Response to HER-2 pulsed DC1 vaccines is predicted by both HER-2 and estrogen receptor expression in DCIS

Patients with estrogen-independent (ER(neg)) human epidermal growth factor receptor-2 (HER-2)-positive ductal carcinoma in situ (DCIS) treated with lumpectomy alone or lumpectomy and radiation are at increased risk of developing subsequent breast cancer events.

Thirty-eight patients with HER-2 expressing DCIS received a HER-2 pulsed autologous dendritic cell (DC1) vaccine administered over 4-6 weeks before surgical resection. HER-2 and estrogen receptor (ER) expression were determined by immunohistochemistry. In 35 patients, CD4(pos) T-cell sensitization to HER-2 peptides was identified by ELISPOT. In 19 patients, CD8(pos) T-cell responses were identified by ELISA. Clinical and immune responses postvaccination were compared between intermediate-expressing HER-2 (2+) and high-expressing HER-2 (3+) patients, as well as ER(neg) and estrogen-dependent (ER(pos)) patients.

There was no significant difference in immune response after HER-2 vaccination in patients with HER-2 (2+) and (3+) tumors or ER(neg) and ER(pos) tumors. Complete tumor regression rates were similar in patients with HER-2 (2+) and (3+) DCIS. Overall, clinical response rates were similar in patients with ER(neg) and ER(pos) DCIS, but complete tumor regression was significantly more common in patients with ER(neg) DCIS.

Despite equivalent immune responses after vaccination in patients with HER-2 (2+), HER-2 (3+), ER(neg) and ER(pos) DCIS, HER-2 pulsed DC1 induces more complete responses in patients with ER(neg) DCIS. These data provide a rationale for developing vaccinations to reduce recurrence in patients with ER(neg) DCIS for whom there are currently limited adjuvant options.