Phase I-II trial of concurrent capecitabine and oxaliplatin with preoperative intensity-modulated radiotherapy in patients with locally advanced rectal cancer

Prospective study of neoadjuvant chemoradiotherapy using intensity-modulated radiotherapy and 5 fluorouracil for locally advanced rectal cancer - toxicities and response assessment

Aims and objectives

The past 2 decades witnessed the strengthening of evidence favoring the role of neoadjuvant chemoradiation (CHRT) in the treatment of locally advanced rectal cancer. The study aims to evaluate the response and acute toxicities to neoadjuvant CHRT using intensity-modulated radiotherapy (IMRT) in the treatment of rectal cancer. Predictive factors to achieve pathological complete response (pCR) were analyzed, as a secondary endpoint.

Materials and methods

All consecutive patients who underwent IMRT as part of neoadjuvant CHRT in the treatment of rectal cancer between August 2014 and December 2016 at a tertiary cancer care center were accrued for the study. The cohort underwent CHRT with IMRT technique at a dose of 50.4 Gy in 28 fractions concurrent with continuous infusion of 5 fluorouracil during the first and the last 4 days of CHRT. Surgery was performed 6 weeks later and the pathological response to CHRT was noted.

Results

Forty-three subjects were accrued for the study. Radiation dermatitis and diarrhea were the only observed grade ≥3 acute toxicities. Sphincter preservation rate (SPR) was 43.3%. pCR was observed in 32.6%. Univariate and multivariate logistic regression showed that carcinoembryonic antigen was the only independent predictive factor to achieve pCR.

Conclusion

IMRT as part of neoadjuvant CHRT in the treatment of locally advanced rectal cancer is well tolerated and gives comparable results with respect to earlier studies in terms of pathological response and SPR. Further randomized controlled studies are needed to firmly state that IMRT is superior to 3-dimensional conformal radiotherapy.

Rectal Radiotherapy--Intensity-modulated Radiotherapy Delivery, Delineation and Doses

The use of intensity-modulated radiotherapy in rectal cancer is attractive in that it may reduce acute and late toxicities and potentially facilitate dose escalation. Intensity-modulated radiotherapy probably has a role in selected patients, but further investigation is required to identify the parameters for selection. Delineation of specific nodal groups allows maximal sparing of bladder and small bowel. In locally advanced tumours a simultaneous integrated boost allows dose escalation incorporating hypofractionation and a shorter overall treatment time. However, due to a sparsity of data on late toxicity in doses ≥ 60 Gy, doses at this level should be used with caution, ideally within prospective trials. Future studies investigating dose escalation must ascertain late toxicity as well as local control, as both can significantly affect quality of life and without both, the risk-benefit ratio cannot be calculated.

Clinical significance of cellular and acellular mucin pools in rectal carcinoma following preoperative chemoradiotherapy

BACKGROUND AND OBJECTIVES

The standard treatment for locally advanced rectal cancer (LARC) is neoadjuvant chemoradiotherapy (CRT) followed by surgery. Pathological findings remain the most significant prognostic factor. The presence of mucin pools and their prognostic significance is a controversial issue. The aim of this study was to analyze the incidence of cellular and acellular mucin pools and their clinical significance.

METHODS

Four-hundred and forty-six consecutive prospectively collected specimens from patients with LARC treated with long-course preoperative CRT and surgery were analyzed. Kaplan-Meier analysis was performed.

RESULTS

Mucin pools were present in 182 specimens (40.8 %); 66 (14.7 %) were acellular, and viable tumor cells were identified in 116 (26 %). The complete pathological response rate was 13.5 % (60 of 446). With a median follow-up of 79.0 months, the 5- and 10-year disease-free survivals for patients with acellular and cellular mucin pools were 81.5, 78.1, 63.7 and 61.2 %, respectively (p ≤ 0.026). The presence of cells in the colloid response to treatment was associated with a 17.8 and 16.9 % decrease in 5- and 10-year disease survival vs. acellular colloid response.

