Phase II study of preoperative helical tomotherapy for rectal cancer

On the trail of CBCT-guided adaptive rectal boost radiotherapy, does daily delineation require a radiation oncologist?

Introduction

Dose-escalation radiotherapy for rectal tumours is increasingly considered as a non-operative approach, with online-adaptive radiotherapy (oART) supporting this approach by correcting inter-fraction tumour position errors. However, using cone-beam computed tomography (CBCT)-guided oART requires daily target volume delineation by different operators, leading to inter-operator delineation variability and potential dosimetric issues. This study aims to compare and quantify the inter-operator and inter-professional delineation variability of the rectal boost volume on CBCT, including volumes by an automatically delineated oART treatment planning system.

Materials and methods

A rectal boost volume, defined as the primary tumour extended to the entire adjacent rectal wall, was delineated on 10 CBCTs from 5 patients by 15 operators: 4 expert radiation oncologists (ROs), 4 radiation therapists (RTTs) and 7 non-expert ROs. These contours were compared between the different professional groups. A comparison to the average volume of the group (ROs, RTTs, or non-expert ROs) with the lowest delineation variability was also performed for each individual volume including the volume automatically generated by an oART treatment planning system.

Results

Delineation variability was the highest in the superior (range: 2.3-6.0 mm), and inferior (2.3-12.4 mm) directions, compared to the left (0.2-4.4 mm), right (0.3-2.0 mm), anterior (0.1-2.9 mm), and posterior (0.5-4.0 mm) directions. Non-expert ROs, RTTs, and automatic oART volume showed similar ranges of delineation errors when compared to the expert ROs' volume, which was chosen as reference volume since this professional group showed the lowest variability.

Discussion

Expert ROs showed consistent results. Other professional groups exhibit similar variability, comparable to the automatic oART volume. Therefore, RTTs could safely perform the rectal boost delineation without non-expert ROs supervision in the absence of expert ROs during CBCT-based oART. Moreover, these findings provide quantitative data to compute accurate margins for the rectal boost planning target volume in a CBCT-guided oART workflow.

Preoperative Radiotherapy with a Simultaneous Integrated Boost Compared to Chemoradiotherapy for cT3-4 Rectal Cancer: Long-Term Results of a Multicenter Randomized Study

BACKGROUND

Preoperative chemoradiotherapy (CRT) is the standard treatment for T3-4 rectal cancer. Here, we compared image-guided and intensity-modulated RT (IG-IMRT) with a simultaneous integrated boost (SIB) (instead of concomitant chemotherapy) versus CRT in a multi-centric randomized trial.

METHODS

cT3-4 rectal cancer patients were randomly assigned to receive preoperative IG-IMRT 46 Gy/23 fractions plus capecitabine 825 mg/m² twice daily (CRT arm) or IG-IMRT 46 Gy/23 fractions with an SIB to the rectal tumor up to a total dose of 55.2 Gy (RTSIB arm).

RESULTS

A total of 174 patients were randomly assigned between April 2010 and May 2014. Grade 3 acute toxicities were 6% and 4% in the CRT and RTSIB arms, respectively. The mean fractional change in SUVmax at 5 weeks after completion of preoperative RT were -55.8% (±24.0%) and -52.9% (±21.6%) for patients in the CRT arm and RTSIB arm, respectively (p = 0.43). The pathologic complete response rate was 24% with CRT compared to 14% with RTSIB. There were no differences in 5-year overall survival (OS), progression-free survival (PFS) or local control (LC).

CONCLUSIONS

The preoperative RTSIB approach was not inferior to CRT in terms of metabolic response, toxicity, OS, PFS and LC, and could be considered an available option for patients unfit for fluorouracil-based CRT.

Dichloroacetate Radiosensitizes Hypoxic Breast Cancer Cells

Mitochondrial metabolism is an attractive target for cancer therapy. Reprogramming metabolic pathways can potentially sensitize tumors with limited treatment options, such as triple-negative breast cancer (TNBC), to chemo- and/or radiotherapy. Dichloroacetate (DCA) is a specific inhibitor of the pyruvate dehydrogenase kinase (PDK), which leads to enhanced reactive oxygen species (ROS) production. ROS are the primary effector molecules of radiation and an increase hereof will enhance the radioresponse. In this study, we evaluated the effects of DCA and radiotherapy on two TNBC cell lines, namely EMT6 and 4T1, under aerobic and hypoxic conditions. As expected, DCA treatment decreased phosphorylated pyruvate dehydrogenase (PDH) and lowered both extracellular acidification rate (ECAR) and lactate production. Remarkably, DCA treatment led to a significant increase in ROS production (up to 15-fold) in hypoxic cancer cells but not in aerobic cells. Consistently, DCA radiosensitized hypoxic tumor cells and 3D spheroids while leaving the intrinsic radiosensitivity of the tumor cells unchanged. Our results suggest that although described as an oxidative phosphorylation (OXPHOS)-promoting drug, DCA can also increase hypoxic radioresponses. This study therefore paves the way for the targeting of mitochondrial metabolism of hypoxic cancer cells, in particular to combat radioresistance.

Dose-time fractionation schedules of preoperative radiotherapy and timing to surgery for rectal cancer

Chemoradiotherapy (CRT) is extensively used prior to surgery for rectal cancer to provide significantly better local control, but the radiotherapy (RT), as the other component of CRT, has been subject to less interest than the drug component in recent years. With considerable developments in RT, the use of advanced techniques, such as intensity-modulated radiotherapy (IMRT) in rectal cancer, is garnering more attention nowadays. The radiation dose can be better conformed to the target volumes with possibilities for synchronous integrated boost without increased complications in normal tissue. Hopefully, both local recurrence and toxicities can be further reduced. Although those seem to be of interest, many issues remain unresolved. There is no international consensus regarding the radiation schedule for preoperative RT for rectal cancer. Moreover, an enormous disparity exists regarding the RT delivery. With the advent of IMRT, variations will likely increase. Moreover, time to surgery is also quite variable, as it depends upon the indication for RT/CRT in the clinical practices. In this review, we discuss the options and problems related to both the dose-time fractionation schedule and time to surgery; furthermore, it addresses the research questions that need answering in the future.

Concomitant dose escalation with image-guided Tomotherapy in locally advanced mid-low rectal cancer: a single-center study

Purpose

The purpose of this study was to evaluate the efficacy and toxicity of concomitant dose-escalated Tomotherapy in locally advanced mid–low rectal cancer.

