OBJECTIVE: To assess the rate of geographic miss on conventional radiotherapy planning of patients with cervical cancer, using magnetic resonance imaging. MATERIALS AND METHODS: Thirty-two patients with squamous cell carcinoma of the uterine cervix were studied. Magnetic resonance imaging of the pelvis was performed after clinical staging. Magnetic resonance imaging findings were compared with the classic fields described for the "box" technique. Target volume within less than 1 cm margins of the fields' limits was considered as geographic miss. RESULTS: Classical radiation field limits were inadequate in 24 cases (75%), all in the anterior (46%) or posterior (40%) border of the lateral fields. CONCLUSION: Magnetic resonance detected a high probability of geographic miss on conventional radiotherapy planning in this population, both in initial and advanced stages of the disease.

Keywords: Uterine cervix cancer, Radiotherapy, Magnetic resonance imaging

Radiotherapy techniques for esophageal cancer were compared using a three-dimensional planning system. We studied the following treatment techniques used for a patient with squamous cell carcinoma of the middle third of the esophagus: two antero-posterior and two latero-lateral parallel opposed fields, three fields ("Y" and "T"), and four fields ("X"). Dose-volume histograms were obtained considering spinal cord and lungs as organs at risk. Analysis was performed comparing doses in these organs as recommended by the Normal Tissue Complication Probability (NTCP) and Tumor Control Probability (TCP). When only the lungs were considered the best technique was two antero-posterior parallel opposed fields. The spinal cord was best protected using latero-lateral fields. We suggest the combination of at least two treatment techniques: antero-posterior fields with "Y" or "T" techniques, or latero-lateral fields in order to balance the doses in the lungs and the spinal cord. Another option may be the use of any of the three-field techniques during the whole treatment.

Keywords: Conformal radiotherapy, Esophageal cancer, Radiotherapy techniques, NTCP