Update on advances and controversy in rectal cancer treatment

"Rectal cancer survival: A retrospective analysis of MRI features and their association with prognosis"

PURPOSE

To assess rectal cancer aggressiveness using magnetic resonance (MR) imaging features and to investigate their relationship with patient prognosis.

MATERIALS AND METHODS

Clinical information and Pelvic MR scans of 106 consecutive patients with primary rectal cancer (RC) were analyzed. Clinical symptoms, age, sex, tumor location, and patient´s survival were recorded. The variables investigated by MR were: depth or mural/extramural tumor involvement, distance to mesorectal margin, lymph node involvement, vascular, peritoneal or sphincter complex infiltration. The association between imaging features and disease-free survival (DFS) was also assessed using a Kaplan-Meier model. Differences between survival curves were tested for significance using the Mantel-Cox LogRank test.

RESULTS

The final study population was 106 patients (65 males, 41 females). The median age was 69.5 years (range, 39-92 years). No significant differences were found between death risk and sex, age or tumor location (p>0,05). However, the relative risk (RR) of tumor mortality increased significantly with the presence of the variables: vascular infiltration (×5), T4 tumors (× 4.57), N2 lymph node involvement (more than 3 affected nodes × 4.11) and mesorectal fascia involvement (× 3,77).

CONCLUSION

Tumor extension, number of pathological lymph nodes, mesorectal fascia involvement and vascular infiltration values obtained on initial MR imaging staging showed a significant difference for disease-free survival in RC at six years of control.

Focusing the management of rectal cancer

Rectal cancer treatment has undergone major changes over the last 15 years with a focus on individualized care based around MRI assessment of the relationship of the tumour to the mesorectal fascia, improved surgical techniques and targeted use of pre-operative oncological therapies in patients with locally advanced disease. The recognition that some tumours responded completely to pre-operative chemoradiotherapy, and the selective use of a non-operative policy has led to a quest to further identify those patients and their tumour in whom this approach could be used, irrespective of MRI stage. With no clear patient factors identified, the tumour and its gene expression has become a target for research to identify individual single-nucleotide polymorphisms, which may indicate a response to specific treatment, or not. To date some agents have been identified and trialed, such as cetuximab, with individual tumours being assessed for response allowing directed treatment. The reviewed paper by Sebio and colleagues report a study that links polymorphisms in the DNA repair gene XRCC1 with response to neoadjuvant 5-Fluorouracil treatment in rectal cancer patients. However, genetic heterogeneity alone may not explain the variations of drug response and environmental factors may lead to epigenetic effects and therefore alter responses. Therefore whilst this study demonstrates the impact of different single nucleotide polymorphisms (SNPs), it is only one step forward, but perhaps a step in the right direction.