Patients and methods

Patients with locally advanced (T3/T4 or N+), low–mid (≤10 cm from anal verge) rectal carcinoma treated with neoadjuvant chemoradiotherapy followed by surgery between May 2012 and October 2017 in Peking Union Medical College Hospital were included in this study. A dose of 45/50 Gy in 25 fractions was delivered to the pelvis with Tomotherapy, and 55 Gy was prescribed for the primary tumor with a simultaneous, integrated boost. Megavolt computed tomography was performed before every delivery. The concurrent chemotherapy regimen included capecitabine alone and XELOX.

Results

A total of 141 patients were enrolled; 129 patients (91.5%) had stage cT3 or cT4, and 121 patients (85.8%) had positive lymph nodes. The location of the tumors was in the lower rectum in 88 patients (62.4%). After neoadjuvant chemoradiotherapy, 113 patients (80.1%) underwent sphincter-preserving resection. Downstaging was observed in 121 patients (85.8%), including 80 patients (56.7%) with T downstaging and 101 patients (83.5%) with N downstaging. Thirty-two patients (22.7%) obtained pathological complete response (pCR). The median follow-up was 38.5 months (range, 9.3–73.6 months). Only 36 patients (25.5%) experienced treatment failure, including distant metastasis in 29 patients (20.6%) and pelvic recurrent in 7 patients (5.0%). The estimated 5-year overall survival (OS), disease-free survival (DFS), and local control (LC) rates of patients were 75.1%, 70.9%, and 95.5%, respectively. pCR was an independent prognostic factor for DFS (HR 0.13, 95% CI: 0.02–0.93, P = 0.043), but it did not improve OS or LC. Grade 3 or greater acute leukopenia and diarrhea rates were 5.7% and 7.8%, respectively, and 15 patients (10.6%) developed postoperative complications.

Conclusion

This study indicates that neoadjuvant, image-guided Tomotherapy with 55 Gy boosted to the primary tumor was well tolerated and resulted in high rates of sphincter-preserving surgery, pCR, LC, and DFS for locally advanced rectal cancer.

The first thermic treatment predicts following chemoradiation response with concurrent thermal therapy for the treatment of rectal cancer

The present study aimed to evaluate whether the neoadjuvant chemoradiation response with concurrent thermal therapy for the treatment of rectal cancer can be predicted following the first thermic treatment. Eighty patients with primary rectal adenocarcinoma (≤12 cm from the anal verge) were included in this study. Fifty-four received surgery and pathological response was evaluated. Intensity-modulated radiotherapy was administered conventionally once daily 5 times/week. Neoadjuvant radiotherapy consisted of 50 Gy delivered to the planning target volume in 25 fractions. Concurrent neoadjuvant chemotherapy was delivered in 5-day courses. Capecitabine was administered orally at 1,700 mg/m²/day for 5 days/week. Thermic treatment was performed using the Thermotron-RF 8 and administered once/week for 5 weeks with 50 min irradiation. Patients with a gross tumor volume (GTV) ≤32 cm³ and a radiofrequency (RF) output difference (RO difference) ≥77 Watt/min exhibited pathological complete response (pCR) and CR rates of 50 and 75%, respectively. Those with a GTV ≥80 cm³ and a RO difference ≥77 Watt/min exhibited pCR and CR rates of 42.9 and 42.9%, respectively. The changes in the skin temperature during RF treatment in patients with pCR with a RO difference ≥77 Watt/min increased significantly compared with those of other outcomes, and progressive disease. These data suggest a strategy for predicting which patients will respond best following the first thermic treatment. The results identified that the group of patients with a GTV ≤32 cm³ and a RO difference ≥77 Watt/min (outputable/heatable patients) may respond best.

Preoperative intensity-modulated radiotherapy with a simultaneous integrated boost combined with Capecitabine in locally advanced rectal cancer: short-term results of a multicentric study

BACKGROUND

Preoperative radiotherapy (RT) in combination with fluoropyrimidine-based chemotherapy (CT) is the standard of care in patients with locally advanced, T3-T4 N0-2, rectal cancer (LARC). Given the correlation between RT dose-tumor response and the prognostic role of the tumor regression grade (TRG), treatment intensification represents an area of active investigation. The aim of the study was to analyze the role of RT dose-intensification in the preoperative treatment of LARC in terms of feasibility, efficacy and toxicity.

METHODS

We retrospectively analyzed patients with LARC treated with intensity-modulated radiotherapy (IMRT) and simultaneous integrated boost (SIB) at five Italian radiation oncology centers. Concurrent Capecitabine was administered. Treatment response was evaluated in terms of disease down-staging and TRG. Acute toxicity was evaluated according to the CTC-AE 4.0 scale.

RESULTS

A total of 76 patients were identified for this analysis. A dose of 45 Gy was prescribed to the entire mesorectum and pelvic lymph nodes with a median SIB dose of 54 Gy (range 52.5-57.5) to the tumor and corresponding mesorectum. Overall, 74/76 (97.4%) patients completed the planned RT, whereas 64/76 (84.2%) patients completed the prescribed CT. Eight (10.5%) patients developed grade 3-4 acute toxicity. Overall, 72/76 patients underwent surgery. The tumor and nodal down-staging was documented in 51 (70.8%) and 43 (67%) patients, respectively. Twenty (27.8%) patients obtained a pathologic complete response. Surgical morbidity was reported in 13/72 patients (18.1%).

CONCLUSIONS

Although retrospective in design, this study indicates that IMRT-SIB with a dose range of 52.5-57.5 Gy (median 54 Gy) and concomitant Capecitabine appears feasible, well tolerated and effective in terms of disease down-staging and pathological complete response. Long-term toxicity and the impact on disease control and patient survival will be evaluated with a longer follow-up time.

TRIAL REGISTRATION

NA.

Chemoradiotherapy and concurrent radiofrequency thermal therapy to treat primary rectal cancer and prediction of treatment responses

The present study aimed to evaluate a previously reported predictive formula of output-limiting symptoms induced by radiofrequency (RF) to determine the efficacy of this neoadjuvant chemoradiation (NACR) and concurrent RF thermal therapy. The present study included 81 consecutive patients with confirmed diagnoses of rectal adenocarcinoma that was localized in the mid-low rectum (up to 12 cm from the anal verge) who received NACR [intensity-modulated radiotherapy (IMRT), 50 Gy/25 fractions, capecitabine 1,700 mg/m2/day for 5 days/week)] with concurrent thermal therapy (Thermotron-RF8, once a week for 5 weeks with 50 min irradiation). Patients with progressive disease (PD) did not receive RF outputs higher than the predicted value. Some patients who were predicted to receive more output in fact received more than the predicted output. In patients who were predicted to receive moderately higher outputs, 37.5% of the patients experienced pathological complete responses, which was the highest rate, while in those who did not receive more than the predicted output, 66.7% of the patients experienced PD, which was the highest rate in the present study. We speculate that RF thermal therapy may offset the chemoradiation effects in some patients. Adding thermal therapy as a multimodality therapy to NACR potentially affects patients with lower predicted outputs and actual observed outputs slightly higher than the predictive value. Our predictive equation for initial energy output, in which output‑limiting symptoms can be used to predict treatment efficacy, consequently, can be used to decide whether to continue this treatment modality.

