the target and organs at risk (OARs), allowing for daily online adaptive radiation therapy (OART). We hypothesized that MRI-g OART would improve OAR sparing and target coverage in patients with pancreatic cancer treated with stereotactic body radiation therapy (SBRT).

Dosimetric comparison of liver tumour radiotherapy in all respiratory phases and in one phase using 4DCT

Purpose

Delineation of target volume could be performed on all respiratory phases and radiation is delivered during free breathing cycle, or on the basis of one respiratory phase and deliver gated treatment choosing a specific phase for irradiation. We performed the comparison of both techniques in terms of target and normal tissue dose distributions.

Materials and methods

We analysed 26 metastatic liver tumours using 4DCT to characterize tumour motion and to create treatment volumes: GITV4D was based on all 8 respiratory phases and GTVGAT was based on one specific phase. A 5 mm automatic expansion was added to the GTVs to create PTVs. Two treatment plans were prepared to the total dose of 36 Gy in 3 fractions and dose-volume distributions were analysed for the target and organs at risk. Target motion along the superior-inferior direction was greatest with the mean of 1.1 cm ± 0.3, and in the lateral the mean was 0.7 cm ± 0.3.

Results

GTV and PTV volumes were larger in the 4D than in the GAT, mean 30.7 vs. 19.3 cm³, and 66.7 vs. 45.1 cm³. We achieved similar dose coverage in PTV4D, for the 4D plan, and PTVGAT for the GAT plan, but a decrease in the average minimum dose to 17.8 Gy and the average mean dose to 35.3 Gy was found in PTV4D in the GAT plan. Radiotherapy delivered using GAT resulted in lower liver doses than using 4D with reduction of mean volume receiving 5 Gy by 6.5% ± 5, V_15Gy by 4.5% ± 3.4, V_21Gy by 3.4% ± 2.8 and reduction of mean kidney volume receiving 5 Gy by 9.1% ± 7.9, V_15Gy by 4.1% ± 6.4, V_21Gy by 3.2% ± 5.6. We also found correlations between PTV volume reduction with GAT, GTV motion and doses to normal tissues.

Conclusions

Gated radiotherapy could potentially allow a reduction in PTV volumes from those delineated on all respiratory phases, maintaining acceptable target coverage. Smaller target volumes improve doses distribution in normal tissue especially in the liver and kidney, but also spinal cord and intestine. A significant correlation has been found between dose and volume reduction in the OARs and both GTV motion and PTV volume reduction.     

Protons offer reduced bone marrow,small bowel,and urinary bladder exposure for patients receiving neoadjuvant radiotherapy for resectable rectal cancer

Background

To assess the potential benefit of proton therapy (PT) over photon therapy, we compared 3-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and PT plans in patients undergoing neoadjuvant chemoradiation for resectable rectal cancer at our institution.

Methods

Eight consecutive patients with resectable (T2-T3) rectal cancers underwent 3DCRT, IMRT, and 3-dimensional conformal PT treatment planning. Initial target volumes (PTV1) were contoured using the Radiation Therapy Oncology Group anorectal atlas guidelines. Boost target volumes (PTV2) consisted of the gross rectal tumor plus a uniform 2-cm expansion. Plans delivered 45 Gray (Gy) or Cobalt Gray Equivalent (CGE) to the PTV1 and a 5.4-Gy (CGE) boost to the PTV2. Ninety-five percent of the PTVs received 100% of the target dose and 100% of the PTVs received 95% of the target dose. Standard normal-tissue constraints were utilized. Wilcoxon paired t-tests were performed to compare various dosimetric points between the 3 plans for each patient.

Results

All plans met all normal-tissue constraints and were isoeffective in terms of PTV coverage. The proton plans offered significantly reduced median normal-tissue exposure over the 3DCRT and IMRT plans with respect to pelvic bone marrow at the V5Gy, V10Gy, V15Gy, and V20Gy levels and the small bowel space at the V10Gy and V20Gy levels. The proton plans also offered significantly reduced median normal-tissue exposure over the 3DCRT plans with respect to the small bowel at the V30Gy and V40Gy levels and the urinary bladder at the V40Gy level.

Conclusions

By reducing bone marrow exposure, PT may reduce the acute hematologic toxicity of neoadjuvant chemoradiation and increase the likelihood of uninterrupted chemotherapy delivery. Bone marrow sparing may also facilitate the delivery of salvage chemotherapy for patients who subsequently develop hematogenous metastasis. Reduced small bowel exposure using PT may also reduce toxicity and possibly facilitate the use of more-aggressive chemotherapy with radiotherapy.     

