Calculation of organ doses from breast cancer radiotherapy: a Monte Carlo study.

The current study aimed to: a) utilize Monte Carlo simulation methods for the assessment of radiation doses imparted to all organs at risk to develop secondary radiation induced cancer, for patients undergoing radiotherapy for breast cancer; and b) evaluate the effect of breast size on dose to organs outside the irradiation field. A simulated linear accelerator model was generated. The in-field accuracy of the simulated photon beam properties was verified against percentage depth dose (PDD) and dose profile measurements on an actual water phantom. Off-axis dose calculations were verified with thermoluminescent dosimetry (TLD) measurements on a humanoid physical phantom. An anthropomorphic mathematical phantom was used to simulate breast cancer radiotherapy with medial and lateral fields. The effect of breast size on the calculated organ dose was investigated. Local differences between measured and calculated PDDs and dose profiles did not exceed 2% for the points at depths beyond the depth of maximum dose and the plateau region of the profile, respectively. For the penumbral regions of the dose profiles, the distance to agreement (DTA) did not exceed 2 mm. The mean difference between calculated out-of-field doses and TLD measurements was 11.4% ± 5.9%. The calculated doses to peripheral organs ranged from 2.32 cGy up to 161.41 cGy depending on breast size and thus the field dimensions applied, as well as the proximity of the organs to the primary beam. An increase to the therapeutic field area by 50% to account for the large breast led to a mean organ dose elevation by up to 85.2% for lateral exposure. The contralateral breast dose ranged between 1.4% and 1.6% of the prescribed dose to the tumor. Breast size affects dose deposition substantially.

Phase I/II trial of external irradiation plus medium-dose brachytherapy given concurrently to liposomal doxorubicin and cisplatin for advanced uterine cervix carcinoma.

BACKGROUND AND PURPOSE: Although the standard of care for patients with locally advanced uterine cervix carcinoma is cisplatin-(CDDP-)based chemotherapy and irradiation (RT), the optimal regimen remains to be elucidated. A phase I/II study was conducted to evaluate the dose limiting toxicity (DLT) and the maximum tolerated dose (MTD) of liposomal doxorubicin (Caelyx) combined with CDDP and RT for cervical cancer. PATIENTS AND METHODS: 24 patients with stage IIB-IVA were enrolled (Table 1). They all received external RT (up to 50.4 Gy) and two medium-dose rate (MDR) brachytherapy implants (20 Gy each at point A). The Caelyx starting dose of 7 mg/m2/week was increased in 5-mg/m2 increments to two levels. The standard dose of CDDP was 20-25 mg/m2/week. RESULTS: Concurrent chemoradiation (CCRT) sequelae and the DLTs (grade 3 myelotoxicity and grade 3 proctitis in five patients treated at the 17 mg/m2/week Caelyx dose level) are shown in Tables 2, 3, 4, and 5. After a median follow-up time of 17.2 months (range 4-36 months), four patients had died, 15 showed no evidence of progressive disease, and five (20.8%, 95% confidence interval [CI]: 12.5-29.1%) were alive with relapse (Figure 1). There were seven complete (29.1%, 95% CI: 19.8-38.4%) and 17 partial clinical responses (95% CI: 61.1-80.1%). The median progression-free survival was 10.4 months. Causes of death were local regional failure with or without paraaortic node relapse combined with distant metastases (Table 6). CONCLUSION: The MTD of Caelyx given concurrently with CDDP and RT was determined at the 12 mg/m2/week dose level. The above CCRT schema is a well-tolerated regimen, easy to administer in ambulatory patients, and results appear promising.