A novel strategy of radiofrequency hyperthermia (neothermia) in combination with preoperative chemoradiotherapy for the treatment of advanced rectal cancer: a pilot study

The safety of weekly regional hyperthermia performed with 8 MHz radiofrequency (RF) capacitive heating equipment has been established in rectal cancer. We aimed to standardize hyperthermia treatment for scientific evaluation and for assessing local tumor response to RF hyperthermia in rectal cancer. Forty-nine patients diagnosed with rectal adenocarcinoma were included in the study. All patients received chemoradiation with intensity-modulated radiation therapy 5 days/week (dose, 50 Gy/25 times) concomitant with 5 days/week for five times of capecitabine (1700 mg/m(2) per day) and once a week for five times of 50 min irradiations by an 8 MHz RF capacitive heating device. Thirty-three patients underwent surgery 8 weeks after treatment. Three patients did not undergo surgery because of progressive disease (PD) and 13 refused. Eight (16.3%) patients had a pathological complete response (ypCR) after surgery. Among patients without surgery, 3 (6.1%) had clinical complete response (CR) and 3 (6.1%) had local CR but distant PD (CRPD). Ninety percent of ypCR + CR patients were shown in 6.21 W min(-1) m(-2) /treatment or higher group of average total accumulated irradiation output with 429°C min(-1) m(-2) or higher group of total accumulated thermal output. However, a patient with CRPD was in the higher total accumulated thermal output group. We propose a new quantitative parameter for the hyperthermia and demonstrated that patients can benefit from mild irradiation with mild temperature. Using these parameters, the exact output, optimal thermal treatment, and contraindications or indications of this modality could be determined in a multi-institutional, future study.

Advances in radiotherapy delivery for rectal cancer: a European perspective

Preoperative chemoradiotherapy and radiotherapy with an integrated boost offer excellent local control rates in patients with rectal cancer. The introduction of intensity-modulated radiotherapy and image-guided radiotherapy has drastically improved the tolerance of these treatments. The new challenge is developing organ-preserving strategies and curative treatments for medically inoperable patients. Contact radiotherapy seems efficient for small tumors. Tumor hypoxia limits the success of radiotherapy for locally advanced cancers. Modulation of the L-arginine/iNOS pathway and implementation of hypoxia imaging in radiotherapy planning may overcome this hurdle.

Breast conserving treatment for breast cancer: dosimetric comparison of sequential versus simultaneous integrated photon boost

BACKGROUND

Breast conserving surgery followed by whole breast irradiation is widely accepted as standard of care for early breast cancer. Addition of a boost dose to the initial tumor area further reduces local recurrences. We investigated the dosimetric benefits of a simultaneously integrated boost (SIB) compared to a sequential boost to hypofractionate the boost volume, while maintaining normofractionation on the breast.

METHODS

For 10 patients 4 treatment plans were deployed, 1 with a sequential photon boost, and 3 with different SIB techniques: on a conventional linear accelerator, helical TomoTherapy, and static TomoDirect. Dosimetric comparison was performed.

RESULTS

PTV-coverage was good in all techniques. Conformity was better with all SIB techniques compared to sequential boost (P = 0.0001). There was less dose spilling to the ipsilateral breast outside the PTVboost (P = 0.04). The dose to the organs at risk (OAR) was not influenced by SIB compared to sequential boost. Helical TomoTherapy showed a higher mean dose to the contralateral breast, but less than 5 Gy for each patient.

CONCLUSIONS

SIB showed less dose spilling within the breast and equal dose to OAR compared to sequential boost. Both helical TomoTherapy and the conventional technique delivered acceptable dosimetry. SIB seems a safe alternative and can be implemented in clinical routine.

Helical tomotherapy for cancer treatment: a rapid health technology assessment

OBJECTIVES

Helical tomotherapy (HT) can be applied to treat complex malignant cancer with high-precise radiotherapy, and it can reduce the damage to normal tissues and improve treatment effects. But the procurement of HT must be approved by relevant departments of administration affairs. This study, appointed by the National Health and Family Planning Commission of China and undertook by the National Health Development Research Center and the Chinese Evidence-Based Medicine Centre, was aimed to rapidly assess the effectiveness, safety, costs, and applicability of HT, so as to provide currently available best evidence for decision-makers of health policies.

METHODS

We electronically searched databases including PubMed, EMbase, The Cochrane Library, CNKI, WanFang Data, VIP, CBM, and other professional websites. Two reviewer independently screened literature according to the inclusion and exclusion criteria, extracted data, assessed quality, and then performed descriptive analysis.

RESULTS

(i) We finally included 150 studies, encompassing 5 HTAs, 18 CCTs, and 127 observational studies. (ii) The included HTAs were published during 2006-2009, providing fairly less evidence of low quality and the results of 145 primary studies showed that: HT had been used mainly in the treatments of 14 kinds of cancer, with low total toxicity and high survival rates. Although the quality of the included studies was poor, there was much evidence about prostate cancer, head and neck cancer, nasopharynx cancer, cervical cancer, lung cancer and liver cancer, with enough sample and fairly reliable results in HT efficacy and safety. And (iii) a total of 56 clinical trials were registered in Clinicaltrials.gov, most of which were registered by the occident. Among them, 9 were completed but the results had not been published yet.

CONCLUSIONS

The evidence of this study showed that, HT is safe and effective in clinic. But the abovementioned conclusion needs to be verified by conducting more high-quality studies with long-term follow-up. The costs of HT in procurement, maintenance, and application are high; and the skills, training, and qualification of operators are required. We suggest that the procurement of HT should be reduced; it should be allocated rationally and effectively used after comprehensive assessment in China's cancer epidemiology characteristics, health resource allocation, disease burden, medical service level, etc.; and also high-quality studies with long-term follow-up should be financially supported on the basis of establishing projects, so as to provide local evidence and consistently guide and improve scientific decision-making.