Reirradiation and stereotactic radiotherapy for tumors in the lung: Dose summation and toxicity

Purpose

To assess the accumulated dose and the toxicity after reirradiation for tumors in the lung using non-rigid registration.

Material and methods

Twenty patients with a tumor in the lung were reirradiated with or after stereotactic radiotherapy. The summed dose distribution was calculated using non-rigid registration. All doses were recalculated to an equivalent dose of 2 Gy per fraction (EQD2). The median follow-up time was 12 months (range 2–52).

Results

The median D_max of the lung in the summed plans was 363 Gy₃ (range 123–590). The median accumulated V20 of the lungs was 15.2%. Seven patients had in the heart and the trachea an accumulated dose ?70 Gy₃, with a median D_max of the heart of 115 Gy₃ and 89 Gy₃ for the trachea. Eight patients had in the esophagus an accumulated dose ?70 Gy₃, with a median accumulated dose of 85 Gy₃. No grade 3–5 toxicity was observed.

Conclusion

Reirradiation of the lung with or after stereotactic radiotherapy is feasible to a median D_max of 363 Gy₃ to the lung, as low toxicity was observed.     

Dosimetric comparisons of helical tomotherapy and step-and-shoot intensity-modulated radiotherapy in nasopharyngeal carcinoma

PURPOSE: The study evaluates and quantifies the potential dosimetric gains of helical tomotherapy (HT) versus step-and-shoot intensity-modulated radiotherapy (SaS-IMRT) for nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: Twenty consecutive NPC patients curatively treated by HT were examined. Each case was planned by HT and SaS-IMRT (ADAC Pinnacle(3)) planning system, respectively. Dose plans were compared using dose volume histograms (DVH), conformity index (CI), homogeneity index (HI), and minimal dose to 1cc (D(min_1cc)) of the planned target volume (PTV) and a comprehensive quality index (CQI) of ten organs at risk (OARs). The prescribed dose/fractionation was 72Gy to the PTV, 64.8Gy to the elective PTV, and 54Gy to the clinically negative neck region. The plan of 54Gy to the PTV (PTV(54)) was used to evaluate the CI and HI in the target. The cumulative doses of the three PTV plans to the OARs were calculated. RESULTS: We observed the HT plans significantly improved the CI (improvement ratio: 11.9+/-5.5%) and HI (improvement ratio: 8.8+/-1.5%) of the PTV(54) compared with SaS-IMRT plans. In addition, the mean/maximal dose of most of the OARs except chiasm was significantly reduced in HT plans, with the CQI of 0.92+/-0.08. A negative result of HT in chiasm was observed but only significantly revealed in cases without skull base infiltration. CONCLUSIONS: A dosimetric gain in CI and HI of PTV and sparing of OARs was significantly obtained in HT versus SaS-IMRT plans in NPC patients. Whether such dosimetric superiority in HT could transfer into clinical advantages needs further investigation.     

Detailed dosimetric evaluation of intensity-modulated radiation therapy plans created for stage C prostate cancer based on a planning protocol

Background

Intensity-modulated radiation therapy (IMRT) has been employed as a precision radiation therapy with higher conformity to the target. Although clinical outcomes have been reported for many investigations, detailed treatment planning results have not been mentioned to date. The aim of this study was to evaluate the dose specifications of our IMRT treatment plans for locally advanced prostate cancer.

Methods

Seventy-seven clinically applied IMRT plans treated between September 2003 and December 2005, in which patients were irradiated with 78?Gy in the prone position, were retrospectively analyzed. Dosimetric data output from dose volume histograms were evaluated in detail.

Results

The mean dose?±?standard deviation, homogeneity index, and conformity index to the planning target volume (PTV) were 78.3?±?0.7?Gy (100.4?±?0.9%), 13.7?±?3.0, and 0.83?±?0.04, respectively. For the clinical target volume, the mean dose was 80.3?±?0.7?Gy (102.9?±?0.9%).The V40, V60, and V70?Gy of the rectal wall were 58.3?±?2.8, 29.6?±?2.7, and 15.2?±?3.0%, respectively. Planning difficulties were encountered in patients whose bowels were displaced downward, as constraints imposed by the bowel position altered the dose index of the PTV. In many cases, additional bowel optimization parameters were required to satisfy constraints for organs at risk. However, major deviation could be avoided by inverse planning with computer optimization.

Conclusion

IMRT allowed the creation of acceptable and practical treatment plans for locally advanced prostate cancer. Reports regarding detailed dosimetric evaluations are mandatory for interpreting clinical outcomes in the future.     