CONCLUSIONS

Our results suggest that cellular mucin pools are an indicator of an aggressive phenotype and harbingers of a worse prognosis.

Impact of perineural and lymphovascular invasion on oncological outcomes in rectal cancer treated with neoadjuvant chemoradiotherapy and surgery

BACKGROUND

The prognostic significance of perineural and/or lymphovascular invasion (PLVI) and its relationship with tumor regression grade (TRG) in patients with locally advanced rectal cancer (LARC) treated with neoadjuvant chemoradiotherapy (CRT) and surgery.

METHODS

A total of 324 patients with LARC were treated with CRT and operated on between January 1992 and June 2007. Tumors were graded using a quantitative 5-grade TRG classification and the presence of PLVI was histologically studied.

RESULTS

At a median follow-up of 79.0 months (range 3-250 months), a total of 80 patients (24.7%) relapsed. The observed 5- and 10-year overall survival (OS) was 83.2 and 74.9 %, respectively. The 5- and 10-year disease-free survival (DFS) was 75.1 and 71.4%, respectively. A significant correlation was found between the TRG and survival (log rank, p < 0.001). The 10-year OS was 32.7% for grade 1, 63.8% for grade 2, 75.0% for grade 3, 90.4% for grade 3+, and 96.0%,for grade 4. The 10-year DFS was 31.8% for grade 1, 58.6% for grade 2, 70.4% for grade 3, 88.4% for grade 3+, and 97.1% for grade 4. In patients with PLVI, the TRG had no impact on survival. When excluding patients with PLVI, the TRG was an independent prognostic factor for OS and DFS.

CONCLUSIONS

The presence of PLVI is a more powerful prognostic factor than TRG in LARC patients treated with neoadjuvant CRT followed by surgery. PLVI denotes an aggressive phenotype, suggesting that these patients may benefit from adjuvant systemic therapy.

Current treatment of rectal cancer adapted to the individual patient

Preoperative radiochemotherapy and total mesorectal excision surgery is a recommended standard therapy for patients with locally advanced rectal cancer. However, some subgroups of patients benefit more than others from this approach. In order to avoid long-term complications of radiation and chemotherapy, efforts are being made to subdivide T3N0 stage using advanced imaging techniques, and to analyze prognostic factors that help to define subgroup risk patients. Long-course radiochemotherapy has the potential of downsizing the tumor before surgery and may increase the chance of sphincter preservation in some patients. Short-course radiotherapy (SCRT), on the other hand, is a practical schedule that better suits patients with intermediated risk tumors, located far from the anal margin. SCRT is also increasingly being used among patients with disseminated disease, before resection of the rectal tumor. Improvements in radiation technique, such as keeping the irradiation target below S2/S3 junction, and the use of IMRT, can reduce the toxicity associated with radiation, specially long-term small bowel toxicity.

Prognosis factors for recurrence in patients with locally advanced rectal cancer preoperatively treated with chemoradiotherapy and adjuvant chemotherapy

BACKGROUND

Neoadjuvant chemoradiotherapy followed by total mesorectal excision has improved the outcome of locally advanced rectal carcinoma.

OBJECTIVE

The aim of this study was to identify independent prognosis factors of disease recurrence in a group of patients treated with this approach.

DESIGN AND PATIENTS

This study was retrospective in design. Data from patients with locally advanced rectal cancer who had completed treatment from 2000 to 2010 were reviewed.

SETTINGS

The analysis was performed in a tertiary referral center.

MAIN OUTCOME MEASURES

The primary outcomes measured were the recurrence risk factors.

