A Growing Divide? Social Determinants of the Use of Nonoperative Management of Rectal Cancer and Its Impact on Survival

INTRODUCTION

Nonoperative management (NOM) of locally advanced rectal cancer was described as early as 2004. Initial national data demonstrated increase in utilization of NOM from 1998 to 2010, but newer national utilization data are not available.

METHODS

We performed a retrospective cohort study using the National Cancer Database to assess utilization and 5-y overall survival (OS) of NOM of locally advanced rectal cancer. All patients had American Joint Committee on Cancer stage 2 or 3 rectal cancer, were over 40 y old, received both chemotherapy and radiation therapy, and were not being treated with palliative intent.

RESULTS

74,780 patients were analyzed. 64,540 (86.2%) underwent a definitive resection, 10,330 (13.8%) had NOM. Utilization of NOM steadily increased from 11.3% in 2010 to 18.6% in 2018. Multivariate regression identified the highest predictors of utilization of NOM to be uninsured status, government insurance, Black race, and treatment at a community cancer center. Multivariate regression identified NOM as the highest hazard for mortality (hazard ratio = 2.286, confidence interval 2.209-2.366). After propensity score matching, the mean estimated 5-y OS was 52.0% for those managed operatively compared to 39.8% for those managed nonoperatively.

CONCLUSIONS

From 2004 to 2018, the utilization of NOM of locally advanced rectal cancer significantly increased. However, there was a significant discrepancy in OS in comparison to surgical resection for these patients. Further study is needed to determine the long-term oncologic safety of NOM.

Impact of Prediagnosis Risk of Major Depressive Disorder and Health-Related Quality of Life on Treatment Choice for Stage II-III Rectal Cancer

PURPOSE

We hypothesized that depressive symptoms and health-related quality of life (HRQOL) reported by patients before their cancer diagnoses would be associated with treatment choice for stage II and III rectal cancer, specifically whether patients underwent surgery.

METHODS

The Surveillance, Epidemiology, and End Results and Medicare Health Outcomes Survey linked data set was used to identify patients with stage II-III rectal adenocarcinoma diagnosed between 2004 and 2013 who had completed the health outcomes survey within 36 months before their cancer diagnoses. Risk for major depressive disorder (MDD) was determined on the basis of responses to screening questions for depressive disorders. HRQOL was assessed using the Mental Component Summary and Physical Component Summary of the 36-Item Short Form Survey and Veterans RAND 12-Item Health Survey. Using univariable and multivariable analyses, we assessed for associations between health survey responses and ultimate treatment modality.

RESULTS

We identified 142 evaluable patients, of whom 109 (76.8%) underwent surgery. Thirty patients (21.1%) met criteria for being at risk for MDD before their cancer diagnoses. Patients at risk for MDD underwent surgery less often than those not at risk (P = .0499), and this association strengthened after adjusting for patient characteristics (odds ratio, 0.17; 95% CI, 0.04 to 0.82; P = .027). There was a nonsignificant trend between higher Mental Component Summary scores (indicating higher self-reported mental HRQOL) and increased frequency of undergoing surgery (P = .081). There were no significant associations between the Physical Component Summary and treatment modality.

CONCLUSION

In Medicare beneficiaries with stage II-III rectal cancer, those at risk for MDD underwent standard-of-care treatment with surgery less frequently. Further studies are warranted to assess the effect of mental health on clinical decision making in this patient population.

Predicting Neoadjuvant Treatment Response in Rectal Cancer Using Machine Learning: Evaluation of MRI-Based Radiomic and Clinical Models

BACKGROUND

Radiomics is an approach to medical imaging that quantifies the features normally translated into visual display. While both radiomic and clinical markers have shown promise in predicting response to neoadjuvant chemoradiation therapy (nCRT) for rectal cancer, the interrelationship is not yet clear.

METHODS

A retrospective, single-institution study of patients treated with nCRT for locally advanced rectal cancer was performed. Clinical and radiomic features were extracted from electronic medical record and pre-treatment magnetic resonance imaging, respectively. Machine learning models were created and assessed for complete response and positive treatment effect using the area under the receiver operating curves.

