Factors associated with failure to start consolidation durvalumab after definitive chemoradiation for locally advanced NSCLC

Introduction

The introduction of consolidation immunotherapy after chemoradiotherapy has improved outcome for patients with locally advanced non-small cell lung cancer. However, not all patients receive this treatment. This study identifies factors associated with failure to start durvalumab as consolidation therapy with the aim of optimizing treatment, supportive care and prehabilitation to ensure that more patients complete the planned treatment.

Materials and methods

Patients from two clinical trials and a named patient use program, were included in this study. All patients received platinum-doublet chemotherapy concomitant with radiotherapy to a total dose of 60-66 gray. Patient characteristics, cancer treatment, toxicity, performance status and laboratory data before and after chemoradiotherapy were recorded and patients who never started durvalumab were compared with those who did.

Results

A total of 101 patients were included, of which 83 started treatments with durvalumab after chemoradiotherapy. The 18 patients who did not start durvalumab had significantly higher lactate dehydrogenase at baseline and a worse performance status, cumulative toxicity and higher c-reactive protein after completed chemoradiotherapy. Data also suggest that pre-treatment diabetes and reduced hemoglobin and/or diffusion capacity of the lungs for carbon monoxide contribute to the risk of treatment abruption.

Conclusion

Treatment plan disruption rate was 18%. Systemic inflammation and performance status were associated with failure to receive durvalumab after chemoradiation. Further studies are needed to confirm findings and prospective trials should investigate whether prehabilitation and supportive treatment could help more patients finishing the planned treatment.

Clinical Trial Registration

clinicaltrials.gov, identifier NCT03798535; NCT04392505.

One course of adjuvant BEP in clinical stage I nonseminoma mature and expanded results from the SWENOTECA group

BACKGROUND

SWENOTECA has since 1998 offered patients with clinical stage I (CS I) nonseminoma, adjuvant chemotherapy with one course of bleomycin, etoposide and cisplatin (BEP). The aim has been to reduce the risk of relapse, sparing patients the need of toxic salvage treatment. Initial results on 312 patients treated with one course of adjuvant BEP, with a median follow-up of 4.5 years, have been previously published. We now report mature and expanded results.

PATIENTS AND METHODS

In a prospective, binational, population-based risk-adapted treatment protocol, 517 Norwegian and Swedish patients with CS I nonseminoma received one course of adjuvant BEP. Patients with lymphovascular invasion (LVI) in the primary testicular tumor were recommended one course of adjuvant BEP. Patients without LVI could choose between surveillance and one course of adjuvant BEP. Data for patients receiving one course of BEP are presented in this study.

RESULTS

At a median follow-up of 7.9 years, 12 relapses have occurred, all with IGCCC good prognosis. The latest relapse occurred 3.3 years after adjuvant treatment. The relapse rate at 5 years was 3.2% for patients with LVI and 1.6% for patients without LVI. Five-year cause-specific survival was 100%.

CONCLUSIONS

The updated and expanded results confirm a low relapse rate following one course of adjuvant BEP in CS I nonseminoma. One course of adjuvant BEP should be considered a standard treatment in CS I nonseminoma with LVI. For patients with CS I nonseminoma without LVI, one course of adjuvant BEP is also a treatment option.

Craniotomy for brain metastases: a consecutive series of 316 patients

OBJECTIVE

To assess the incidence of craniotomy for brain metastases, overall survival (OS), surgical mortality, and prognostic factors in a large, contemporary, consecutive series from a well-defined catchment area.

MATERIAL AND METHODS

All patients ≥ 18 years who underwent craniotomies for intracranial metastases at Oslo University Hospital, Rikshospitalet and Ullevål, between 2005 and June 30, 2009 were included (n = 316). Patients were identified from our prospectively collected database and a thorough review of all charts to validate the entered data was performed.

RESULTS

The annual incidence of first-time craniotomy for a brain metastasis was 2.6/100,000 inhabitants. Patient age ranged from 25 to 87 years (median 64 years). The 30-day mortality rate was 3.8%. Median OS was 9.2 months. Recursive partitioning analysis was class I in 19.6%, class II in 59.2%, and class III in 21.2% with median OS of 16.2, 8.9, and 5.6 months, respectively (P < 0.001). Lung cancer and melanoma were associated with a higher risk (>1% per year) of developing brain metastases. Significant negative prognostic factors were age ≥ 65, a poor performance score, unstable extracranial disease, presence of extracranial metastases, multiplicity, metastasis in eloquent area, and no post-operative radiotherapy.