RESULTS

The cohort consisted of 228 patients; 69.3% of them were men, and median age was 59 years. Stage III rectal cancer was found in 64.9% of patients. The most frequently administered therapy was concurrent capecitabine, oxaliplatin, and 7-field radiotherapy, followed by 3-field radiotherapy and fluoropyrimidines. After a median follow-up of 49 months, 23.7% of the patients experienced disease recurrence: 2.6% had local recurrence, 21.1% had distant metastases, and 0.5% had both. Factors significantly correlated with recurrence risk in multivariate logistic regression were y-pathological stage (III vs I/II: OR = 2.51), tumor regression grade (1/2 vs 3+/4: OR = 3.34; 3 vs 3+/4: OR = 1.20), and low rectal location (OR = 2.36). The only independent prognosis factor for liver metastases was tumor regression grade (1/2 vs 3+/4: OR = 4.67; 3 vs 3+/4: OR = 1.41), whereas tumor regression grade (1-2 vs 3+/4: OR = 5.5; 3 vs 3+/4: OR = 1.84), low rectal location (OR = 3.23), and previous liver metastasis (OR = 7.73) predicted lung recurrence.

LIMITATIONS

This is a single institutional experience, neoadjuvant combined therapy is not homogeneous, and the analysis has been performed in a retrospective manner.

CONCLUSIONS

Patients with low third locally advanced rectal cancer with a poor response to neoadjuvant chemoradiotherapy (high y-pathological stage or low tumor regression grade) are at high risk of recurrence. Intense surveillance and the design of alternative therapeutic approaches aimed to lower the distant failure rate seem warranted.

The role of capecitabine in locally advanced rectal cancer treatment: an update

Preoperative infusional 5-fluorouracil (5-FU) and concurrent radiation therapy (RT) followed by total mesorectal surgery is the current standard of care for locally advanced rectal cancer (LAR). When compared with postoperative 5-FU-based chemoradiation, this strategy is associated with significantly lower rates of local relapse, lower toxicity and better compliance. Capecitabine is a rationally designed oral prodrug that is converted into 5-FU by intracellular thymidine phosphorylase. Substitution of infusional 5-FU with capecitabine is an attractive option that provides a more convenient administration schedule and, possibly, increased efficacy. Indeed, incorporation of capecitabine in combined modality neoadjuvant therapy for LAR has been under intense investigation during the last 10 years. Phase I and II clinical trials showed that a regimen consisting of capecitabine 825mg/m(2) twice daily for 7 days/week continuous oral administration in combination with RT is an active and well tolerated regimen, thereby being the preferred concurrent regimen. The definitive demonstration that efficacy of capecitabine/RT is similar to 5-FU/RT has been provided by the NSABP-R-04 and the German Margit trials. One approach to improve outcomes in rectal cancer is to deliver a second RT-sensitizing drug with effective systemic activity. Oxaliplatin and irinotecan are therefore good candidates. However, two phase III trials demonstrated that incorporation of oxaliplatin to capecitabine with RT did not improve early outcomes and, by contrast, increased toxicity. Capecitabine has also been combined with irinotecan. This regimen showed encouraging results in phase I and II clinical trials, which led to an ongoing phase III clinical trial. New strategies with induction chemotherapy with or without chemoradiation prior to surgery are currently under investigation. Whether or not capecitabine has a role in this setting is being investigated in ongoing trials. Incorporation of agents directed towards new targets, such as anti-epidermal growth factor receptor (EGFR) antibodies or antiangiogenic agents, in combination preoperative regimens, is being hampered by results of early trials in which efficacy outcomes with cetuximab were poor and an excessive rate of surgical complications with bevacizumab was observed. The lack of improvements in efficacy with the addition of cetuximab or bevacizumab in the adjuvant treatment of colon cancer led to concerns about further development of these agents in rectal cancer. The role of capecitabine in the postoperative adjuvant setting is the aim of the ongoing Dutch SCRIPT trial. The prediction of response associated with capecitabine has been based on expression of thymidylate synthase and dihydropyrimidine dehydrogenase, as well as on gene expression arrays. All these procedures require further validation and should be considered as investigational. In conclusion, capecitabine can safely and effectively replace intravenous continuous infusion of 5-FU in the preoperative chemoradiation setting for rectal cancer management. The addition of other new antineoplastic agents to a fluoropyrimidine-based regimen remains investigational.

