Volumetric analysis of small bowel displacement from radiation portals with the use of a pelvic tissue expander.

PURPOSE: Many techniques and devices have been used in an attempt to minimize gastrointestinal morbidity of pelvic irradiation. The value of a temporary intrapelvic tissue expander to displace small bowel from pelvic radiotherapy fields was analyzed by comparing volumetric treatment parameters of patients with and without such a device. METHODS AND MATERIALS: Between 1983 and 1991, 77 patients with a diagnosis of endometrial (n = 35), colorectal (n = 41), or anal carcinoma (n = 1) received adjuvant postoperative radiotherapy after undergoing treatment planning simulation with the use of small bowel oral contrast medium. Fourteen of these patients underwent surgical placement of a temporary intrapelvic tissue expander prior to radiotherapy, and 63 patients did not. Small bowel volume within the treatment portals was measured for both initial pelvic and conedown fields for all cases, and compared between the two patient groups. RESULTS: The volume of small bowel within the initial pelvic fields receiving full dose irradiation was significantly less among patients with a tissue expander. For patients with a tissue expander, mean volume receiving full dose irradiation was 25 cm3 (median 0 cm3, range 0-297 cm3), whereas the corresponding volume was 239 cm3 (median 181 cm3, range 0-943 cm3) without a tissue expander (p < .0001). A similar reduction of irradiated small bowel volume was noted in the conedown fields with the use of a tissue expander (p = .07). Volumes receiving less than full dose irradiation were also less within the initial pelvic (p = .0001) and conedown (p = .002) fields with a tissue expander. Multivariate analysis of patient and treatment-related parameters showed the use of a tissue expander to be the only factor correlated with decreased small bowel volume within the treatment field (p = .003). Morbidity related to placement and removal of the tissue expander was acceptable. Acute radiation-related morbidity was significantly less in patients irradiated with a tissue expander in place (p < .001). CONCLUSIONS: Placement of an intrapelvic tissue expander was correlated with decreased small bowel volume within the radiotherapy treatment field. Diminished radiation-induced acute gastrointestinal morbidity was noted with use of a tissue expander.

The results of radiation therapy for isolated local regional recurrence after mastectomy.

Between 1967 and 1988 128 patients with isolated local-regional recurrence of breast cancer after mastectomy were treated with definitive radiation therapy. Recurrence was confined to a single site in 108 patients and multiple sites in 20. The chest wall was the most common location (86) and the supraclavicular region was the second most common (20). Surgical treatment for recurrence prior to irradiation consisted of excision of all gross disease in 78 patients and incisional biopsy in 49 patients. Irradiation was directed to the entire chest wall in 19% of patients with isolated chest wall recurrences and to the chest wall and regional nodes in 81%. In patients with isolated nodal failures, treatment was directed to the nodal site and chest wall in 87% and to the regional site alone in 13%. Patients with multiple sites received treatment to the chest wall and regional nodes in all cases. Electively treated sites usually received 4500-5000 cGy. Following excision of chest wall disease, the median dose was 6000 cGy. Gross disease on the chest wall received a median dose of 6100 cGy. Gross disease in nodal sites received a median dose of 5600 cGy; 66 patients received systemic therapy at recurrence. The 5-year actuarial local-regional control was 43%. In a multivariate analysis only the estrogen receptor status of the recurrence remained significant (p = .002). The 5-year actuarial survival was 49% with a relapse-free survival of 24%. In a multivariate analysis for survival, the disease-free interval (p = .007), local regional control (p = .006), and excisional biopsy for recurrence (p = .03) remained significant. In a multivariate analysis for relapse-free survival, the disease-free interval (p = .03), excisional biopsy (p = .0001), and the extent of axillary nodal involvement (p = .007) remained significant. In the subgroup of patients with a disease-free interval greater than or equal to 24 months, excisional biopsy, and local regional control, the 5-year survival was 61% with a relapse-free survival of 59%. This subgroup represents 18% of the entire group and has a relatively good prognosis after recurrence.

Three-dimensional photon treatment planning of the intact breast.

Three-dimensional treatment planning for the intact breast was performed on two patients who had undergone CT scanning. A total of 38 treatment plans were evaluated. Multiple plans were evaluated for each patient including plans with and without inhomogeneity corrections, plans using varying photon energies of 60Co, 4 MV, 6 MV, 10 MV, and 15 MV, and three-dimensionally unconstrained plans. Increased hot spots were appreciated in the central axis plane when lung inhomogeneity corrections were used. Additional hot spots were appreciated in off-axis planes towards the cephalad and caudad aspects of the target volume because of lung inhomogeneity corrections and changes in the breast contour. The use of 60Co was associated with an increase in the magnitude and volume of hot spots, whereas the use of higher energy photons such as 10 MV and 15 MV was associated with an unacceptable target coverage at shallow depths. Therefore, for the two patients studied, the use of a medium energy photon beam (such as from a 6 MV linear accelerator) appeared to be the energy of choice for treatment of the intact breast. The three-dimensionally unconstrained plans were able to improve slightly upon the standard plans, particularly with relationship of dose to normal tissue structures. Areas for future research were identified, including the use of tissue compensators.

Prospective prediction of post-radiation therapy lung function using quantitative lung scans and pulmonary function testing.

Surgeons have made use of quantitative perfusion lung scanning (QS) and forced expiratory volume in one second (FEV1) to predict a patient's ability to tolerate lung resection. In this study QS and FEV1 were used to predict prospectively pulmonary function following lung irradiation (XRT). Twenty-two patients have had QS and FEV1 determined before XRT and at planned intervals post-XRT. Serial determination of lung function post-XRT allows comment on the temporal nature of the XRT effect on lung function. Seventeen patients had QS and FEV1 determined at an interval of 2-6 months post-irradiation with a drop in the groups mean FEV1 from 1.91 to 1.87L. or 2% during that interval. In the interval from 6-12 months post-XRT, 13 patients had studies with the groups mean FEV1 dropping from 1.79 to 1.58L or 12% of the original. In the interval from 12-18 months, 6 patients had a decline in mean FEV1 from 1.73 to 1.56L. or 10% of the original. In 22 patients a predicted final FEV1 was compared with a measured value at an interval from XRT. Fourteen of these determinations were at intervals greater than 6 months from the start of XRT and 6 at intervals of greater than 1 year. FEV1 was seen to drop during the follow-up intervals toward the predicted value. In only 2 patients did the final FEV1 drop below the predicted FEV1 and never by more than 0.12L. (6%). In summary, a method for predicting post-XRT pulmonary function using QS and FEV1 is described. Serial follow-up revealed a latent period followed by a late phase where FEV1 fell toward, but not significantly below, the predicted value. Such a determination can be of value in formulating a treatment plan for patients with significantly diminished pulmonary function.