A quantitative treatment planning study evaluating the potential of dose escalation in conformal radiotherapy of the oesophagus

Dosimetric and Radiobiological Comparison of External Beam Radiotherapy Using Simultaneous Integrated Boost Technique for Esophageal Cancer in Different Location

Objectives: To compare treatment plans of intensity modulated radiotherapy (IMRT), volumetric modulated arc radiotherapy (VMAT), and helical tomotherapy (HT) with simultaneous integrated boost (SIB) technique for esophageal cancer (EC) of different locations using dosimetry and radiobiology. Methods: Forty EC patients were planned for IMRT, VMAT, and HT plans, including 10 cases located in the cervix, upper, middle, and lower thorax, respectively. Dose-volume metrics, conformity index (CI), homogeneity index (HI), tumor control probability (TCP), and normal tissue complication probability (NTCP) were analyzed to evaluate treatment plans. Results: HT showed significant improvement over IMRT and VMAT in terms of CI (p = 0.007), HI (p < 0.001), and TCP (p < 0.001) in cervical EC. IMRT yielded more superior CI, HI and TCP compared with VMAT and HT in upper and middle thoracic EC (all p < 0.05). Additionally, V30 (27.72 ± 8.67%), mean dose (1801.47 ± 989.58cGy), and NTCP (Niemierko model: 0.44 ± 0.55%; Lyman-Kutcher-Burman model: 0.61 ± 0.59%) of heart in IMRT were sharply reduced than VMAT and HT in middle thoracic EC. For lower thoracic EC, the three techniques offered similar CI and HI (all p > 0.05). But VMAT dramatically lowered liver V30 (9.97 ± 2.84%), and reduced NTCP of lungs (Niemierko model: 0.47 ± 0.48%; Lyman-Kutcher-Burman model: 1.41 ± 1.07%) and liver (Niemierko model: 0.10 ± 0.08%; Lyman-Kutcher-Burman model: 0.17 ± 0.17%). Conclusions: HT was a good option for cervical EC with complex target coverage but little lungs and heart involvement as it achieved superior dose conformity and uniformity. Due to potentially improving tumor control and reducing heart dose with acceptable lungs sparing, IMRT was a preferred choice for upper and middle thoracic EC with large lungs involvement. VMAT could ameliorate therapeutic ratio and lower lungs and liver toxicity, which was beneficial for lower thoracic EC with little thoracic involvement but being closer to heart and liver. Individually choosing optimal technique for EC in different location will be warranted.

Docetaxel, cisplatin, and 5-fluorouracil combination chemoradiotherapy for patients with cervical esophageal cancer: a single-center retrospective study

BACKGROUND

To evaluate the efficacy of docetaxel, cisplatin, and 5-fluorouracil as combination chemoradiotherapy (DCF-RT) for cervical esophageal cancer (CEC), we performed a retrospective analysis of CEC patients treated by DCF-RT at a single institution.

METHODS

We conducted a single-center retrospective study. Twenty-one patients with CEC who underwent DCF-RT between 1999 and 2017 at our institute were included in this study. Chemotherapy consisted of intravenous docetaxel at 50 mg/m² on day 1, intravenous CDDP at 60 mg/m² on day 1, and intravenous 5-FU at 600 mg/m² on days 1-4, repeated every 4 weeks for two cycles. Among the 21 patients, six were irradiated using three-dimensional conformal RT (3D- conformal RT) and 15 were treated using intensity-modulated RT (IMRT) consisting of 60 Gy in 30 fractions.

RESULTS

The median follow-up period was 49.6 months (range 4.6-97.6). The overall complete response (CR) and local CR rates were 61.9% and 81.0% for all patients, and 76.9% and 84.6% for patients without hypopharyngeal and/or thoracic esophageal invasion, respectively. The 3-year overall survival (OS), progression-free survival (PFS), and local failure-free survival (LFFS) rates were 79.6, 52.4, and 74.7%, respectively. Grade 3-4 leucopenia developed in 12 patients (70.6%), neutropenia developed in 13 patients (81.2%), and mucositis developed in 2 patients (9.5%). There were no treatment-related deaths.

CONCLUSIONS

The 3-year OS and LFFS of patients who underwent DCF-RT were higher than those in the previous studies. Although the high rate of myelosuppression requires careful management, DCF-RT is a safe and effective modality for CEC.

Current trends in multimodality treatment of esophageal and gastroesophageal junction cancer - Review article

PURPOSE

Multimodality treatment has now been widely introduced in the curatively intended treatment of esophageal and gastroesophageal junction cancer. We aim to give an overview of the scientific evidence for the available treatment strategies and to describe which trends that are currently developing.

METHODS

We conducted a review of the scientific evidence for the different curatively intended treatment strategies that are available today. Relevant articles of randomized controlled trials, cohort studies, and meta analyses were included.

