Radiotherapy of prostate cancer with or without intensity modulated beams: a planning comparison.

PURPOSE: To evaluate whether intensity modulated radiotherapy (IMRT) by static segmented beams allows the dose to the main portion of the prostate target to escalate while keeping the maximal dose at the anterior rectal wall at 72 Gy. The value of such IMRT plans was analyzed by comparison with non-IMRT plans using the same beam incidences. METHODS AND MATERIALS: We performed a planning study on the CT data of 32 consecutive patients with localized adenocarcinoma of the prostate. Three fields in the transverse plane with gantry angles of 0 degrees, 116 degrees, and 244 degrees were isocentered at the center of gravity of the target volume (prostate and seminal vesicles). The geometry of the beams was determined by beam's eye view autocontouring of the target volume with a margin of 1.5 cm. In study 1, the beam weights were determined by a human planner (3D-man) or by computer optimization using a biological objective function with (3D-optim-lim) or without (3D-optim-unlim) a physical term to limit target dose inhomogeneity. In study 2, the 3 beam incidences mentioned above were used and in-field uniform segments were added to allow IMRT. Plans with (IMRT-lim) or without (IMRT-unlim) constraints on target dose inhomogeneity were compared. In the IMRT-lim plan, target dose inhomogeneity was constrained between 15% and 20%. After optimization, plans in both studies were normalized to a maximal rectal dose of 72 Gy. Biological (tumor control probability [TCP], normal tissue complication probability [NTCP]) and physical indices for tumor control and normal tissue complication probabilities were computed, as well as the probability of the uncomplicated local control (P+). RESULTS: The IMRT-lim plan was superior to all other plans concerning TCP (p < 0.0001). The IMRT-unlim plan had the worst TCP. Within the 3D plans, the 3D-optim-unlim had the best TCP, which was significantly different from the 3D-optim-lim plan (p = 0.0003). For rectal NTCP, both IMRT plans were superior to all other plans (p < 0.0001). The IMRT-unlim plan was significantly better than the IMRT-lim plan (p < 0.0001). Again, 3D-optim-unlim was superior to the other 3D plans (p < 0. 0007). Physical endpoints for target showed the mean minimal target dose to be the lowest in the IMRT-unlim plan, caused by a large target dose inhomogeneity (TDI). Medial target dose, 90th percentile, and maximal target dose were significantly higher in both IMRT plans. Physical endpoints for the rectum showed the IMRT-unlim plan to be superior compared to all other plans. There was a strong correlation between the 65th percentile (Rp65) and rectal NTCP (correlation coefficient > or =89%). For bladder, maximal bladder dose was significantly higher in the IMRT-unlim plan compared to all other plans (p < or = 0.0001).P+ was significantly higher in both IMRT-plans than in all other plans. The 3D-optim-unlim plan was significantly better than the two other 3D plans (p < 0.0001). CONCLUSION: IMRT significantly increases the ratio of TCP over NTCP of the rectum in the treatment of prostate cancer. However, constraints for TDI are needed, because a high degree of TDI reduced minimal target dose. IMRT improved uncomplicated local control probability. In our department, IMRT by static segmented beams is planned and delivered in a cost-effective way. IMRT-lim has replaced non-modulated conformal radiotherapy as the standard treatment for prostate cancer.

The single-isocentre treatment of head and neck cancer: time gain using MLC and automatic set-up.

PURPOSE: In this manuscript, we studied the difference in the treatment time required to execute a single-isocentre three-field irradiation of the head and neck, using either tray-mounted cerrobend blocks or a multileaf collimator (MLC) for field shaping and automatic set-up. MATERIALS AND METHODS: A total of twenty consecutive, unselected patients (16 males, four females), were eligible for this study because the dose they were to received was 44 Gy (2 Gy/fraction) to the head, neck and supraclavicular regions. Patients were randomly allocated to one of two treatment groups. The first group (n = 11) was treated on a Philips SL-75 linear accelerator (SL-75), using 5 MV photons and tray-mounted cerrobend blocks. The second group (n = 9) was treated on a Philips SL-25 linear accelerator (SL-25-MLC), using 6 MV photons and a MLC. Patients of the second group were treated using the automatic set-up facility of the SL-25-MLC, without entering the treatment room between consecutive fields. RESULTS: Overall treatment time was significantly shorter on the SL-25-MLC than on the SL-75 (P < 0.0001). The difference in total treatment-execution time was in the range of 157 s per treatment session. The largest difference was observed in the set-up time. There was an average of a 125 s time gain per treatment day (P < 0.0001) in favour of the SL-25-MLC. CONCLUSIONS: Compared to tray-mounted cerrobend blocks, a MLC and automatic set-up results in a significant time advantage when a single isocentre technique is used to treat head and neck cancer.

Collagen vascular diseases and radiation therapy: a critical review.

PURPOSE: Although many oncologists have the impression that patients with collagen vascular disease tolerate radiotherapy less well than other patients, until now this was never described in a review article. METHODS AND RESULTS: The principal objective was to determine whether patients with collagen vascular diseases have a greater risk of severe radiation therapy complications, than those without a collagen vascular disease. However, most of the publications found on this topic are short anecdotal case reports of patients with increased toxicity after radiation. Consequently, the true incidence of these side effects is unknown. CONCLUSIONS: Unless further studies on this subject are reported, each radiation oncologist should be cautious in treating these patients.

Primary sinonasal mucosal melanoma: three different therapeutic approaches to inoperable local disease or recurrence and a review of the literature.

Sinonasal melanoma is an uncommon disease with a bad prognosis and a high local recurrence rate. The use of radiotherapy in such conditions remains controversial. A review of the literature is presented in an attempt to answer some of the questions regarding therapeutic options. Data on incidence, aetiology, pathology and prognosis are also provided. Case studies are reported of three patients with sinonasal melanoma referred to our department in a relatively short time period and needing radiotherapy as a single treatment modality, using a conformal three-dimensional treatment technique. One patient was also treated with temporary 1251 seeds, while another was treated using intensity modulation. Both intensity modulation and temporary 1251 seeds are feasible techniques, providing satisfactory dose distributions encompassing the tumour volume while sparing critical structures. Surgery remains the treatment of choice for sinonasal melanoma. Radiotherapy should be used postoperatively and is a good alternative in cases of inoperable disease. Adjacent critical structures limit the radiation dose to the tumour area, especially when high fraction doses are used. Therefore, beam intensity modulation and 1251 seeds can be used to increase the tumour dose without exceeding the radiation tolerance of the surrounding structures.