Oxaliplatin as a radiosensitiser for upper and lower gastrointestinal tract malignancies: what have we learned from a decade of translational research?

Some of the greatest advances in the treatment of solid malignancies have resulted from the combination of chemotherapy and radiotherapy treatments. This article comprehensively reviews the current clinical evidence for oxaliplatin-based chemo-radiotherapy that may improve local control and survival. In order to understand how clinical studies should be designed, the pre-clinical evidence for the use of oxaliplatin chemotherapy as a radiosensitising agent is appraised. Particular focus is placed on oxaliplatin's biological mechanisms of action, including cell cycle effects, the formation of DNA adducts and interstrand cross-links and the role of DNA repair proteins. At a clinical level, there is currently no evidence to suggest that oxaliplatin provides an additional benefit to concurrent chemo-radiation regimes that utilise fluoropyrimidines; we evaluate the reasons for this observation, the limitations of clinical trial design and the opportunities that currently exist to design clinical trials which are underpinned by an understanding of the basic biology.

Four-week neoadjuvant intensity-modulated radiation therapy with concurrent capecitabine and oxaliplatin in locally advanced rectal cancer patients: a validation phase II trial

PURPOSE

To validate tolerance and pathological complete response rate (pCR) of a 4-week preoperative course of intensity-modulated radiation therapy (IMRT) with concurrent capecitabine and oxaliplatin (CAPOX) in patients with locally advanced rectal cancer.

METHODS AND MATERIALS

Patients with T3 to T4 and/or N+ rectal cancer received preoperative IMRT (47.5 Gy in 19 fractions) with concurrent capecitabine (825 mg/m(2) b.i.d., Monday to Friday) and oxaliplatin (60 mg/m(2) on Days 1, 8, and 15). Surgery was scheduled 4 to 6 weeks after the completion of chemoradiation. Primary end points were toxicity and pathological response rate. Local control (LC), disease-free survival (DFS), and overall survival (OS) were also analyzed.

RESULTS

A total of 100 patients were evaluated. Grade 1 to 2 proctitis was observed in 73 patients (73%). Grade 3 diarrhea occurred in 9% of the patients. Grade 3 proctitis in 18% of the first 50 patients led to reduction of the dose per fraction to 47.5 Gy in 20 treatments. The rate of Grade 3 proctitis decreased to 4% thereafter (odds ratio, 0.27). A total of 99 patients underwent surgery. A pCR was observed in 13% of the patients, major response (96-100% of histological response) in 48%, and pN downstaging in 78%. An R0 resection was performed in 97% of the patients. After a median follow-up of 55 months, the LC, DFS, and OS rates were 100%, 84%, and 87%, respectively.

CONCLUSIONS

Preoperative CAPOX-IMRT therapy (47.5 Gy in 20 fractions) is feasible and safe, and produces major pathological responses in approximately 50% of patients.

Unique considerations in the patient with rectal cancer

In the past two decades, substantial progress has been made in the adjuvant management of colorectal cancer. Chemotherapy has improved overall survival in patients with node-positive (N+) disease. In contrast with colon cancer, which has a low incidence of local recurrence, patients with rectal cancer have a higher incidence requiring the addition of pelvic radiation therapy (chemoradiation). Patients with rectal cancer have a number of unique management considerations: for example, the role of short-course radiation, whether postoperative adjuvant chemotherapy is necessary for all patients, and if the type of surgery following chemoradiation should be based on the response rate. More accurate imaging techniques and/or molecular markers may help identify patients with positive pelvic nodes to reduce the chance of overtreatment with preoperative therapy. Will more effective systemic agents both improve the results of radiation as well as modify the need for pelvic radiation? This review will address these and other controversies specific to patients with rectal cancer.