RESULTS

After a systematic search of relevant papers we have included 64 articles in the review. The results show that adenocarcinomas and squamous cell carcinomas of the esophagus and gastroesophageal junction are two separate entities and should be analysed and studied as two different diseases. Neoadjuvant treatment followed by surgical resection is the gold standard of the curatively intended treatment today. There is no scientific evidence to support the use of chemoradiotherapy over chemotherapy in the neoadjuvant setting for esophageal or junctional adenocarcinoma. There is reasonable evidence to support definitive chemoradiotherapy as a treatment option for squamous cell carcinoma of the esophagus.

CONCLUSION

The evidence base for curatively intended treatments of esophageal and gastroesophageal junction cancer is not very strong. Several on-going trials have the potential to change the gold standard treatments of today.

Radiobiological evaluation of simultaneously dose-escalated versus non-escalated intensity-modulated radiation therapy for patients with upper thoracic esophageal cancer

OBJECTIVE

To compare the radiobiological response between simultaneously dose-escalated and non-escalated intensity-modulated radiation therapy (DE-IMRT and NE-IMRT) for patients with upper thoracic esophageal cancer (UTEC) using radiobiological evaluation.

METHODS

Computed tomography simulation data sets for 25 patients pathologically diagnosed with primary UTEC were used in this study. DE-IMRT plan with an escalated dose of 64.8 Gy/28 fractions to the gross tumor volume (GTV) and involved lymph nodes from 25 patients pathologically diagnosed with primary UTEC, was compared to an NE-IMRT plan of 50.4 Gy/28 fractions. Dose-volume metrics, tumor control probability (TCP), and normal tissue complication probability for the lung and spinal cord were compared. In addition, the risk of acute esophageal toxicity (AET) and late esophageal toxicity (LET) were also analyzed.

RESULTS

Compared with NE-IMRT plan, we found the DE-IMRT plan resulted in a 14.6 Gy dose escalation to the GTV. The tumor control was predicted to increase by 31.8%, 39.1%, and 40.9% for three independent TCP models. The predicted incidence of radiation pneumonitis was similar (3.9% versus 3.6%), and the estimated risk of radiation-induced spinal cord injury was extremely low (<0.13%) in both groups. Regarding the esophageal toxicities, the estimated grade ≥2 and grade ≥3 AET predicted by the Kwint model were increased by 2.5% and 3.8%. Grade ≥2 AET predicted using the Wijsman model was increased by 14.9%. The predicted incidence of LET was low (<0.51%) in both groups.

CONCLUSION

Radiobiological evaluation reveals that the DE-IMRT dosing strategy is feasible for patients with UTEC, with significant gains in tumor control and minor or clinically acceptable increases in radiation-induced toxicities.

The effect of dose escalation on gastric toxicity when treating lower oesophageal tumours: a radiobiological investigation

PURPOSE

Using radiobiological modelling to estimate normal tissue toxicity, this study investigates the effects of dose escalation for concurrent chemoradiation therapy (CRT) in lower third oesophageal tumours on the stomach.

METHODS AND MATERIALS

10 patients with lower third oesophageal cancer were selected from the SCOPE 1 database (ISCRT47718479) with a mean planning target volume (PTV) of 348 cm(3). The original 3D conformal plans (50 Gy3D) were compared to newly created RapidArc plans of 50 GyRA and 60 GyRA, the latter using a simultaneous integrated boost (SIB) technique using a boost volume, PTV2. Dose-volume metrics and estimates of normal tissue complication probability (NTCP) were compared.

RESULTS

There was a significant increase in NTCP of the stomach wall when moving from the 50 GyRA to the 60 GyRA plans (11-17 %, Wilcoxon signed rank test, p = 0.01). There was a strong correlation between the NTCP values of the stomach wall and the volume of the stomach wall/PTV 1 and stomach wall/PTV2 overlap structures (R = 0.80 and R = 0.82 respectively) for the 60 GyRA plans.

CONCLUSION

Radiobiological modelling suggests that increasing the prescribed dose to 60 Gy may be associated with a significantly increased risk of toxicity to the stomach. It is recommended that stomach toxicity be closely monitored when treating patients with lower third oesophageal tumours with 60 Gy.

A Meta-Analysis of Concurrent Chemoradiotherapy for Advanced Esophageal Cancer

Background

Concurrent chemoradiotherapy is a standard treatment for local advanced esophageal cancer, but the outcomes are controversial. Our goals were to compare the therapeutic effects of concurrent chemoradiotherapy and radiotherapy alone in local advanced esophageal cancer using meta-analysis.

Methods

MEDLINE, EMBASE and the Cochrane library were searched for studies comparing chemoradiotherapy with radiotherapy alone for advanced esophageal cancer. Only randomized controlled trials were included, and extracted data were analyzed with Review Manager Version 5.2. The pooled relative risks (RR) and their 95% confidence intervals (CI) were calculated for statistical analysis.