CONCLUSIONS

In this population study, the annual incidence of a first-time craniotomy for a brain metastasis was 2.6/100,000, the 30-day mortality rate was 3.8%, and median OS was 9.2 months. The well-known prognostic factors were confirmed.

A prospective study of neuropsychological functioning in testicular cancer patients

BACKGROUND

Whether systemic chemotherapy has a negative effect on cognitive function in patients, concern oncologists. In testicular cancer patients (TCPs) treated with cisplatin-based chemotherapy, only few cross-sectional studies have addressed this concern. We prospectively studied neuropsychological functioning in TCPs.

PATIENTS AND METHODS

In a consecutive sampling, 122 TCPs were examined at baseline (after orchidectomy, before any additional treatment) and then at follow-up at a median of 12 months after end of treatment. The examinations included a neuropsychological test battery, interview on background variables and questionnaires on mental distress, fatigue and neurotoxic symptoms. Changes in neuropsychological functioning from baseline to follow-up were compared between three treatments groups: no chemotherapy (N = 31), one cycle of chemotherapy (N = 38) and two or more cycles of chemotherapy (N = 53). Variables associated with a decline in neuropsychological test performance from baseline to follow-up were explored.

RESULTS

No statistically significant differences in proportions of TCPs with a decline in neuropsychological test performance were observed between the three treatment groups. Decline in neuropsychological test performance was not associated with demographic variables, distress, fatigue or with chemotherapy.

CONCLUSION

No negative effect of systemic chemotherapy on neuropsychological test performance in TCPs at 1-year follow-up was found in this study.

Overall survival, prognostic factors, and repeated surgery in a consecutive series of 516 patients with glioblastoma multiforme

OBJECTIVES

To study overall survival (OS), prognostic factors, and repeated surgery in glioblastoma multiforme (GBM).

MATERIAL AND METHODS

Retrospective study of 516 consecutive adult patients who underwent primary surgery for a GBM in year 2003-2008.

RESULTS

Median age at primary surgery was 63.7 years (range 18.0-88.0). Median OS was 9.9 months. Age > 60 years, poor preoperative ECOG score, bilateral tumor, biopsy rather than resection, and no temozolomide chemoradiotherapy were negative risk factors. Repeat surgery was performed in 65 patients (13%). Median time between first and second surgery was 7 months. Indications for second surgery were increasing neurological deficits (35.4%), raised ICP (33.8%), asymptomatic but reoperated because of tumor progression verified on MRI (20.0%), and epileptic seizures (11%). Patients who underwent repeated surgery had longer OS; 18.4 months vs 8.6 months (P < 0.001).

CONCLUSIONS

OS for adult GBM patients was 9.9 months. Negative prognostic factors were increasing age, poor neurological function, bilateral tumor involvement, biopsy instead of resection, and RT alone compared to temozolomide chemoradiotherapy. Our rate of repeated surgery for GBM was 13% and the main indications for second surgery were raised ICP and increasing neurological deficits. In a carefully selected group of patients, repeat surgery significantly prolongs OS.

Treatment-time-dependence models of early and delayed radiation injury in rat small intestine

BACKGROUND

The present study modeled data from a large series of experiments originally designed to investigate the influence of time, dose, and fractionation on early and late pathologic endpoints in rat small intestine after localized irradiation. The objective was to obtain satisfactory descriptions of the regenerative response to injury together with the possible relationships between early and late endpoints.

METHODS

Two- and 26-week pathologic radiation injury data in groups of Sprague-Dawley rats irradiated with 27 different fractionation schedules were modeled using the incomplete repair (IR) version of the linear-quadratic model with or without various time correction models. The following time correction models were tested: (1) No time correction; (2) A simple exponential (SE) regenerative response beginning at an arbitrary time after starting treatment; and (3) A bi-exponential response with its commencement linked to accumulated cellular depletion and fraction size (the 'intelligent response model' [INTR]). Goodness of fit of the various models was assessed by correlating the predicted biological effective dose for each dose group with the observed radiation injury score.

