Set-up errors and planning target volume margins in head and neck cancer radiotherapy: a clinical study of image guidance with on-line cone-beam computed tomography.

BACKGROUND: Set-up errors represent a source of uncertainty in head and neck (H&N) cancer radiotherapy. The present study evaluated set-up accuracy with the use of cone-beam computed tomography (CBCT) in order to establish the proper clinical target volume (CTV) to planning target volume (PTV) margins to be adopted. METHODS: Local set-up accuracy was analysed for 44 H&N cancer patients since the implementation of CBCT. An on-line correction protocol was adopted, with the first 3 scans used to correct systematic errors with a 3-mm action level. The overall mean displacement (M), the population systematic (Σ) and random (σ) errors and the 3D vector length were calculated. PTV margins were calculated according to the van Herk formula (2.5Σ + 0.7σ). RESULTS: A total of 420 CBCT scans were analysed. A systematic correction was needed in 43% of patients. The value of M was <1 mm in all directions; the values of Σ and σ ranged over 1-1.2 and 1.4-1.9 mm, respectively. Pre-correction PTV margins were 3.48, 4.08 and 4.33 mm along the 3 axes. The PTV margins calculated after online correction were <2.5 mm in all directions. CONCLUSIONS: Kilovoltage CBCT is effective in evaluating set-up accuracy in H&N patients. CTV-PTV margins of 5 mm are safe and are currently adopted at our centre; however, some special situations, such as re-irradiation or the close proximity of organs at risk and high-dose regions, could benefit from daily image registration and lower (i.e., 3 mm) margins.

Impact of radiotherapy technique on the outcome of early breast cancer treated with conservative surgery: A multicenter observational study on 1,176 patients.

PURPOSE: To quantify the impact of radiotherapy technique on cosmetic outcome and on 5-year local control rate of early breast cancer treated with conservative surgery and adjuvant radiation. METHODS AND MATERIALS: A total of 1,176 patients irradiated to the breast in 1997 were entered by eight centers into a prospective, observational study. Surgical procedure was quadrantectomy in 97% of patients, with axillary dissection performed in 96%; pT-stage was T1 in 81% and T2 in 19% of cases; pN-stage was N0 in 71%, N + (1-3) in 21%, and N + (>3) in 8% of cases. An immobilization device was used in 17% of patients; external contour-based and computed tomography-based treatment planning were performed in 20% and 72% of cases, respectively; 37% of patients were treated with a telecobalt unit and 63% with a linear accelerator; portal verification was used in 55% of patients; a boost dose to the tumor bed was delivered in 60% of cases. RESULTS: With a median follow-up of 6.2 years, local, regional, and distant control rates at 5 years are 98%, 99%, and 92%, respectively. Use of less sophisticated treatment technique was associated with a less favorable cosmetic outcome. Local control was comparable between centers despite substantial technical differences. In a multivariate analysis including clinical and technical factors, only older age and prescription of medical adjuvant treatment significantly predicted for better local control, whereas use of portal verification was of borderline significance. CONCLUSIONS: Radiation technical factors impacted negatively on cosmetic outcome, but had relatively small effects on local control compared with other clinical factors.

Are international guidelines for the prescription of adjuvant treatment for early breast cancer followed in clinical practice? Results of a population-based study on 1547 patients.

AIMS AND BACKGROUND: The results of several randomized trials and meta-analyses have been reported on adjuvant treatment for early breast cancer and treatment guidelines have been defined accordingly, but detailed data are lacking on the appropriateness of treatment prescription in clinical practice. METHODS: We performed a prospective, observational, multicenter study to monitor the prescription, delivery and effectiveness of radiotherapy following conservative surgery for early breast cancer; 1610 patients treated with postoperative radiation to the breast in 1997 were entered by 12 centers in Lombardy, Italy. Here we report the results of a secondary analysis focused on the prescription of medical adjuvant treatment (1547 eligible patients). RESULTS: Chemotherapy only was prescribed to 526 patients (33%), hormonal therapy only to 539 (33%), and both treatments to 85 patients (5%); 460 women (29%) received no medical adjuvant treatment. We compared the collected data with guidelines defined in 1995 by the St Gallen Consensus Conference. Undertreatment was most frequent in node-negative patients at intermediate/high risk, no treatment (instead of tamoxifen or chemotherapy) being prescribed in 21-45% of cases. Node-negative patients at low risk, on the other hand, were overtreated with tamoxifen in 31% of cases. In node-positive, premenopausal women compliance with guidelines was far better, with a 91-96% rate of chemotherapy prescription. In node-positive, postmenopausal, estrogen receptor-positive patients chemotherapy was unduly prescribed in as many as 56% of cases. Comparison of clinical practice with the next version of the guidelines (1998) showed a somewhat better compliance. CONCLUSIONS: Despite the availability of official and authoritative guidelines, adjuvant treatment prescription for early breast cancer in Lombardy in 1997 was suboptimal, especially in well-defined subgroups of patients.