Panitumumab Plus Radiotherapy for Rectal Cancer Fails To Meet Endpoint

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Investigators enrolled 98 patients to receive preoperative treatment with intravenous panitumumab plus concurrent radiotherapy.
Investigators enrolled 98 patients to receive preoperative treatment with intravenous panitumumab plus concurrent radiotherapy.

Preoperative panitumumab plus external radiotherapy did not meet a pre-specified pathologic complete response (pCR) rate endpoint among patients with locally advanced rectal cancer, according to a study published in The Oncologist.1

For the phase 2 RaP/STAR-03 study, investigators enrolled 98 patients with locally advanced rectal adenocarcinoma to receive preoperative treatment with intravenous panitumumab 6 mg/kg every 2 weeks for 3 cycles plus concurrent radiotherapy. Patients underwent rectal surgery 6 to 8 weeks after treatment and received adjuvant FOLFOX therapy.

Ninety-two patients completed therapy and surgery and were evaluable for pathologic response. No intraoperative complications were noted, though only 10 (10.9%) patients reached pCR, failing to meet the pre-specified 16% pCR requirement necessary for further testing.

The most frequently observed grade 3 or worse adverse events were skin rash, which occurred among 16 (16.3%) patients, and diarrhea (2.1%). Eighty-nine, 32, and 14 patients experienced any-grade rash, diarrhea, and anemia, respectively. No grade 4 adverse events were reported.

Although the primary endpoint was not reached, toxicity and compliance outcomes were favorable. The authors concluded that “further analysis of NRAS and BRAF on tissue and circulating levels of the EGFR ligands and vascular factors (soluble vascular endothelial growth factor, E-selectin) may provide insight on the potential molecular pathways involved in the anti-EGFR response.”


  1. Pinto C, Di Bisceglie M, Di Fabio F, et al. Phase II study of preoperative treatment with eternal radiotherapy plus panitumumab in low-risk, locally advanced rectal cancer (RaP Study/STAR-03). Oncologist. 2018 Mar 9. doi: 10.1634/theoncologist.2017-0484 [Epub ahead of print]

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