Intensity-modulated Radiotherapy For Rectal Cancer Research Articles

Intensity-modulated Radiotherapy for Rectal Cancer in the UK in 2020

AimsPreoperative (chemo)radiotherapy followed by total mesorectal excision is the current standard of care for patients with locally advanced rectal cancer. The use of intensity-modulated radiotherapy (IMRT) for rectal cancer is increasing in the UK. However, the extent of IMRT implementation and current practice was not previously known. A national survey was commissioned to investigate the landscape of IMRT use for rectal cancer and to inform the development of national rectal cancer IMRT guidance. Materials and methodsA web-based survey was developed by the National Rectal Cancer IMRT Guidance working group in collaboration with the Royal College of Radiologists and disseminated to all UK radiotherapy centres. The survey enquired about the implementation of IMRT with a focus on the following aspects of the workflow: dose fractionation schedules and use of a boost; pre-treatment preparation and simulation; target volume/organ at risk definition; treatment planning and treatment verification. A descriptive statistical analysis was carried out. ResultsIn total, 44 of 63 centres (70%) responded to the survey; 30/44 (68%) and 36/44 (82%) centres currently use IMRT to treat all patients and selected patients with rectal cancer, respectively. There was general agreement concerning several aspects of the IMRT workflow, including patient positioning, use of intravenous contrast and bladder protocols. Greater variation in practice was identified regarding rectal protocols; use of a boost to primary/nodal disease; target volume delineation; organ at risk delineation and dose constraints and treatment verification. Delineation of individual small bowel loops and daily volumetric treatment verification were considered potentially feasible by most centres. ConclusionThis survey identified that IMRT is already used to treat rectal cancer in many UK radiotherapy centres, but there is heterogeneity between centres in its implementation and practice. These results have been a valuable aid in framing the recommendations within the new National Rectal Cancer IMRT Guidance.

Evaluation of small bowel motion and feasibility of using the peritoneal space to replace bowel loops for dose constraints during intensity-modulated radiotherapy for rectal cancer

BackgroundThe goal of this study was to assess small bowel motion and explore the feasibility of using peritoneal space (PS) to replace bowel loops (BL) via the dose constraint method to spare the small bowel during intensity-modulated radiotherapy (IMRT) for rectal cancer.MethodsA total of 24 patients with rectal cancer who underwent adjuvant or neoadjuvant radiotherapy were selected. Weekly repeat CT scans from pre-treatment to the fourth week of treatment were acquired and defined as Plan, 1 W, 2 W, 3 W, and 4 W. The 4 weekly CT scans were co-registered to the Plan CT, BL and PS contours were delineated in all of the scans, an IMRT plan was designed on Plan CT using PS constraint method, and then copied to the 4 weekly CT scans. The dose-volume, normal tissue complication probability (NTCP) of the small bowel and their variations during treatment were evaluated.ResultsOverall, 109 sets of CT scans from 24 patients were acquired, and 109 plans were designed and copied. The BL and PS volumes were 250.3 cc and 1339.3 cc. The V15 of BL and PS based plan of pre-treatment were 182.6 cc and 919.0 cc, the shift% of them were 28.9 and 11.3% during treatment (p = 0.000), which was less in the prone position than in the supine position (25.2% vs 32.1%, p = 0.000; 9.9% vs 14.9%, p = 0.000). The NTCPC and NTCPA based plan of pre-treatment were 2.0 and 59.2%, the shift% during treatment were 46.1 and 14.0% respectively. Majority of BL’s Dmax and V15 were meet the safety standard during treatment using PS dose limit method except 3 times (3/109) of V15 and 5 times of Dmax (5/109).ConclusionsThis study indicated that small bowel motion may lead to uncertainties in its dose volume and NTCP evaluation during IMRT for rectal cancer. The BL movements were significantly greater than PS, and the prone position was significantly less than the supine position. It is feasibility of using PS to replace BL to spare the small bowel, V15 < 830 cc is the dose constraint standard.

Utilization of Neoadjuvant Intensity-modulated Radiation Therapy for Rectal Cancer in the United States.

Advances in technology have expanded the use of intensity-modulated radiotherapy (IMRT). The goal of this study was to investigate trends in the utilization of IMRT for rectal cancer (RC) in USA. The National Cancer Database was queried for RC patients receiving neoadjuvant chemoradiotherapy with either IMRT or three-dimensional conformal radiation therapy (3DCRT). Differences in factors associated with receipt of 3DCRT versus IMRT were determined and temporal trends were analyzed. From 2005 to 2009, IMRT utilization increased, but remained constant and roughly equivalent to 3DCRT from 2010 to 2014. Patients who received IMRT were more likely to have T4 disease (p=0.014), while patients diagnosed in 2004-2006 (p<0.0001) and 2007-2008 (p=0.015) were less likely to receive IMRT. There were no significant differences in postoperative outcomes between patients receiving 3DCRT and IMRT. IMRT utilization initially increased, but is now used at similar frequencies to 3DCRT and offers similar short-term postoperative outcomes.