RESULTS

(1) The incomplete repair model without time correction did not provide a satisfactory description of either the 2- or 26-week data. (2) The models using SE time correction performed better, providing modest descriptions of the data. (3) The INTR model provided reasonable descriptions of both the 2- and 26-week data, confirming a treatment time dependence of both early and late pathological endpoints. (4) The most satisfactory descriptions of the data by the INTR model were obtained when the regenerative response was assumed to cease 2 weeks after irradiation rather than at the end of irradiation. A fraction-size-dependent delay of the regenerative response was also suggested in the best fitting models. (5) Late endpoints were associated with low-fractionation sensitivity and treatment-time dependence even in animal groups that exhibited minimal early mucosal reactions.

CONCLUSION

Radiation injury scores in this rat small intestinal experimental model cannot be adequately described without time correction. 'Consequential' mechanisms contribute to the development of late effects, even in animals that do not develop severe early mucosal injuries. The initiation of the regenerative response is subject to a fraction-size-dependent mitotic delay and is linked to the level of accumulated cellular depletion. The response does not cease at the end of therapy but probably continues until maximal healing has taken place.

[Can radiotherapy reduce the frequency of restenosis after coronary angioplasty?]

Today, percutaneous transluminal coronary angioplasty (PTCA) is the most important treatment modality for coronary artery disease. However, restenosis occurs in 20-40% of the vessels in spite of the use of stents. Intravascular radiation therapy has reduced the frequency of restenosis in both animal studies and clinical trials. Recent randomized trials have shown a reduction in the order of 30% after irradiation. A number of techniques which use different sources of radiation (beta vs. gamma radiation) are under investigation. This review gives and update of intravascular radiation therapy, including a discussion of ongoing trials. There is a great need, also in Norway, for treatment modalities that reduce the frequency of restenosis after PTCA. It would seem imperative that we start a discussion of whether and when intravascular radiation therapy should be available in Norway. Implementation requires planning on a national level with regard to investment in equipment and training.

[Normal tissue radiation toxicity in radiotherapy of localized prostatic cancer]

Radical radiotherapy of prostate cancer has to balance tumour control against the risk of radiation injury of normal tissue. The normal tissue toxicity is the main dose-limiting factor, and consequently a limiting factor of the curative potential of prostate cancer by irradiation. The SOMA scale is a new toxicity scoring system that registers late side effects from the most important anatomical sites. The SOMA scale is internationally approved and facilitates a standardised evaluation of radiation toxicity. The scoring system is based on four main components: subjective, objective, management and analysis. The SOMA scoring system was applied to a group of 21 patients from Ullevaal Hospital who were given intentionally curative radiation therapy for localised prostate cancer. The SOMA scale scoring system appears to be a valuable tool in the evaluation of normal tissue toxicity. It may contribute to a new standard in quality assurance of radiation therapy of prostate cancer.

[Temporary radiation-induced hypo-salivation in a child]

This case report deals with the diagnosis and treatment of hyposalivation after radical radiation therapy and cytotoxic treatment of a metastasising nasopharyngeal carcinoma in an eight-year old girl. After cancer treatment the patient suffered from xerostomia, and pronounced hyposalivation was demonstrated. Frequent chewing of sugar-free gum and use of lozenges was recommended, and the patient was followed up for one year. During this time, the values for unstimulated whole saliva increased by a factor of five, and stimulated whole saliva values increased as well, but less so. Two years after cancer treatment, the patient no longer suffers from xerostomia.

Increased transforming growth factor beta (TGF-beta) immunoreactivity is independently associated with chronic injury in both consequential and primary radiation enteropathy

PURPOSE

Radiation enteropathy is characterized by sustained increase in transforming growth factor beta (TGF-beta) immunoreactivity and connective tissue mast cell (CTMC) hyperplasia that may be responsible for progressive fibrosis and lead to clinical complications. We examined to what extent these chronic molecular and cellular phenomena are associated with acute mucosal breakdown (consequential injury) and/or direct (primary) radiation injury in late-responding compartments.