RESULTS

Of 131 rectal cancer patients evaluated, 68 (51.9%) were identified to have a positive treatment effect and 35 (26.7%) had a complete response. On univariate analysis, clinical T-stage (OR 0.46, p = 0.02), lymphovascular/perineural invasion (OR 0.11, p = 0.03), and statin use (OR 2.45, p = 0.049) were associated with a complete response. Clinical T-stage (OR 0.37, p = 0.01), lymphovascular/perineural invasion (OR 0.16, p = 0.001), and abnormal carcinoembryonic antigen level (OR 0.28, p = 0.002) were significantly associated with a positive treatment effect. The clinical model was the strongest individual predictor of both positive treatment effect (AUC = 0.64) and complete response (AUC = 0.69). The predictive ability of a positive treatment effect increased by adding tumor and mesorectal radiomic features to the clinical model (AUC = 0.73).

CONCLUSIONS

The use of a combined model with both clinical and radiomic features resulted in the strongest predictive capability. With the eventual goal of tailoring treatment to the individual, both clinical and radiologic markers offer insight into identifying patients likely to respond favorably to nCRT.

Current trends in nonoperative management for rectal adenocarcinoma: An unequal playing field?

BACKGROUND AND OBJECTIVES

Increasing evidence suggests patient-oriented benefits of nonoperative management (NOM) for rectal cancer. However, vigilant surveillance requires excellent access to care. We sought to examine patient, socioeconomic, and facility-level factors associated with NOM over time.

METHODS

Using the National Cancer Database (2006-2017), we examined patients with Stage II-III rectal adenocarcinoma, who received neoadjuvant chemoradiation and received NOM versus surgery. Factors associated with NOM were assessed using multivariable logistic regression with backward stepwise selection.

RESULTS

There were 59,196 surgical and 8520 NOM patients identified. NOM use increased from 12.9% to 15.9% between 2006 and 2017. Patients who were Black (adjusted odds ratio [aOR]: 1.36, 95% confidence interval [CI]: 1.26-1.47), treated at community cancer centers (aOR: 1.22, 95% CI: 1.12-1.30), without insurance (aOR: 1.87, 95% CI: 1.68-2.09), and with less education (aOR: 1.53, 95% CI: 1.42-1.65) exhibited higher odds of NOM. Patients treated at high-volume centers (aOR: 0.79, 95% CI: 0.74-0.84) and those who traveled >25.6 miles for care (aOR: 0.59, 95% CI: 0.55-0.64) had lower odds of NOM.

CONCLUSIONS

Vulnerable groups who traditionally have difficulty accessing comprehensive cancer care were more likely to receive NOM, suggesting that healthcare disparities may be driving utilization. More research is needed to understand NOM decision-making in rectal cancer treatment.

Factors associated with refusing surgery versus planned nonoperative management for rectal cancer

BACKGROUND

Increasingly, patients with rectal cancer receive nonoperative management. A growing body of retrospective evidence supporting the safety of this approach has likely contributed to its growing popularity. However, patients may also undergo nonoperative management because of refusal of surgical resection. We hypothesize that patients who refuse surgery are more likely to be from groups who traditionally face barriers accessing care.

METHODS

We used the National Cancer Database (2006-2017) to analyze patients with nonmetastatic rectal adenocarcinoma who underwent nonoperative management following radiation. We identified 2 groups: (1) planned nonoperative management and (2) nonoperative management because of refusal of surgery. We performed logistic regression to compare the groups along patient, socioeconomic, and facility-level factors.

RESULTS

In total, 9,613 and 2,039 patients were included in the planned nonoperative management and refused nonoperative management groups, respectively. Of the total study cohort (ie, planned nonoperative management + refused nonoperative management), 21% of these patients diagnosed in 2017 underwent refused nonoperative management, versus 12% in 2006. Patients who were Black (adjusted odds ratio 1.47, 95% confidence interval 1.26-1.71) or Asian/Pacific Islander (adjusted odds ratio 1.51, 95% confidence interval 1.18-1.92), age ≥65 years (adjusted odds ratio 1.55, 95% confidence interval 1.37-1.77), with more advanced disease stage (stage III adjusted odds ratio 1.30, 95% confidence interval 1.10-1.53), and government insurance (adjusted odds ratio 1.19, 95% confidence interval 1.04-1.36) were associated with increased utilization of refused nonoperative management. Conversely, lower education (adjusted odds ratio 0.62, 95% confidence interval 0.50-0.76) and female sex (adjusted odds ratio 0.88, 95% confidence interval 0.79-0.97) were associated with planned nonoperative management.

CONCLUSION

Our findings suggest that the refused nonoperative management group is demographically distinct. Outreach efforts to better understand the rationale behind patient decision making in rectal cancer will be paramount to ensuring appropriate implementation of nonoperative management.