Results

Nine studies were included. Of 1,135 cases, 612 received concurrent chemoradiotherapy and 523 were treated with radiotherapy alone. The overall response rate (complete remission and partial remission) was 93.4% for concurrent chemoradiotherapy and 83.7% for radiotherapy alone (P = 0.05). The RR values of 1-year, 3-year, and 5-year survival rates were 1.14 (95% CI: 1.04 - 1.24, P = 0.006), 1.66 (95% CI: 1.34 - 2.06, P < 0.001), and 2.43 (95% CI: 1.63 - 3.63, P < 0.001), respectively. The RR value of the merged occurrence rate of acute toxic effects was 2.34 (95% CI: 1.90 - 2.90, P <0.001). There was no difference in the incidence of late toxic effects, which had an RR value of 1.21 (95% CI: 0.96 - 1.54, P = 0.11). The RR level of persistence and recurrence was 0.71 (95% CI: 0.62 - 0.81, P <0.001), and for the distant metastasis rate, the RR value was 0.79 (95% CI: 0.61 - 1.02, P = 0.07).

Conclusions

Concurrent chemoradiotherapy significantly improved overall survival rate, reduced the risk of persistence and recurrence, but had little effect on the primary tumor response, and increased the occurrence of acute toxic effects.

Comparison of Acuros (AXB) and Anisotropic Analytical Algorithm (AAA) for dose calculation in treatment of oesophageal cancer: effects on modelling tumour control probability

AIM

To investigate systematic changes in dose arising when treatment plans optimised using the Anisotropic Analytical Algorithm (AAA) are recalculated using Acuros XB (AXB) in patients treated with definitive chemoradiotherapy (dCRT) for locally advanced oesophageal cancers.

BACKGROUND

We have compared treatment plans created using AAA with those recalculated using AXB. Although the Anisotropic Analytical Algorithm (AAA) is currently more widely used in clinical routine, Acuros XB (AXB) has been shown to more accurately calculate the dose distribution, particularly in heterogeneous regions. Studies to predict clinical outcome should be based on modelling the dose delivered to the patient as accurately as possible.

METHODS

CT datasets from ten patients were selected for this retrospective study. VMAT (Volumetric modulated arc therapy) plans with 2 arcs, collimator rotation ± 5-10° and dose prescription 50 Gy / 25 fractions were created using Varian Eclipse (v10.0). The initial dose calculation was performed with AAA, and AXB plans were created by re-calculating the dose distribution using the same number of monitor units (MU) and multileaf collimator (MLC) files as the original plan. The difference in calculated dose to organs at risk (OAR) was compared using dose-volume histogram (DVH) statistics and p values were calculated using the Wilcoxon signed rank test. The potential clinical effect of dosimetric differences in the gross tumour volume (GTV) was evaluated using three different TCP models from the literature.

RESULTS

PTV Median dose was apparently 0.9 Gy lower (range: 0.5 Gy - 1.3 Gy; p < 0.05) for VMAT AAA plans re-calculated with AXB and GTV mean dose was reduced by on average 1.0 Gy (0.3 Gy -1.5 Gy; p < 0.05). An apparent difference in TCP of between 1.2% and 3.1% was found depending on the choice of TCP model. OAR mean dose was lower in the AXB recalculated plan than the AAA plan (on average, dose reduction: lung 1.7%, heart 2.4%). Similar trends were seen for CRT plans.

CONCLUSIONS

Differences in dose distribution are observed with VMAT and CRT plans recalculated with AXB particularly within soft tissue at the tumour/lung interface, where AXB has been shown to more accurately represent the true dose distribution. AAA apparently overestimates dose, particularly the PTV median dose and GTV mean dose, which could result in a difference in TCP model parameters that reaches clinical significance.

Radiobiological determination of dose escalation and normal tissue toxicity in definitive chemoradiation therapy for esophageal cancer

PURPOSE

This study investigated the trade-off in tumor coverage and organ-at-risk sparing when applying dose escalation for concurrent chemoradiation therapy (CRT) of mid-esophageal cancer, using radiobiological modeling to estimate local control and normal tissue toxicity.

METHODS AND MATERIALS

Twenty-one patients with mid-esophageal cancer were selected from the SCOPE1 database (International Standard Randomised Controlled Trials number 47718479), with a mean planning target volume (PTV) of 327 cm(3). A boost volume, PTV2 (GTV + 0.5 cm margin), was created. Radiobiological modeling of tumor control probability (TCP) estimated the dose required for a clinically significant (+20%) increase in local control as 62.5 Gy/25 fractions. A RapidArc (RA) plan with a simultaneously integrated boost (SIB) to PTV2 (RA62.5) was compared to a standard dose plan of 50 Gy/25 fractions (RA50). Dose-volume metrics and estimates of normal tissue complication probability (NTCP) for heart and lungs were compared.

RESULTS

Clinically acceptable dose escalation was feasible for 16 of 21 patients, with significant gains (>18%) in tumor control from 38.2% (RA50) to 56.3% (RA62.5), and only a small increase in predicted toxicity: median heart NTCP 4.4% (RA50) versus 5.6% (RA62.5) P<.001 and median lung NTCP 6.5% (RA50) versus 7.5% (RA62.5) P<.001.