Chemoradiation for rectal cancer: rationale, approaches, and controversies

The standard adjuvant treatment of cT3 and/or N+ rectal cancer is preoperative chemoradiation. However, there are many controversies regarding this approach. These controversies include the role of short course radiation, whether postoperative adjuvant chemotherapy is necessary for all patients, and if the type of surgery following chemoradiation should be based on the response rate. More accurate imaging techniques and/or molecular markers may help identify patients with positive pelvic nodes to reduce the chance of overtreatment with preoperative therapy. Will more effective systemic agents both improve the results of radiation, as well as modify the need for pelvic radiation? These questions and others remain active areas of clinical investigation.

Combined modality therapy for rectal cancer

The standard adjuvant treatment for cT3 and/or N+ rectal cancer is preoperative chemoradiation. However, there are many controversies regarding this approach. These include the role of short course radiation, whether postoperative adjuvant chemotherapy necessary for all patients and whether the type of surgery after chemoradiation should be based on the response rate. More accurate imaging techniques and/or molecular markers may help identify patients with positive pelvic nodes to reduce the chance of overtreatment with preoperative therapy. Will more effective systemic agents both improve the results of radiation as well as modify the need for pelvic radiation? These questions and others remain active areas of clinical investigation.

Patterns of response after preoperative intensity-modulated radiation therapy and capecitabine/oxaliplatin in rectal cancer: is there still a place for ecoendoscopic ultrasound?

PURPOSE

The main goals of preoperative chemoradiotherapy (CHRT) in rectal cancer are to achieve pathological response and to ensure tumor control with functional surgery when possible. Assessment of the concordance between clinical and pathological responses is necessary to make decisions regarding alternative conservative procedures. The present study evaluates the patterns of response after a preoperative CHRT regimen, and the value of endoscopic ultrasound (EUS) in assessing response.

METHODS AND MATERIALS

A total of 51 EUS-staged T3 to T4 and/or N0 to N+ rectal cancer patients received preoperative CHRT (intensity-modulated radiation therapy and capecitabine/oxaliplatin (XELOX) followed by radical resection. Clinical response was assesed by EUS. Rates of pathological tumor regression grade (TRG) and lymph node (LN) involvement were determined in the surgical specimen. Clinical and pathological responses were compared, and the accuracy of EUS in assessing response was calculated.

RESULTS

Twenty-four patients (45%) achieved a major pathological response (complete or >95% pathological response (TRG 3+/4)). Sensitivity, specificity, negative predictive value, and positive predictive value of EUS in predicting pathological T response after preoperative CHRT were 77.8%, 37.5%, 60%, and 58%, respectively. The EUS sensitivity, specificity, negative predictive value, and positive predictive value for nodal staging were 44%, 88%, 88%, and 44%, respectively. Furthermore, EUS after CHRT accurately predicted the absence of LN involvement in 7 of 7 patients (100%) with major pathological response of the primary tumor.

CONCLUSION

Preoperative IMRT with concomitant XELOX induces favorable rates of major pathological response. EUS has a limited ability to predict primary tumor response after preoperative CHRT, but it is useful for accurately determining LN status. EUS may have a potential value in identifying patients with a very low risk of LN involvement in association with a good pathological response as potential candidates for conservative local surgical protocols.

Radiation, chemotherapy and biological therapy in the curative treatment of locally advanced rectal cancer

OBJECTIVE

To review the published evidence relating to the use of radiotherapy (RT), chemotherapy and biological therapy as adjuncts to surgery in the curative treatment of rectal cancer.

METHODS

Searches were carried out of the MEDLINE and CANCERLIT databases together with conference abstracts from key meetings including the American Society of Clinical Oncology Annual Meeting and Gastrointestinal Cancers Symposium and the ECCO/ESMO Multidisciplinary Congress.