Helical tomotherapy combined with capecitabine in the preoperative treatment of locally advanced rectal cancer

The aim of this study was to evaluate the efficacy of helical tomotherapy plus capecitabine as a preoperative chemoradiotherapy (CRT) in patients with locally advanced rectal cancer (LARC). Thirty-six LARC patients receiving preoperative CRT were analyzed. Radiotherapy (RT) consisted of 45 Gy to the regional lymph nodes and simultaneous-integrated boost (SIB) 50.4 Gy to the tumor, 5 days/week for 5 weeks. Chemotherapy consisted of capecitabine 850 mg/m(2), twice daily, during the RT days. Patients underwent surgery 6-8 weeks after completion of CRT. Information was collected for patient characteristics, treatment response, and acute and late toxicities. Grade 3/4 (G3+) toxicities occurred in 11.1% of patients (4/36). Sphincter preservation rate was 85.2% (23/27). Five patients (14.3%) achieved pathological complete response. Tumor, nodal, and ypT0-2N0 downstaging were noted in 60% (21/35), 69.6% (16/23), and 57.1% (20/35). Tumor regression grade 2~4 was achieved in 28 patients (80%). After a median follow-up time of 35 months, the most common G3+ late morbidity was ileus and fistula (5.7%, 2/35). The study showed that capecitabine plus helical tomotherapy with an SIB is feasible in treatment of LARC. The treatment modality can achieve a very encouraging sphincter preservation rate and a favorable ypT0-2N0 downstaging rate without excessive toxicity.

Advances in radiotherapy and targeted therapies for rectal cancer

The last decade witnessed a significant progress in understanding the biology and immunology of colorectal cancer alongside with the technical innovations in radiotherapy. The stepwise implementation of intensity-modulated and image-guided radiation therapy by means of megavolt computed tomography and helical tomotherapy enabled us to anatomically sculpt dose delivery, reducing treatment related toxicity. In addition, the administration of a simultaneous integrated boost offers excellent local control rates. The novel challenge is the development of treatment strategies for medically inoperable patient and organ preserving approaches. However, distant control remains unsatisfactory and indicates an urgent need for biomarkers that predict the risk of tumor spread. The expected benefit of targeted therapies that exploit the tumor genome alone is so far hindered by high cost techniques and pharmaceuticals, hence hardly justifying rather modest improvements in patient outcomes. On the other hand, the immune landscape of colorectal cancer is now better clarified with regard to the immunosuppressive network that promotes immune escape. Both N2 neutrophils and myeloid-derived suppressor cells (MDSC) emerge as useful clinical biomarkers of poor prognosis, while the growing list of anti-MDSC agents shows promising ability to boost antitumor T-cell immunity in preclinical settings. Therefore, integration of genetic and immune biomarkers is the next logical step towards effective targeted therapies in the context of personalized cancer treatment.

Preoperative intensity-modulated and image-guided radiotherapy with a simultaneous integrated boost in locally advanced rectal cancer: report on late toxicity and outcome

BACKGROUND AND PURPOSE

The addition of chemotherapy to preoperative radiotherapy has been established as the standard of care for patients with cT3-4 rectal cancer. As an alternative strategy, we explored intensity-modulated and image-guided radiotherapy (IMRT-IGRT) with a simultaneous integrated boost (SIB) in a prospective phase II study. Here, we report outcome and late toxicity after a median follow-up of 54 months.

METHODS AND MATERIALS

A total of 108 patients were treated preoperatively with IMRT-IGRT, delivering a dose of 46 Gy in fractions of 2 Gy. Patients (n=57) displaying an anticipated circumferential resection margin (CRM) of less than 2mm based on magnetic resonance imaging received a SIB to the tumor up to a total dose of 55.2 Gy.

RESULTS

The absolute incidence of grade ≥3 late gastrointestinal and urinary toxicity was 9% and 4%, respectively, with a 13% rate of any grade ≥3 late toxicity. The actuarial 5-year local control (LC), progression-free survival (PFS) and overall survival (OS) were 97%, 57%, and 68%. On multivariate analysis, R1 resection and pN2 disease were associated with significantly impaired OS.

CONCLUSIONS

The use of preoperative IMRT-IGRT with a SIB resulted in a high 5-year LC rate and non-negligible late toxicity.

Future directions in combined modality therapy for rectal cancer: reevaluating the role of total mesorectal excision after chemoradiotherapy

Most patients who develop rectal cancer present with locoregionally advanced (T3 or node-positive) disease. The standard management of locoregionally advanced rectal cancer is neoadjuvant concurrent chemoradiotherapy (nCRT), followed by radical resection (low-anterior resection or abdominoperineal resection with total mesorectal excision). Approximately 15% of patients can have a pathologic complete response (pCR) at the time of surgery, indicating that some patients can have no detectable residual disease after nCRT. The actual benefit of surgery in this group of patients is unclear. It is possible that omission of surgery in these patients, termed selective nonoperative management, can limit the toxicities associated with standard, multimodal combined modality therapy without compromising disease control. In this review, we discuss the clinical experiences to date using selective nonoperative management and various attempts at escalation of nCRT to improve the number of patients who have a pCR. We also explore several clinical, laboratory, imaging, histopathologic, and genetic biomarkers that have been tested as tools to predict which patients are most likely to have a pCR after nCRT.

Integrated peripheral boost in preoperative radiotherapy for the locally most advanced non-resectable rectal cancer patients

BACKGROUND AND PURPOSE

Few studies have explored the potential clinical advantages of dose escalation and integrated boosts for patients with non-resectable locally advanced rectal cancer. The possibility of escalating dose to non-resectable regions in these patients was the aim of this study.

PATIENTS AND METHODS

Seven patients with locally very advanced rectal tumours (sacrum overgrowth or growth into pelvic side walls) were evaluated. Intensity modulated photon and pencil beam scanning proton plans with simultaneously integrated boosts (45 Gy to elective lymph nodes, 50 Gy to tumour and 62.5 Gy to boost area in 25 fractions) were compared.

RESULTS

Target coverage was achieved with both photon and proton plans. Estimated risks of acute side effects put the two patients with the largest tumours at unacceptable risk for intestinal toxicity, regardless of modality. The remaining five patients had beneficial sparing of dose to the small intestine with protons.

CONCLUSIONS

Adding boost to areas where rectal tumours infiltrate adjacent non-resectable organs is an attractive option which appears possible using both photon and proton irradiation. Proton plans reduced dose to organs at risk. Integrated peripheral boosts should be considered more frequently in these very advanced tumours.

Implementation of HybridArc treatment technique in preoperative radiotherapy of rectal cancer: dose patterns in target lesions and organs at risk as compared to helical Tomotherapy and RapidArc

Purpose

HybridArc is a novel treatment technique blending aperture-enhanced optimized arcs with discrete IMRT-elements, allowing selection of arcs with a set of static IMRT-beams. This study compared this new technique to helical Tomotherapy, and RapidArc, in preoperative radiotherapy of rectal cancer.