Cost-effectiveness of Total Neoadjuvant Therapy With Short-Course Radiotherapy for Resectable Locally Advanced Rectal Cancer

IMPORTANCE

Short-course radiotherapy and total neoadjuvant therapy (SCRT-TNT) followed by total mesorectal excision (TME) has emerged as a new treatment paradigm for patients with locally advanced rectal adenocarcinoma. However, the economic implication of this treatment strategy has not been compared with that of conventional long-course chemoradiotherapy (LCCRT) followed by TME with adjuvant chemotherapy.

OBJECTIVE

To perform a cost-effectiveness analysis of SCRT-TNT vs LCCRT in conjunction with TME for patients with locally advanced rectal cancer.

DESIGN, SETTING, AND PARTICIPANTS

A decision analytical model with a 5-year time horizon was constructed for patients with biopsy-proven, newly diagnosed, primary locally advanced rectal adenocarcinoma treated with SCRT-TNT or LCCRT. Markov modeling was used to model disease progression and patient survival after treatment in 3-month cycles. Data on probabilities and utilities were extracted from the literature. Costs were evaluated from the Medicare payer's perspective in 2020 US dollars. Sensitivity analyses were performed for key variables. Data were collected from October 3, 2020, to January 20, 2021, and analyzed from November 15, 2020, to April 25, 2021.

EXPOSURES

Two treatment strategies, SCRT-TNT vs LCCRT with adjuvant chemotherapy, were compared.

MAIN OUTCOMES AND MEASURES

Cost-effectiveness was evaluated using the incremental cost-effectiveness ratio and net monetary benefits. Effectiveness was defined as quality-adjusted life-years (QALYs). Both costs and QALYs were discounted at 3% annually. Willingness-to-pay threshold was set at $50 000/QALY.

RESULTS

During the 5-year horizon, the total cost was $41 355 and QALYs were 2.21 for SCRT-TNT; for LCCRT, the total cost was $54 827 and QALYs were 2.12, resulting in a negative incremental cost-effectiveness ratio (-$141 256.77). The net monetary benefit was $69 300 for SCRT-TNT and $51 060 for LCCRT. Sensitivity analyses using willingness to pay at $100 000/QALY and $150 000/QALY demonstrated the same conclusion.

CONCLUSIONS AND RELEVANCE

These findings suggest that SCRT-TNT followed by TME incurs lower cost and improved QALYs compared with conventional LCCRT followed by TME and adjuvant chemotherapy. These data offer further rationale to support SCRT-TNT as a novel cost-saving treatment paradigm in the management of locally advanced rectal cancer.

Effects of exercise during and after neoadjuvant chemoradiation on symptom burden and quality of life in rectal cancer patients: a phase II randomized controlled trial

PURPOSE

We previously demonstrated that exercise during and after neoadjuvant chemoradiation (NACRT) for rectal cancer may improve the rate of pathologic complete/near complete response. Here, we report the effects of exercise on symptom management and quality of life (QoL).

METHODS

Rectal cancer patients (N = 36) were randomized to a supervised high-intensity interval training program during NACRT followed by unsupervised continuous exercise after NACRT or usual care. Patient-reported outcomes were assessed at baseline, post-NACRT, and presurgery including symptom burden (M.D. Anderson Symptom Inventory) and QoL (European Organisation for Research and Treatment of Cancer QLQ- C30 and -CR29).

RESULTS

During NACRT, exercise significantly worsened stool frequency (adjusted between-group difference, 25.8; 95% CI, 4.0 to 47.6; p = 0.022), role functioning (adjusted between-group difference, -21.3; 95% CI, -41.5 to -1.1; p = 0.039), emotional functioning (adjusted between-group difference, -11.7; 95% CI, -22.0 to -1.4; p = 0.028), and cognitive functioning (adjusted between-group difference, -11.6; 95% CI, -19.2 to -4.0; p = 0.004) compared to usual care. After NACRT, exercise significantly worsened diarrhea (adjusted between-group difference, 1.2; 95% CI, 0.1 to 2.3; p = 0.030) and embarrassment (adjusted between-group difference, 19.7; 95% CI, 7.4 to 32.1; p = 0.003) compared to usual care.

CONCLUSIONS

Exercise exacerbated some symptoms and worsened QoL during NACRT; however, most negative effects dissipated after NACRT. Larger trials are necessary to confirm these findings.

IMPLICATIONS FOR CANCER SURVIVORS

If the clinical benefit of exercise is confirmed, then the modest symptom exacerbation during NACRT may be considered tolerable. However, in the absence of any clinical benefit, exercise may be contraindicated in this clinical setting.