METHODS AND MATERIALS

Rat small intestine was exposed to 50.4 Gy x-irradiation given either over 18 days (2.8 Gy daily or 5.6 Gy every other day) or 9 days (2.8 Gy twice daily or 5.6 Gy daily). Intestinal complications were recorded and groups of animals were euthanized at 2 and 26 weeks to assess subacute and chronic injury. Histopathologic changes were assessed with a radiation injury scoring system (RIS), total TGF-beta immunoreactivity was quantified with computerized image analysis, and CTMC hyperplasia was assessed in toluidine blue-stained sections.

RESULTS

TGF-beta immunoreactivity and CTMC hyperplasia colocalized in areas of injury and were highly significantly correlated. Increased fraction size and decreased overall treatment time were associated with increased RIS (p < 0.01 and p < 0.00001), increased TGF-beta immunoreactivity (p = 0.01 andp < 0.001), and degree of CTMC hyperplasia (p = 0.01 and p < 0.001). Postradiation CTMC numbers increased across treatment groups from 2 to 26 weeks (p < 0.01). TGF-beta immunoreactivity was independently associated with chronic intestinal wall fibrosis (p = 0.003).

CONCLUSION

This in vivo study supports in vitro evidence linking increased TGF-beta immunoreactivity and mast cell hyperplasia and strongly suggests their involvement in the molecular pathogenesis of both primary and consequential radiation enteropathy.

Optimal interfraction interval to minimize small bowel radiation injury in treatment regimens with two fractions per day: an experimental study in a rat model

BACKGROUND

Normal tissue damage in fractionated radiotherapy is influenced by a number of factors including sublethal damage repair and cellular proliferation. The therapeutic benefit of regimens with multiple fractions per day may thus be offset by increased normal tissue injury if there is insufficient time between daily fractions. We examined the influence of interfraction interval on radiation injury of the intestine, an organ at significant risk during treatment of abdominal and pelvic tumors.

METHODS

A total of 150 male rats were orchiectomized, and a functionally intact loop of small bowel was sutured to the inside of the scrotum. The intestine within this 'artificial hernia' was irradiated twice daily for 9 days with 2.8 Gy fractions at intervals of 0, 2, 4, 6, or 8 h. Animals were observed for development of radiation-induced intestinal complications and euthanized at either 2 weeks and 26 weeks for subsequent histopathologic examination of irradiated and shielded intestine.

RESULTS

Increasing the interfraction interval from 0 to 6 h was associated with a statistically significant reduction in intestinal complications (from 53% to 0%, P < 0.001), and in Radiation Injury Score (RIS) (from 10 to 6, P < 0.01) in long-term observed animals. Extending the interfraction interval to 8 h did not confer additional benefit.

CONCLUSION

An interfraction interval of 6 h minimizes the risk of chronic radiation enteropathy in this rat model.

Association of transforming growth factor beta (TGF-beta) immunoreactivity with specific histopathologic lesions in subacute and chronic experimental radiation enteropathy

Irradiated intestine consistently exhibits increased immunoreactivity of transforming growth factor beta-1 (TGF-beta 1). It is not known whether this increase occurs secondary to mucosal barrier disruption (consequential injury) or to injury in late-responding tissue compartments (primary radiation enteropathy). This study therefore assessed the association between TGF-beta immunoreactivity and specific consequential and primary histopathologic alterations. A small bowel loop was fixed inside the scrotum in male rats and subsequently exposed to either 18 daily fractions of 2.8 Gy or nine daily fractions of 5.6 Gy orthovoltage X-radiation. Radiation-induced induced intestinal complications were recorded and groups of animals were euthanized 2 and 26 weeks post-irradiation. Radiation injury was assessed with a histopathologic radiation injury score (RIS). Total TGF-beta was detected immunohistochemically and measured with interactive computerized image analysis. The image analysis technique yielded highly reproducible quantitation data. The 2.8-Gy group maintained mucosal integrity and had fewer intestinal complications, lower RIS and lower TGF-beta levels than the 5.6-Gy group. There was highly significant correlation between TGF-beta immunoreactivity and radiation injury at both observation times (P < 0.001 and P < 0.0001). At 2 weeks, TGF-beta immunoreactivity correlated with mucosal ulceration (P = 0.002), epithelial atypia (P = 0.005), and serosal thickening (P = 0.0004). At 26 weeks, TGF-beta levels correlated significantly with six of seven histopathologic parameters, most strikingly with vascular sclerosis (P = 0.0003). We conclude that mucosal barrier breakdown is closely associated with increased TGF-beta immunoreactivity in consequential radiation enteropathy. The highly significant correlation between TGF-beta expression levels and alterations in late-responding tissue compartments also suggest a role for TGF-beta in primary radiation enteropathy.

