Impact of PET/CT for Restaging Patients With Locally Advanced Rectal Cancer After Neoadjuvant Chemoradiation

BACKGROUND

A major challenge in identifying candidates for nonoperative management of locally advanced rectal cancer is predicting pathologic complete response (pCR) following chemoradiation. We evaluated pre- and post-CRT PET-CT imaging to predict pCR and prognosis in this set of patients undergoing resection after neoadjuvant therapy.

METHODS

We retrospectively identified patients from 2002 to 2015 with locally advanced rectal cancer who underwent CRT, pre- and post-CRT PET-CT imaging, and resection. Univariate and multivariate analysis was performed and receiver operating characteristic (ROC) curves were generated to evaluate the association of PET-CT characteristics with pCR and survival. ROC curves were generated to define optimal cutoff points for predictive PET-CT characteristics.

RESULTS

125 patients were included. pCR rate was 28%, and follow-up was 48 mo. On multivariable analysis, patients who had a pCR had lower median post-CRT maximal standardized uptake value (SUV_max) (3.2 versus 5.2, P = 0.009) and higher median %SUV decrease (72 versus 58%, P = 0.009). ROC curves were generated for %SUV_max decrease (AUC = 0.70) and post-CRT SUV (AUC = 0.69). Post-CRT SUV_max <4.3 and %SUV_max decrease of >66% were equally predictive of pCR with a sensitivity of 65%, specificity of 72%, PPV of 44%, and NPV of 86%. Median 5-y overall and relapse-free survival were improved for patients with post-CRT SUV <4.3 (OS: 86 versus 66%, P = 0.01; RFS: 75 versus 52%, P = 0.01) or %SUV decrease of >66% (OS, 82 versus 66%, P = 0.05; RFS, 75 versus 54%, P = 0.01).

CONCLUSIONS

PET/CT may be useful in identifying patients who did not achieve pCR, as well as overall survival in patients undergoing CRT for rectal cancer. Patients with a post-CRT SUV of >4.3 should be considered for operative management, as an estimated 86% of these patients will not have a pCR.

Predictive Value of Leukocyte- and Platelet-Derived Ratios in Rectal Adenocarcinoma

BACKGROUND

Advances in treatment of rectal cancer have improved survival, but there is variability in response to therapy. Recent data suggest the utility of the lymphocyte-to-monocyte ratio (LMR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) in predicting survival. Our aim was to examine these ratios in rectal cancer patients and determine whether any association exists with overall survival (OS).

METHODS

Using prospectively maintained institutional data, a query was completed for clinical stage II-III rectal adenocarcinoma patients treated from 2002 to 2016. We included patients who had a complete blood count collected before neoadjuvant chemoradiation (pre-CRT) and again before surgery (post-CRT). The LMR, NLR, and PLR were calculated for the pre-CRT and post-CRT time points. Potential cutpoints associated with OS differences were determined using maximally selected rank statistics. Survival curves were compared using log-rank tests and were adjusted for age and stage using Cox regression.

RESULTS

A total of 146 patients were included. Cutpoints were significantly associated with OS for pre-CRT ratios but not for post-CRT ratios. Within the pretreatment group, a "low" (<2.86) LMR was associated with decreased OS (log-rank P = 0.004). In the same group, a "high" (>4.47) NLR and "high" PLR (>203.6) were associated with decreased OS (log-rank P < 0.001). With covariate adjustment for age, and separately for final pathologic stage, the associations between OS and LMR, NLR, and PLR each retained statistical significance.

CONCLUSIONS

If obtained before the start of neoadjuvant chemoradiation, LMR, NLR, and PLR values are accurate predictors of 5-y OS in patients with locally advanced rectal adenocarcinoma.