Material and methods

Twelve rectal cancer patients treated consecutively with Tomotherapy Hi-Art II system were simulated with HybridArc and RapidArc. Treatment plans were designed to deliver homogeneous dose of 46.0Gy to mesorectum and draining lymph nodes, with a simultaneous-integrated-boost to the primary tumor up to a total dose of 55.2Gy. Planning objectives were 95% of prescribed dose to 95% of PTVs, while minimizing the volume of small bowel receiving more than 15Gy (V15) and the mean bladder dose. Dose gradient towards simultaneous-integrated-boost (GI), calculated by dividing the volume receiving more then 52.4Gy (95% of PTV55.2Gy)to the volume of PTV55.2Gy, was kept below 1.5. Mean beam-on time and amount of MUs were also analyzed.

Results

PTV swere adequately covered by all plans. Significant advantage was found for Tomotherapy in sparing small bowel (V15 = 112.7cm³SD73.4cm³) compared to RapidArc (133.4cm³SD75.3cm³) and HybridArc (143.7cm³SD74.4cm³) (p < 0.01). The mean bladder dose was better with RapidArc (20.6GySD2.2Gy) compared to HybridArc (24.2Gy SD4.3Gy) and Tomotherapy (23.0GySD4.7Gy) (p < 0.01). The mean beam-on time was significantly lower (p < 0.01) for HybridArc (2.7min SD0.8) and RapidArc (2.5min SD0.5) compared to Tomotherapy (11.0min SD0.7). The total amount of MUs was significantly (p < 0.01) lower for RapidArc (547SD44)compared to HybridArc (949 SD153).

Conclusions

HybridArc is a feasible solution for preoperative RT with a simultaneous-integrated-boost in rectal cancer patients. It achieved similar PTV coverage with significant lower beam-on time, but less efficient in sparing small bowel and bladder compared to Tomotherapy and RapidArc. The added value of HybridArc is that the treatment modality can be implemented on every LINAC equipped with Dynamic-Conform-Arc and IMRT treatment techniques, while maintaining the same QA-schemes.

Short course radiotherapy with simultaneous integrated boost for stage I-II breast cancer, early toxicities of a randomized clinical trial

Background

TomoBreast is a unicenter, non-blinded randomized trial comparing conventional radiotherapy (CR) vs. hypofractionated Tomotherapy (TT) for post-operative treatment of breast cancer. The purpose of the trial is to compare whether TT can reduce heart and pulmonary toxicity. We evaluate early toxicities.

Methods

The trial started inclusion in May 2007 and reached its recruitment in August 2011. Women with stage T1-3N0M0 or T1-2N1M0 breast cancer completely resected by tumorectomy (BCS) or by mastectomy (MA) who consented to participate were randomized, according to a prescribed computer-generated randomization schedule, between control arm of CR 25x2 Gy/5 weeks by tangential fields on breast/chest wall, plus supraclavicular-axillary field if node-positive, and sequential boost 8x2 Gy/2 weeks if BCS (cumulative dose 66 Gy/7 weeks), versus experimental TT arm of 15x2.8 Gy/3 weeks, including nodal areas if node-positive and simultaneous integrated boost of 0.6 Gy if BCS (cumulative dose 51 Gy/3 weeks). Outcomes evaluated were the pulmonary and heart function. Comparison of proportions used one-sided Fisher's exact test.

Results

By May 2010, 70 patients were randomized and had more than 1 year of follow-up. Out of 69 evaluable cases, 32 were assigned to CR (21 BCS, 11 MA), 37 to TT (20 BCS, 17 MA). Skin toxicity of grade ≥1 at 2 years was 60% in CR, vs. 30% in TT arm. Heart function showed no significant difference for left ventricular ejection fraction at 2 years, CR 4.8% vs. TT 4.6%. Pulmonary function tests at 2 years showed grade ≥1 decline of FEV1 in 21% of CR, vs. 15% of TT and decline of DLco in 29% of CR, vs. 7% of TT (P = 0.05).

Conclusions

There were no unexpected severe toxicities. Short course radiotherapy of the breast with simultaneous integrated boost over 3 weeks proved feasible without excess toxicities. Pulmonary tests showed a slight trend in favor of Tomotherapy, which will need confirmation with longer follow-up of patients.

Trail registration

ClinicalTrials.gov NCT00459628

Management of local rectal cancer: evidence, controversies and future perspectives in radiotherapy

SUMMARY Rectal cancer comprises approximately 25% of all primary colorectal cancers. The optimal diagnostic and treatment approach for this heterogeneous malignancy is still contentious, and improvements in general multidisciplinary management are required. During recent years a number of randomized studies led by European investigators have shown optimization in preoperative staging, improvements in surgical technique and the histopathological assessment of the resected specimen, and the benefit of combined modality treatment. The main recommendations and the trends in research on radiotherapy and integrated treatments will be summarized with an overview on some relevant points about imaging and pathological staging.

Three-dimensional patient setup errors at different treatment sites measured by the Tomotherapy megavoltage CT

BACKGROUND AND PURPOSE

Reduction of interfraction setup uncertainty is vital for assuring the accuracy of conformal radiotherapy. We report a systematic study of setup error to assess patients' three-dimensional (3D) localization at various treatment sites.

PATIENTS AND METHODS

Tomotherapy megavoltage CT (MVCT) images were scanned daily in 259 patients from 2005-2008. We analyzed 6,465 MVCT images to measure setup error for head and neck (H&N), chest/thorax, abdomen, prostate, legs, and total marrow irradiation (TMI). Statistical comparisons of the absolute displacements across sites and time were performed in rotation (R), lateral (x), craniocaudal (y), and vertical (z) directions.

RESULTS

The global systematic errors were measured to be less than 3 mm in each direction with increasing order of errors for different sites: H&N, prostate, chest, pelvis, spine, legs, and TMI. The differences in displacements in the x, y, and z directions, and 3D average displacement between treatment sites were significant (p < 0.01). Overall improvement in patient localization with time (after 3-4 treatment fractions) was observed. Large displacement (> 5 mm) was observed in the 75(th) percentile of the patient groups for chest, pelvis, legs, and spine in the x and y direction in the second week of the treatment.

CONCLUSION

MVCT imaging is essential for determining 3D setup error and to reduce uncertainty in localization at all anatomical locations. Setup error evaluation should be performed daily for all treatment regions, preferably for all treatment fractions.

Characterisation of rectal motion during neo-adjuvant radiochemotherapy for rectal cancer with image-guided tomotherapy: implications for adaptive dose escalation strategies

BACKGROUND

Interest in boosting the dose to the tumour during neo-adjuvant radiochemotherapy for rectal cancer is ever increasing, especially within the frame of adaptive radiotherapy. Rectal motion remains a potentially important obstacle to the full exploitation of this approach and needs to be carefully investigated.

