Tolerance of retroperitoneal structures to intraoperative radiation

Companion Animals as a Key to Success for Translating Radiation Therapy Research into the Clinic

Many successful preclinical findings fail to be replicated during translation to human studies. This leads to significant resources being spent on large clinical trials, and in some cases, promising therapeutics not being pursued due to the high costs of clinical translation. These translational failures emphasize the need for improved preclinical models of human cancer so that there is a higher probability of successful clinical translation. Companion-animal cancers offer a potential solution. These cancers are more similar to human cancer than other preclinical models, with a natural evolution over time, genetic alterations, intact immune system, and a permanent adaptation to the microenvironment. These advantages have led pioneers in veterinary radiation oncology to aid human medicine by elucidating basic principles of radiation biology. More recently, the veterinary and human radiation oncology fields have increasingly collaborated to achieve advancements in education, radiotherapy techniques, and trial networks. This review describes these advancements, including significant prior research findings and the evolution of the veterinary radiation oncology discipline. It concludes by describing how companion-animal models can help shape the future of human radiotherapy. Taken as a whole, this review suggests companion-animal cancers may become widely used for preclinical radiotherapy research.

Inhibition of mTORC1 signaling protects kidney from irradiation-induced toxicity via accelerating recovery of renal stem-like cells

Background

Irradiation-induced kidney damage is inevitable during radiotherapeutic practice, which limits effective radiotherapy doses on tumor treatment. In the present study, the role of mTOR complex 1 (mTORC1) signaling was investigated in irradiation-induced renal injuries.

Methods

Mice were exposed to 8.0-Gy X-ray of total body irradiation and subsequently treated with rapamycin. Changes of renal morphology were assessed by hematoxylin and eosin staining. Expression of pS6 and CD133 was detected via immunostaining. Cellular apoptosis and proliferation were measured by TUNEL, caspase-3 and BrdU staining. Activation of mTORC1, TGF-β and NF-κB signaling pathways was determined through western blot analysis.

Results

Our data displayed that irradiation disrupted the structures of renal corpuscles and tubules and decreased the density of CD133⁺ renal stem-like cells, which were related with increasing cellular apoptosis and decreasing cell proliferation post exposure. Activation of mTORC1, TGF-β and NF-κB signaling pathways was determined in irradiated renal tissues, which were inhibited by rapamycin treatment. Application of rapamycin after irradiation decreased cellular apoptosis and increased autophagy and cell proliferation in renal tissues. The density of CD133⁺ renal stem-like cells was significantly increased in irradiated kidneys after rapamycin treatment. The morphology of irradiated renal corpuscles and tubules was gradually recovered upon rapamycin treatment.

Conclusions

These findings indicate that inhibition of mTORC1 signaling by rapamycin ameliorates irradiation-induced renal toxicity mediated by decreasing cellular apoptosis and increasing CD133⁺ renal stem-like cells.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0963-5) contains supplementary material, which is available to authorized users.

Current management of locally recurrent rectal cancer

AIM

A review of the literature was undertaken to provide an overview of the surgical management of locally recurrent rectal cancer (LRRC) after the introduction of total mesorectal excision (TME).

METHOD

A systematic literature search was undertaken using PubMed, Embase, Web of Science and Cochrane databases. Only studies on patients having surgery for their primary tumour after 1995, or if more than half of the patients were operated on after 1995, were considered for analysis. Studies concerning only palliative treatments were excluded.

RESULTS

A total of 19 studies fulfilled the inclusion criteria. Locally recurrent rectal cancer still occurred in 5-10% of the patients and was a major clinical problem, due to severe symptoms and poor survival. In most studies, 40-50% of all patients with LRRC could be expected to undergo surgery with a curative intent and of those, 30-45% would have R0 resection. Thus, only 20-30% of all patients with LRRC would have a potentially curative operation. The postoperative complication rate varied considerably, from 15 to 68%. The rate of re-recurrence varied from 4 to 54% after curative surgery. The 5-year overall survival varied between 9 and 39% and the median survival between 21 and 55 months.

CONCLUSION

Compared with previous studies, the proportion of potentially curative resections seems to have increased, probably due to improved staging, neoadjuvant treatment and increased surgical experience in dedicated centres, which has resulted in a tendency to improved survival.

Can unresectable colorectal cancer be cured?

A multimodality regimen that includes EBRT, chemotherapy, maximal surgical resection, and IORT, when used in patients with initially unresectable primary colon or rectal adenocarcinoma, is associated with excellent long-term local control, and a 5-year overall survival of 52%. Distant metastases account for most treatment failures, occurring in roughly 50%. Treatment-related morbidity is high, with a long-term complication rate that approaches 50%. These results suggest that selected patients with advanced unresectable disease benefit from an aggressive approach. Additional effort needs to focus on reducing the rate of systemic failure with more effective chemotherapy regimens and minimizing the frequency of long-term procedural complications.

Toward endobronchial Ir-192 high-dose-rate brachytherapy therapeutic optimization

A number of patients with lung cancer receive either palliative or curative high-dose-rate (HDR) endobronchial brachytherapy. Up to a third of patients treated with endobronchial HDR die from hemoptysis. Rather than accept hemoptysis as an expected potential consequence of HDR, we have calculated the radial dose distribution for an Ir-192 HDR source, rigorously examined the dose and prescription points recommended by the American Brachytherapy Society (ABS), and performed a radiobiological-based analysis. The radial dose rate of a commercially available Ir-192 source was calculated with a Monte Carlo simulation. Based on the linear quadratic model, the estimated palliative, curative and blood vessel rupture radii from the center of an Ir-192 source were obtained for the ABS recommendations and a series of customized HDR prescriptions. The estimated radius at risk for blood vessel perforation for the ABS recommendations ranges from 7 to 9 mm. An optimized prescription may in some situations reduce this radius to 4 mm. The estimated blood perforation radius is generally smaller than the palliative radius. Optimized and individualized endobronchial HDR prescriptions are currently feasible based on our current understanding of tumor and normal tissue radiobiology. Individualized prescriptions could minimize complications such as fatal hemoptysis without sacrificing efficacy. Fiducial stents, HDR catheter centering or spacers and the use of CT imaging to better assess the relationship between the catheter and blood vessels promise to be useful strategies for increasing the therapeutic index of this treatment modality. Prospective trials employing treatment optimization algorithms are needed.

Scanning electron microscopic study of the three-dimensional structure of the collagen sheath surrounding cancer cells after single high-dose irradiation

The effect of single high-dose irradiation on collagen networks in tumor cells was examined by scanning electron microscopy. MM46 tumor cells were transplanted into C3H/He mice and locally irradiated with a 30 Gy dose (6 MeV) 7-8 days posttransplantation. Mice were killed at various time points postirradiation, and tumor tissues were excised and fixed. After 2 N NaOH maceration, tissues were washed and stained with 1% tannic acid. They were then postfixed with 1% OsO4, dehydrated, and dried. The tissues were coated with gold, and the three-dimensional structure of the collagen fibers was observed using scanning electron microscopy. In the control group, the chambers formed by collagen fibers were larger on days 7 and 14 than those on days 1 and 3. In the irradiated group, the chambers were largest and most irregular in shape on day 7. The chamber size had decreased approximately 50% by day 14, and there was evidence of tumor cell regeneration. In addition, several fenestrations in the chamber wall developed in the irradiated group. Fenestrations in the collagen chamber walls surrounding tumor cells might allow transfer of metabolites that provide nutrition to the tumor cells, leading to their regeneration.

Perioperative high-dose-rate brachytherapy in locally advanced and recurrent gynecologic cancer: Initial results of a phase II trial

BACKGROUND

This study was undertaken to determine the feasibility of perioperative high-dose-rate brachytherapy (PHDRB) as an adjunct to salvage surgery in primary advanced or recurrent gynecologic cancer.

METHODS

Twenty-five patients with either locally advanced (n = 4) or recurrent (n = 21) gynecologic cancer suitable for salvage surgery were included. Unirradiated patients were treated with preoperative chemoradiation followed by salvage surgery and PHDRB (R0 and R1 resections receiving 16 or 24 Gy, respectively). Previously irradiated patients were treated with salvage surgery and PHDRB alone with 32 or 40 Gy for R0 or R1 resections, respectively.