Timing of concomitant boost irradiation affects incidence and severity of intestinal complications

PURPOSE

In an effort to increase the therapeutic ratio of radiation therapy, so-called "nonstandard" irradiation regimens are being used more frequently. One such regimen, concomitant boost, entails giving a second daily fraction during part of the treatment course, thus reducing the total treatment time and decreasing the opportunity for tumor cell proliferation during treatment. The probability of tumor control is, therefore, increased for a given total dose. Timing of the boost, i.e., whether it is given early or late during the treatment course, affects both normal tissue and tumor response. This study assessed the influence of timing of a second daily boost on the development of intestinal radiation injury in a rat model.

METHODS AND MATERIALS

A functionally intact segment of distal ileum was sutured to the inside of the scrotum in 52 orchiectomized, male Sprague-Dawley rats. After a 3-week postoperative recovery period, the intestine contained in the "scrotal hernia" was irradiated. All rats received a total dose of 50.4 Gy, given over a 12-day period as two different boost regimens, daily fractions of 2.8 Gy plus six concomitant boost doses of 2.8 Gy. The early boost group received the additional boost during the first 6 days and the late boost group received the additional boost during the last 6 days. The boost was given 6 h after the daily fraction. Groups of rats were sacrificed at 24 h (acute changes), 2 weeks (subacute changes), and 26 weeks (chronic changes) after the end of the irradiation schedule. Radiation injury was assessed by frequency of radiation-induced complications, histopathologic radiation injury score, collagen content, and epithelial cytokinetics.

RESULTS

Radiation injury in the early boost group was significantly more severe than in the late boost group in terms of incidence of complication and histopathologic injury. Relative collagen content of irradiated intestine was significantly increased in the early boost group when compared to the late boost group at 2 weeks and at 26 weeks. Irradiated intestine in the early boost group exhibited decreased labeling index at 2 weeks, whereas irradiated intestine in the late boost group exhibited normal labeling index and increased total crypt cellularity at 2 weeks.

CONCLUSION

When small intestine has to be included in the treatment field during radiation therapy, concomitant boost should be given towards the end of the radiation schedule, after the onset of compensatory proliferation, to minimized the risk of subsequent complications.

Influence of fraction size on the development of late radiation enteropathy. An experimental study in the rat

The use of large fraction sizes in radiotherapy may be associated with an increased risk of complications from late responding normal tissues. However, in the intestine, chronic injury may develop either as primary late effect or secondary to disruption of mucosal integrity as so-called consequential injury. Mucosal damage is relatively less sensitive to changes in fraction size than late reacting, slowly proliferating cells. The relationship between fraction size and chronic radiation enteropathy in a given situation may thus depend on which of the two mechanisms that predominates. Most previous studies of the influence of fraction size on radiation injury are confounded by differences in treatment time. The present study was therefore designed to assess subacute and chronic radiation enteropathy after three different fractionation regimens where fraction size was the only experimental variable. A total of 96 male Sprague-Dawley rats were orchiectomized and a functionally intact loop of small intestine was transposed into the left scrotum. These 'scrotal hernias' containing intestine were subsequently exposed to 50.4 Gy localized fractionated irradiation over 18 days with either 2.8 Gy every 24 h, 4.2 Gy every 36 h, or 5.6 Gy every 48 h. Control animals were sham irradiated. The animals were observed for development of intestinal complications (intestinal obstruction or enterocutaneous fistula formation) up to 6 months after irradiation. Histologic damage was assessed in groups of animals at 2 weeks (subacute injury) and 26 weeks (chronic injury), using a previously validated radiation injury score (RIS). RIS increased significantly with increasing fraction size at both observation times. However, the increase was more pronounced at 26 weeks than at 2 weeks. Increased chronic injury was characterized by increased incidence and severity of mucosal ulceration, serosal thickening, vascular sclerosis and intestinal wall fibrosis. We conclude that increasing fraction size increases both subacute and, even more markedly, chronic injury in the intestine. With the fractionation regimens used here, the chronic radiation enteropathy develops as a combined consequential and primary late effect, but the primary mechanism predominates.