CONCLUSIONS

Dose escalation to the GTV to improve local control is possible when overlap between PTV and organ-at-risk (<8% heart volume and <2.5% lung volume overlap for this study) generates only negligible increase in lung or heart toxicity. These predictions from radiobiological modeling should be tested in future clinical trials.

Chemoradiotherapy in the management of locally advanced squamous cell carcinoma esophagus: is surgical resection required?

PURPOSE

The present study aims to evaluate benefit of adding surgery to chemoradiotherapy alone in management of carcinoma esophagus.

METHODS

We retrospectively analyzed 45 eligible patients of squamous cell esophageal carcinoma which were enrolled from February 2008 to April 2009. All patients were treated with chemoradiotherapy (50.40 Gy with 40 mg/m(2) of weekly cisplatin). Tumor response was assessed after 6 weeks of treatment. Patients with resectable disease were subjected to surgical resection (arm A) and remaining was kept on regular clinical follow-up (arm B). Overall survival (OS) was selected as the primary endpoint. The secondary end points were disease-free survival (DFS) and clinical toxicities.

RESULTS

Median follow-up was 13.6 months. Pathological complete response was seen in 60.9 % patients in arm A. In arm B, 77.3 % patients attained radiological complete response (p = 0.194). The median OS was 16.4 and 19.1 months (p = 0.388) and median DFS was 5.8 and 4.1 months (p = 0.347) in arm A and B, respectively. The 2-year survival probability was 39.1 and 36.4 % (p = 0.387) in arm A and B, respectively. The recurrence probability was 56.5 % (SE = 5.6 %) and 45.5 % (SE = 4.2 %) (p = 0.328) in arm A and B, respectively. The probability of loco regional recurrence was more in arm B than in arm A (p = 0.002).

CONCLUSIONS

The study suggests that there is no difference in clinical toxicity profiles or survival outcomes with either definitive chemoradiotherapy or chemoradiation followed by surgery in management of locally advanced esophageal cancer.

Definitive chemoradiotherapy for esophageal carcinoma

Radiation therapy plays an important role in the treatment of esophageal cancer. Radiation therapy may be combined with chemotherapy, used as a component of induction therapy, used in the adjuvant setting, or used for palliation of advanced disease. Chemotherapy is also occasionally used as a solitary treatment modality for patients with esophageal cancer. Current treatment protocols include multiple agents, and agents directed against specific molecular targets have been investigated in clinical trials. This article discusses future directions related to the selection of radiation treatment protocols, novel targeted chemotherapeutic agents, and the selection of patients for surgery.

A randomized controlled trial of conventional fraction and late course accelerated hyperfraction three-dimensional conformal radiotherapy for esophageal cancer

We compared the curative and side-effects in esophageal carcinoma treated by conventional fraction (CF) and late course accelerated hyperfraction (LCAF) three-dimensional conformal radiotherapy. Ninety-eight patients were randomly assigned to two different radiotherapy model groups. Fifty patients were treated using CF three-dimensional conformal radiotherapy at a total dose of 60-68 Gy; 2 Gy/F; 5 fractions/week (median 64 Gy), 48 patients were treated with LCAF (First CF-treated at the dose 40 Gy. Later, LCAF-treated 1.5 Gy/F; 2 fractions/day; 21-27 Gy; a total dose of 61-67 Gy; median 64 Gy). The data showed that the 1-, 2- and 3-year-survival rates in LCAF group were 79.2, 56.3, and 43.8%, compared to 74, 54, and 36% in CF group (P = 0.476). The 1-, 2- and 3-year-local control rates in LCAF group were 81.3, 62.5, and 50%, compared to 78, 58, and 42% in CF group (P = 0.454). In CF group, the incidence of radiation-induced esophagitis was lower than that in LCAF group (72 vs. 93.8%; P = 0.008) and there was no significant difference between rates of radiation-induced pneumonitis in CF and LCAF groups (10 vs. 6.25%; P = 0.498). It was concluded that the 1-, 2- and 3-year-local control and survival rates of esophageal carcinoma patients treated with LCAF were slightly better than CF radiotherapy; however, the radiation side-effects in LCAF group were greater than those in CF group.

Volumetric modulated arc therapy planning for distal oesophageal malignancies

OBJECTIVES

Volumetric modulated arc therapy (VMAT) is a novel form of intensity-modulated radiation therapy that allows the radiation dose to be delivered in a single gantry rotation using conformal or modulated fields. The capability of VMAT to reduce heart and cord dose, while maintaining lung receiving 20 Gy <20%, was evaluated for chemoradiation for oesophageal cancer.

METHODS

An optimised forward-planned four-field arrangement was compared with inverse-planned coplanar VMAT arcs with 35 control points for 10 patients with lower gastro-oesophageal tumours prescribed 54 Gy in 30 fractions. Conformal (cARC) and intensity-modulated (VMATi) arcs were considered. Plans were assessed and compared using the planning target volume (PTV) irradiated to 95% of the prescription dose (V95), volumes of lung irradiated to 20 Gy (V20), heart irradiated to 30 Gy (V30), spinal cord maximum dose and van't Riet conformation number (CN). The monitor units per fraction and delivery time were recorded for a single representative plan.