RESULTS

Resections were categorized as R0 in 9 patients (36.0%) and R1 in 16 (64.0%). Four previously irradiated patients suffered fatal pelvic bleeding between 8 and 13 months after surgery and PHDRB. After a median follow-up of 20 months (3-55+), the 4-year actuarial local and pelvic controls were 88.1% and 80.8%, respectively. The 4-year distant metastases-free survival was 40.9%. Four-year actuarial overall survival was 34.0%, with a median survival of 27.1 months (95% confidence interval: 17.5-36.8).

CONCLUSIONS

Local and pelvic control results are excellent for this very high-risk-disease population. PHDRB dose in previously irradiated patients has been shifted to the closest lower level due to unacceptable vascular toxicity.

IVUS-based dosimetry on patients with repeat-radiated coronary arteries to the same site

BACKGROUND AND PURPOSE

Intracoronary radiation reduces recurrent in-stent restenosis (ISR). Repeat radiation may become necessary due to recurrent ISR. This study reports outcome-related dose calculations for twice-radiated coronary artery segments.

MATERIALS AND METHODS

A total of 22 patients with angiographic evidence of ISR in a previously treated native coronary artery were assigned for repeat percutaneous coronary intervention and intravascular brachytherapy (IVBT). Intravascular brachytherapy was performed either with a 192Ir- or a 90Sr/Y-source (prescription dose: 14-18 and 23 Gy each at 2 mm from the center of the source), or a 32P-source (20 Gy 1-mm deep to the vessel wall). The mean time interval between the two IVBT treatments was 394+/-306 days. For each patient, angiograms and intravascular ultrasound cross sections were reviewed, on the basis of anatomical landmarks, matched, and the twice-radiated vessel segment identified.

RESULTS

Clinical follow-up at 379+/-146 days revealed a target vessel revascularization rate of 18.2% and a target lesion revascularization rate of 13.6%. One death was reported. Maximal dose and average dose at the endothelium were 261 and 124+/-72.3 Gy, and maximal dose and average dose at the adventitia-media border were 159 and 50.3+/-29.3 Gy. Fourteen patients had 1.71 times longer recurrence-free interval compared to the interval between both IVBT treatments.

CONCLUSIONS

Repeat IVBT to the same ISR site is safe without any adverse clinical events at an average 12 months' follow-up. A second IVBT treatment led to a prolonged ISR-free survival for the majority of patients. The choice of isotope did not influence outcome.

EFFECT OF RESECTION AND OUTCOME IN PATIENTS WITH RETROPERITONEAL SARCOMA

BACKGROUND

A consecutive series of 47 patients with retroperitoneal sarcoma (RPS) were resected and prospectively followed.

METHOD

Between July 1994 and March 2005, 47 patients (24 men, 23 women; mean age, 56 years; range, 17-82 years) were evaluated.

RESULTS

A total of 23 patients had primary RPS and 24 patients had recurrent RPS. A total of 30 out of 47 patients (64%) underwent removal of contiguous intra-abdominal organs. The peroperative mortality was nil and significant preoperative complications occurred in eight cases only (17%). High tumour grade and incomplete resection were significant variables for a worse survival in all 47 patients, both in the univariate and multivariate analyses (P = 0.008 and P = 0.016, respectively). Among 28 radically resected patients, only histological grade affected overall survival (90% 5-year survival for low-grade tumour vs 26% 5-year survival for high-grade tumour; P = 0.006) with a similar effect noted for disease-free survival.

CONCLUSIONS

Histological grade was the only factor that affected overall and disease-free survival for RPS tumours. An aggressive surgical approach in both primary and recurrent RPS is associated with long-term survival.

The change of proliferating cell nuclear antigen and apoptosis of the MM46 mammary cancer cells of the mouse after single high-dose irradiation

The effects of intraoperative radiotherapy on tumor cells were elucidated by immunohistochemical examination of changes in the level of proliferating cell nuclear antigen. In addition, the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling method was used to examine the level of apoptosis in mouse MM46 tumor cells after a single high dose of irradiation (30 Gy, 6 MeV). A significant decrease in the number of tumor cells compared to controls was observed on the 3rd, 7th, and 14th days following irradiation, but not on the 1st day. Consistent with these results, the proliferating cell nuclear antigen labeling index of irradiated cells decreased significantly on the 3rd, 7th, and 14th days following irradiation, but not on the 1st day. By comparison, the regrowth area on day 14 only showed no difference compared to the control group. The apoptotic index increased on the 7th and 14th day after irradiation, but at a lower rate than the observed decrease in the level of proliferating cell nuclear antigen. We speculate that the major mechanism of single high-dose radiation effect is inhibition of DNA synthesis.

Normal tissue tolerance to intraoperative radiotherapy

Much experimental evidence has been accumulated assessing the tolerance of various tissues to IORT, and much of the tolerance data have resulted from the use of canine models. Guidelines of IORT tissue tolerance established in experimental models have been used in the clinical application of IORT at numerous institutions. Although the radiotolerance of differing tissues can vary among species, sufficient clinical experience has accumulated to validate the canine tissue tolerance model as representative of human tissue responses to IORT. Cellular effects from radiation principally stem from direct damage to DNA, and thus proliferating tissues are among the most radiosensitive, with arrested or abnormal cell division. These tissues can manifest striking early toxicity, reflecting the rate of cell division that is affected by the radiation. Irradiation of nonproliferating or slowly proliferating tissues may show little or no early toxicity, but late effects can be manifested to considerable and varying degrees. In much of this late toxicity, pathologic changes develop from progressive ischemia, brought about by the gradual obliteration of small blood vessels. Irradiated endothelium often becomes replaced by a thickened fibrous layer, which, in small vessels, leads to occlusion and ischemic necrotic changes in the supplied tissue. In larger vessels, fibrosis can lead to wall weakening and aneurysmal dilatation, rupture, or thrombosis. The common denominator, then, of radiation damage to many tissues is related to vascular effects. Although the tolerance to IORT-induced toxicity can vary considerably among tissues, doses ranging to 25 Gy can generally be tolerated without significant toxicity. Vital areas where IORT dose must be carefully monitored include critical vasculature, gastrointestinal viscera, ureter, significant motor or sensory nerve trunks, and central nervous system structures. Higher doses can generally be delivered safely to anatomic areas at risk for tumor that are at a distance from sensitive organs or tissues. The general principle providing the rationale of IORT should always be practiced: maximize the radiation dose to the tumor and tumor-harboring tissues while minimizing dose exposure to surrounding normal tissues.

High-dose-rate intraoperative irradiation: current status and future directions

Intraoperative irradiation (IORT) refers to the delivery of a single high dose of radiation therapy at the time of surgery when the tumor bed can be precisely defined and adjacent normal tissue maximally protected. It can be effectively delivered using either electrons (IOERT) or photons produced from a high-dose-rate gamma emitting radioisotope (HDR-IORT) and has been explored primarily for locally advanced or recurrent tumors at high risk for local failure despite extensive resection and full dose external beam radiation. With coordinated multidisciplinary interaction, IORT can be integrated in a combined-modality setting without undue additional toxicity. The purpose of this review will be to summarize the growing HDR-IORT experience in the treatment of various cancers, to compare its efficacy and toxicity vis a vis the IOERT data, and to discuss future trials as well as new areas of potential application.

Abdominosacral resection for primary irresectable and locally recurrent rectal cancer

PURPOSE

The purpose of this study was to present a technique of abdominosacral resection and its results in patients with locally advanced primary or locally recurrent rectal cancer with dorsolateral fixation.

METHODS

Between 1994 and 1999, 13 patients with locally advanced primary rectal cancer and 37 patients with locally recurrent rectal cancer underwent abdominosacral resection as part of a multimodality treatment, i.e., preoperative irradiation, surgery, and intraoperative irradiation. After the abdominal phase, the patient was turned from supine to prone position to perform the transsacral phase of the resection.

RESULTS

Margins were microscopically negative in 26 patients (52 percent), microscopically positive in 18 (36 percent), and positive with gross residual disease in 6 patients. Operation time ranged from 210 to 590 (median, 390) minutes, and blood loss ranged from 400 to 10,000 (median, 3,500) ml. No operative or hospital deaths occurred. Postoperative complications occurred in 41 patients (82 percent); most notable were perineal wound infections or dehiscence (n = 24, 48 percent). Other complications were postoperative urinary retention or incontinence (n = 9, 18 percent), peritonitis (n = 4), grade II neuropathy (n = 1), and fistula formation (n = 3). Kaplan-Meier 3-year overall survival, disease-free survival, and local control rates were, respectively, 41 percent, 31 percent, and 61 percent. Completeness of the resection (negative vs. positive margins) was a significant factor influencing survival (P = 0.04), disease-free survival (P = 0.0006), and local control (P = 0.0002).