Racial Disparities in the Management of Locoregional Colorectal Cancer

Racial disparities pervade nearly all aspects of management of locoregional colorectal cancer, including time to treatment, receipt of resection, adequacy of resection, postoperative complications, and receipt of neoadjuvant and adjuvant multimodality therapies. Disparate gaps in treatment translate into enduring effects on survivorship, recurrence, and mortality. Efforts to reduce these gaps in care must be undertaken on a multilevel basis and focus on modifiable factors that underlie racial disparity.

Clinical Complete Response in Patients With Rectal Adenocarcinoma Treated With Short-Course Radiation Therapy and Nonoperative Management

PURPOSE

This study aimed to determine the clinical efficacy and safety of nonoperative management (NOM) for patients with rectal cancer with a clinical complete response (cCR) after short-course radiation therapy and consolidation chemotherapy.

METHODS AND MATERIALS

Patients with stage I-III rectal adenocarcinoma underwent short-course radiation therapy followed by consolidation chemotherapy between January 2018 and May 2019 (n = 90). Clinical response was assessed by digital rectal examination, pelvic magnetic resonance imaging, and endoscopy. Of the patients with an evaluable initial response, those with a cCR (n = 43) underwent NOM, and those with a non-cCR (n = 43) underwent surgery. The clinical endpoints included local regrowth-free survival, regional control, distant metastasis-free survival, disease-free survival, and overall survival.

RESULTS

Compared with patients with an initial cCR, patients with initial non-cCR had more advanced T and N stage (P = .05), larger primary tumors (P = .002), and more circumferential resection margin involvement on diagnostic magnetic resonance imaging (P < .001). With a median follow-up of 30.1 months, the persistent cCR rate was 79% (30 of 38 patients) in the NOM cohort. The 2-year local regrowth-free survival was 81% (95% confidence interval [CI], 70%-94%) in the initial cCR group, and all patients with local regrowth were successfully salvaged. Compared with those with a non-cCR, patients with a cCR had improved 2-year regional control (98% [95% CI, 93%-100%] vs 85% [95% CI, 74%-97%], P = .02), distant metastasis-free survival (100% [95% CI, 100%-100%] vs 80% [95% CI, 69%-94%], P < .01), disease-free survival (98% [95% CI, 93%-100%] vs 71% [95% CI, 59%-87%], P < .01), and overall survival (100% [95% CI, 100%-100%] vs 88% [95% CI, 79%-98%], P = .02). No late grade 3+ gastrointestinal or genitourinary toxicities were observed in the patients who underwent continued NOM.

CONCLUSIONS

Short-course radiation therapy followed by consolidation chemotherapy may be a feasible organ preservation strategy in rectal cancer. Additional prospective studies are necessary to evaluate the safety and efficacy of this approach.

Recent Trends and Overall Survival of Young Versus Older Adults With Stage II to III Rectal Cancer Treated With and Without Surgery in the United States, 2010-2015

BACKGROUND

The omission of surgery via nonoperative management (NOM) for rectal cancer may be increasing, and this strategy could be particularly attractive for younger patients, whose incidence of rectal cancer has been rising. We sought to assess trends in NOM in young (younger than 55 y) versus older adult (55 y and older) rectal cancer cohorts.

METHODS

The National Cancer Database was used to identify patients diagnosed with stage II to III rectal cancer between 2010 and 2015. Multivariable logistic regression defined the association between sociodemographic variables and odds of NOM, including an age (18 to 54 vs. 55+ y)×surgery (surgery vs. NOM) interaction term. Adjusted Cox regression models compared overall survival between NOM versus surgery.

RESULTS

Among 22,561 patients with a median follow-up of 37.5 months, the utilization rate of NOM increased from 10.7% (2010) to 15.2% (2015). Older patients were more likely to receive NOM, although rates also increased among young (7.1% to 10.6%). Black patients were also more likely to receive NOM (P<0.001). Among the entire cohort, NOM was associated with worse overall survival (adjusted hazard ratio [AHR]=2.90, 95% confidence interval [CI]: 2.67-3.15) and there was a statistically significant age×NOM interaction (P=0.01) such that the effect of NOM on survival was worse for younger (AHR=3.37, 95% CI: 2.82-4.02) as compared with older patients (AHR=2.49, 95% CI: 2.27-2.74).

CONCLUSIONS

The increasing trend for NOM in stage II to III rectal cancer may be driven by disparities in treatment. Management with NOM appears to be associated with poorer survival, particularly in younger patients and could worsen outcomes for groups already at risk for suboptimal cancer care.