RESULTS

RT reduces local pelvic recurrence when used as an adjunct to surgery, even when this is performed optimally by total mesorectal excision (TME). RT is usually given as short-course preoperative radiotherapy (SCPRT) followed by immediate surgery which produces no or very little downstaging or long-course concurrent chemoradiation (CRT) followed by a 6-8 week gap prior to surgery which produces significant downstaging. The prognostic importance of achieving a clear histological circumferential resection margin is now well recognised and pathological assessment of the quality of surgery can predict long-term outcomes. Internationally there is considerable heterogeneity in the staging modalities and criteria used in deciding which approach might be used, in the reporting of histological results and in RT parameters (time/dose/fractionation/volume). Attempts to increase the potency of CRT have included the addition of concurrent chemotherapeutic and biological agents to the standard fluoropyrimidine although there is little randomised data and none with regard to long-term survival outcomes. Neither SCPRT nor downstaging CRT have been shown to reduce the rate of subsequent distant metastatic relapse which remains a significant clinical problem. The potential additional benefit of neoadjuvant or adjuvant chemotherapy in addition to SCPRT or long-course CRT remains ill-defined. Late morbidity can include bowel and sexual dysfunction, pelvic fractures and second malignancies with considerably more being known in relation to SCPRT than long-course CRT.

CONCLUSIONS

Improvements in imaging, pathology and surgical technique combined with multimodality treatment using RT and chemotherapy are leading to continuing improvements in the long term outcome for patients with rectal cancer although much remains to be learnt regarding the optimum strategy for use of these in different clinical contexts and their relationship to long-term morbidity.

Phase I study of preoperative chemoradiation with s-1 and oxaliplatin in patients with locally advanced resectable rectal cancer

PURPOSE

To perform a Phase I study of preoperative chemoradiation (CRT) with S-1, a novel oral fluoropyrimidine, plus oxaliplatin in patients with locally advanced rectal cancer, to determine the maximum tolerated dose and the recommended dose.

METHODS AND MATERIALS

Radiotherapy was delivered to a total of 45 Gy in 25 fractions and followed by a coned-down boost of 5.4 Gy in 3 fractions. Concurrent chemotherapy consisted of a fixed dose of oxaliplatin (50 mg/m2/week) on Days 1, 8, 22, and 29 and escalated doses of S-1 on Days 1-14 and 22-35. The initial dose of S-1 was 50 mg/m2/day, gradually increasing to 60, 70, and 80 mg/m2/day. Surgery was performed within 6±2 weeks.

RESULTS

Twelve patients were enrolled and tolerated up to Dose Level 4 (3 patients at each dose level) without dose-limiting toxicity. An additional 3 patients were enrolled at Dose Level 4, with 1 experiencing a dose-limiting toxicity of Grade 3 diarrhea. Although maximum tolerated dose was not attained, Dose Level 4 (S-1 80 mg/m2/day) was chosen as the recommended dose for further Phase II studies. No Grade 4 toxicity was observed, and Grade 3 toxicities of leukopenia and diarrhea occurred in the same patient (1 of 15, 6.7%). Pathologic complete responses were observed in 2 of 15 patients (13.3%).

CONCLUSIONS

The recommended dose of S-1 was determined to be 80 mg/m2/day when combined with oxaliplatin in preoperative CRT, and a Phase II trial is now ongoing.

Cetuximab and chemoradiation for rectal cancer--is the water getting muddy?

The epidermal growth factor receptor (EGFR) inhibitor cetuximab has been successfully combined with radical radiotherapy in head and neck cancer. In colorectal cancer, increased response rates are achieved by cetuximab and panitumumab within standard chemotherapy schedules, but not in chemoradiation regimens. This review examines the clinical evidence and potential mechanisms for an interaction when EGFR inhibitors are added to fluoropyrimidine-based chemoradiation in rectal adenocarcinoma.

METHODS

This review was compiled by searching PubMed and Medline for English language articles published until 2009 with established search strategies, supplemented by hand searching of abstracts from the proceedings of relevant international meetings. The primary outcome measure was pathological complete response (pCR).

RESULTS

Only 13 publications and three presentations in abstract of 13 phase I/II trials of preoperative chemoradiation with cetuximab in rectal cancer were identified. A total of 316 patients were identified who received cetuximab in combination with radiotherapy and 5-fluorouracil or capecitabine preoperatively. One hundred and thirty eight of these patients received either additional irinotecan or oxaliplatin. One study with panitumumab with safety but no efficacy results was identified, and two studies with gefinitib. The pCR rate ranged from 0-20%. The overall pooled pCR for cetuximab based chemoradiation was 9.1% (29/316). The rate of G3/G4 gastrointestinal toxicity, in terms of diarrhoea, varied from 5-30%, with an overall pooled rate of 47/313 (15%).

