Positron emission tomography as predictor of rectal cancer response during or following neoadjuvant chemoradiation

Difference between carbohydrate antigen 19-9 and fluorine-18 fluorodeoxyglucose positron emission tomography in evaluating the treatment efficacy of neoadjuvant treatment in patients with resectable and borderline resectable pancreatic ductal adenocarcinoma: Results of a dual-center study

BACKGROUND

An accurate evaluation of neoadjuvant treatment is important to maximize the prognostic benefit of this strategy in each individual patient. The main aim of the present study is to investigate the difference between carbohydrate antigen 19-9 and fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in evaluating the response to neoadjuvant treatment for resectable and borderline resectable pancreatic ductal adenocarcinoma (PDAC) patients.

METHODS

Pancreatic ductal adenocarcinoma patients with positive standard uptake values (SUV) on FDG-PET before neoadjuvant chemoradiotherapy (NACRT) were enrolled (n = 141). In all patients, CA19-9 and FDG-PET were evaluated before the initiation of and after the completion of NACRT. The statuses of CA19-9 and FDG uptake alterations during NACRT were assessed in association with survival and tumor recurrence profiles.

RESULTS

A favorable response in each CA19-9 and FDG-PET was significantly related to better survival, respectively, than the unfavorable response (44.3% vs 19.5%, P < .001 and 45.8% vs 24.6%, P < .001). The status of CA19-9 was significantly associated with the incidence of distant recurrence whereas the status of FDG-PET was significantly associated with the incidence of local recurrence, and only patients with a favorable response in both CA19-9 and PET statuses showed a significantly better survival than the others (5-year survival: 56% vs 24%, P < .001), and those with unfavorable response in either of CA19-9 or PET status showed similar poor survival to those with unfavorable in both (P = .164).

CONCLUSION

CA19-9 and PET evaluation provided oncologically different risk assessments in terms of tumor recurrence profile, and favorable response in both CA19-9 and FDG-PET were necessary to achieve prognostic benefit from NACRT.

Junior E, Machado AM, Mamede M. Individualized threshold for tumor segmentation in 18F-FDG PET/CT imaging: The key for response evaluation of neoadjuvant chemoradiation therapy in patients with rectal cancer?

Summary Introduction: The standard treatment for locally advanced rectal cancer (RC) consists of neoadjuvant chemoradiation followed by radical surgery. Regardless the extensive use of SUVmax in 18F-FDG PET tumor uptake as representation of tumor glycolytic consumption, there is a trend to apply metabolic volume instead. Thus, the aim of the present study was to evaluate a noninvasive method for tumor segmentation using the 18F-FDG PET imaging in order to predict response to neoadjuvant chemoradiation therapy in patients with rectal cancer. Method: The sample consisted of stage II and III rectal cancer patients undergoing 18F-FDG PET/CT examination before and eight weeks after neoadjuvant therapy. An individualized tumor segmentation methodology was applied to generate tumor volumes (SUV2SD) and compare with standard SUVmax and fixed threshold (SUV40%, SUV50% and SUV60%) pre- and post-therapy. Therapeutic response was assessed in the resected specimens using Dworak's protocol recommendations. Several variables were generated and compared with the histopathological results. Results: Seventeen (17) patients were included and analyzed. Significant differences were observed between responders (Dworak 3 and 4) and non-responders for SUVmax-2 (p<0.01), SUV2SD-2 (p<0.05), SUV40%-2 (p<0.05), SUV50%-2 (p<0.05) and SUV60%-2 (p<0.05). ROC analyses showed significant areas under the curve (p<0.01) for the proposed methodology with sensitivity and specificity varying from 60% to 83% and 73% to 82%, respectively. Conclusion: The present study confirmed the predictive power of the variables using a noninvasive individualized methodology for tumor segmentation based on 18F-FDG PET/CT imaging for response evaluation in patients with rectal cancer after neoadjuvant chemoradiation therapy.

FDG-PET predicts treatment efficacy and surgical outcome of pre-operative chemoradiation therapy for resectable and borderline resectable pancreatic cancer

BACKGROUND

The efficacy of neoadjuvant chemoradiotherapy (NACRT) for resectable and borderline resectable pancreatic cancer is important for predicting outcomes after radical surgery, but few clinical indicators predict outcome before resection. This study examined the utility of FDG-PET in predicting the efficacy of NACRT and outcome after radical surgery.

METHODS

Eighty-three pancreatic cancer patients who underwent FDG-PET before and after NACRT and had positive standard uptake values (SUVs) before NACRT were enrolled in this study. Peri-operative clinical factors, including FDG-PET findings, were examined to predict the efficacy of NACRT and outcome after surgery.