Effect of different patient positions on target dose coverage in rectal cancer IMRT

Objective To compare the effect between the supine and prone patient positions upon target dose coverage during intensity-modulated radiotherapy (IMRT) for rectal cancer, aiming to provide clinical reference for the selection of position for rectal cancer patients. Methods Twenty-four patients diagnosed with rectal cancer receiving postoperative adjuvant radiotherapy were selected and divided into the supine (n=12) and prone position groups (n=12). Before and during the IMRT (1-4 weeks), all patients received CT scans, which were defined as: Plan, 1W, 2W, 3W and 4W, respectively. The organs at risk were delineated based on CT scan images. Plan, 1W, 2W, 3W and 4W CT scan images were fused. The CTV and PTV from Plan CT scan were copied to the 1-4W CT scan images, and the therapeutic plans from Plan CT scan were copied as well. The target dose coverage was assessed and the failure rate of target dose coverage was calculated. The couch-position data for each patient during each cycle of IMRT were recorded by using the MOSAIQ network and the overall deviation (S) of couch position was calculated. Results The failure rates of CTV and PTV target dose coverage in the prone position group were higher than those in the supine position group (18.60% VS 0%, 69.76% VS 53.65%). The S value was significantly correlated with the target dose coverage (r=-0.683, P=0.000). The S value in the prone position group was (1.23±0.76) cm, significantly greater than (0.28±0.18) cm in the supine position (P=0.001), and the most significant deviation was noted in the y (head and foot) and z (frontal and dorsal) directions (P=0.003 and 0.003). Compared with the supine group, the V5 and V10 of the small intestine were significantly less (P=0.003 and 0.004) and the chronic toxicity (NTCPC) was considerably reduced (P=0.041) in the prone position group. Conclusions A better target dose coverage can be maintained during IMRT with a supine position during rectal cancer IMRT, whereas the positioning repeatability is worsened with a prone position due to use of the belly board, thereby affecting the target dose coverage. Although the prone position combined with belly board can reduce the tolerated dosage of the small intestine, effective measures should be taken to guarantee the patient positioning repeatability. Key words: Rectal neoplasms/intensity-modulated radiotherapy; Radiotherapy dosage; Belly board

Uncertainty of small bowel dose-volume and normal tissue complication probability assessment due to small bowel motility during intensity-modulated radiotherapy for rectal cancer

Objective To evaluate the uncertainty of the small bowel dose-volume and the normal tissue complication probability (NTCP) during intensity-modulated radiotherapy (IMRT) for rectal cancer, and to provide a reference for the dose limit and protection of the small bowel during IMRT for rectal cancer. Methods A total of 20 patients with rectal cancer who received postoperative adjuvant radiotherapy from March 2014 to August 2015 were enrolled in this study, including 10 patients receiving CT scan in the supine position and 10 patients in the prone position. All patients received computed tomography (CT) scan before the treatment and at weeks 1, 2, 3, and 4 of treatment, and they were defined as Plan, 1W, 2W, 3W, and 4W CT groups, respectively. The small bowel loop (BL) and peritoneal space (PS) were delineated on the images. The IMRT plan based on the Plan CT was copied to the 1W, 2W, 3W, and 4W CT groups, and then the small bowel dose-volume and NTCP were assessed for all CT groups. The paired t-test was used for comparison between groups. The Pearson method was used to analyze the correlation between NTCPC (chronic NTCP) and dose-volume. Results A total of 89 CT images of 20 patients were obtained. In all the patients, the volumes of BL and PS were 251.21 cm3 and 1324.16 cm3, respectively, and the shift% was 23.15% and 11.34%, respectively. The V15 of BL and PS was 184.86 cm3 and 792.45 cm3, respectively, and the shift% was 31.69% and 3.70%, respectively. The V30 of BL and PS was 88.01 cm3 and 645.73 cm3, respectively, and the shift% was 37.66% and 10.49%, respectively. The V15 of BL in 35% of patients and V15 of PS in 20% of patients, the Dmax of BL in 50% of patients, and the NTCP of 15% of patients in the course of treatment exceeded the safety limits. The 1-4W CT groups had a significantly higher NTCPC than the Plan CT group (4.02% vs. 3.20%, P=0.104), and their SD% was 41.68%. There was a significant correlation between NTCPC and V30-V50 of BL (R>0.400, P=0.000). The NTCPA (acute NTCP) and NTCPC in the supine position were significantly higher than those in the prone position (62.30% vs. 56.74%, P=0.061; 4.88% vs. 3.22%, P=0.145). Conclusions Small bowel motility leads to an uncertainty of the adverse event assessment during IMRT for rectal cancer. The change in BL is significantly larger than that in PS and the change in BL and PS in the supine position is significantly larger than that in the prone position. Using the prone position and minimizing V15 and V30 when designing the treatment plan can reduce the NTCPA and NTCPC in the small bowel. Key words: Rectal neoplasms/intensity-modulated radiotherapy; Small bowel; Normal tissue complication probability