MATERIAL AND METHODS

The main purposes of this work were to: a) quantify rectal motion on all fractions of a treatment course; and b) assess margins for adaptive boosting in the second part of the treatment in order to benefit of tumour reduction during treatment. Ten consecutive patients treated with image-guided tomotherapy (41.4 Gy, 18 fractions) were selected. The cranial half of the rectum (subject to motion) was contoured by a single observer on daily MVCTs. The variations of rectal volume and of the envelope of rectum positions were investigated (169 MVCTs). The impact of applying different margins to the rectum in including all its possible positions was also investigated when considering the planning kVCT, the first fraction MVCT, the half-treatment MVCT or the median rectal contours of the whole or second half of treatment as reference volumes.

RESULTS

Rectal volume reduced during treatment in all patients, with a significant time-trend in 6/10 patients. The median values of the envelope volumes were 129 cm(3) and 87 cm(3) in the first and second half of the treatment, respectively. On average, 95% of the rectal envelope was included by an isotropic expansion of 12 mm and 5 mm of the median contours when considering the whole or the second half of the treatment, respectively.

CONCLUSION

A significant reduction of rectal volume was found in the second part of the treatment where rectal mobility was limited. As a consequence, relatively small margins may be used around the residual tumour volume when adaptive boost is delivered in the second half of the treatment.

Phase II study of preoperative helical tomotherapy with a simultaneous integrated boost for rectal cancer

PURPOSE

The addition of concomitant chemotherapy to preoperative radiotherapy is considered the standard of care for patients with cT3-4 rectal cancer. The combined treatment modality increases the complete response rate and local control (LC), but has no impact on survival or the incidence of distant metastases. In addition, it is associated with considerable toxicity. As an alternative strategy, we explored prospectively, preoperative helical tomotherapy with a simultaneous integrated boost (SIB).

METHODS AND MATERIALS

A total of 108 patients were treated with intensity-modulated and image-guided radiotherapy using the Tomotherapy Hi-Art II system. A dose of 46 Gy, in daily fractions of 2 Gy, was delivered to the mesorectum and draining lymph nodes, without concomitant chemotherapy. Patients with an anticipated circumferential resection margin (CRM) of less than 2 mm, based on magnetic resonance imaging, received a SIB to the tumor up to a total dose of 55.2 Gy. Acute and late side effects were scored using the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0.

RESULTS

A total of 102 patients presented with cT3-4 tumors; 57 patients entered the boost group and 51 the no-boost group. One patient in the no-boost group developed a radio-hypersensitivity reaction, resulting in a complete tumor remission, a Grade 3 acute and Grade 5 late enteritis. No other Grade ≥3 acute toxicities occurred. With a median follow-up of 32 months, Grade ≥3 late gastrointestinal and urinary toxicity were observed in 6% and 4% of the patients, respectively. The actuarial 2-year LC, progression-free survival and overall survival were 98%, 79%, and 93%.

CONCLUSIONS

Preoperative helical tomotherapy displays a favorable acute toxicity profile in patients with cT3-4 rectal cancer. A SIB can be safely administered in patients with a narrow CRM and resulted in a promising LC.

Dosimetric and clinical review of helical tomotherapy

As a modality for delivering rotational therapy, helical tomotherapy offers dosimetric advantages by combining a continuously rotating gantry with a binary multileaf collimator. Helical tomotherapy, embodied in the TomoTherapy(®) Hi-Art II(®) system, delivers intensity-modulated fan beams in a helical pattern using binary multileaf collimator leaves while the couch is translated through the gantry. Helical tomotherapy offers the possibility of treating a variety of cases--from simple to complex--with improved target conformality and sensitive structure sparing compared with 3D or conventional static field IMRT plans, thereby allowing biologically effective dose escalation. For precise irradiation and possible treatment adaptation, the fully integrated on-board image-guidance system provides online volumetric images of patient anatomy using 3.5-MV x-ray beams and the xenon computed tomography detector. Several review articles were published before the year 2007 but emphasized the technical aspects of helical tomotherapy. In this article, we review very recent papers and focus on the dosimetric and clinical aspects of helical tomotherapy.

Two-year clinical experience with tomotherapy: the French national cancer institute project on implementing new technology

The pooled 2-year clinical experience using three tomotherapy units installed in France in 2007 is presented. Treatment indications and protocols were devised for each disease site and were the result of a consensus. A total of 642 patients were treated for central nervous system, head and neck, thoracic, abdominal, and pelvic tumors. Overall, grade 3, 4, and 5 acute toxicity was 10.7%, 0.3%, and 0.2%, respectively. Grade 3 chronic toxicity was 1.2%. There was no grade 4 or 5 chronic toxicity. The use of tomotherapy in a broad clinical practice is safe, and acute and chronic toxicity both are acceptable for all anatomical locations.

[Preoperative radiochemotherapy for rectal cancer: forecasting the next steps through ongoing and forthcoming studies]

Protracted preoperative radiochemotherapy with a 5-FU-based scheme, or a short course of preoperative radiotherapy without chemotherapy, are the standard neoadjuvant treatments for resectable stage II-III rectal cancer. Local failure rates are low and reproducible, between 6 and 15% when followed with a "Total Mesorectal Excision". Nevertheless, the therapeutic strategy needs to be improved: distant metastatic recurrence rates remain stable around 30 to 35%, while both sphincter and sexual sequels are still significant. The aim of the present paper was to analyse the ongoing trials listed on the following search engines: the Institut National du Cancer in France, the National Cancer Institute and the National Institute of Health in the United States, and the major cooperative groups. Keywords for the search were: "rectal cancer", "preoperative radiotherapy", "phase II-III", "preoperative chemotherapy", "adjuvant chemotherapy" and "surgery". Twenty-three trials were selected and classified in different groups, each of them addressing a question of strategy: (1) place of adjuvant chemotherapy; (2) optimization of preoperative radiotherapy; (3) evaluation of new radiosensitization protocols and/or neoadjuvant chemotherapy; (4) optimization of techniques and timing of surgery; (5) place of radiotherapy for non resectable or metastatic tumors.

Primary tumor response to preoperative chemoradiation with or without oxaliplatin in locally advanced rectal cancer: pathologic results of the STAR-01 randomized phase III trial

PURPOSE

To investigate oxaliplatin combined with fluorouracil-based chemoradiotherapy as preoperative treatment for locally advanced rectal cancer.

PATIENTS AND METHODS

Seven hundred forty-seven patients with resectable, locally advanced (cT3-4 and/or cN1-2) adenocarcinoma of the mid-low rectum were randomly assigned to receive pelvic radiation (50.4 Gy in 28 daily fractions) and concomitant infused fluorouracil (225 mg/m(2)/d) either alone (arm A, n = 379) or combined with oxaliplatin (60 mg/m(2) weekly × 6; arm B, n = 368). Overall survival is the primary end point. A protocol-planned analysis of response to preoperative treatment is reported here.

