A randomized study of the effect of patient positioning on setup reproducibility and dose distribution to organs at risk in radiotherapy of rectal cancer patients.

BACKGROUND: The patient positioning in pelvic radiotherapy (RT) should be decided based on both reproducibility and on which position that yields the lowest radiation dose to the organs at risk (OAR), and thereby less side effects to patients. The present randomized study aimed to evaluate the influence of patient positioning on setup reproducibility and dose distribution to OAR in rectal cancer patients. METHODS: Ninety-one patients were randomized into receiving RT in either supine or prone position. The recruitment period was from 2005 to 2008. Position deviations were derived from electronic portal image registrations, and setup errors were defined as deviations between the expected and the actual position of bony landmarks. Setup deviations were expressed into three table shift values (∆x, ∆y, ∆z) from which the deviation vector [Formula: see text] were calculated. The estimated lengths of [Formula: see text] defined the main outcome and were compared between prone and supine positions using linear mixed model statistics. The mean volume of each 5 Gy increments between 5 and 45 Gy was calculated for the small bowel and the total bowel, and the dose volumes were compared between prone and supine position. RESULTS AND CONCLUSION: Data from 83 patients was evaluable. The mean [Formula: see text] was 5.8 mm in supine position and 7.1 mm in prone position (p = 0.024), hence the reproducibility was significantly superior in supine position. However, the difference was marginal and may have borderline clinical importance. The irradiated volumes of the small bowel and the total bowel were largest in the supine position for all dose levels, but none of those were significantly different. The patient positioning in RT of rectal cancer patients may therefore be decided based on other factors such as the most comfortable position for the patients.

Relative biological effectiveness of photon energies used in brachytherapy and intraoperative radiotherapy techniques for two breast cancer cell lines.

BACKGROUND: Partial breast irradiation (IORT or brachytherapy) differ from external radiation of whole breast in terms of irradiated volumes, fractionation, radiation energy and dose rate; all factors influencing the treatment outcome in a complex manner. Theoretically obtained RBE values comparing effects of radiation used in IORT and external therapy are published, but experimental studies are required to confirm these data. The aim of this study is to establish such RBE values for two breast cancer cell lines. MATERIALS AND METHODS: Colony formation of breast cancer cell lines (MCF-7 and T-47D) were studied after photon irradiation with qualities and dose rates used in IORT, brachytherapy and external radiation. RBE values from survival data were used to compare effects. RESULTS: Increasing the photon energy (dose rate 0.2 Gy/min) from 50 kV (Intrabeam) to 380 keV (¹9²Ir source) and 6 MV (linear accelerator) yielded an increase in the cell survival, whereas increasing the dose rate to 6 Gy/min had minor effect. Average RBE values for 50 kV with 6 MV as reference radiation varied from about 1.4 (for doses < 5 Gy) to > 1.9 (for doses < 0.02 Gy) for MCF-7 cells and from about 1.4 to > 3.1 for T-47D cells for the same dose levels. Corresponding RBE values for 380 keV radiation were about 1.4 for MCF-7 cells and 1.3-2.3 for T-47D cells. CONCLUSION: RBE data for breast cancer cells exposed to radiation used in IORT, brachytherapy or external radiation differ among the cell lines tested. The values are in agreement with published theoretical and experimental work.

Cervical carcinoma: postoperative radiotherapy: fifteen-year experience in a Norwegian health region.

INTRODUCTION: To study the results in cervical carcinoma after a combined treatment with surgery and radiotherapy with regard to survival and side effects. METHODS: A retrospective analysis of 71 patients who underwent radical hysterectomy and postoperative radiotherapy between January 1, 1987, and December 31, 2001, was performed. RESULTS: Median follow-up periods were 162 months for surviving patients and 62 months for deceased patients. The 5-year overall survival and disease-specific survival for all stages were 80.3% and 82.7%, respectively. The 5-year actuarial incidence of late reactions for grade 1 + 2 was as follows: for upper gastrointestinal tract, 36%; for rectum, 37%; for urinary tract, 19%; for vagina, 26%; and for lymph edema, 19%. The 5-year actuarial incidence of late reactions for grade 3 + 4 was as follows: for upper gastrointestinal tract, 12%; and for rectum, 3%. CONCLUSIONS: Careful pretreatment workup and well-defined criteria for postoperative radiotherapy are essential, and new treatment options such as intensity-modulated radiation therapy should be considered.

Effects of growth factors on growth and radiation sensitivity of the human breast cancer cell line T-47D.

Different growth factors are supposed to be involved in evolution of breast cancer. Radiation therapy is used in treatment of breast cancer patients, and the possible relationships between the influence of growth factors on cells and their radiation sensitivity are therefore of interest. Cell growth and radiation sensitivity of the human oestrogen and progesterone receptor positive cell line T-47D were investigated following exposure to the growth factors IGF-1, TGF-alpha and TGF-beta. Experiments were done with standard medium and in growth factor defined medium. Changes in cell cycle distribution were investigated by flow cytometry. The cell growth was significantly decreased by removal of growth factors in the culture medium, an effect which partly could be reversed by supplementation of growth factors. The growth factors decreased the cellular doubling time in standard medium, but to a smaller extent than seen in growth factor defined medium. The radiation sensitivity and plating efficiency were slightly affected by growth factor defined versus standard growth conditions. Additional growth factor exposure was able to some extent to change the radiation sensitivity, mainly by effects due to changes in repair of sublethal damage. Only minor changes were seen in phase distribution of these cells. Cellular growth was dependent on presence of different growth factors, and changes in growth factor conditions greatly influenced the cellular doubling time in vitro. Corresponding changes in radiation sensitivity were minor for doses relevant for radiation therapy.