Designing equivalent treatment regimens for prostate radiotherapy based on equivalent uniform dose.

The purpose of this work was to determine alternative radiotherapy (RT) regimens that are biologically equivalent to clinically proven treatments using different RT modalities or different fractionation schemes. The concept of equivalent uniform dose (EUD) is used with the linear quadratic model to determine equivalent treatment regimens using two representative sets of parameters derived from clinical data: (i) alpha/beta = 3.1 Gy and alpha = 0.15 Gy(-1), and (ii) alpha/beta = 1.5 Gy and alpha = 0.04 Gy(-1). The EUD values for the critical structure (rectum) are also calculated. Representative dose volume histograms were used to account for dose inhomogeneities for different RT modalities. A series of alternative and equivalent fractionation regimens that can be used with different radiotherapy modalities for localized prostate cancer were determined. For example, the alternative regimens, calculated with the alpha/beta ratio of 3.1 Gy, that would be biologically equivalent to external beam RT (EBRT) of 76 Gy (38x2.0 Gy) include: EBRT hypofractionation of 21x3.0 Gy; I-125 implant of 156 Gy; Pd-103 implant of 128 Gy; high dose rate (HDR) brachytherapy of 4x10.5 Gy; I-125 implant of 65 Gy combined with EBRT of 23x2.0 Gy; and HDR brachytherapy of 3x5.9 Gy combined with EBRT of 23x2.0 Gy. Similar data for other parameters are also presented. With caution, the data presented may be useful in designing clinical trials to explore new RT strategies, such as image-guided intensity-modulated RT.

Nonhomologous end-joining of ionizing radiation-induced DNA double-stranded breaks in human tumor cells deficient in BRCA1 or BRCA2.

Mutations in the BRCA1 or BRCA2 genes predispose to a wide spectrum of familial cancers. The functions of the proteins encoded by BRCA1 and BRCA2 remain to be elucidated, but their interaction and colocalization with hRAD51 suggest a role in homologous recombination and DNA double-strand break (DSB) repair. The role of BRCA1 and BRCA2 in the rejoining of ionizing radiation (IR)-induced DNA DSBs, which may represent a step in the overall process of repair, remains uncertain because recent reports provide conflicting results. Because elucidation of the role of these proteins in DNA DSB rejoining is important for their functional characterization, we reexamined this end point in cells with mutations in either BRCA1 or BRCA2. We show that two pancreatic carcinoma cell lines known to have either wild-type (BxPC3) or mutant forms (Capan-1) of BRCA2 rejoin IR-induced DNA DSBs to a similar extent following biphasic kinetics characterized by a fast and a slow component. Importantly, inactivation of DNA-dependent protein kinase (DNA-PK) by wortmannin generates similar shifts from the fast to the slow component of rejoining in BRCA2-proficient and BRCA2-deficient cells. This suggests that the functioning of either the fast, DNA-PK-dependent component or the slow, DNA-PK-independent component of rejoining is not affected by mutations in BRCA2. Also, a human breast cancer cell line with mutated BRCA1 shows normal rejoining of IR-induced DNA DSBs and levels of inhibition by wortmannin commensurate with the degree of DNA-PK inhibition. These observations fail to confirm a direct role for BRCA1 or BRCA2 in the rejoining of IR-induced DSBs in the genome of human tumor cells and, as a result, an involvement in nonhomologous end-joining. They are in line with similar observations with mutants deficient in genes implicated in homologous recombination and support the view that the radiosensitivity to killing of cells deficient in BRCA1 or BRCA2 derives from defects in this repair pathway.

Standard off-cord lung oblique fields do not include the entire mediastinum: a computed tomography simulator study.