CONCLUSION

The abdominosacral resection provides wide access and may be the therapeutic solution for the accomplishment of a radical resection for distally situated, dorsally or dorsolaterally fixed primary or locally recurrent rectal cancers.

Temporal CT changes after hepatic and renal interstitial radiotherapy in a canine model

PURPOSE

The purpose of this work was to define the temporal CT characteristics of hepatic and renal ablation following point-source radioablation utilizing a low energy, photon X-ray source emitted from a miniature probe.

METHOD

Twelve mongrel dogs underwent each of three hepatic and two renal point-source radiation ablations. Animals underwent serial, dual phase, spiral CT scans and were killed at 1, 3, and 6 months after treatment.

RESULTS

Ablative lesions were clearly visible at 1 month following therapy and consistently diminished in size over the 6 months of follow-up. Lesion size tended to be proportional to dose delivered. Both hepatic and renal lesions were low in attenuation with frequent rim enhancement that diminished over time. Hepatic lesions frequently showed transient hepatic attenuation differences (THADs). Lesion size appeared independent of proximity to vessels.

CONCLUSION

Following hepatic or renal interstitial radiotherapy, lesions are generated that are similar in CT appearance to those produced by other ablative techniques. The presence of rim or THAD enhancement can be seen early on as part of the normal tissue-healing response.

Results and complications of surgery combined with intra-operative radiation therapy for the treatment of locally advanced or recurrent cancers in the pelvis

Intra-operative radiation therapy (IORT) can benefit patients with pelvic tumors by delivering a high dose of radiation with precise delineation of tumor bed and maximal protection of surrounding normal tissues. The IORT experience has been particularly promising for locally advanced primary or recurrent rectal cancers in which a gross total resection is achieved. However, its potential benefit must be weighed against added toxicity. The main dose-limiting toxicity of pelvic IORT is peripheral neuropathy and ureteral stenosis. We will review the techniques for optimal IORT delivery, the results of the major studies investigating IORT treatment of rectal cancer, and the pelvic complications associated with combining surgery and IORT. A team of surgeons and radiation oncologists providing close multidisciplinary coordination is essential to integrate IORT with combined modality regimens in a safe and effective manner.

Intraoperative electron beam radiation therapy for locally recurrent rectal carcinoma

PURPOSE

Treatment results for locally recurrent rectal cancers are poor. This is a result of the fact that surgery is hampered due to the severance of the anatomical planes during the primary procedure and that radiotherapy is limited by normal tissue tolerance, especially after previous irradiation. This paper describes the results of a combined treatment modality in this patient group.

METHODS AND MATERIALS

From 1994 to 1998, 37 patients with locally recurrent rectal cancer, but without distant metastatic disease, received a combined treatment consisting of 50.4 Gy preoperative irradiation or, in case of previous radiotherapy, 30 Gy reirradiation or no irradiation, followed by radical surgery and intraoperative electron beam radiotherapy boost.

RESULTS

Fifteen patients received a radical resection (R0), eight a microscopic irradical resection (R1), and 14 a macroscopic irradical resection (R2). The overall 3-year local control (LC), disease-free survival (DFS), and overall survival rates were 60%, 32%, and 58% respectively. Radicality of resection (R0/R1 vs. R2) turned out to be the significant factor for improved survival (p < 0.05), DFS (p = 0.0008), and LC (p = 0.01). Preoperative (re-)irradiation is the other significant factor in survival (p = 0.005) and DFS (p = 0.001) and was almost significant for LC (p = 0.08). After external beam radiation therapy (EBRT) a significantly higher resection rate was obtained (R0/R1 vs. R2 p = 0.001). Symptomatic peripheral local recurrences have a significantly worse prognosis and higher rate of R2-resection (p = 0.0005).

CONCLUSION

Centralization of locally recurrent rectal cancer patients enabled the development of an aggressive multimodality treatment, which in turn led to promising results. Distant failure is still a drawback.

Brachytherapy for the interventional cardiologist and vascular surgeon

PURPOSE

There has been recent interest in the use of brachytherapy for the possible prevention of restenosis after angioplasty. However, this field is unfamiliar to most interventional cardiologists. This article is meant to serve as an introduction to the principles of brachytherapy especially as it applies to intravascular brachytherapy. Because the intended audience is the interventional cardiologist, the details of physics, radiobiology, and radiation jargon has been kept at a minimum.

METHODS

The main advantages of brachytherapy are that it can irradiate small volumes and conform to the target volume while sparing the surrounding normal tissues from the deleterious effects of irradiation. Various gamma- or beta-emitting radioisotopes can deliver the brachytherapy dose. In general, the beta emitters have fewer radiation exposure hazards, but the limited penetration of beta emitters can be a problem if deeper tissues need to be irradiated. Gamma sources can irradiate deeper but suffer from greater radiation exposure hazards. It should be remembered that the biological effects of radiation depend on a number of parameters, including the radiation modality, dose, dose rate, fractionation, treatment duration, dose prescription point, and the volume irradiated. The use of low energy isotopes, beta emitters, and remote-controlled afterloading has reduced the radiation exposure to the medical caregivers.

CONCLUSION

Intravascular brachytherapy is currently considered to be experimental. Those wishing to start a new intravascular brachytherapy program should comply with the required federal and state regulatory guidelines issued by the Nuclear Regulatory Commission, Food and Drug Administration, and their individual Institutional Review Board.

Feasibility of intraoperative high-dose rate brachytherapy to boost low dose external beam radiation therapy to treat pediatric soft tissue sarcomas

PURPOSE

To determine if a single intraoperative high-dose-rate brachytherapy (IOHDR) dose can be used in conjunction with low dose external beam radiation therapy (EBRT) to treat soft tissue malignancies in children with reduced morbidity.

METHODS

From March 1992 to February 1995, six pediatric patients (4 boys, 2 girls; ages ranging from 4-13 years; median 10.5 years) were treated with IOHDR in conjunction with EBRT, chemotherapy, and radical surgery at nine sites not treatable by standard intraoperative electron beam radiation therapy techniques. The IOHDR dose was 10 Gy (at 7 sites with microscopic residual disease) or 12.5 Gy (at 2 sites with minimal gross residual disease) prescribed at 0.5 cm depth. The treatment volume varied from 9-96 cc (mean 30.3 cc). IOHDR was used in these patients because the tumor locations prevented positioning and insertion of conventional intraoperative electron beam applicators. The EBRT dose was limited to 27-30.6 Gy (median dose 27.4 Gy) postoperatively in all patients to minimize growth retardation or altered organ function. The median initial EBRT field size was 211 cm2 (range 25-483), with a median of two fields per patient (range 1-2).

RESULTS

After a median follow-up of 40 months (range 22-62 months), all the patients were alive, five of them without evidence of disease. The other patient, with stage IV undifferentiated synovial sarcoma developed regrowth of pulmonary metastases at 14 months and local failure at 34 months. Toxicity was seen in two patients. One patient developed recurrent urinary infections and ureteral stenosis after 6 months and required a left nephrectomy. Another developed mild to moderate loss of visual acuity and impaired orbital growth after 6 months.

CONCLUSIONS

Use of IOHDR in conjunction with low dose EBRT to obtain local control and long-term disease-free survival in pediatric soft tissue sarcomas is feasible with acceptable toxicity. Tumor beds not treatable with standard electron beam intraoperative radiation therapy could be satisfactorily encompassed with IOHDR.

Locally advanced primary colorectal cancer: intraoperative electron and external beam irradiation +/- 5-FU

PURPOSE

For locally advanced primary colorectal cancer, our institution has combined intraoperative electron irradiation (IOERT) with external beam irradiation (EBRT) +/- 5-fluorouracil (5-FU) and surgical resection. Disease control and survival were compared with the current IOERT and prior non-IOERT regimens.

METHODS AND MATERIALS

From April 1981 through August 1995, 61 patients received an IOERT dose of 10-20 Gy, usually combined with 45-55 Gy of fractionated EBRT; 56 had minimum follow-up of 18 months. The amount of residual disease remaining at IOERT after exploration and maximal resection in the 56 patients was gross in 16, < or = microscopic in 39, and unresected in 1.