RESULTS

VMATi provided a significant reduction in the heart V30 (31% vs 55%; p=0.02) with better CN (0.72 vs 0.65; p=0.01) than the conformal plan. The treatment delivery was 1 min 28 s for VMAT compared with 3 min 15 s.

CONCLUSION

For similar PTV coverage, VMATi delivers a lower dose to organs at risk than conformal plans in a shorter time, and this has warranted clinical implementation.

Conventional fractionated versus late course accelerated hyperfractionated three-dimensional conformal radiotherapy for esophageal cancer: a randomized controlled trial

AIM: To compare the efficacy and safety of conventional fractionated (CF) versus late course accelerated hyperfractionated (LCAF) three-dimensional conformal radiotherapy (3D-CRT) for esophageal cancer.

METHODS: Ninety-eight patients with esophageal carcinoma were divided into two groups: 55 treated by CF-3D-CRT (a total dose of 60-68 Gy, 2 Gy/F, 5 fractions a week) and 48 by LCAF-3D-CRT (a total dose of 61-67 Gy, first by CF-3D-CRT to a dose of 40 Gy, followed by LCAF-3D-CRT: 1.5 Gy/F, 2 fractions a day, 21-27 Gy).

RESULTS: The 1-, 2-, and 3-year survival rates were 79.2%, 56.3% and 43.8% in the LCAF group, and 74%, 54% and 36% in the CF group, respectively. The 1-, 2-, and 3-year local control rates were 81.3%, 62.5% and 50% in the LCAF group, and 78%, 58% and 42% in the CF group, respectively. The incidence of radiation-induced esophagitis was significantly lower in the CF group than in the LCAF group (72% vs 93.8%, P = 0.008). However, the rate of radiation-induced pneumonitis showed no significant difference between the two groups (10% vs 6.25%, P = 0.498).

CONCLUSION: The 1-, 2- and 3-year local control rates and survival rates of patients with esophageal carcinoma treated by LCAF-3D-CRT are superior to those treated by CF-3D-CRT though the incidence of radiation-induced esophagitis is higher in the LCAF group than in the CF group.

High-dose chemoradiotherapy followed by surgery versus surgery alone in esophageal cancer: a retrospective cohort study

Background

We aimed to assess whether high-dose preoperative chemoradiotherapy (CRT) improves outcome in esophageal cancer patients compared to surgery alone and to define possible prognostic factors for overall survival.

Methods

Hundred-and-seven patients with disease stage IIA - III were treated with either surgery alone (n = 45) or high-dose preoperative CRT (n = 62). The data were collected retrospectively. Sixty-seven patients had adenocarcinomas, 39 squamous cell carcinomas and one undifferentiated carcinoma. CRT was given as three intensive chemotherapy courses by cisplatin 100 mg/m² on day 1 and 5-fluorouracil 1000 mg/m²/day, from day 1 through day 5 as continuous infusion. One course was given every 21 days. The last two courses were given concurrent with high-dose radiotherapy, 2 Gy/fraction and a median dose of 66 Gy. Kaplan-Meier survival analysis with log rank test was used to obtain survival data and Cox Regression multivariate analysis was used to define prognostic factors for overall survival.

Results

Toxicity grade 3 of CRT occurred in 30 (48.4%) patients and grade 4 in 24 (38.7%) patients of 62 patients. One patient died of neutropenic infection (grade 5). Fifty percent (31 patients) in the CRT group did undergo the planned surgery. Postoperative mortality rate was 9% and 10% in the surgery alone and CRT+ surgery groups, respectively (p = 1.0). Median overall survival was 11.1 and 31.4 months in the surgery alone and CRT+ surgery groups, respectively (log rank test, p = 0.042). In the surgery alone group one, 3 and 5 year survival rates were 44%, 24% and 16%, respectively and in the CRT+ surgery group they were 68%, 44% and 29%, respectively. By multivariate analysis we found that age of patient, performance status, alcoholism and > = 4 pathological positive lymph nodes in resected specimen were significantly associated with overall survival, whereas high-dose preoperative CRT was not.

Conclusion

We found no significant survival advantage in esophageal cancer stage IIA-III following preoperative high-dose CRT compared to surgery alone. Patient's age, performance status, alcohol abuse and number of positive lymph nodes were prognostic factors for overall survival.