The routinely recommended target volume for off-cord lung oblique fields in the treatment of postoperative bronchogenic carcinoma includes the entire mediastinum, as defined by coverage of the contralateral mainstem bronchus and subcarinal space. However, this may be difficult to accomplish with the field angles of 20 degrees to 40 degrees, recommended in the recently completed Intergroup Trial (Radiation Therapy Oncology Group 91-05). This project was undertaken to define the oblique angle necessary to encompass the entire mediastinum as determined by computerized tomography simulator verification. Axial computerized tomography simulation images of 25 patients with non-small-cell lung cancer were used in this study. Ten patients had prior lobectomy or pneumonectomy as part of their management. The contralateral mainstem bronchus, subcarinal space (SS), and the spinal cord were each contoured as separate volumes. The length of the contralateral mainstem bronchus was defined as extending from the carina to the bifurcation of the lobar bronchi. The subcarinal space was defined as a triangular space (in a coronal plane) with the carina at the apex, the mainstem bronchi superiorly, and a horizontal line 5 cm below the carina as the base of the triangle. The minimal angle to encompass the contralateral mainstem bronchus and subcarinal space, and to exclude the spinal cord was determined for each patient. The contoured volumes did not have additional margin added. The position of the carina was scored as "midline" if located in the midsagittal plane, or "off-midline" if deviated to either side from midline. Midline deviation was determined at the level of the carina to evaluate possible anatomical distortion relating to the tumor or prior surgery, and its effect on the minimal angle was assessed. The median minimal angle measured was 45 degrees (range: 28-65 degrees) for the entire group, and in 64% of those evaluated, this oblique angle was significantly greater than the 40 degrees recommended in Radiation Therapy Oncology Group guidelines (p = 0.017). In patients without midline deviation (n = 17), the median minimal angle was 45 degrees (range: 28-60 degrees), and in patients with midline deviation (n = 8), it was determined to be 44 degrees (range: 27-65 degrees), with no statistical difference noted between the two groups (p = NS). Although midline deviation was present in 4 of 10 patients previously resected, the above relationship remained unchanged. Based on computerized tomography simulation verification, off-cord oblique field angles of 20 degrees to 40 degrees do not adequately cover the entire mediastinum in most patients. To adequately encompass the entire mediastinum as defined in the Intergroup Trial (Radiation Therapy Oncology Group 91-05) with off-cord oblique fields, treatment angles greater than 40 degrees are necessary. Whether the potential increase in lung volume exposed to radiation from these larger angles results in a poorer therapeutic ratio requires further investigation.

DNA-dependent protein kinase stimulates an independently active, nonhomologous, end-joining apparatus.

Double-strand breaks (DSBs) can be efficiently removed from the DNA of higher eukaryotes by nonhomologous end-joining (NHEJ). Genetic studies implicate the DNA-dependent protein kinase (DNA-PK) in NHEJ, but the exact function of this protein complex in the rejoining reaction remains to be elucidated. We compared rejoining of DNA DSBs in a human glioma cell line, M059-J, lacking the catalytic subunit of DNA-PK (DNA-PKcs), and their isogenic but DNA-PK-proficient counterpart, M059-K. In both cell lines, rejoining of DNA DSBs was biphasic, with a fast and a slow component operating with a half-life of approximately 22 min and 12 h, respectively. Deficiency in DNA-PK activity did not alter the half-times of either of these components of rejoining but increased from 17 to 72% the proportion of DNA DSB rejoining with slow kinetics. DNA DSB rejoining was nearly complete in both cell lines, and there was only a small increase in the number of unrejoined breaks in M059-J as compared with M059-K cells after 30 h of incubation. Wortmannin radiosensitized to killing M059-K cells and strongly inhibited DNA DSB rejoining. Wortmannin did not affect the radiosensitivity to killing and produced only a modest inhibition in DNA DSB rejoining in M059-J cells, suggesting that, for these end points, DNA-PK is the principal target of the drug. These observations demonstrate that DNA-PK deficiency profoundly decreases the proportion of DNA DSB rejoining with fast kinetics but has only a small effect on the fraction remaining unrejoined. We propose that in higher eukaryotes, an evolutionarily conserved, independently active, but inherently slow NHEJ pathway is stimulated 30-fold by DNA-PKcs to rapidly remove DNA DSBs from the genome. The stimulation is expected to be of local nature and the presence of DNA-PKcs in the vicinity of the DNA DSB determines whether rejoining will follow fast or slow kinetics. Structural and regulatory functions of DNA-PKcs may mediate this impressive acceleration of DNA DSB rejoining, and regions of chromatin within a certain range from this large protein may benefit from these activities. We propose the term DNA-PK surveillance domains to describe these regions.

Brachytherapy radiation doses to the neurovascular bundles.

PURPOSE: To investigate the role of radiation dose to the neurovascular bundles (NVB) in brachytherapy-related impotence. METHODS AND MATERIALS: Fourteen Pd-103 or I-125 implant patients were studied. For patients treated with implant alone, the prostate and margin (clinical target volume [CTV]) received a prescription dose of 144 Gy for I-125 or 115 Gy for Pd-103. Two patients received Pd-103 (90 Gy) with 46 Gy supplemental external beam radiation (EBRT). Axial CT images were acquired 2 to 4 hours postoperatively for postimplant dosimetry. Because the NVBs cannot be visualized on CT, NVB calculation points were determined according to previously published anatomic descriptions. Bilateral NVB points were considered to lie posterior-laterally, approximately 2 mm from the prostatic capsule. NVB doses were recorded bilaterally, at 0.5-cm intervals from the prostatic base. RESULTS: For Pd-103, the average NVB doses ranged from 150 Gy to 260 Gy, or 130% to 226% of the prescription dose. For I-125, the average NVB dose ranged from 200 Gy to 325 Gy, or 140% to 225% of the prescription dose. These was no consistent relationship between the NVB dose and the distance from the prostatic base. To examine the possible effect of minor deviations of our calculation points from the true NVB location, we performed NVB calculations at points 2 mm medial or lateral from the NVB calculation point in 8 patients. Doses at these alternate calculation points were comparable, although there was greater variability with small changes in the calculation point if sources were located outside the capsule, near the NVB calculation point. Three patients who developed early postimplant impotence had maximal NVB doses that far exceeded the average values. CONCLUSIONS: In the next few years, we hope to clarify the role of high NVB radiation doses on potency, by correlating NVB dose calculations with a large number of patients enrolled in an ongoing I-125 versus Pd-103 trial for early-stage patients, for whom detailed dosimetric and potency data are being collected prospectively. In the future, we anticipate that NVB doses may be incorporated into dosimetry guidelines to maximize tumor control and minimize treatment-related morbidity.

