Personalized chemotherapy for rectal cancer results in high rates of pathologic response, indicate the results of a pilot study.
"These data show that it is feasible to guide the selection of chemotherapy in patients with rectal cancer applying a simple, affordable, and practical algorithm," say Antonio Cubillo (Universidad EU San Pablo, Madrid, Spain) and colleagues.
The study included 16 patients with T3 and/or node-positive disease. Six to 8 weeks before surgery, patients received capecitabine 5 days per week, intensity-modulation radiotherapy, and additional treatment according to an algorithm.
Only four patients received just capecitabine, while four patients with high Topo-1-positive tumors received irinotecan, and eight of those with tumors negative for both Topo-1 and ERCC-1 received oxaliplatin. Additionally, 10 patients with KRAS- or BRAF-mutated tumors received bevacizumab, and six patients with wild type mutations received cetuximab.
In all, 11 patients had downstaging of the T stage, and only one patient advanced from T2 to T3. No patients presented with new lymph node involvement, and eight patients experienced downstaging of the N stage.
In total, 81% had no node involvement after treatment, and 50% had a complete pathologic response. The authors say that this compares to a typical rate of 16% reported in meta-analyses.
Interestingly, the authors found that positron emission topography (PET) was a poor predictor of outcomes, with only two patients with negative PET results showing tumor regression of grade 4. They say that this could be because they performed the PET study at the end of treatment, while recent research suggests it may be better to perform it a week after pretreatment begins.
While the authors say that their results are encouraging and describe the patient outcomes as "remarkable," they caution that the small size of their study limits the interpretation of the results.
"This strategy should be tested in a randomized phase II study compared with conventional 5-fluoroacil-based chemoradiation," they conclude in the American Journal of Clinical Oncology.
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