A Case of Sigmoid Colon Cancer in which Somatic Pain was Rapidly Alleviated after Panitumumab Administration Despite Tumor Progression

We present a 72-year-old woman with sigmoid colon cancer in whom the somatic pain was alleviated rapidly after the administration of anti-epidermal growth factor antibodies. Our patient had received 4 cycles of FOLFIRI therapy (irinotecan, 5-fluorouracil, and leucovorin) in combination with panitumumab (Pmab) for the treatment of unresectable primary cancer accompanied with multiple liver metastases and peritonitis carcinomatosa. As grade 3 paronychia eventually occurred, chemotherapy was stopped. After recovery of the grade 3 paronychia, Pmab was re-introduced and administered every alternate cycle to reduce the extent of adverse events. The patient had complained of somatic pain in the lower right abdomen just before re-initiating Pmab administration. The pain intensity decreased immediately after the administration of Pmab. On the next day her pain had remarkably alleviated and she was free from pain for a week. This phenomenon was repeatedly observed. After the re-introduction of Pmab, tumor response was evaluated on computed tomography, which showed progressive disease. We demonstrated that Pmab was effective in the alleviation of somatic pain, although the size of the tumors gradually increased.