Relationship between intestinal fibrosis and histopathologic and morphometric changes in consequential and late radiation enteropathy

Intestinal fibrosis is a marked feature of late radiation enteropathy. This study assessed the time dose fractionation relationships of radiation-induced fibrosis in order to elucidate possible pathogenetic mechanisms. In 290 male Sprague-Dawley rats, a loop of small bowel was transposed to the left side of the scrotum. Three weeks later, the transposed segment was irradiated with either single dose or various fractionated regimens. The animals were observed for radiation-induced intestinal complications and killed in groups, 2 and 26 weeks after completion of irradiation. A semiquantitative histopathologic radiation injury score, morphometry of the submucosa, submucosal arterioles, intestinal surface area, and relative collagen content were used as endpoints. Fibrosis, measured by collagen assay and radiation injury score, increased with total dose, increasing fraction size and reduction in overall treatment time. This paralleled the results of morphometric assessment of mucosal surface area. Differences in vascular morphometry were only statistically significant in response to changes in total dose and fraction size and not with changes in overall treatment time. We conclude that fibrosis increases with increasing observation time, increasing fraction size, increasing total dose, and reduction of interfraction interval. Consequential injury, occurring as a result of disruption of mucosal integrity, seems to be an important mechanism for development of intestinal fibrosis. In contrast, vascular injury is relatively independent of this mechanism.

Models for estimating the risk of ulcers in the small intestine after localized single or fractionated irradiation

Subacute and chronic ulcerations of the intestinal mucosa are important causes of serious complications following radiation therapy for abdominal or pelvic tumours. We describe dose-response models for estimating the risk of mucosal ulcers in the small intestine after uniform, localized single or fractionated (once-daily) X-ray exposure. The models were fitted to data for ulceration incidence, based on a 26 week post-irradiation follow-up of male Sprague-Dawley rats which received a wide range of single and fractionated once-daily 250 kV X-ray doses to a short loop (partial volume) of transposed, but functionally intact, small intestine. The models presented for single (Weibull (W)) and fractionated (modified Weibull (MW)) exposures of a partial volume of tissue allow estimation of the risk of radiation-induced injury. While the W model is not new, its adaptation to partial volume irradiation and the MW model are. Isoeffect relationships are presented for the uniform fractional dose Ds(i%) associated with an i% (e.g. 0%, 5%, 10%, 50%) risk of intestinal mucosal ulcers as a function of the number of once-daily dose fractions, where Ds(0%) represents the threshold fractional dose. Although the Ds(5%) and Ds(0%) estimates provided for intestinal mucosal ulcers are based on animal data, the ratio Ds(0%)/Ds(5%) and more generally ratios Ds(j%)/Ds(i%) (where i not equal to j), are presumed to apply to humans. The indicated ratios are predicted to be independent of the partial volume irradiated and the number of once-daily dose fractions, and may be independent of radiation quality. Isoeffect equations are also presented that apply to circumstances where different partial volumes within the same reference volume (i.e. the total volume of tissue considered) receive different doses, but the dose within a given partial volume is uniformly distributed. These isoeffect equations provide a means of converting non-uniform dose within a reference volume to uniform isoeffect dose to the total reference volume and may have applications outside the field of radiation therapy (e.g. evaluating effects of non-uniform exposure of the small intestine or skin by a hot particle).

Expression of fibrogenic cytokines in rat small intestine after fractionated irradiation