On the performances of different IMRT treatment planning systems for selected paediatric cases

Background

To evaluate the performance of seven different TPS (Treatment Planning Systems: Corvus, Eclipse, Hyperion, KonRad, Oncentra Masterplan, Pinnacle and PrecisePLAN) when intensity modulated (IMRT) plans are designed for paediatric tumours.

Methods

Datasets (CT images and volumes of interest) of four patients were used to design IMRT plans. The tumour types were: one extraosseous, intrathoracic Ewing Sarcoma; one mediastinal Rhabdomyosarcoma; one metastatic Rhabdomyosarcoma of the anus; one Wilm's tumour of the left kidney with multiple liver metastases. Prescribed doses ranged from 18 to 54.4 Gy. To minimise variability, the same beam geometry and clinical goals were imposed on all systems for every patient. Results were analysed in terms of dose distributions and dose volume histograms.

Results

For all patients, IMRT plans lead to acceptable treatments in terms of conformal avoidance since most of the dose objectives for Organs At Risk (OARs) were met, and the Conformity Index (averaged over all TPS and patients) ranged from 1.14 to 1.58 on primary target volumes and from 1.07 to 1.37 on boost volumes. The healthy tissue involvement was measured in terms of several parameters, and the average mean dose ranged from 4.6 to 13.7 Gy. A global scoring method was developed to evaluate plans according to their degree of success in meeting dose objectives (lower scores are better than higher ones). For OARs the range of scores was between 0.75 ± 0.15 (Eclipse) to 0.92 ± 0.18 (Pinnacle³ with physical optimisation). For target volumes, the score ranged from 0.05 ± 0.05 (Pinnacle³ with physical optimisation) to 0.16 ± 0.07 (Corvus).

Conclusion

A set of complex paediatric cases presented a variety of individual treatment planning challenges. Despite the large spread of results, inverse planning systems offer promising results for IMRT delivery, hence widening the treatment strategies for this very sensitive class of patients.     

Impact of robust treatment planning on single- and multi-field optimized plans for proton beam therapy of unilateral head and neck target volumes

Background

Proton beam therapy is promising for the treatment of head and neck cancer (HNC), but it is sensitive to uncertainties in patient positioning and particle range. Studies have shown that the planning target volume (PTV) concept may not be sufficient to ensure robustness of the target coverage. A few planning studies have considered irradiation of unilateral HNC targets with protons, but they have only taken into account the dose on the nominal plan, without considering anatomy changes occurring during the treatment course.

Methods

Four pencil beam scanning (PBS) proton therapy plans were calculated for 8 HNC patients with unilateral target volumes: single-field (SFO) and multi-field optimized (MFO) plans, either using the PTV concept or clinical target volume (CTV)-based robust optimization. The dose was recalculated on computed tomography (CT) scans acquired during the treatment course. Doses to target volumes and organs at risk (OARs) were compared for the nominal plans, cumulative doses considering anatomical changes, and additional setup and range errors in each fraction. If required, the treatment plan was adapted, and the dose was compared with the non-adapted plan.

Results

All nominal plans fulfilled the clinical specifications for target coverage, but significantly higher doses on the ipsilateral parotid gland were found for both SFO approaches. MFO PTV-based plans had the lowest robustness against range and setup errors. During the treatment course, the influence of the anatomical variation on the dose has shown to be patient specific, mostly independent of the chosen planning approach. Nine plans in four patients required adaptation, which led to a significant improvement of the target coverage and a slight reduction in the OAR dose in comparison to the cumulative dose without adaptation.

Conclusions

The use of robust MFO optimization is recommended for ensuring plan robustness and reduced doses in the ipsilateral parotid gland. Anatomical changes occurring during the treatment course might degrade the target coverage and increase the dose in the OARs, independent of the chosen planning approach. For some patients, a plan adaptation may be required.

     

Dose escalation in the radiotherapy of non-small-cell lung cancer with aperture-based intensity modulation and photon beam energy optimization for non-preselected patients

Purpose

To verify the potential of aperture-based intensity-modulated radiotherapy (AB-IMRT) to realize dose escalation plans for non-preselected non-small-cell lung cancer (NSCLC) patients, using photon beam energy optimization.

Methods and materials

Seven cases of NSCLC were retrospectively studied. Clinical reference plans were made at 60 Gy by an experienced dosimetrist. Dose escalation was applied to PTV2, a subvolume within the main PTV1. Escalation plans were optimized by considering beam angles (table and gantry), energy (6 and 23 MV) and weights, for an increasing dose to the PTV2, starting from 66 Gy and keeping 30 fractions.