RESULTS

Survival (SR) and disease control were analyzed as a function of potential prognostic factors. Factors that achieved statistical significance for improved overall survival included treatment sequence of preop EBRT + 5-FU (vs. postoperative EBRT + 5-FU, p = 0.003) and < or = microscopic residual disease after maximal resection (vs. gross residual, p = 0.005). Those that appeared to favorably impact disease-free survival included EBRT + 5-FU (vs. EBRT alone, p = 0.01), < or = microscopic residual (vs. gross, p = 0.0014), and colon site of primary (vs. rectum, p = 0.009). Failures within an irradiation field have occurred in 4 of 16 patients (25%) who presented with gross residual after partial resection vs. 2 of 39 (5%) with < or = microscopic residual after gross total resection (p = 0.01). The significant prognostic factors for a decrease in distant metastases were the same as for disease-free SR with respective p-values of 0.013 (EBRT + 5-FU), 0.008 (microscopic residual), and 0.03 (colon primary). The current data suggests a relationship between IOERT dose and incidence of Grade 2 or 3 neuropathy (< or = 12.5 Gy--1 of 29 or 3%, > or = 15 Gy--6 of 26 or 23%, p = 0.03).

CONCLUSIONS

Both overall survival and disease control appear to be improved with the addition of IOERT to standard treatment. More routine use of systemic therapy is indicated as a component of IOERT containing treatment regimens because the incidence of distant metastases was 50% of patients at risk.

Intraoperative electron and external beam irradiation with or without 5-fluorouracil and maximum surgical resection for previously unirradiated, locally recurrent colorectal cancer

PURPOSE/OBJECTIVE

1) Disease control and survival will be evaluated for treatment regimens containing intraoperative electron irradiation (IOERT) for locally recurrent, previously unirradiated colorectal cancers. 2) Various prognostic factors will be evaluated to determine whether they have an impact on disease control or survival.

MATERIALS AND METHODS

From April 1981 through August 1995, 123 patients with previously unirradiated locally recurrent colorectal cancers received IOERT at our institution, usually as a supplement to external beam irradiation (EBRT) and maximum resection. All received EBRT with or without concomitant 5-fluorouracil-based chemotherapy. Forty-five Gy in 25 fractions was given to the tumor or tumor bed plus 3-cm to 5-cm margins in 121 of 123 patients and a boost of 5.4 to 9 Gy in 3 to 5 fractions to the tumor plus 2-cm margins. Maximum resection was performed before or after EBRT. IOERT doses ranged from 10 to 20 Gy in 119 of 123 patients, with dose dependent on resection margins (130 fields in 123 patients). Maintenance chemotherapy was given to only two patients.

RESULTS

Disease relapse and survival were evaluated. Central failure (within the IOERT field) was documented in 13 of 123 patients (11 percent) with a five-year actuarial rate of 26 percent. Local relapse (in EBRT field) occurred in 24 patients (20 percent); five-year rate was 37 percent. Distant metastases occurred in 66 patients (54 percent); five-year rate was 72 percent. Median survival was 28 months, with overall survival at two, three, and five years of 62, 39, and 20 percent, respectively. Tolerance data suggest a relationship between IOERT dose and incidence of Grade 2 or 3 neuropathy (< or = 12.5 Gy, 2 of 29 or 7 percent; > or = 15 Gy, 19 of 101 or 19 percent; P = 0.12). Survival and disease control were analyzed as a function of potential prognostic factors. None of the prognostic factors had a significant impact on disease control or survival. Although there was a trend for reduction in local relapse rates with gross total vs. partial resection, this neither achieved statistical significance nor translated into improved survival. Patients with gross residual disease after maximum resection had three-year and five-year survival rates of 36 and 18 percent, respectively, which paralleled results for patients with gross total resection at 41 and 24 percent, respectively.

CONCLUSION

Encouraging trends for improved local control with or without survival exist in separate locally recurrent colorectal IOERT analyses from our institution and other institutions. Therefore, continued evaluation of IOERT approaches seems warranted. Disease control within the IOERT and external fields is decreased when the surgeon is unable to accomplish a gross total resection. Therefore, it is reasonable to consistently add 5-fluorouracil or other dose modifiers during EBRT and to evaluate the use of dose modifiers in conjunction with IOERT (sensitizers and hyperthermia). In view of high systemic failure rates of > 50 percent in patients with locally recurrent disease, more routine use of systemic therapy is indicated as a component of IOERT-containing treatment regimens (use existent chemotherapy and/or develop effective immunotherapy and gene transfer therapy). Even with locally recurrent lesions, the aggressive multimodality approaches including IOERT have resulted in improved local control and long-term survival rates of 20 percent vs. an expected 5 percent with conventional techniques.

Intraoperative radiotherapy for pancreatic carcinoma. Experimental and clinical studies

Intraoperative radiotherapy (IORT) is an innovative treatment approach that has been tested in several Phase I-II studies and small Phase III trials in patients with resectable and unresectable pancreatic cancer. The technical approach and dose guidelines for adjacent normal tissues have been established in a series of experiments using a large animal (canine) model. This article reviews the experimental and clinical studies of IORT in cancer of the pancreas.

Tumors in dogs exposed to experimental intraoperative radiotherapy

PURPOSE

The frequency of radiation-induced neoplasms was determined in dogs enrolled in the National Cancer Institute canine trials of intraoperative radiotherapy (IORT).

METHODS AND MATERIALS

Twelve protocols assessing normal tissue response to IORT involved 238 dogs in a 15-year trial. Eighty-one dogs were followed for > 24 months postoperatively and were assessed for tumor development; 59 of these animals received IORT.

RESULTS

Twelve tumors occurred in the 59 dogs receiving IORT. Nine were in the IORT portals and were considered to be radiation induced. No tumors occurred in 13 sham animals or in 9 animals treated with external beam radiotherapy alone. The frequency of radiation-induced malignancies in dogs receiving IORT was 15%, and was 25% in animals receiving > or = 25 Gy IORT. Frequency of all tumors, including spontaneous lesions, was 20%.

CONCLUSIONS

Intraoperative radiotherapy contributed to a high frequency of sarcoma induction in these dogs. Unknown to date in humans involved in clinical trials of IORT, this potential complication should be looked for as long-term survivors are followed.

Complications of combined intraoperative radiation (IORT) and external radiation (ERT) of the upper abdomen: an experimental model

An experimental model in the rabbit is presented which is suitable for analysis of clinically relevant, early side-effects of combined upper abdominal IORT and ERT. Fractionated ERT alone given through an upper abdominal a.-p. field including the entire stomach caused gastric ulcerations within < or = 58 days. Latent times decreased with increasing dose and the ED50 for occurrence of ulcers was 39 +/- 3.3 Gy. Single doses of IORT of 20-40 Gy alone administered through a 2-cm diameter field localized on the coeliac axis and carefully excluding any intestinal mucosa caused neither gastric ulcerations nor other clinical symptoms. When ERT with 40 Gy was preceded by IORT with 20-40 Gy or by sham IORT, 13 out of 15 animals developed ulcers after latent times which in a life-table analysis were shown to be significantly shorter than after ERT alone. However, a statistically significant IORT dose-dependence of latent time or incidence of ulcers could not be demonstrated in the present experiment. The most significant histological changes were observed in the areas of gastric ulcers. Already during ERT, the mucosal epithelium was depleted and regenerative activity was evident in spite of ongoing fractionated irradiation. However, profound irregularities in glandular structure and distribution, as well as number of proliferating epithelial cells were still present in healed ulcers at 80 days. In summary, IORT to the coeliac artery did precipitate the development of gastric ulcers induced by subsequent ERT. On the one hand, the data indicate that the surgical procedure of IORT did contribute to this effect. On the other hand, IORT to the coeliac artery could cause transient, functional alterations in blood supply to the depending organs, i.e. the stomach, and could thus precipitate the development of radiation-induced ulcers.

Intraoperative irradiation after palliative surgery for locally recurrent rectal cancer

BACKGROUND

In patients with locally recurrent rectal cancer, long-term disease control and survival is uncommon with single-modality therapy. This report evaluates results achieved at the Mayo Clinic (Rochester, MN) with single- or combined-modality treatment, including intraoperative irradiation.

METHODS

From 1981 to 1988, 106 patients underwent palliative surgical resections at the Mayo Clinic for locally recurrent rectal cancer. None had evidence of extrapelvic disease, and 42 received intraoperative electron beam irradiation (IORT) as a component of treatment. Gross residual disease remained after maximal surgical resection in 34 of the 42 patients and 61 of the patients who did not receive IORT. The IORT dose was 15-20 Gy in 39 patients and 10, 25, and 30 Gy in the other 3. External beam irradiation (EBRT) was administered to 41 of the 42 patients (doses > or = 45 Gy to 38 patients).

