3-dimensional conformal radiotherapy (3D-CRT) combines multiple radiation treatment fields to deliver very precise doses of radiation to the breast and spare surrounding normal tissue. Planning breast cancer radiation on a CT scan allows both maximal lung and heart avoidance as well as thorough coverage of the lumpectomy site and lymph nodes.

Intensity modulated radiation therapy (IMRT) is a form of 3D-CRT that further modifies the radiation by varying the intensity of the radiation beams. It is currently being studied for treating breast cancer. Available in a few clinics for a very select group of patients, partial breast irradiation techniques are used after a lumpectomy to deliver radiation to the tumor site rather than the entire breast. These techniques include 3-D conformal partial breast irradiation, brachytherapy, and intra-operative radiation therapy (IORT). The long-term results of these techniques are still being studied. Talk with your radiation oncologist if you would like more information.

A Phase III randomized trial and several single institution trials have confirmed the advantage of high dose radiotherapy for patients with localized prostate cancer.

An update of the Phase III trial from MD Anderson was reported by Pollack. The study enrolled 301 patients with T1-T3 prostate cancer of which 150 were treated to 70 Gy (conventional RT) and 151 were treated to 78 Gy (with a 3D boost). The PSA relapse-free survival outcomes for the 78 and 70 Gy arms were 70% and 64%. A significant advantage for dose escalation was detected among patients with pre-treatment PSA levels >10 ng/ml. In this latter group the PSA control for the 78 and 70 Gy arms were 62% and 43% respectively.

The experience from Memorial Sloan Kettering Cancer Center was reported by Zelefsky. A total of 1100 patients were treated through December 1998. The radiation dose was systematically increased from 64.8 to 86.4 Gy. While the MSKCC study was initially designed to evaluate whether a safe escalation of dose could be achieved, it has also generated extensive information on the efficacy of dose escalation both on local control and long-term disease-free survival. Local control was assessed by prostate biopsies performed at > 2.5 years after 3D-CRT in 220 patients. Of the patients receiving a dose of 81 Gy, 91% had negative biopsies, compared with 76% after 75.6 Gy, 66% after 70.2 Gy, and 48% after 64.8 Gy.

High radiation dose levels (> 75.6 Gy) also had a significant impact on PSA relapse. PSA relapse was defined as three successive increases in the PSA value after a post treatment low was achieved. Patients with stages T1-T2, pretreatment PSA = 10 ng/mL and Gleason score = 6 were classified as a favorable prognosis group. An increase in one of the variables classified the patient in the intermediate and an increase in two or more in the unfavorable prognosis groups. The 5-year actuarial PSA relapse-free survival rate for patients with favorable disease who received 70.2 Gy was 80%, compared to 91% for those treated to > 75.6 Gy.

For patients with intermediate prognosis, the corresponding rates were, respectively, 47% and 70%, and for the unfavorable prognosis group, they were 24% and 47%. Furthermore, the 5-year PSA relapse-free survival rate for unfavorable risk patients who received 81 Gy was 69% compared to 43% for those treated to 75.6 Gy. Investigators from the Fox Chase Cancer Center have confirmed the direct relationship between dose and PSA outcome in patients treated to dose levels ranging from 66 to 79 Gy. In a matched-pair analysis, 357 patients who received > 74 Gy with 3D-CRT were compared to 357 patients treated to < 74 Gy with either conventional or conformal techniques. The 5-year PSA relapse-free survival rates were 71% and 56%, respectively, for the high- and low-dose groups. Dose also had a significant affect on the 5-year freedom from distant metastasis (97% vs. 88%) and overall survival (88% vs. 79%).