RESULTS

Grade 3 to 4 adverse events during preoperative treatment were more frequent with oxaliplatin plus fluorouracil and radiation than with radiation and fluorouracil alone (24% v 8% of treated patients; P < .001). In arm B, 83% of the patients treated with oxaliplatin had five or more weekly administrations. Ninety-one percent, compared with 97% in the control arm, received ≥ 45 Gy (P < .001). Ninety-six percent versus 95% of patients underwent surgery with similar rates of abdominoperineal resections (20% v 18%, arm A v arm B). The rate of pathologic complete responses was 16% in both arms (odds ratio = 0.98; 95% CI, 0.66 to 1.44; P = .904). Twenty-six percent versus 29% of patients had pathologically positive lymph nodes (arm A v arm B; P = .447), 46% versus 44% had tumor infiltration beyond the muscularis propria (P = .701), and 7% versus 4% had positive circumferential resection margins (P = .239). Intra-abdominal metastases were found at surgery in 2.9% versus 0.5% of patients (arm A v arm B; P = .014).

CONCLUSION

Adding oxaliplatin to fluorouracil-based preoperative chemoradiotherapy significantly increases toxicity without affecting primary tumor response. Longer follow-up is needed to assess the impact on efficacy end points.

Evidence and research perspectives for surgeons in the European Rectal Cancer Consensus Conference (EURECA-CC2)

PURPOSE

Although surgery remains the most important treatment of rectal cancer, the management of this disease has evolved to become more multidisciplinary to offer the best clinical outcome. The International Conference on Multidisciplinary Rectal Cancer Treatment: Looking for an European Consensus' (EURECA-CC2) had the duty to identify the degree of consensus that could be achieved across a wide range of topics relating to the management of rectal cancer helping shape future programs, investigational protocols and guidelines for staging and treatment throughout Europe.

MATERIALS AND METHODS

Consensus was achieved using the Delphi method. Eight chapters were identified: epidemiology, diagnostics, pathology, surgery, radiotherapy and chemotherapy, treatment toxicity and quality of life, follow-up, and research questions. Each chapter was subdivided by topic, and a series of statements were developed. Each committee member commented and voted, sentence by sentence three times. Sentences which did not reach agreement after voting round #2 were openly debated during the Conference in Perugia (Italy) December 2008. The Executive Committee scored percentage consensus based on three categories: "large consensus", "moderate consensus", "minimum consensus".

RESULTS

The total number of the voted sentences was 207. Of the 207, 86% achieved large consensus, 13% achieved moderate consensus, and only 3 (1%) resulted in minimum consensus. No statement was disagreed by more than 50% of members. All chapters were voted on by at least 75% of the members, and the majority was voted on by 85%.

CONCLUSIONS

This Consensus Conference represents an expertise opinion process that may help shape future programs, investigational protocols, and guidelines for staging and treatment of rectal cancer throughout Europe. In spite of substantial progress, many research challenges remain.

Rectal cancer radiotherapy: towards European consensus

BACKGROUND AND PURPOSE

During the first decade of the 21st century several important European randomized studies in rectal cancer have been published. In order to help shape clinical practice based on best scientific evidence, the International Conference on 'Multidisciplinary Rectal Cancer Treatment: Looking for an European Consensus' (EURECA-CC2) was organized. This article summarizes the consensus about imaging and radiotherapy of rectal cancer and gives an update until May 2010.

METHODS

Consensus was achieved using the Delphi method. Eight chapters were identified: epidemiology, diagnostics, pathology, surgery, radiotherapy and chemotherapy, treatment toxicity and quality of life, follow-up, and research questions. Each chapter was subdivided by topic, and a series of statements were developed. Each committee member commented and voted, sentence by sentence three times. Sentences which did not reach agreement after voting round # 2 were openly debated during the Conference in Perugia (Italy) December 2008. The Executive Committee scored percentage consensus based on three categories: "large consensus", "moderate consensus", "minimum consensus".

RESULTS

The total number of the voted sentences was 207. Of the 207, 86% achieved large consensus, 13% achieved moderate consensus, and only three (1%) resulted in minimum consensus. No statement was disagreed by more than 50% of members. All chapters were voted on by at least 75% of the members, and the majority was voted on by >85%. Considerable progress has been made in staging and treatment, including radiation treatment of rectal cancer.

CONCLUSIONS

This Consensus Conference represents an expertise opinion process that may help shape future programs, investigational protocols, and guidelines for staging and treatment of rectal cancer throughout Europe. In spite of substantial progress, many research challenges remain.

Volumetric imaging by megavoltage computed tomography for assessment of internal organ motion during radiotherapy for cervical cancer

PURPOSE

To assess the internal organ motion of the cervix and uterus by megavoltage computed tomography (MVCT) during intensity-modulated radiotherapy (IMRT).

METHODS AND MATERIALS

Ten patients with Stage IIB-IVA cervical cancer underwent daily MVCT imaging. Internal organ motion was evaluated on 150 pretreatment MVCT images by measuring shifts in their boundaries between the MVCT and kilovoltage (kV) planning CT scan in the anterior, posterior, left and right lateral, and superior and inferior direction. Additional intrafractional patient movement was evaluated on 50 posttreatment MVCT images.

RESULTS

Measured cervical motion (mean +/- SD) was 0.4 +/- 10.1 mm in the anterior, -3.0 +/- 6.9 mm in the posterior direction, -3.5 +/- 4.9 mm in the left and 0.2 +/- 4.5 mm in the right lateral direction, 2.2 +/- 8.0 mm in the superior and 0.5 +/- 5.0 mm in the inferior direction. Compared to the cervix, larger uterine motion was observed. Patient movement during treatment was limited to 1.1 +/- 1.3 mm, -0.3 +/- 1.6 mm, and 0.2 +/- 2.3 mm in anteroposterior, laterolateral and superoinferior direction respectively.

CONCLUSIONS

MVCT imaging can be used to study patient setup accuracy and cervical and uterine motion during IMRT. This data may be used to refine treatment margins.

Multidisciplinary Rectal Cancer Management: 2nd European Rectal Cancer Consensus Conference (EURECA-CC2)

BACKGROUND AND PURPOSE

During the first decade of the 21st century a number of important European randomized studies were published. In order to help shape clinical practice based on best scientific evidence from the literature, the International Conference on 'Multidisciplinary Rectal Cancer Treatment: Looking for an European Consensus' (EURECA-CC2) was organized in Italy under the endorsement of European Society of Medical Oncology (ESMO), European Society of Surgical Oncology (ESSO), and European Society of Therapeutic Radiation Oncology (ESTRO).