Feasibility of placing a dose constraint to peritoneal space instead of bowel loop in protection of the small intestine during intensity-modulated radiotherapy for rectal cancer

Objective To compare the dose volume and normal tissue complication probability (NTCP) of small intestine between intensity-modulated radiotherapy (IMRT) with dose constraints to the peritoneal space (PS) and the bowel loop (BL) in the treatment of rectal cancer, and to investigate the feasibility of placing a dose constraint to the PS instead of the BL in protection of the small intestine. Methods A total of 24 patients with rectal cancer undergoing postoperative adjuvant radiotherapy were enrolled as subjects. In the 24 patients, 12 were treated in supine position and 12 in prone position. The weekly computed tomography (CT) scans from pre-treatment to weeks 1-4 of treatment were defined as Plan, 1 W, 2 W, 3 W, and 4 W. Contours of PS and BL were delineated on all CT images. Based on the Plan CT images, two IMRT plans, PPS and PBL, were designed with dose constraints to the PS and BL, respectively. The method was applied to 1-4 W CT images. For each CT scan, the dose volume and NTCP of the small intestine were evaluated in PPS and PBL. Results A total of 109 sets of CT images were acquired from 24 patients, and 218 plans were designed and copied. The median volume of the PS and BL was 1339.28 and 250.27 cm3, respectively. For the Plan CT scans, V15 values of the PS in PPS plan and the BL in PBL plan were 918.96 and 199.57 cm3, respectively. For all CT scans, the dose volume of the small intestine in PPS, in most cases, was lower than that in PBL, while V15 values in PPS and PBL were 170.07 and 178.58 cm3(P=0.000). The dose volume of the small intestine was correlated with V15(P=0.000). PPS had significantly lower NTCP of chronic and acute adverse reactions than PBL (2.80% vs. 3.00%, P=0.018; 57.32% vs. 58.64%, P=0.000). In patients with prone and supine treatment positions, most of the dose volume and NTCP of the small intestine in PPS were significantly lower than those in PBL (P<0.05 for V10, V15, V30, and NTCP of acute adverse reactions). Conclusions It is feasible to place a dose constraint to the PS instead of the BL for protection of the small intestine during IMRT for rectal cancer. V15<830 cm3 can be referred to as the objective function of dose restraint. Key words: Rectal neoplasms/intensity modulated radiotherapy; Peritoneal space; Small bowel; Normal tissue complication probability

Reduced Acute Bowel Toxicity in Patients Treated With Intensity-Modulated Radiotherapy for Rectal Cancer

We have previously shown that intensity-modulated radiotherapy (IMRT) can reduce dose to small bowel, bladder, and bone marrow compared with three-field conventional radiotherapy (CRT) technique in the treatment of rectal cancer. The purpose of this study was to review our experience using IMRT to treat rectal cancer and report patient clinical outcomes. A retrospective review was conducted of patients with rectal cancer who were treated at Mayo Clinic Arizona with pelvic radiotherapy (RT). Data regarding patient and tumor characteristics, treatment, acute toxicity according to the Common Terminology Criteria for Adverse Events v 3.0, tumor response, and perioperative morbidity were collected. From 2004 to August 2009, 92 consecutive patients were treated. Sixty-one (66%) patients were treated with CRT, and 31 (34%) patients were treated with IMRT. All but 2 patients received concurrent chemotherapy. There was no significant difference in median dose (50.4 Gy, CRT; 50 Gy, IMRT), preoperative vs. postoperative treatment, type of concurrent chemotherapy, or history of previous pelvic RT between the CRT and IMRT patient groups. Patients who received IMRT had significantly less gastrointestinal (GI) toxicity. Sixty-two percent of patients undergoing CRT experienced ≥Grade 2 acute GI side effects, compared with 32% among IMRT patients (p = 0.006). The reduction in overall GI toxicity was attributable to fewer symptoms from the lower GI tract. Among CRT patients, ≥Grade 2 diarrhea and enteritis was experienced among 48% and 30% of patients, respectively, compared with 23% (p = 0.02) and 10% (p = 0.015) among IMRT patients. There was no significant difference in hematologic or genitourinary acute toxicity between groups. In addition, pathologic complete response rates and postoperative morbidity between treatment groups did not differ significantly. In the management of rectal cancer, IMRT is associated with a clinically significant reduction in lower GI toxicity compared with CRT. Further study is needed to evaluate differences in late toxicity and long-term efficacy.