RESULTS

Kaplan-Meier survival estimates at 3 and 5 years were analyzed for the 106 patients. Palliative surgical resection alone (12 patients) resulted in a 3-year survival of 8% and a 5-year survival of 0%. Statistically significant factors relative to survival based on the univariate analysis of all patients included amount of residual tumor (microscopic vs. gross, P = 0.032) treatment method (P = 0.005), IORT versus no IORT (P = 0.0006), type of symptoms (P = 0.0075), type of fixation (P < 0.0001), and preoperative Eastern Cooperative Oncology Group status (P = 0.03). For patients who received IORT, 3-year survival with gross residual tumor or presentation with pain was 44% and 43%, respectively. Factors not associated with survival (univariate) included extended versus conventional surgical resection, grade, age, and sex. The 3-year cumulative probability of distant metastasis was 60% in the patients who received IORT and 54% in those who did not. The 3-year local relapse rates were 40% versus 93% in patients who received IORT versus those who did not.

CONCLUSIONS

Although the addition of IORT to external irradiation and maximal surgical resection appears to improve local tumor control and survival in patients who undergo palliative surgical resection for locally recurrent rectal cancer, further gains in treatment are necessary. Considering the high rates of distant metastasis, more routine systemic therapy with 5-fluorouracil (5-FU) leucovorin, 5-FU levamisole, or all three needs to be incorporated into aggressive treatment approaches. In patients with gross residual tumor after maximum surgical resection, local tumor control is inadequate despite treatment combinations including IORT. The evaluation of radiation sensitizers or biologic modifiers during external irradiation and IORT is indicated.

Tolerance of the bladder to intraoperative radiation in a canine model: a five-year follow-up

PURPOSE

Late effects of intraoperative radiation therapy (IORT) on bladder were investigated in a canine model.

METHODS AND MATERIALS

After laporatomy and cystotomy in adult female foxhounds weighing 25-35 kg, 12 MeV electrons were delivered intraoperatively to a 5 cm circular bladder field which included the trigone and both uretero-vesicle junctions. Each animal received doses of 0, 20, 25, 30, 35, or 40 Gy. All the dogs were followed 5 years postoperatively. An unoperated dog receiving no surgery or radiation treatment was followed as a control. Close clinical monitoring was performed with regular cystometrics and intravenous pyelography. Animals were killed as scheduled with complete necropsies, including histopathology, with special attention to genitourinary structures.

RESULTS

There were no acute or late bladder complications detected clinically in any animal. The dog receiving 30 Gy IORT developed rhabdomyosarcoma in the treatment field at 58 months. On follow-up testing over 5 years, there was no loss of bladder contractility on cystometry, and mild changes in the ureters on intravenous pyleography when animals receiving IORT were compared with baseline pretreatment values or with control animals. Histologically, a difference was evident between irradiated and unirradiated animals, but the changes were not clearly dose-related.

CONCLUSION

Intraoperative radiation therapy may by safely delivered to the canine bladder with few acute or chronic complications. It is an approach which has potential for clinical use and should continue to be explored in human clinical trials.

Experimental and clinical studies of intraoperative radiation therapy

Intraoperative radiation therapy (IORT) is an innovative treatment modality that has recently been given considerable attention as an approach toward controlling various locally advanced cancers. IORT involves surgical extirpation or debulking of the malignant lesion and the delivery of a large single dose of radiation to the tumor bed or to residual disease. This strategy allows for a theoretical enhancement of the therapeutic effect of radiation for three reasons: (1) the biologic effectiveness of a single large radiation dose is higher than for the same dose given in a fractionated regimen; (2) the dose of radiation is precisely given to the area at greatest risk of tumor recurrence (or persistence); and (3) irradiation of dose-limiting normal tissues may be avoided by operative mobilization of the tissues from the treatment volume by customized lead shielding of anatomically fixed structures or by judicious choice of electron beam energies or use of a bolus to limit dose to deep structures. Electrons are generally used for IORT because of sharp dose falloff. This avoids potential toxic effects to normal structures that may lie deep to the treatment volume. Conventional external beam photon radiation therapy (EBRT) allows less accurate tumor volume delineation (even with sophisticated treatment planning technique) and dose limitations necessitated by normal tissues incidentally in the treatment volume. A considerable amount of experimental and clinical data are available on the acute and late effects of IORT on normal tissues. Dose tolerances of many organs have been described in large animal models, and clinical toxicities are evident in several trials. Clinical IORT treatments are provided in more than 250 U.S. and foreign centers at the present time. Given the current interest in IORT, this monograph will review IORT methods and experimental and clinical results with emphasis on its present and future role for locally advanced cancers.

Effects of intraoperative radiotherapy on vascular grafts in a canine model

PURPOSE

The effects of intraoperative radiotherapy +/- external beam radiotherapy on prosthetic vascular grafts were investigated in a canine model.

METHODS AND MATERIALS

In 1986 and 1987, 30 adult beagles underwent laparotomy with transection and segmental resection of the infrarenal aorta followed by immediate reconstruction with a prosthetic graft. Intraoperative radiotherapy at varying doses from 0-30 Gy was then administered to all animals. Half of the dogs received 36 Gy external beam radiotherapy in 10 fractions postoperatively. Animals were sacrificed and necropsied at predetermined intervals and as clinically indicated to assess early (< or = 6 months) and late (> 6 months) effects to the vascular graft and surrounding normal tissue.

RESULTS

Histopathologic analyses of irradiated vascular structures were performed and correlations were made with the clinical outcome. The most frequent early clinical toxicity was graft thrombosis, occurring in 7 of 10 animals followed for < or = 6 months. Early graft thrombus formation appeared unrelated to radiotherapy dose and probably represented a technical surgical complication. Anastomotic stenosis of varying severity occurred in most animals followed > 6 months. Late (> 6 months) graft stenosis was correlated with intraoperative radiotherapy dose. At < or = 20 Gy of intraoperative irradiation, 3 of 14 animals developed late graft occlusion; at > 25 Gy, five of six animals developed late occlusion. On histopathologic review, increasing intraoperative dose and increasing total radiotherapy dose (intraoperative+external beam) appeared to correspond with increasing severity of graft changes seen after 6 months of follow-up.

CONCLUSIONS

Thrombus formation is a frequent early complication of vascular graft placement of the infrarenal aorta in our beagle dog model. Intraoperative doses up to 20 Gy appear to contribute minimally to late graft occlusion, while doses > or = 25 Gy contribute to late occlusion with high likelihood. Both intraoperative dose and total radiotherapy dose correlated with late graft occlusion, and with histopathologic changes in the graft and anastomoses.

Late effects of intraoperative radiation therapy on retroperitoneal tissues, intestine, and bile duct in a large animal model

PURPOSE

The late histopathological effects of intraoperative radiotherapy (IORT) on retroperitoneal tissues, intestine, and bile duct were investigated in dogs.

METHODS AND MATERIALS

Fourteen adult foxhounds were subjected to laparotomy and varying doses (0-45 Gy) of IORT (11 MeV electrons) delivered to retroperitoneal tissues including the great vessels and ureters, to a loop of defunctionalized small bowel, or to the extrahepatic bile duct. One control animal received an aortic transection and reanastomosis at the time of laparotomy; another control received laparotomy alone. This paper describes the late effects of single-fraction IORT occurring 3-5 years following treatment.

RESULTS AND CONCLUSION

Dogs receiving IORT to the retroperitoneum through a 4 x 15 cm portal showed few gross or histologic abnormalities at 20 Gy. At doses ranging from 30-45 Gy, radiation changes in normal tissues were consistently observed. Retroperitoneal fibrosis with encasement of the ureters and great vessels developed at doses > or = 30 Gy. Radiation changes were present in the aorta and vena cava at doses > or = 40 Gy. A 30 Gy dog developed an in-field malignant osteosarcoma at 3 years which invaded the vertebral column and compressed the spinal cord. A 40 Gy animal developed obstruction of the right ureter with fatal septic hydronephrosis at 4 years. Animals receiving IORT through a 5 cm IORT portal to an upper abdominal field which included a defunctionalized loop of small bowel, showed a few gross or histologic abnormalities at a dose of 20 Gy. At 30 Gy, hyaline degeneration of the intestinal muscularis layer of the bowel occurred. At a dose of 45 Gy, internal intestinal fistulae developed. One 30 Gy animal developed right ureteral obstruction and hydronephrosis at 5 years. A dog receiving 30 Gy IORT through a 5 cm portal to the extrahepatic bile duct showed diffuse fibrosis through the gastroduodenal ligament. These canine studies contribute to the area of late tissue tolerance to IORT.