Evolving Treatment Options and Future Directions for Locally Advanced Rectal Cancer

Locally advanced rectal cancer can be biologically heterogeneous, but imaging advances have improved clinical assessment of primary tumor and involved lymph nodes in relation to pelvic structures and intended surgical planes. Contemporary treatment for rectal cancer is tailored to the individual patient through multidisciplinary collaboration among diagnosticians, surgeons, medical oncologists, and radiation oncologists to minimize local recurrence and distant metastases. Furthermore, patient preferences and quality of life preservation are becoming more relevant in the decision-making, and upcoming treatment strategies specifically are designed to minimize toxicities and long-term morbidity. Accumulating data have continued to support the use of total neoadjuvant therapy, namely the completion of: (1) multiagent cytotoxic chemotherapy; and (2) pelvic radiation with or without a radiosensitizing agent, before surgery. The total neoadjuvant therapy strategy not only eliminates potentially occult metastases early but also opens up the possibility of nonsurgical management for those who decline or are unfit for surgery. Finally, noncytotoxic agents in combination with established chemotherapy agents along with potentially predictive biomarkers are also being actively investigated to further improve the clinical outcomes of rectal cancer.

Evaluating Surveillance Patterns after Chemoradiation-Only Compared with Conventional Management for Older Patients with Rectal Cancer

BACKGROUND

Upfront chemoradiation with omission of surgery (CR-only) is increasingly being used to treat rectal cancer. When CR-only is used with curative intent, intense surveillance is recommended. We hypothesized that in practice, few patients treated with CR-only receive intensive post-treatment surveillance.

STUDY DESIGN

Using Surveillance, Epidemiology, and End Results (SEER)-Medicare, all nonmetastatic rectal cancer patients (≥66 years old) diagnosed from 2004 to 2012, who received upfront chemoradiation, were included. Patients who received CR-only were compared with patients receiving neoadjuvant therapy plus proctectomy. In the 24 months after treatment, markers of surveillance, including carcinoembryonic antigen testing (CEA), endoscopy, and imaging, were compared between groups.

RESULTS

A total of 2,482 individuals met the inclusion criteria: 21% (n = 514) had CR-only and 79% had conventional treatment (ie chemoradiation plus proctectomy). Only 2.5% and 3.4% of those in the CR-only and conventional treatment groups, respectively, were in complete compliance with National Comprehensive Cancer Network surveillance guidelines during the first 2 years post-treatment (p < 0.01). The CR-only group was less likely than the conventional treatment group to receive: CEA (adjusted risk ratio [aRR] 0.57; 95% CI 0.50 to 0.65), endoscopy (aRR 0.76; 95% CI 0.66 to 0.87), and office visits (aRR 0.88; 95% CI 0.84 to 0.92), respectively. However, there were similar rates of cross-sectional imaging between groups (aRR 1.31; 95% CI 0.93 to 1.85).

CONCLUSIONS

Adherence to guideline-recommended surveillance was poor for all Medicare patients with rectal cancer. Despite recommendations for closer follow-up, patients treated with CR-only were less likely to receive surveillance than those treated with conventional treatment. Efforts should be made to increase adherence to surveillance guidelines for all rectal cancer patients treated with curative intent, but particularly for those with higher risk of recurrence, such as those treated with CR-only.

Tumour necrosis factor-α-induced protein 8-like 2 is a novel regulator of proliferation, migration, and invasion in human rectal adenocarcinoma cells

Tumour necrosis factor‐α‐induced protein 8‐like 2 (TIPE2) is a tumour suppressor in many types of cancer. However, the mechanism of action of TIPE2 on the growth of rectal adenocarcinoma is unknown. Our results showed that the expression levels of TIPE2 in human rectal adenocarcinoma tissues were higher than those in adjacent non‐tumour tissues. Overexpression of TIPE2 reduced the proliferation, migration, and invasion of human rectal adenocarcinoma cells and down‐regulation of TIPE2 showed reverse effects. TIPE2 overexpression increased apoptosis through down‐regulating the expression levels of Wnt3a, phospho (p)‐β‐Catenin, and p‐glycogen synthase kinase‐3β in rectal adenocarcinoma cells, however, TIPE2 knockdown exhibited reverse trends. TIPE2 overexpression decreased autophagy by reducing the expression levels of p‐Smad2, p‐Smad3, and transforming growth factor‐beta (TGF‐β) in rectal adenocarcinoma cells, however, TIPE2 knockdown showed opposite effects. Furthermore, TIPE2 overexpression reduced the growth of xenografted human rectal adenocarcinoma, whereas TIPE2 knockdown promoted the growth of rectal adenocarcinoma tumours by modulating angiogenesis. In conclusion, TIPE2 could regulate the proliferation, migration, and invasion of human rectal adenocarcinoma cells through Wnt/β‐Catenin and TGF‐β/Smad2/3 signalling pathways. TIPE2 is a potential therapeutic target for the treatment of rectal adenocarcinoma.