High-dose definitive concomitant chemoradiotherapy in non-metastatic locally advanced esophageal cancer: toxicity and outcome

This study is a retrospective analysis of high-dose definitive concomitant chemoradiotherapy in locally advanced esophageal cancer in a single institution. The aim of the study was to identify and quantify the toxicity associated with the high-dose treatment and to analyze the outcome of this treatment. Forty-six patients (41 men and 5 women, median age of 67.5 years) with disease stage IIA-III esophageal cancer were treated with high-dose definitive chemoradiotherapy. Thirty patients had squamous cell carcinomas and 16 had adenocarcinomas. The patients were treated with three courses of chemotherapy. Each chemotherapy course consisted of cisplatin 100 mg/m(2), day 1 and 5-Fluorouracil 1000 mg/m(2)/day, day 1-5. One course was given every 3 weeks. Concurrent radiotherapy (66 Gy/33 fractions) was administered during the last two courses of chemotherapy. Toxicity grades three and four were seen in 47.5% and 40% of the patients, respectively. Treatment related mortality occurred in one patient (2.5%) due to neutropenic septicemia. Follow-up time for surviving patients (2/46) was 45 and 112 months. For the entire study population, the median time to local recurrence in the radiotherapy field was 33 months and the median time to distant metastasis was 8.7 months, whereas median overall survival was 10.8 months and median disease-specific survival 11 months. For responders to chemoradiotherapy, the median time to local recurrence was 76 months, the median time to distant metastasis 16.8 months, the median overall survival and the median disease-specific survival for the responders were both 17 months. The 2, 3 and 5-year survival rates were 22%, 15% and 11% for the entire study population, and 31%, 24% and 17% for the responders to chemoradiotherapy, respectively. By multivariate analysis response to chemoradiotherapy and lower disease stage were positive prognostic factors for survival. The results of our study have shown that concurrent high-dose chemoradiotherapy provides long-term local tumor control in locally advanced esophageal cancer. However, toxicities following this high-dose treatment, while manageable, were significant. Survival rates were not improved by high-dose chemoradiotherapy compared with what is reported in previous studies applying lower doses of definitive chemoradiotherapy.

The potential of proton beam radiation therapy in gastrointestinal cancer

A group of Swedish oncologists and hospital physicists have estimated the number of patients in Sweden suitable for proton beam therapy. The estimations have been based on current statistics of tumour incidence, number of patients potentially eligible for radiation treatment, scientific support from clinical trials and model dose planning studies and knowledge of the dose-response relations of different tumours and normal tissues. In gastrointestinal cancers, it is assessed that at least 345 patients, mainly non-resectable rectal cancers, oesophageal and liver cancers, are eligible. Great uncertainties do however exist both in the number of patients with gastrointestinal cancers suitable for radiation therapy, and in the proportion of those where proton beams may give sufficiently better results.

Feasibility of using intensity-modulated radiotherapy to improve lung sparing in treatment planning for distal esophageal cancer

BACKGROUND AND PURPOSE

To evaluate the feasibility whether intensity-modulated radiotherapy (IMRT) can be used to reduce doses to normal lung than three-dimensional conformal radiotherapy (3 DCRT) in treating distal esophageal malignancies.

PATIENTS AND METHODS

Ten patient cases with cancer of the distal esophagus were selected for a retrospective treatment-planning study. IMRT plans using four, seven, and nine beams (4B, 7B, and 9B) were developed for each patient and compared with the 3 DCRT plan used clinically. IMRT and 3 DCRT plans were evaluated with respect to PTV coverage and dose-volumes to irradiated normal structures, with statistical comparison made between the two types of plans using the Wilcoxon matched-pair signed-rank test.

RESULTS

IMRT plans (4B, 7B, 9B) reduced total lung volume treated above 10 Gy (V(10)), 20 Gy (V(20)), mean lung dose (MLD), biological effective volume (V(eff)), and lung integral dose (P<0.05). The median absolute improvement with IMRT over 3DCRT was approximately 10% for V(10), 5% for V(20), and 2.5 Gy for MLD. IMRT improved the PTV heterogeneity (P<0.05), yet conformity was better with 7B-9B IMRT plans. No clinically meaningful differences were observed with respect to the irradiated volumes of spinal cord, heart, liver, or total body integral doses.

CONCLUSIONS

Dose-volume of exposed normal lung can be reduced with IMRT, though clinical investigations are warranted to assess IMRT treatment outcome of esophagus cancers.

Inverse planning in three-dimensional conformal and intensity-modulated radiotherapy of mid-thoracic oesophageal cancer

The aim of this study is to demonstrate the use of inverse planning in three-dimensional conformal radiation therapy (3DCRT) of oesophageal cancer patients and to evaluate its dosimetric results by comparing them with forward planning of 3DCRT and inverse planning of intensity-modulated radiotherapy (IMRT). For each of the 15 oesophageal cancer patients in this study, the forward 3DCRT, inverse 3DCRT and inverse IMRT plans were produced using the FOCUS treatment planning system. The dosimetric results and the planner's time associated with each of the treatment plans were recorded for comparison. The inverse 3DCRT plans showed similar dosimetric results to the forward plans in the planning target volume (PTV) and organs at risk (OARs). However, they were inferior to that of the IMRT plans in terms of tumour control probability and target dose conformity. Furthermore, the inverse 3DCRT plans were less effective in reducing the percentage lung volume receiving a dose below 25 Gy when compared with the IMRT plans. The inverse 3DCRT plans delivered a similar heart dose as in the forward plans, but higher dose than the IMRT plans. The inverse 3DCRT plans significantly reduced the operator's time by 2.5 fold relative to the forward plans. In conclusion, inverse planning for 3DCRT is a reasonable alternative to the forward planning for oesophageal cancer patients with reduction of the operator's time. However, IMRT has the better potential to allow further dose escalation and improvement of tumour control.