DISCUSSION

Potential reasons for the disappointing results of EGFR inhibition with fluoropyrimidine-based preoperative chemoradiation include a less critical role of repopulation in rectal adenocarcinoma using a non-curative radiation dose; or antagonistic effects on 5FU-based chemoradiation and oxaliplatin, if some cells arrest in G1 or G2-M and fail to pass through S phase.

CONCLUSION

Cetuximab combined with fluoropyrimidine-based chemoradiation is not currently recommended. A better understanding of the mechanisms involved in combinations of chemotherapy and radiotherapy might allow more effective future scheduling of biological and chemical agents in combination with radiation.

Colorectal cancer

Substantial progress has been made in colorectal cancer in the past decade. Screening, used to identify individuals at an early stage, has improved outcome. There is greater understanding of the genetic basis of inherited colorectal cancer and identification of patients at risk. Optimisation of surgery for patients with localised disease has had a major effect on survival at 5 years and 10 years. For rectal cancer, identification of patients at greatest risk of local failure is important in the selection of patients for preoperative chemoradiation, a strategy proven to improve outcomes in these patients. Stringent postoperative follow-up helps the early identification of potentially radically treatable oligometastatic disease and improves long-term survival. Treatment with adjuvant fluoropyrimidine for colon and rectal cancers further improves survival, more so in stage III than in stage II disease, and oxaliplatin-based combination chemotherapy is now routinely used for stage III disease, although efficacy must be carefully balanced against toxicity. In stage II disease, molecular markers such as microsatellite instability might help select patients for treatment. The integration of targeted treatments with conventional cytotoxic drugs has expanded the treatment of metastatic disease resulting in incremental survival gains. However, biomarker development is essential to aid selection of patients likely to respond to therapy, thereby rationalising treatments and improving outcomes.

Intensity-modulated radiation therapy (IMRT) vs. 3D conformal radiotherapy (3DCRT) in locally advanced rectal cancer (LARC): dosimetric comparison and clinical implications

Purpose

To compare target dose distribution, comformality, normal tissue avoidance, and irradiated body volume (IBV) in 3DCRT using classic anatomical landmarks (c3DCRT), 3DCRT fitting the PTV (f3DCRT), and intensity-modulated radiation therapy (IMRT) in patients with locally advanced rectal cancer (LARC).

Materials and methods

Fifteen patients with LARC underwent c3DCRT, f3DCRT, and IMRT planning. Target definition followed the recommendations of the ICRU reports No. 50 and 62. OAR (SB and bladder) constraints were D5 ≤ 50 Gy and Dmax < 55 Gy. PTV dose prescription was defined as PTV95 ≥ 45 Gy and PTVmin ≥ 35 Gy. Target coverage was evaluated with the D95, Dmin, and Dmax. Target dose distribution and comformality was evaluated with the homogeneity indices (HI) and Conformity Index (CI). Normal tissue avoidance of OAR was evaluated with the D5 and V40. IBV at 5 Gy (V5), 10 Gy (V10), and 20 Gy (V20) were calculated.

Results

The mean GTV95, CTV95, and PTV95 doses were significantly lower for IMRT plans. Target dose distribution was more inhomogeneous after IMRT planning and 3DCRTplans had significantly lower CI. The V40 and D5 values for OAR were significantly reduced in the IMRT plans .V5 was greater for IMRT than for f3DCRT planning (p < 0.05) and V20 was smaller for IMRT plans(p < 0.05).

Conclusions

IMRT planning improves target conformity and decreases irradiation of the OAR at the expense of increased target heterogeneity. IMRT planning increases the IBV at 5 Gy or less but decreases the IBV at 20 Gy or more.