RESULTS

Evans grade I, IIA, IIB, III, and IV was determined in 11, 31, 27, 11, and 3 patients, respectively. The maximum SUVs after NACRT (post SUV-max) and tumor size were significantly decreased compared to pretreatment values (p < 0.001 and p = 0.007, respectively). The post SUV-max and regression index were significantly related to grade III/IV (p = 0.04 and p < 0.001, respectively), but only the regression index predicted NACRT efficacy (p = 0.002). The AUC of the regression index for the detection of grade III/IV was 0.822, and 13 of 14 grade III/IV patients were picked up using 50% as the threshold (p < 0.001). Patients with a regression index >50% had a significantly better prognosis after radical resection than patients with <50% (p = 0.032). Regression index as well as pathological lymph node status and resectability status were independent prognostic factors in multivariate analysis (exp 2.086, p = 0.043).

CONCLUSION

The regression index is potentially a good indicator of the efficacy of NACRT and outcome after radical resection for pancreatic cancer.

Impact of neoadjuvant therapy in downstaging of lower rectal adenocarcinoma and the role of pelvic magnetic resonance in staging

ABSTRACT Objective: to evaluate the effect of neoadjuvant therapy on the stage (TNM) of patients with rectal adenocarcinoma and validate the use of MRI as a method of determining locoregional stage. Methods: we conducted a retrospective study of 157 patients with lower rectum adenocarcinoma, whom we divided into two groups: Group 1, 81 patients (52%) who had undergone surgical treatment initially, with the purpose to analyze the accuracy of locoregional staging by pelvic magnetic resonance imaging throug the comparison of radiological findings with pathological ones; Group 2, 76 patients (48%), who had been submitted to neoadjuvant therapy (chemotherapy and radiation) prior to definitive surgical treatment, so as to evaluate its effects on the stage by comparing clinical and radiological findings with pathology. Results: In group 1, the accuracy of determining tumor depth (T) and lymph node involvement (N) was 91.4% and 82.7%, respectively. In group 2, neoadjuvant therapy decreased the T stage, N stage and TNM stage in 51.3%, 21% and 48.4% of cases, respectively. Conclusion: neoadjuvant therapy in patients with rectal adenocarcinoma is effective in decreasing disease stage, and pelvic magnetic resonance imaging is effective for locoregional staging.

Role of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography in predicting the pathologic response to preoperative chemoradiation therapy in patients with resectable T3 pancreatic cancer

BACKGROUND

The purpose of this study was to evaluate whether (18)F-fluorodeoxyglucose positron emission tomography in combination with computed tomography (FDG-PET/CT) could correctly predict the pathologic response to preoperative chemoradiation therapy (CRT) for resectable pancreatic cancer.

METHODS

Each of the 40 patients underwent FDG-PET/CT before and after preoperative CRT. The maximum standard uptake value (SUV) was measured for the primary tumor before and after preoperative CRT, defined as pre-CRT SUV and post-CRT SUV, respectively. The proportional alteration of the SUV decline (regression index) between post-CRT SUV and pre-CRT SUV was also calculated. These three indicators were associated with the pathologic response.

RESULTS

Patients were classified as 21 responders and 19 nonresponders according to the histologic features. A pre-CRT SUV ≥ 4.7 was seen in 15 (71 %) of 21 responders and in 6 (32 %) of 19 nonresponders (p = 0.03). A regression index ≥ 0.46 was seen in 15 (71 %) responders and 5 (26 %) nonresponders (p = 0.01).

CONCLUSIONS

A better pathological response can be expected for pancreatic cancer patients who have a high regression index (≥ 0.46) and a high pre-CRT SUV (≥ 4.7). The SUV measurement using FDG-PET/CT is a useful tool for predicting the pathologic response to preoperative CRT.

Avoiding radical surgery after pre-operative chemoradiotherapy: a possible therapeutic option in rectal cancer?

BACKGROUND

In this modern era of multi-modality treatment there is increasing interest in the possibility of avoiding radical surgery in complete responders after neo-adjuvant long-course chemoradiotherapy (LCPRT). In this article, we present a systematic review of such treatments and discuss their therapeutic applicability for the future.

METHODS

We searched the PubMed online libraries to identify studies that reported on the long-term surgical and pathological outcomes after local excision together with those that explored the possibility of clinical observation only in patients achieving a complete clinical response after LCPRT.

RESULTS

Several retrospective (n = 10), one single-arm prospective, and one small randomised series have reported on the use of local excision after LCPRT and demonstrated acceptably low levels of local recurrence with survival comparable to patients progressing to conventional surgery. One prospective series allocated patients to observation or radical surgery based on histological parameters after local excision (ypT0 and ypT1) and showed no differences in outcomes. Two retrospective series from the same group on a Brazilian cohort of patients reported excellent long-term outcomes after "wait and watch" in complete clinical responders. However, other reports have shown no direct correlation between clinical and pathological response.

CONCLUSION

Local excision may be an appropriate option for selected patients developing good clinical response after LCPRT. In our opinion, a policy of clinical observation in complete clinical responders after LCPRT may not be a safe strategy, unless we had robust predictive models for accurate identification of pathological complete response. In order to identify patients that may be potentially appropriate for such an approach we propose a clinical algorithm incorporating important clinical, radiological, and pathological parameters. The proposed model will require validation in a prospective study. Finally, we need randomised data for demonstrating the non-inferiority of clinical observation compared to conventional surgery before this can be considered as standard possible therapeutic option.