Target dose conformity in 3-dimensional conformal radiotherapy and intensity modulated radiotherapy

BACKGROUND AND PURPOSE

Dose conformity to the planning target volume is an important criterion in radiotherapy treatment planning, for which the conformity index is a useful assessment tool. The purpose of this study is to compare the differences in CI for the treatment planning of four cancers including the nasopharynx, oesophagus, lung and prostate.

PATIENTS AND METHODS

Seventy patients with cancers of nasopharynx (30), oesophagus (15), lung (15) and prostate (10) were recruited. Each of these patients was planned with three sets of treatment plans using the FOCUS treatment planning system: the forward and inverse 3DCRT plans and the IMRT plan. The CI was generated for each treatment plan. The mean CI from each cancer patient group was calculated and compared with the other three cancer groups. The mean value of CI was also compared among the three planning methods.

RESULTS

The oesophageal and lung cancers demonstrated relatively higher overall mean CI values (0.64 and 0.62, respectively), whereas that of the nasopharynx and prostate were lower (0.54 and 0.50, respectively). With regards to the planning method groups, the IMRT plans produced the highest overall mean CI (0.62), while those for the forward and inverse 3DCRT were similar (0.57 and 0.55, respectively).

CONCLUSION

For the four selected cancers, oesophageal and lung cancers were easier to conform than the nasopharyngeal and prostate cancers. The IMRT plans were more effective in achieving better dose conformity than that of the 3DCRT.

Elimination of importance factors for clinically accurate selection of beam orientations, beam weights and wedge angles in conformal radiation therapy

A method of simultaneously optimizing beam orientations, beam weights, and wedge angles for conformal radiotherapy is presented. This method removes the need for importance factors by optimizing one objective only, subject to a set of rigid constraints. This facilitates the production of inverse solutions which, without trial-and-error modification of importance factors, precisely satisfy the specified constraints. The algorithm minimizes an objective function which is based upon the single objective to be optimized, but which is forced to an artificially high value when the constraints are not met, so that only satisfactory solutions are allowed. Due to the complex nature of the objective function space, including multiple local minima separated by large regions of plateau, a random search technique equivalent to fast simulated annealing is used for producing inverse plans. To illustrate the novel features of the new algorithm, a simulation is first presented, for the case of a cylindrical phantom. The morphology of the objective function space is shown to be significantly different for the new algorithm, compared to that for a conventional quadratic objective function. Clinical cases for prostate and craniopharyngioma are then presented. For the prostate case, the objective is to reduce irradiated rectal volume. Three-field, four-field, and six-field optimizations, with or without orientation optimization, are shown to provide solutions which are consistent with previously reported plans and class solutions. For the craniopharyngioma case, which involves the use of a high-precision stereotactic conformal technique, the objective is to reduce the irradiated volume of normal brain. Practically feasible beam angles are produced which, compared to a standard plan, provide a small but worthwhile sparing of normal brain. The algorithm is thereby shown to be robust and suitable for clinical application.

Commissioning and quality assurance of the Pinnacle(3) radiotherapy treatment planning system for external beam photons

The commissioning of a Pinnacle(3) treatment planning system is described. Four Elekta linear accelerators were commissioned for external beam photons. Measured data were used to derive parameter values for the Pinnacle(3) beam model by (1). fitting a Monte Carlo model of the accelerator head to measured data and then extracting the parameters for the Pinnacle(3) beam model, and by (2). using the auto-modelling facility within Pinnacle(3). Both of these methods yielded dose distributions in accord with published recommendations. A separate small-field beam model, customized for an in-house compact blocking system, was also created, which satisfied appropriate acceptance criteria for stereotactically guided conformal brain treatments. Inhomogeneous, oblique, asymmetrical and irregular fields were also assessed, with calculated and measured doses agreeing to within +/-3%. Dose-volume histogram calculation was found to be accurate to within +/-5% dose or volume for a grid size of 4 mm x 4 mm x 4 mm, with better accuracy being achieved for finer grids. Isocentric doses were compared between Pinnacle(3)'s collapsed cone convolution algorithm and the Bentley-Milan algorithm within the Target-2 treatment planning system. Dose differences were generally less than 3% in the dose prescribed, with larger values for breast plans, where the Pinnacle(3) algorithm calculated scatter more accurately. Pelvic and thoracic plans were also verified using an anthropomorphic phantom, with local dose differences between calculated and delivered dose of up to 8%, but mainly less than 3%, and with no systematic difference. Ionization chamber verifications using START and RT-01 trial procedures demonstrated differences between calculated and measured doses of less than 2%. Following satisfactory performance in the commissioning process, Pinnacle(3) has now been introduced into routine clinical use.