Optimal management of localized rectal cancer in older patients

In advising the optimal management for older patients, health care professionals try to balance the risks from frailty, vulnerability, and comorbidity against the patient's ultimate prognosis, potential functional outcomes and quality of life (QOL). At the same time it is important to involve the patient and incorporate their preferences. But how can we present and balance the potential downside of radical radiotherapy and risks of unsalvageable recurrence against the potential risks of postoperative morbidity and mortality associated with radical surgery? There are currently no nationally approved and evidence-based guidelines available to ensure consistency in discussions with older adults or frail and vulnerable patients. In this overview we hope to provide an insightful discussion of the relevant issues and options currently available.

Decreased Use of Sphincter-Preserving Procedures Among African Americans with Rectal Cancer

BACKGROUND

Improved multimodality rectal cancer treatment has increased the use of sphincter-preserving surgery. This study sought to determine whether African American (AA) patients with rectal cancer receive sphincter-preserving surgery at the same rate as non-AA patients.

METHODS

The study used the Nationwide Inpatient Sample for years 1998-2012 to compare AA and non-AA patients with rectal cancer undergoing low anterior resection or abdominoperineal resection. The logistic regression model was used to adjust for age, gender, admission type, Elixhauser comorbidity index, and hospital factors such as size, location (urban vs.rural), teaching status, and procedure volume.

RESULTS

The search identified 22,697 patients, 1600 of whom were identified as AA. After adjustment for age and gender, the analysis showed that AA patients were less likely to undergo sphincter-preserving surgery than non-AA patients [odds ratio (OR) 0.70; 95% confidence interval (CI) 0.63-0.78; p < 0.0001). After further adjustment for the Elixhauser comorbidity index, admission type, hospital-specific factors, and insurance status, the analysis showed that AA patients still were less likely to undergo sphincter-preserving surgery (OR 0.78; 95% CI 0.70-0.87; p < 0.0001). Although the proportion of non-AA patients undergoing sphincter-preserving surgery increased during the study period (p = 0.0003), this trend was not significant for the AA patients (p = 0.13).

CONCLUSION

In this data analysis, the AA patients with rectal cancer had lower rates of sphincter-preserving surgery than the non-AA patients, even after adjustment for patient- and hospital-specific factors. Further work is required to elucidate why. Eliminating racial disparities in rectal cancer treatment should continue to be a priority for the surgical community.

Feasibility evaluation of diffusion-weighted imaging using an integrated MRI-radiotherapy system for response assessment to neoadjuvant therapy in rectal cancer

OBJECTIVE

To evaluate the feasibility of on-board diffusion-weighted imaging (DWI) with an integrated low-field MRI radiotherapy system to assess responses to neoadjuvant chemoradiation (NAC) in rectal cancer.

METHODS

A spin echo-based planar imaging diffusion sequence on a 0.35-T MRI radiotherapy system was acquired over the course of NAC. The apparent diffusion coefficients (ADCs) from the tumour regions of interest (ROIs) were calculated. A functional diffusion map (fDM) was created showing a pixelwise ADC analysis of the ROI over the course of treatment. Surgical pathology was correlated with ADC data.

RESULTS

Consecutive patients treated on a 0.35-T MRI radiotherapy system were evaluated. Patient A had the worst pathological response to NAC with a tumour regression score of 1 and was the only patient with a negative slope in the change of ADC values over the entire course of NAC, and during both the first and second half of NAC. The fDM from the first half of NAC for Patient A showed discrete dark areas in the tumour ROI, reflecting subregions with decreasing ADC values during NAC. Patient C had the most favourable pathological response to NAC with a Grade 3 response and was the only patient who had an increase in the slope in the change of ADC values from the first to the second half of NAC.

CONCLUSION

DWI using a low-field MRI radiotherapy system for evaluating the responses to NAC is feasible. Advances in knowledge: ADC values obtained using a 0.35-T MRI radiotherapy system over the course of NAC for rectal cancer correlate with pathological responses.