PATTERNS OF FAILURE OF COMPLETE RESPONDERS FOLLOWING HIGH-DOSE CHEMOTHERAPY AND AUTOLOGOUS BONE MARROW TRANSPLANTATION FOR METASTATIC BREAST CANCER: IMPLICATIONS FOR THE USE OF ADJUVANT RADIATION THERAPY

Abstract Purpose: To determine the pattern of failure and outcome of patients achieving a complete response following high-dose chemotherapy and autologous bone marrow transplantation for metastatic breast cancer, and to evaluate the use of involved field radiation therapy in this setting. Methods and Materials: Thirty-one patients with metastatic breast cancer treated on three successive high-dose chemotherapy and autologous bone marrow transplantation trials between January 1987 and March 1992 who achieved a complete response were evaluated. Twenty-three patients (74.2%) had initially Stage I–II disease. Initial therapy consisted of mastectomy in 19 (74.2%), adjuvant chemotherapy in 19 (61.3%), and adjuvant radiation therapy in 11 (35.5%). All patients underwent induction chemotherapy prior to high-dose intensification. High-dose chemotherapy consisted of cytoxan, thiotepa ± carmustine. Fourteen patients received radiation therapy prior to (7) or following the high-dose chemotherapy (7) with either the intent to palliate a symptomatic disease site (4) or to attain/maintain a complete response (10). The four palliatively treated sites received 30 Gy in 3.0 Gy fractions, the sites treated definitively received a mean dose of 43.9 Gy (range, 18–64.8 Gy) in 1.5–2.0 Gy fractions. Seventy-two disease sites were present in the 31 patients. The most common sites involved were nodal (23), bone (14), and chest wall/breast (11). Nineteen sites were bulky (>2 cm in size). Twenty-three sites were irradiated (19 definitively, 4 palliatively). Median follow-up was 18 months (range, 2–49 months). Results: Twenty (64.5%) of the 31 patients relapsed. Eleven of the 17 patients not receiving radiation failed. Seven (63.6%) failed first solely in sites of previous disease involvement and four (36.4%) failed in new sites. This failure pattern was reversed in the patients receiving radiation therapy. Nine of the 14 (64.3%) patients relapsed. Two (22.2%) failed solely in old sites and six (66.7%) solely in new sites. One patient (11.1%) failed simultaneously in both old and new sites. Patients receiving radiation therapy had a similar 2-year actuarial disease-free survival compared to those not treated with radiation (28.3% vs. 32.1%) ( p = 0.14). However, patients with less than three sites of disease had a better disease-free survival at 2 years with the addition of radiation therapy (30.0% vs. 17.6%) ( p = 0.03). Patients with locoregional disease only had a lower rate of local failure (one out of four vs. three out of five) and a longer mean time to any failure (4.0 months vs. 17.5 months) with the addition of radiation therapy. Of the 72 sites idenlified, 59 (81.9%) were amenable to radiation therapy either prior to or following the transplant. The use of radiation therapy resulted in a borderline significant improvement in 2-year actuarial control of all sites (82.4% vs. 64.3%) ( p = 0.09) as well as of bulky sites (80.0% vs. 51.4%) ( p = 0.08). Excluding the four sites treated with palliative intent only, the 2-year actuarial local control of the irradiated sites was 92.8%. None of the 14 treated patients experienced untoward sequelae. Conclusion: The predominant site of initial failure in patients with metastatic breast cancer achieving a complete response following high-dose chemotherapy and autologous bone marrow transplantation is in sites of previous disease involvement. Radiation therapy given in conjunction with the high-dose chemotherapy is capable of improving the control of these sites, the majority of which are amenable to treatment with radiation therapy. Our data suggests that patients with less than three sites of disease, bulky disease, and locoregional disease only should be considered for radiation therapy in addition to high-dose chemotherapy.