Tissue tolerance of normal and surgically manipulated canine liver to intraoperative radiation therapy (IORT)

PURPOSE

The purpose of the study is to obtain dose guidelines for the delivery of intraoperative radiotherapy to the liver of patients with colorectal liver metastases. Following partial resection of the liver, a single high dose of 10, 20, 25, and 30 Gy intraoperative radiotherapy was applied to both the resection plane as well as a nonsurgically manipulated part of the liver of 25 beagles. The temporal sequence of histological and ultrastructural changes of these irradiated parts of the liver tissue was investigated.

METHODS AND MATERIALS

The feasibility of delivering single large dose of intraoperative electron beam radiotherapy to the normal and partially hepatectomized liver was experimentally investigated in a canine study.

RESULTS

There were no postoperative complications, no morbidity or mortality with a minimal follow-up of 1 year. Autopsy performed 3 months following irradiation showed only mild histopathological changes. One year following intraoperative radiotherapy more distinct histopathological changes consisting of capsular thickening, diffuse parenchymal fibrosis and subcapsular hepatocellular atrophy were found. The liver function remained intact.

CONCLUSION

This study demonstrated that intraoperative radiotherapy to part of the liver in the canine model can be safely applied and doses up to 30 Gy are well tolerated.

The influence of surgical margins on advanced cancer treated with intraoperative radiation therapy (IORT) and surgical resection

Intraoperative radiation therapy (IORT) has been used successfully in the treatment of malignancies, alone and as an adjunct to surgical resection. This study examined a single institution's experience with combined IORT and surgical resection in the treatment of advanced cancer. The records of 41 consecutive patients undergoing intraoperative radiation therapy (IORT) at the Fox Chase Cancer Center, from July 1987 through March 1990, were retrospectively reviewed. All patients had locally advanced disease, of whom 73% had failed previous multimodality therapy and 44% had undergone prior radiation therapy (XRT). The 2-year actuarial survival for the entire cohort was 72%. Disease-free survival was 47% at 1 year and 5% at 2 years. The only important prognostic factor predicting outcome was status of the surgical margin. Positive surgical margins decreased the 2-year actuarial survival from 100% to 59%, and increased the local failure rate from 21% to 52%. Margin status had no effect on the later development of metastatic disease. Higher IORT doses, field sizes > 7 cm, and multiple IORT fields were used for larger tumors and larger amounts of residual disease. These parameters alone did not correlate with improved local control. This analysis suggests the usefulness of aggressive surgical resection with IORT in extending survival for locally advanced or recurrent cancer. Negative margin status is the best predictor of a favorable outcome and should be used to select patients who may benefit from IORT. The use of radiation sensitizing agents should be explored in patients with positive margins, since in-field failure continues to be the major pattern of failure. IORT in conjunction with aggressive surgical resection should continue to be studied in prospective randomized clinical trials.

External beam and intraoperative electron irradiation for locally advanced soft tissue sarcomas

PURPOSE

Intraoperative irradiation with electrons was used in conjunction with external beam irradiation and maximal surgical resection in 20 patients with locally advanced soft tissue sarcomas or desmoids. This manuscript presents results with regard to tolerance of treatment and its impact on tumor control and survival.

METHODS AND MATERIALS

Ten patients presented with previously untreated primary sarcomas and 10 at the time of local recurrence (two had recurrent desmoid tumors). Tumor location was retroperitoneal in 19 and in the low anterior neck in one. A partial or gross total resection was performed prior to the external beam or intraoperative component of irradiation in every patient, but all had positive resection margins. Patients received 4500-6000 cGy of fractionated, external beam irradiation and an IORT dose of 1000-2000 cGy. Chemotherapy was given only at the time of disease progression.

RESULTS

Fourteen of 20 patients (70%) were alive; 11 (55%) were free of disease (4/10 primary, 7/10 recurrent), but 1 required hemipelvectomy for salvage. Progression within the intraoperative irradiation field was documented in only 1 patient (5%) and within the external beam field in 3/20 (15%). Blood born distant metastasis occurred in 5 patients (25%) and peritoneal seeding in 1 (5%). The distant failure incidence by grade was 1/8 (13%) for Grades 1, 2 and 5/12 (42%) for Grades 3, 4. Only 1 patient (5%) developed a > or = severe neuropathy, and small bowel obstruction requiring exploration also occurred in a single patient.

CONCLUSION

In view of acceptable tolerance and the high current rate of local tumor control, in spite of incomplete surgical resections, further evaluation of intraoperative irradiation as a component of treatment is indicated for locally advanced primary and recurrent soft tissue sarcomas.

Effect of intraoperative radiation on the tensile strength of small bowel anastomoses

Increasing interest in the use of preoperative or intraoperative radiation therapy for cancer has led to concerns regarding tissue healing and integrity subsequent to treatment. This is especially so for intestinal anastomoses incorporating irradiated bowel, where poor healing may lead to anastomotic disruption and sepsis. One hundred thirty Sprague-Dawley rats were randomized into five groups as follows: both limbs, one limb, or neither limb of an anastomosis received 2,000 R of radiation intraoperatively. A fourth group had a segment of small bowel irradiated, with no anastomosis; a fifth group had the gut exposed by celiotomy. The control groups and all anastomoses underwent tensile strength measurements on the seventh postoperative day, with findings as follows: no anastomosis, no irradiation, 143.75 g; no anastomosis, irradiated, 114.50 g; anastomosis, no irradiation, 85.273 g; anastomosis, one limb irradiated, 78.100 g; anastomosis, both limbs irradiated, 59.00 g. There was no statistical difference in tensile strength of the anastomosis between when neither limb and when just one limb was irradiated. However, when both limbs were irradiated, the loss of strength was statistically significant (P = 0.002). Irradiation damage scores were assigned using Black et al.'s histologic scoring system. These scores were not significantly different between the irradiated segments. Inflammation and fibrosis scores for the anastomoses were also not significantly different. These results indicate that, in rats, anastomotic healing is impaired only when both limbs of the anastomosed intestine are irradiated. The normal strength of the anastomosis with only one limb irradiated cannot be explained by differences in inflammation, fibrosis, or radiation damage and is caused by an undetermined factor.

Long term tolerance of thoracic organs to intraoperative radiotherapy

The tolerance of mediastinal structures to intraoperative radiotherapy (IORT) was investigated in 3 separate animals trials using 49 adult foxhounds and one limited Phase I trial in 4 patients with Stage II or III non-small cell lung cancer (NSCLC). The 1- to 2-year results of these trials have been previously reported with significant toxicity found at dose levels over 20 Gy. We now report the results of five dogs reserved for long term studies and one Stage II NSCLC patient alive at 5 years. Two dogs received 20 Gy IORT and one received 30 Gy IORT to the esophagus, all three to a single 6 cm field with 9 MeV electrons. One control dog underwent surgery without irradiation. One dog received 20 Gy IORT to a single 5 cm mediastinal field with 13 MeV electrons following left pneumonectomy. At 5 years, all five dogs reserved for a long term evaluation were alive and evaluable with minimal endoscopic and radiographic abnormalities. The one patient alive at 5 years for evaluation received 25 Gy IORT to two matched 6 cm fields with 13 MeV electrons. She has stable dyspnea on exertion and there is no evidence of cancer by endoscopy. We conclude, based on these limited data, that IORT in the mediastinum may be safe at dose levels that do not exceed 20 Gy, and further careful evaluation at these lower treatment doses is warranted to determine efficacy.

Arteriodigestive fistula: a complication associated with intraoperative and external beam radiotherapy following surgery for gastric cancer

Intestinal hemorrhage due to arteriodigestive fistula is described to be a rare and serious complication of radiotherapy. Three cases of this type of fistula in gastric cancer patients treated with gastrectomy, intraoperative electron boost (15 Gy), and fractionated external beam irradiation (46 Gy) are reported. Selective angiography is most helpful in the diagnosis and immediate surgery could be lifesaving. An attempt to explain the etiopathogenesis is made.