METHODS

Consensus was achieved using the Delphi method. The document was available to all Committee members as a web-based document customized for the consensus process. Eight chapters were identified: epidemiology, diagnostics, pathology, surgery, radiotherapy and chemotherapy, treatment toxicity and quality of life, follow-up, and research questions. Each chapter was subdivided by a topic, and a series of statements were developed. Each member commented and voted, sentence by sentence thrice. Sentences upon which an agreement was not reached after voting round # 2 were openly debated during a Consensus Conference in Perugia (Italy) from 11 December to 13 December 2008. A hand-held televoting system collected the opinions of both the Committee members and the audience after each debate. The Executive Committee scored percentage consensus based on three categories: "large consensus", "moderate consensus", and "minimum consensus".

RESULTS

The total number of the voted sentences was 207. Of the 207, 86% achieved large consensus, 13% achieved moderate consensus, and only 3 (1%) resulted in minimum consensus. No statement was disagreed by more than 50% of the members. All chapters were voted on by at least 75% of the members, and the majority was voted on by >85%.

CONCLUSIONS

This Consensus Conference represents an expertise opinion process that may help shape future programs, investigational protocols, and guidelines for staging and treatment of rectal cancer throughout Europe.

Helical Tomotherapy Significantly Reduces Dose to Normal Tissues When Compared to 3D-CRT for Locally Advanced Rectal Cancer

Combined modality treatment (neoadjuvant chemoradiotherapy followed by surgery) for locally advanced rectal cancer requires special attention to various organs at risk (OAR). As a result, the use of conformal dose delivery methods has become more common in this disease setting. Helical tomotherapy is an image-guided intensity modulated delivery system that delivers dose in a fan-beam manner at 7 degree intervals around the patient and can potentially limit normal tissue from high dose radiation while adequately treating targets. In this study we dosimetrically compare helical tomotherapy to 3D-CRT for stage T3 rectal cancer. The helical tomotherapy plans were optimized in the TomoPlan system to achieve an equivalent uniform dose of 45 Gy for 10 patients with T3N0M0 disease that was at least 5cm from the anal verge. The GTV included the rectal thickening and mass evident on colonoscopy and CT scan as well as with the help of a colorectal surgeon. The CTV included the internal iliac, obturator, and pre-sacral lymphatic chains. The OAR that were outlined included the small bowel, pelvic bone marrow, femoral heads, and bladder. Anatom-e system was used to assist in delineating GTV, CTV and OAR. These 10 plans were then duplicated and optimized into 3-field 3D-CRT plans within the Pinnacle planning system. The V[45], V[40], V[30], V[20], V[10], and mean dose to the OAR were compared between the helical tomotherapy and 3D-CRT plans. Statistically significant differences were achieved in the doses to all OAR, including all volumes and means except for V[10] for the small bowel and the femoral heads. Adequate dosimetric coverage of targets were achieved with both helical tomotherapy and 3D-CRT. Helical tomotherapy reduces the volume of normal tissue receiving high-dose RT when compared to 3D-CRT treatment. Both modalities adequately dose the tumor. Clinical studies addressing the dosimetric benefits are on-going.

Predicting grade 3 acute diarrhea during radiation therapy for rectal cancer using a cutoff-dose logistic regression normal tissue complication probability model

PURPOSE

Understanding the dose-volume relationship of small bowel irradiation and severe acute diarrhea may help reduce the incidence of this side effect during adjuvant treatment for rectal cancer.

METHODS AND MATERIALS

Consecutive patients treated curatively for rectal cancer were reviewed, and the maximum grade of acute diarrhea was determined. The small bowel was outlined on the treatment planning CT scan, and a dose-volume histogram was calculated for the initial pelvic treatment (45 Gy). Logistic regression models were fitted for varying cutoff-dose levels from 5 to 45 Gy in 5-Gy increments. The model with the highest LogLikelihood was used to develop a cutoff-dose normal tissue complication probability (NTCP) model.

RESULTS

There were a total of 152 patients (48% preoperative, 47% postoperative, 5% other), predominantly treated prone (95%) with a three-field technique (94%) and a protracted venous infusion of 5-fluorouracil (78%). Acute Grade 3 diarrhea occurred in 21%. The largest LogLikelihood was found for the cutoff-dose logistic regression model with 15 Gy as the cutoff-dose, although the models for 20 Gy and 25 Gy had similar significance. According to this model, highly significant correlations (p <0.001) between small bowel volumes receiving at least 15 Gy and toxicity exist in the considered patient population. Similar findings applied to both the preoperatively (p = 0.001) and postoperatively irradiated groups (p = 0.001).

CONCLUSION

The incidence of Grade 3 diarrhea was significantly correlated with the volume of small bowel receiving at least 15 Gy using a cutoff-dose NTCP model.

Preoperative helical tomotherapy and megavoltage computed tomography for rectal cancer: impact on the irradiated volume of small bowel

PURPOSE

Preoperative (chemo)radiotherapy is considered to be standard of care in locally advanced rectal cancer, but is associated with significant small-bowel toxicity. The aim of this study was to explore to what extent helical tomotherapy and daily megavolt (MV) CT imaging may reduce the irradiated volume of small bowel.

METHODS AND MATERIALS

A 3D-conformal radiotherapy (3D-CRT) plan with CTV-PTV margins adjusted for laser-skin marks (15, 15, and 10 mm for X, Y, and Z directions, respectively) was compared with helical tomotherapy (IMRT) using the same CTV-PTV margins, and to helical tomotherapy with margins adapted to daily MV-CT imaging (IMRT/IGRT; 8, 11, 7, and 10 mm for X, Y(ant), Y(post) and Z resp.) for 11 consecutive patients. The planning goals were to prescribe 43.7 Gy to 95% of the PTV, while minimizing the volume of small bowel receiving more than 15 Gy (V(15 SB)).

RESULTS

The mean PTV was reduced from 1857.4 +/- 256.6 cc to 1462.0 +/- 222.3 cc, when the CTV-PTV margins were adapted from laser-skin marks to daily MV-CT imaging (p < 0.01). The V(15 SB) decreased from 160.7 +/- 102.9 cc to 110.9 +/- 74.0 cc with IMRT and to 81.4 +/- 53.9 cc with IMRT/IGRT (p < 0.01). The normal tissue complication probability (NTCP) for developing Grade 2+ diarrhea was reduced from 39.5% to 26.5% with IMRT and to 18.0% with IMRT/IGRT (p < 0.01).

CONCLUSION

The combination of helical tomotherapy and daily MV-CT imaging significantly decreases the irradiated volume of small bowel and its NTCP.