246 Radiation Oncology, Biology, Physics Volume 30, Supplement 1

William F. Hartsell, M.D., Dennis L. Galinsky, M.D., Katherine L. Griem, M.D., Diane C. Recine, M.D. and Anantha K. Murthy, M.D.

Department of Radiation Oncology, Rush-Presbyterian-St, Luke’s Medical Center, Chicago, Illinois

Pnrpoae: In the NSABP B-06 trial a boost dose to the tumor bed was not used for the patienta receiving breast conserving therapy (L + RT); despite this, many large retrospective eerie8 routinely use a boost to the tumor bed.

Me&h& and Materials: We treated 976 patient8 with invaeive breast cancer using L + RT from 4/80 to 12/91. The microscopic margim~ were known to be negative in 745 of these patient& 271 patients received a boost to the tumor bed, use of boost was by physician preference and was more common earlier in the series. The remaining 474 patients were treated with radiation of the whole breast without a boost; these patienta form the basis of our review. Dose was 1.8-2.0 Gy per fraction to 44-66 Gy (410 patients received 49-51 Gy). Dose was prescribed to isocenter, with most patients receiving f 5% of prescribed dose to entire breast. When indicated, wedgee were used to give homogeneous dose to the target volume. Age range was 25-87 years (median 56). Tumor atage was Tl in 382, T2 in 91 and unknown in 1. Twenty- seven patients had close margins (c 1 hpf). Thirty-four patienta did not have axillary dissection:, of the other 440 patients, 100 patients had positive nodes. 122 patients received chemotherapy and 129 were given tamonfen.

Reaulte: Median follow up is 54 months. There have been 12 breast recurrences, and 2 regional (eupraclavicular) actuarial local failure (LF) rates of 3.6 and 8% at 5 and 8 years. LF at 5 years was l%, 2% and 6% for those receiving tamoxifen, chemotherapy and no eystemic treatment. Cox regreeeion analysis wae performed; tumor size, wide vs. close margins, age, T stage, and nodal status were all evaluated but none were predictive of local failure.

Conclusion: Local failure ia uncommon when the whole breast is irradiated to 50 Gy in selected patients with tumor < 4 cm and microscopically clear margins of resection. The addition of systemic therapy, especially tamoxifen, further reduces the risk of local failure. A boost dose of radiation to the tumor bed is not necessary in these patients.

1007 PROGNOSTIC SIGNIFICANCE OF A MORE ACCURATE DETERMINATION OF TUMOR SIZE AND VOLUME IN BREAST

CONSERVATION THERAPY

Kayihan Engin, M.D., Lydia Komarnicky, M.D., Carl M. Mansfield, M.D., Alia Benammar, M.B.A., Janet Taylor, R.N.

Dept. of Radiation Oncology & Nuclear Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, PA 19107

PURPOSE/OBJECTIVE: We analyzed the effects of a more accurate determination of initial tumor size and volume on patient prognosis in 325 early-stage breast cancer patients who were treated with breast conservation therapy (BCT). The correlations between these two tumor parameters, i.e., tumor size and volume, and other tumor parameters (e.g., age, estrogen and progesteron receptor status and nodal status) were also analyzed.

m: Three hundred and twenty-five out of 1,135 patients who were treated with breast conservation therapy, i.e., lumpectomy and radiation therapy between 1983 and 1990 were analyzed retrospectively for the predictive effect of a more accurate determination of tumor size and volume. Tumor size was based on the TNM category using the largest one dimensional measurement obtained from the pathology specimen or mammogram. Tumor volume was based on the three dimensional measurements of the pathology specimen or mammogram. Clinical measurements were not used. After tumor excision, 45 Gy external radiation therapy was administered to the whole breast using tangential fields in 25 fractions over 5 weeks. Tumor site was given an additional boost of 20 Gy either with Ir192 implants or electrons (2 Gy per fraction). Ir192 . implants were performed perioperatively in all cases. Tumors were grouped by tumor size (TS) and tumor volume (TV). For tumor size; Group ITS = 0.1-1.0 cm (32%), Group IITS = 1.1-2.0 cm (42%), Group I&S = 2.1-3.0 cm (19%), Group IVTS = 3.1-4.0 cm (5%) and Group VTS = A.0 (2%). For tumor volume; Group ITV = 0.1-1.0,cm3 (36%). Group IITV = 1.1-8.0 cm3 (43%). Group IIITv = 8.1-27.0 cm3 (18%) and Group IVTV = >27.1 cm3 (36%). Correlations between these two factors (TS and TV) and local control, survival and other tumor parameters were analyzed.

RESULTS: Five and ten year local control (LC) rates by NmOr size and volume were not significantly different from each other. However other end points were influenced by tumor size and volume. For instance, actuarial overall 5- and IO-year overall survival (OS) was 94% and 94% for Group ITS and 60% and 60% for Group VTS. By NmOr volume, 5- and lo-year overall survival was 95% and 95% for Group 1~ and 58% and 58% for Group IVTV. Disease-specific survival (DSS) at 5 and 10 years by tumor size was 96% and 96% for Group ITS and 60% and 60% for Group VTS. A trend was observed in 5- and lo-year DSS rates by tumor volume; 96% and 96% for Grou ITV and 66% and 66% for Group IVTV. At 5 and 10 years, rates of patients with no evidence of disease (NED) by tumor size were as P fo lows; 91% and 76% for Group 1~8 and 41% and 41% for Group VTS. NED by tumor volume was 90% and 75% for Group ITV and 38% and 38% for Group IVTV. For all patients, 5- and lo-year LC was 93% and 89%, OS was 88% and 74%. DSS was 89% and 79% and NED was 81% and 67%.

CONCLUSIONS: Gur results indicate that the local control after breast conservation therapy is not affected by tumor size or volume. In contrast, actuarial overall survival appears to be influenced by tumor size and volume. Tumor volume was more predictive than tumor size for OS, DSS and NED. There was also a correlation between ER and PR status and NmOr volume.