Intraoperative radiation therapy for recurrent head and neck cancer

Forty-seven patients with recurrent head and neck cancer in a previously irradiated field were treated with surgical resection and intraoperative radiation therapy (IORT). Recurrent disease occurred at a median of 18 months from primary treatment, and was at the primary tumor site in 31 and metastatic to regional lymph nodes in 16. Recurrences were squamous cell carcinomas in 42 and adenoid cystic in five. Surgical resection left microscopic residual disease in 41 and gross residual in six. All patients received IORT with a median of 20 Gy. Two-year actuarial survival is 54.9%, and 15 patients are alive and disease free with a median survival of 29 months. Two-year actuarial local control is 61.5%. A trend toward increased survival (P less than 0.09) and local recurrence control (P = 0.05) was noticed when treating microscopic residual disease as opposed to gross residual disease. Perioperative mortality was seen in 8.5% and there was no increase in morbidity secondary to IORT. The authors believe that surgical resection and IORT is an effective treatment modality for head and neck cancers recurrent in previously irradiated fields and is adaptable to tertiary care hospitals.

Muscle injury following experimental intraoperative irradiation

The paraaortic region of beagle dogs was irradiated to 15 to 55 Gy intraoperative irradiation, 10 to 47.5 Gy intraoperative irradiation following 50 Gy external beam irradiation in 25 fractions, or 50 to 80 Gy external beam irradiation in 30 fractions. Six MeV electrons were used for intraoperative irradiation, and external beam irradiation was done using photons from a 6 MV linear accelerator. The psoas muscle in the irradiation field was examined histomorphometrically 2 or 5 years after irradiation. The percentage of muscle fibers and capillaries decreased, whereas the percentage of connective tissue increased with increased dose for both intraoperative irradiation only and intraoperative irradiation plus external beam irradiation. The dose causing a 50% decrease in the percentage of muscle fibers was 21.2 Gy and 33.8 Gy at 2 and 5 years, respectively, after intraoperative irradiation alone, and 22.9 Gy and 25.2 Gy at 2 and 5 years, respectively, after intraoperative irradiation combined with 50 Gy external beam irradiation. The ED50 for severe vessel lesions was 19.2 Gy and 25.8 Gy at 2 and 5 years, respectively, after intraoperative irradiation alone and 16.0 Gy and 18.0 Gy at 2 and 5 years, respectively, after intraoperative irradiation combined with 50 Gy external beam irradiation. External beam irradiation alone caused a slight decrease in percentage of muscle fibers with increased dose, and vessel lesions were infrequent or mild. Radiation-induced muscle injury was characterized by loss of muscle fibers, decreased fiber size, severe vessel lesions, hemorrhage, inflammation, coagulation necrosis, and fibrosis. These histopathologic characteristics distinguish this muscle injury from that caused by neurogenic atrophy. These data indicate that radiation-induced muscle injury most likely was caused by injury of the supporting vasculature. The lesions produced were largely a function of the single intraoperative dose rather than the external beam fractionated doses. Furthermore, it appears that 20 to 25 Gy intraoperative irradiation combined with 50 Gy external beam irradiation may be near the maximum tolerated dose by sublumbar musculature and its supporting vasculature.

Tumor induction following intraoperative radiotherapy: late results of the National Cancer Institute canine trials

Intraoperative radiotherapy has been employed in human cancer research for over a decade. Since 1979, trials to assess the acute and late toxicity of IORT have been carried out at the National Cancer Institute in an adult dog model in an attempt to establish dose tolerance guidelines for a variety of organs. Of the 170 animals entered on 12 studies with a minimum follow-up of 2 years, 148 dogs received IORT; 22 control animals received only surgery. Animals were sacrificed at designated intervals following IORT, usually at 1, 6, 12, 24, and 60 month intervals. 102 of 148 irradiated dogs were sacrificed less than 24 months; 46 dogs were followed greater than or equal to 24 months after IORT. To date, 34 of the 46 animals have been sacrificed; the 12 remaining animals are to be followed to 5 years. These 12 animals have minimum follow-up of 30 months. In the irradiated group followed for greater than or equal to 24 months, 10 tumors have arisen in 9 animals. One animal developed an incidental spontaneous breast carcinoma outside the IORT port, discovered only at scheduled post-mortem exam. The remaining nine tumors arose within IORT ports. Two tumors were benign neural tumors--a neuroma and a neurofibroma. One animal had a "collision" tumor comprised of grade I chondrosarcoma adjacent to grade III osteosarcoma arising in lumbar vertebrae. Two other grade III osteosarcomas, one grade III fibrosarcoma, and one grade III malignant fibrous histiocytoma arose in retroperitoneal/paravertebral sites. An embryonal rhabdomyosarcoma (sarcoma botryoides) arose within the irradiated urinary bladder of one animal. No sham irradiated controls nor IORT animals sacrificed less than 24 months have developed any spontaneous or radiation-induced tumors. The time range of diagnoses of tumors was 24-58 months (median 40 months). The IORT dose range associated with tumor development was 20-35 Gy (median 30 Gy). The carcinogenesis capability of single fraction, high dose radiation in animals is discussed, as are the implications of these data for continued research and clinical usage of IORT in the treatment of humans.

Combination of intraoperative radiation with resection of cancer of the pancreas

The utility of intraoperative radiation therapy (IORT) as an adjuvant to the surgical resection of pancreatic cancer was studied. In 1976, as our first trial with this combined therapy, we applied IORT with 30 Gy of electron beam with 8 MeV to 15 patients to prevent local recurrence around the celiac axis and superior mesenteric artery after standard pancreatectomy. However, the combined therapy did not show an improvement in survival rate as compared to that of 19 patients with standard operation alone. Autopsies of three patients with the combined therapy did not show involved lymph nodes in the radiation field, but did show local recurrence around the aorta outside the radiation field. By comparison, we performed extended operation without IORT on nine patients, with almost complete dissection of the lymph nodes around the aorta, from the diaphragm to the level of the inferior mesenteric artery. This extended surgery did not improve survival time, and autopsy showed local recurrence in spite of the dissection of lymph nodes. Therefore, since 1984, we have performed IORT with a dose of 30 Gy, 9 MeV, and an extended radiation field from the diaphragm above to the inferior mesenteric artery below, following extended operation on 14 patients. The five-year cumulative survival rate of these cases was 33.3%. Four autopsies showed improvement of local control rate. No radiation-related complications were noticed postoperatively in patients who underwent extended IORT following pancreatectomy. We were encouraged to continue this approach for the cure of pancreatic cancer.

Management of primary and recurrent soft-tissue sarcoma of the retroperitoneum

From 1982 to 1987, 114 patients underwent operation at Memorial Sloan-Kettering Cancer Center for soft-tissue sarcoma of the retroperitoneum. A retrospective analysis of these patients defines the biologic behavior, surgical management of primary and recurrent disease, predictive factors for outcome, and impact of multimodality therapy. Complete resection was possible in 65% of primary retroperitoneal sarcomas and strongly predicts outcome (p less than 0.001). The rate of complete resection was not altered by histologic type, size, or grade of tumor. These patients had a median survival of 60 months compared to 24 months for those undergoing partial resection and 12 months for those with unresectable tumors. Forty-nine per cent of completely resected patients have had local recurrence. This is the site of first recurrence in 75% of patients. These patients undergo reoperation when feasible. Complete resection of recurrent disease was performed in 39 of 88 (44%) operations, with a 41-month median survival time after reoperation. Tumor grade was a significant predictor of outcome (p less than 0.001). High-grade tumors (n = 65) were associated with a 20-month median survival time compared to 80 months for low-grade tumors (n = 49). Gender, histologic type, size, previous biopsy, and partial resection versus unresectable tumors did not predict outcome by univariate analysis. Adjuvant radiation therapy and chemotherapy could not be shown to have significant impact on survival. Concerted attempt at complete resection of both primary and recurrent retroperitoneal soft-tissue sarcoma is indicated.

Peripheral nerve and ureteral tolerance to intraoperative radiation therapy: clinical and dose-response analysis

Between April 1981 and July 1984, 51 patients received intraoperative radiation therapy (IORT) as a component of therapy for the management of primary or recurrent pelvic malignancies which were initially unresectable for cure. For these patients, curative surgical alternatives did not exist, or would have involved extensive procedures such as pelvic exenteration, distal sacrectomy, hemipelvectomy, or hemicorporectomy. The primary disease was colorectal in 38 patients. Treatment consisted of external beam radiation (range 3000 to 6890 cGy, median 5040 cGy), surgical debulking when feasible, and an intraoperative electron beam boost to the gross or microscopic residual disease (dose range 1000 to 2500 cGy, median 1750 cGy) utilizing 9-18 MeV electrons. The most common IORT associated toxicities were peripheral neuropathy and ureteral obstruction. None were life-threatening or fatal in severity. Of the 50 patients evaluable for neurotoxicity analysis, 16 (32%) developed peripheral neuropathy consisting of pain in 16 patients, numbness and tingling in 11, and weakness in 8. The pain, numbness and tingling resolved in about 40% of patients, while weakness resolved in only 1 of 8. Sixteen ureters were initially unobstructed by tumor at the time of IORT. Of these, 10 (63%) subsequently showed evidence of obstruction and hydronephrosis. The development of neurotoxicity was more common at IORT doses of 1500 cGy or more versus 1000 cGy. Ureteral obstruction with hydronephrosis occurred more frequently at IORT doses of 1250 cGy or more compared to 1000 cGy. There was no relationship between the likelihood of developing complications and the total external beam dose. The observed dependence of human nerve toxicity primarily on the IORT dose is consistent with data generated from animal experiments.