Repair of DNA double-strand breaks and radiosensitivity to killing in an isogenic group of p53 mutant cell lines.

PURPOSE: Accumulation of the p53 protein can result in G1 arrest that may facilitate DNA repair, or alternatively, it may lead to apoptosis. Mutations that alter p53's ability to mediate these responses are expected to alter cell radiosensitivity to killing. However, the relationship between p53 status and cell radiosensitivity has proven to be complex. Several studies have suggested that p53 mutations are associated with increased radioresistance to killing, while others have shown no such correlation. These differences may be derived from the fact that different mutations of p53 exert different effects on cell radiosensitivity. METHODS AND MATERIALS: To address this question, we examined a group of isogenic cell lines that express different "hot spot" mutant forms of p53. These cells were generated from human osteosarcoma (SAOS) cells, a p53 null cell line, by transfection with vectors expressing different p53 mutants. Vectors with the following p53 mutations were utilized: 143Ala, 175His, 248Try, 273His, and 281Gly. As controls, we used the original SAOS cells and cells transfected with the vector alone. Results were compared to those obtained with a cell line expressing wild-type p53 (wt p53). Radiosensitivity to killing was determined in the exponential phase of growth by measuring loss of colony-forming ability. Induction and repair of DNA double-strand breaks (dsb) was measured in irradiated cells using pulsed-field gel electrophoresis. Apoptosis was assessed using morphologic evaluation of DAPI-stained cells after treatment either with radiation or paclitaxel. RESULTS: Transfected SAOS-2 cell lines expressed a mutant form of p53 that could not be induced by radiation, and which was transcriptionally inactive. Among the 7 cell lines studied, we observed no difference in cellular radiosensitivity to killing (p = NS). When examining DNA repair, no difference in either the induction or repair of DNA dsb was noted in any of the cell lines studied (p = NS). Also, induction of apoptosis, either after exposure to radiation or paclitaxel, was low, and similar in all cell lines (p = NS). Non-isogenic cells expressing wt p53 were more radioresistant to killing by radiation, but showed similar kinetics of dsb rejoining. CONCLUSION: The results suggest that expression of different p53 mutants does not alter the yields of radiation-induced dsb, or the ability of cells to repair this type of lesion. In addition, the same p53 mutants do not affect cellular radiosensitivity to killing, or the induction of apoptosis after exposure to radiation or paclitaxel.

Uncommon causes of anterior knee pain: a case report of infrapatellar contracture syndrome.

The uncommon causes of anterior knee pain should always be considered in the differential diagnosis of a painful knee when treatment of common origins become ineffective. A case is presented in which the revised diagnosis of infrapatellar contracture syndrome was made after noting delayed progress in the rehabilitation of an active female patient with a presumed anterior horn medial meniscus tear and a contracted patellar tendon. The patient improved after the treatment program was augmented with closed manipulation under arthroscopy and infrapatellar injection of both corticosteroids and a local anesthetic. Infrapatellar contraction syndrome and other uncommon sources of anterior knee pain, including arthrofibrosis, Hoffa's syndrome, tibial collateral ligament bursitis, saphenous nerve palsy, isolated ganglions of the anterior cruciate ligament, slipped capital femoral epiphysis, and knee tumors, are subsequently discussed. Delayed functional advancement in a rehabilitation program requires full reassessment of the patient's diagnosis and treatment plan. Alternative diagnoses of knee pain are not always of common origins. Ample knowledge of uncommon causes of anterior knee pain is necessary to form a full differential diagnosis in patients with challenging presentations.

The number of positive margins influences the outcome of women treated with breast preservation for early stage breast carcinoma.