[Probabilities of controlling tumors and complications (TCP/NTCP) after radiotherapy: methodologic, physical, and biological aspects]

Radiotherapy is aimed at getting the best possible therapeutic ratio (tumor local control versus morbidity). Physicists and radiation oncologists have to evaluate explicitly or implicitly the probability of induced complications to normal surrounding tissues. This is based on published data and clinician's experience. Quantitative methods have been introduced with different models in order to predict the impact of partial or global irradiation on a normal organ. These models correspond to the Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP). These biological models may be useful to evaluate the quality of a treatment planning or for the optimization process. The methodologies used and the clinical data are developed and discussed.

Speed versus accuracy in a fast convolution photon dose calculation for conformal radiotherapy

A convolution dose calculation for megavoltage photon beams is described and the compromise between speed and accuracy examined. The algorithm is suitable for treatment planning optimization, where the need is for a fast, flexible method requiring minimal beam data but providing an accurate result. The algorithm uses a simple tabular beam model, together with a discrete scatter kernel. These beam parameters are fitted either to a measured dose distribution, or to a dose distribution calculated using a more accurate dose calculation algorithm. The calculation is then applied to pelvic and thoracic conformal plans, and the results compared with those provided by a commercial radiotherapy treatment planning system (Pinnacle3, Philips Radiation Oncology Systems, Milpitas, CA), which has been verified against measurements. The calculation takes around 4 s to compute a 100 x 100 mm field, and agreement of the dose-volume histograms with the commercial treatment planning system is to within 5% dose or 8% volume. Use of a grid resolution coarser than 5 x 5 x 5 mm is found to be inaccurate, whereas calculating primary dose on a coarse grid and interpolating is found to increase speed without significantly reducing accuracy. Kernel resolution influences the speed and accuracy, but using 12 discrete points provides a fast result with a limited error. Thus, the algorithm is suitable for optimization applications.

Influence of staging thoracic computed tomography on radiation therapy planning for esophageal carcinoma

Radiation therapy with concurrent chemotherapy is frequently used as definitive treatment for esophageal carcinoma. Although thoracic computed tomography (CT) is widely used in staging esophageal carcinoma, its application to radiation therapy planning has been regarded as optional rather than mandatory. Conventional radiation therapy planning is esophagogram-based rather than CT-based. The treatment port is generated by adding 5 cm to the proximal and distal margins of the tumor-involved segment as seen on esophagogram performed in the treatment position. Historically, a maximum port length of 15 cm was recommended to avoid excessive treatment morbidity. The authors examined the limitations of such a planning protocol by projecting conventional treatment ports onto the thoracic CT of 75 consecutive newly diagnosed cases of nondisseminated esophageal squamous cell carcinoma. The authors assessed the adequacy of coverage of the primary tumor and metastatic nodes, with respect to data from thoracic CT and neck ultrasonography. It was found that up to 38% of T2-T3 tumors and 30% of short-length (< or =5 cm) tumors had metastatic nodes outside the port. The addition of neck ultrasonography led to identification of an additional 5% of patients with nonpalpable nodes outside the port. It is concluded that the frequency of inadequate tumor coverage using an esophagogram-based planning protocol, with a maximum port length of 15 cm, is unacceptably high. Thoracic CT should be a mandatory rather than optional imaging investigation in guiding radiation therapy planning for esophageal cancer.

A comparison of conformal and intensity-modulated techniques for oesophageal radiotherapy

BACKGROUND AND PURPOSE

To investigate the potential of intensity-modulated radiotherapy (IMRT) to reduce lung irradiation in the treatment of oesophageal carcinoma with radical radiotherapy.

MATERIALS AND METHODS

A treatment planning study was performed to compare two-phase conformal radiotherapy (CFRT) with IMRT in five patients. The CFRT plans consisted of anterior, posterior and bilateral posterior oblique fields, while the IMRT plans consisted of either nine equispaced fields (9F), or four fields (4F) with orientations equal to the CFRT plans. IMRT plans with seven, five or three equispaced fields were also investigated in one patient. Treatment plans were compared using dose-volume histograms and normal tissue complication probabilities.

RESULTS

The 9F IMRT plan was unable to improve on the homogeneity of dose to the planning target volume (PTV), compared with the CFRT plan (dose range, 16.9+/-4.5 (1 SD) vs. 12.4+/-3.9%; P=0.06). Similarly, the 9F IMRT plan was unable to reduce the mean lung dose (11.7+/-3.2 vs. 11.0+/-2.9 Gy; P=0.2). Similar results were obtained for seven, five and three equispaced fields in the single patient studied. The 4F IMRT plan provided comparable PTV dose homogeneity with the CFRT plan (11.8+/-3.3 vs. 12.4+/-3.9%; P=0.6), with reduced mean lung dose (9.5+/-2.3 vs 11.0+/-2.9 Gy; P=0.001).

CONCLUSIONS

IMRT using nine equispaced fields provided no improvement over CFRT. This was because the larger number of fields in the IMRT plan distributed a low dose over the entire lung. In contrast, IMRT using four fields equal to the CFRT fields offered an improvement in lung sparing. Thus, IMRT with a few carefully chosen field directions may lead to a modest reduction in pneumonitis, or allow tumour dose escalation within the currently accepted lung toxicity.