Response of aorta and branch arteries to experimental intraoperative irradiation

Injury to the aorta was evaluated in dogs 2 and 5 years after fractionated irradiation (EBRT), intraoperative irradiation (IORT) or a combination. Doses greater than 20 Gy IORT combined with 50 Gy EBRT given in 2 Gy fractions or 30 Gy IORT alone were accompanied by a significant risk of aneurysms or large thrombi as determined at necropsy 4 to 5 years following irradiation. Narrowing of the aorta as detected by aortography occurred at 5 years but was not detected earlier. The ED50 for aortic narrowing was 38.8 Gy IORT and 31 Gy IORT plus 50 Gy EBRT. The ED50 for branch artery injury was 24.8 Gy IORT alone and 19.4 Gy IORT plus 50 Gy EBRT. The difference in ED50s for IORT alone and IORT plus EBRT indicates that the contribution of the EBRT dose in terms of an IORT dose for aortic narrowing was 7.8 Gy and for branch artery injury was 5.4 Gy. The ED50 for incidence of small thrombi in the aorta was about 29 Gy for IORT alone and 23.5 Gy for IORT combined with EBRT. Fibrous thickening of the adventitia was measured and the effect of the 50 Gy EBRT component of a combination of EBRT and IORT was determined to be equivalent to 10 to 12 Gy IORT. Based on the various estimates, IORT doses of 10-15 Gy have an effect of 5 times or greater the amount given in 2 Gy fractions. At all EBRT doses and at lower IORT doses the intima was greatly thickened. At IORT doses of 20 Gy or above there was a dose related decrease in intimal thickness to near normal values. This was probably due to cell killing or inhibition of intimal proliferation that predominated at higher doses. Although the risk of serious vascular complications appears low following IORT of humans, this may be due to short observation times and the fact that IORT doses currently used are usually 20 Gy or less; this may be near the tolerance for late response of larger arteries. Only one dog in this study had complete rupture of the aorta causing death. Five other dogs at high IORT doses had near ruptures of the aorta but were clinically normal.

Ureteral injury following experimental intraoperative radiation

Beagle dogs were randomized to receive a range of total dose delivered in three different protocols. Sixteen dogs received external beam radiation therapy (EBRT), 32 dogs received intraoperative irradiation (IORT), and 32 dogs received combinations of external beam radiation therapy and intraoperative irradiation. A sublumbar field was irradiated which always included the left ureter. Dogs were observed for 5 years; sequential excretory urograms were done at 6 months, and 1 and 5 years. Morphometric analysis of tissues were also done. The canine ureter tolerated 17.5 Gy intraoperative irradiation with no evidence of injury and 25 Gy intraoperative irradiation with a low probability of injury. The ED50 for radiographic abnormalities was 32.9 Gy. When 50 Gy external beam radiation therapy was given prior to intraoperative irradiation, the ureter tolerated 10 Gy intraoperative irradiation with no evidence of injury and 17.5 Gy with a low probability of injury. The ED50 was 29 Gy intraoperative irradiation after EBRT. The external beam radiation therapy had little effect on the ureter when given alone or prior to intraoperative irradiation. Clinical signs of renal disease occurred only in dogs who had received bilateral ureteral irradiation intraoperatively at doses of 32.5 Gy intraoperative irradiation and 25 Gy intraoperative irradiation after external beam radiation therapy. Histologic evidence suggests that the chronic injury of the ureter expressed at 5 years is of vascular etiology. The early injury may be due to ulceration of the epithelium.

Peripheral neuropathies following experimental intraoperative radiation therapy (IORT)

Injury to peripheral nerves in the lumbar para-aortic region was evaluated in beagle dogs 2 years following fractionated irradiation (EBRT), intraoperative irradiation (IORT), or a combination of IORT and EBRT. Time to onset of peripheral neuropathy was determined by means of serially completed neurological and electrophysiological examinations. Peripheral neuropathies were seen beginning as early as 6 months following 35 Gy (or greater) IORT only and 35 Gy plus 50 Gy EBRT. The incidence of peripheral neuropathies increased with increasing IORT doses beginning at 15 Gy. Onsets of peripheral neuropathies following IORT alone were clustered between 6 and 18 months, with onset in some dogs occurring as late as 24 months. The combination of IORT and EBRT resulted in an incidence and latency to onset of neuropathies similar to that seen with IORT alone. Neuropathies were not seen with EBRT alone at doses from 50 Gy to 80 Gy. Recovery of nerve function did not occur in affected dogs. Histological studies of nerves 2 years following irradiation demonstrated loss of axons and myelin, with a corresponding increase in endoneurial, perineurial, and epineurial connective tissue. Percentage of axon and myelin decreased to about 60% of normal at 15 Gy IORT, and additionally at higher doses. An insignificant decrease in percentage of axon and myelin was seen following EBRT alone. A significant lesion occurring in and around nerves at most IORT doses was necrosis and hyalinization of the media of small arteries and arterioles. The dose for a 50% probability for causing severe vessel lesions in the 2-year study was 19.5 Gy IORT only and 18.7 Gy when IORT was combined with EBRT. These lesions were not seen with any EBRT only dose. These studies suggest that peripheral nerve is a dose limiting normal tissue in IORT. Neuropathies appear to result from direct effects of irradiation on nerve and secondary effects to nerve resulting from damage to regional vasculature.

Intraoperative radiotherapy for recurrent and/or residual colorectal cancer

Intraoperative radiotherapy (IORT) is an attractive boosting modality in the combined treatment of recurrent and/or residual colorectal cancer. Twenty seven patients treated with IORT are analysed. Residual disease following resection of the primary tumor was treated in 11 cases (group I). Localized recurrent disease without previous radiotherapy was treated in 11 cases (group II). IORT was used in five additional patients with local recurrences in previously irradiated areas (group III). The treatment program consisted of maximal tumor resection, IORT (10-30 Gy) to the area of residual disease and external beam radiotherapy (46-50 Gy). The median follow-up time for the entire series of patients is 11 months. Local tumor control rates are 90% in group I, 63% in group II and 60% in group III. Toxicity and complications related to IORT observed in this initial experience have been pelvic pain (29%) and lower extremity neuropathy (3%). These early clinical results suggest that the IORT combined with surgery and external beam radiotherapy is feasible in primary and recurrent disease. Local control rates obtained in patients not suitable for curative surgery are encouraging.

Intraoperative radiotherapy in the multidisciplinary treatment of pediatric tumors. A preliminary report on initial results

From September 1984 to July 1987, 33 children received intraoperative radiotherapy as part of a multidisciplinary tumor treatment. Their age ranged from 2 to 17 years. Tumors types: Ewing's sarcoma (n = 11), osteosarcoma (n = 8), soft tissue sarcomas (n = 5), Wilms' tumor (n = 3), neuroblastoma (n = 3), malignant pheochromocytoma (n = 1), Hodgkin's disease (n = 1), and optic nerve glioma (n = 1). In 25 patients the disease was localized while 8 had distant metastases. Intraoperative radiotherapy was used in 26 previously untreated patients as part of a radical treatment program and in 7 cases as an effort to rescue local failures (5 in previously irradiated areas). The intraoperative radiation field included the surgically exposed tumor or tumor bed, and the single doses ranged from 10 to 20 Gy, with 6-20 MeV electrons. Patients with osteosarcoma and recurrent tumor in a previously irradiated area did not receive postoperative external beam radiotherapy. With a median follow-up time of 10 months (1 to 31 + months) 24 out of 33 patients are alive without local recurrence and 9 have died from tumor (5 with local disease progression). Intraoperative radiotherapy seems to be a feasible treatment which might promote local control in pediatric tumors.