Results

In five cases, doses over 78 Gy could be achieved before exceeding organs at risk (OARs) standard tolerance. Peripheral overdosages, as well as lung and spinal cord tolerance doses, limited escalation. Means ± SD V_95% parameters were (97.3 ± 0.9)% for PTV1s and (96.7 ± 2.2)% for PTV2s. Doses to OARs were also maintained at acceptable levels. Optimized plans made use of both low- and high-energy beams and had a similar number of monitor units compared to the 60 Gy clinical plans.

Conclusions

The AB-IMRT system can successfully realize dose escalation for a sizeable number of cases. Plans produced contained few large segments, and are applicable to a wide range of tumor volumes and locations.     

Intensity modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) in a patient with left breast cancer and pectus excavatum

Introduction

Pectus excavatum is a frequent anomaly. It represents a challenge for adjuvant radiotherapy in the conservative treatment of breast cancer. Primary objective of this study is to compare dosimetric outcomes, normal tissue complication probability (NTCP), and integral dose using four radiation techniques. Secondary objective is to describe acute toxicity and setup errors.

Methods and materials

A 57-year-old female patient with an inner quadrant, left breast, ductal carcinoma in situ, was identified. Whole breast was prescribed with 50?Gy in 25 fractions. Boost planning target volume (PTV) was prescribed with 60?Gy in 30 fractions for sequential boost (SB) plans or 57.5?Gy in 25 fractions in the simultaneous integrated boost (SIB) plan. All plans were normalized to deliver 47.5?Gy to 95?% of the breast PTV. Daily image-guided radiotherapy (IGRT) was performed. Setup deviations were described.

Results

Constraints were not accomplished for heart when using intensity modulated radiotherapy (IMRT)?+?SB or conformal radiotherapy with three photon fields and SB. Left lung constraint was not achieved by any of the techniques in comparison. IMRT?+?SIB and conformal photons and electrons?+?SB plan were closer to the objective. Integral doses were lower with IMRT for heart and ipsilateral lung; however, it were higher for contralateral breast and lung. Coverage and tumoral conformity indexes were similar for all techniques in comparison. Greater inhomogeneity was observed with the photons and electrons?+?SB. IMRT?+?SIB treatment was administered daily with grade I skin toxicity. The highest setup error was observed in Y direction.

Conclusion

Planning target volume coverage was similar with the four techniques. Homogeneity was superior with both IMRT plans. A good balance between dose constraints for organs at risk, PTV coverage, homogeneity, and NTCP was observed with IMRT?+?SIB. The documented daily setup error justifies the use of online IGRT.     

Ionizing radiation and inhibition of angiogenesis in a spontaneous mammary carcinoma and in a syngenic heterotopic allograft tumor model: a comparative study

Background

To assess inter-observer variability in delineating target volume and organs at risk in benign tumor adjacent to optic tract as a quality assurance exercise.

Methods

We quantitatively analyzed 21 plans made by 11 clinicians in seven CyberKnife centers. The clinicians were provided with a raw data set (pituitary adenoma and meningioma) including clinical information, and were asked to delineate the lesions and create a treatment plan. Their contouring and plans (10 adenoma and 11 meningioma plans), were then compared. In addition, we estimated the influence of differences in contouring by superimposing the respective contours onto a default plan.

Results

The median planning target volume (PTV) and the ratio of the largest to the smallest contoured volume were 9.22 cm³ (range, 7.17 - 14.3 cm³) and 1.99 for pituitary adenoma, and 6.86 cm³ (range 6.05 - 14.6 cm³) and 2.41 for meningioma. PTV volume was 10.1 ± 1.74 cm³ for group 1 with a margin of 1 -2 mm around the CTV (n = 3) and 9.28 ± 1.8 cm³(p = 0.51) for group 2 with no margin (n = 7) in pituitary adenoma. In meningioma, group 1 showed larger PTV volume (10.1 ± 3.26 cm³) than group 2 (6.91 ± 0.7 cm³, p = 0.03). All submitted plan keep the irradiated dose to optic tract within the range of 50 Gy (equivalent total doses in 2 Gy fractionation). However, contours superimposed onto the dose distribution of the default plan indicated that an excessive dose 23.64 Gy (up to 268% of the default plan) in pituitary adenoma and 24.84 Gy (131% of the default plan) in meningioma to the optic nerve in the contours from different contouring.

Conclusion

Quality assurance revealed inter-observer variability in contour delineation and their influences on planning for pituitary adenoma and meningioma near optic tract.