BACKGROUND: There are conflicting reports regarding whether focally positive surgical margins influence tumor control in breast-conservation therapy. The authors have evaluated the relation between positive surgical margins on tumor control and whether the number of positive margins affects tumor control in patients undergoing reexcision lumpectomy. METHODS: From 1978 to 1994, 453 American Joint Committee on Cancer Stage I/II breast carcinoma patients were treated at Thomas Jefferson University Hospital with breast conservation therapy. Patients underwent excisional biopsy and margin sampling with shaved biopsies of the tumor cavity. The entire breast received 45 grays (Gy) with a 20-Gy iridium-192 implant or an electron boost. Eighty-six patients had microscopically positive margins (19%), and the remainder had confirmed negative margins. The median follow-up time was 45 months. RESULTS: Local tumor control rates for patients with negative margins at 5 and 10 years were 94% and 87%, respectively, compared with 86% and 69%, respectively, for those patients with positive margins (P=0.005). The disease free survival rates for the negative margin group at 5 and 10 years were 91% and 82%, respectively, compared with 76% and 71%, respectively, for the positive margin group (P=0.001). Overall survival rates for patients with negative margins at 5 and 10 years were 95% and 84%, respectively, compared with 87% and 78%, respectively, for those with positive margins (P=0.047). When comparing the negative margin group with the one positive margin group, there was no significant difference in local tumor control (P=0.12). However, women with two or more positive margins had an inferior local tumor control compared with those women with negative margins (P=0.002). CONCLUSIONS: Patients with positive margins have a higher risk for local failure and worse survival when undergoing breast conservation therapy. Inferior local tumor control was noted in those patients with two or more positive margins.

Tumor bed brachytherapy with a mesh template: an accessible alternative to intraoperative radiotherapy.

BACKGROUND AND OBJECTIVES: Locally advanced and recurrent malignancies often require adjuvant radiotherapy to achieve tumor control. We report our experience with a technique that uses an intraoperatively placed mesh template for the delivery of radiotherapy. METHODS: from 1988 to 1996, 14 patients were treated with tumor bed brachytherapy using this mesh technique. Sites of involvement included the head and neck region (n = 6), abdomen/pelvis (n = 4), retroperitoneum (n = 3), and the lower extremity (n = 1). During surgery, plastic catheters were evenly placed within a mesh template (Vicryl or Marlex), which was positioned in the tumor bed. The catheters were afterloaded with radioactive sources once the final pathology had been determined and the patient required limited nursing care. Radiation dose was titrated to the surgico-pathologic findings (e.g., margin status). RESULTS: All of the patients tolerated the procedure without experiencing acute or chronic sequelae. The median survival time was 13 months. Local control was achieved in 11 of 13 evaluable patients, with an actuarial local control of 82% at 6 months. CONCLUSION: Tumor bed brachytherapy with a mesh implant is a practical technique to improve tumor control and warrants further investigation.

Palliative irradiation for focally symptomatic metastatic renal cell carcinoma: support for dose escalation based on a biological model.

PURPOSE: Renal cell carcinoma has traditionally been regarded as a radioresistant cancer, yet controversy continues as to whether escalation of the palliative radiation dose can overcome the inherent resistance of such tumors when they metastasize. Recently, the linear quadratic model has emerged as a paradigm to assess biologically effective dose of radiotherapy. This study was undertaken to determine the ability of radiotherapy to palliate focally symptomatic metastatic renal cell carcinoma and to assess whether the delivery of higher biologically effective dose was more likely to bring about a palliative response. MATERIALS AND METHODS: Between 1966 and 1995, 107 patients with renal cell metastases at 150 sites were irradiated with palliative intent. Sites irradiated included bone (89), soft tissue (16), brain (20), spinal cord (9) and pulmonary (16). To determine dose effectiveness the biologically effective dose was calculated according to the formula, Gy10 = total dose (1 + fractional dose/alpha-beta), using an alpha-beta of 10. RESULTS: For the entire group 86% of patients derived a palliative response after treatment with irradiation, while 49% derived a complete palliative response. The median duration of palliation was 6 months (range 1 to 150). With respect to overall (that is, complete and partial) response rates, those presenting with high Karnofsky performance status were most likely to respond (status 70 or greater versus less than 70, 88% versus 78%, p < 0.04). With respect to the rate of complete palliative response, performance status (status 70 or greater versus less than 70, 55% versus 31%, p < 0.03) and the use of higher biologically effective doses of irradiation (Gy10 50 or greater versus less than 50, 59% versus 39%, p = 0.001) were associated with a statistically significant increased rate of response. The independent prognostic value of performance status and higher biologically effective doses of irradiation were maintained in multivariate analysis. CONCLUSIONS: Despite the prevailing concept that renal cell carcinoma is generally resistant to radiotherapy, the overwhelming majority of patients seen at our institution in whom metastatic renal cell carcinoma developed were palliated with radiotherapy. A complete palliative response is more likely when higher biologically effective doses of irradiation are delivered, especially to patients with a relatively high performance status.