The molecular and cellular mechanisms that regulate the radiation-induced fibrotic response in the intestine are not known. In addition to increased amounts of connective tissue, inflammatory cell aggregates are often found, especially in conjunction with acute or chronic mucosal ulcerations. These inflammatory cells are a major source of cytokines that influence connective tissue metabolism. Hence, a possible link may exist between the cellular inflammatory response and fibrosis. This preclinical study examined the influence of fractionated irradiation on the expression of three inflammatory/fibrogenic cytokines in rat small intestine. A rat intestinal transposition model was used for localized fractionated irradiation of a 3-4-cm segment of small bowel. Fifty-nine male Sprague-Dawley rats were irradiated or sham irradiated with 9 daily fractions of 5.2 Gy. Expression of Interleukin 1 alpha (IL-1 alpha), Transforming growth factor beta 1 (TGF-beta 1), and Platelet derived growth factor-AA (PDGF-AA) was assessed by immunohistochemistry. Irradiated and unirradiated intestine was examined 24 h, 14 days, and 26 weeks after completion of irradiation. Unirradiated intestine exhibited immunohistochemical expression of IL-1 alpha, TGF-beta 1 and PDGF-AA that conformed to known staining patterns in normal tissue. Irradiated intestine showed increased expression of all three cytokines at all assessment times. The increased cytokine expression correlated with fibrosis and inflammatory cell infiltrates in irradiated intestine. This was particularly evident in areas with mucosal ulcerations. Fractionated irradiation of small intestine elicits increased expression of IL-1 alpha, TGF-beta 1, and PDGF-AA in areas of acute and chronic radiation injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of overall treatment time for the development of radiation-induced intestinal complications. An experimental study in the rat

BACKGROUND

Late normal tissue reactions generally are believed to be independent of treatment time. However, previous studies suggest a relationship between acute mucosal injury and development of intestinal obstruction and enterocutaneous fistula formation. Thus, the pathogenesis of late intestinal complications may be complex, and mucosal cell proliferation during treatment may be important. This study assessed the influence of overall radiation treatment time on development of intestinal injury and complications after localized fractionated irradiation of rat ilium.

METHODS

Ninety-four male rats underwent orchiectomy, and a loop of small intestine was transposed to the scrotum. Orthovoltage irradiation was administered to the transposed, but functionally intact, intestine using 9 fractions of 5.6 Gy with interfraction intervals of 24, 48, or 72 hours. The animals were observed for complications and killed in groups 2 and 26 weeks after irradiation for assessment of injury. Incidence of intestinal complications and quantitative and semiquantitative histopathologic assessment of injury were used as endpoints.

RESULTS

Increasing total treatment time by extending interfraction intervals from 24 to 48 hours significantly reduced radiation injury and the incidence of intestinal complications. Differences in mucosal and fibrotic changes were most prominent. No significant differences were found between groups with interfraction intervals of 48 and 72 hours.

CONCLUSIONS

Overall treatment time significantly influenced development of chronic radiation enteropathy. Thus, rapidly proliferating cells, as found in the intestinal mucosa, appear to be involved in the pathogenesis of intestinal complications. This probably represents consequential damage secondary to disruption of mucosal integrity.

Influence of fractionation schedule on development of intestinal complications following localized irradiation. An experimental study in the rat

This study examined the relationship among time-dose-fractionation, development of intestinal complications, and histopathologic radiation injury in rat small bowel. In 177 rats, a functional loop of rat ileum was surgically transposed to the left scrotum. Three weeks later, fractionated irradiation was delivered to the transposed intestine as 2.8 Gy or 5.6 Gy daily fractions, or as 2.8 Gy twice daily with 12 hours' interval. Eleven experimental groups received total doses ranging from 28 Gy to 90 Gy. The animals were observed for intestinal complications, and groups of animals were killed 2 and 26 weeks after completion of irradiation for assessment of injury. Radiation injury was assessed by a semiquantitative histopathologic scoring system and by the frequency of lethal intestinal complications. Both increased fraction size and reduced overall treatment time increased the severity of subacute and chronic radiation injury, as well as frequency of intestinal complications. We conclude that rapidly proliferating cells (mucosal epithelium) play a pivotal role in the pathogenesis of radiation enteropathy and mechanisms other than radiation-induced mitotic cell death are pathogenetically involved.

Tolerance of rat small intestine to localized single dose and fractionated irradiation

The tolerance of rat small intestine to localized single-dose and fractionated irradiation was assessed. In 168 rats, bilateral orchiectomy was performed and a loop of small intestine was transposed to the left part of the scrotum. Beginning 3 weeks postoperatively, single dose (18-24 Gy) or fractionated (4.2 Gy or 5.6 Gy per fraction) x-irradiation was delivered to the transposed intestine. The animals were observed for complications, and groups of animals were killed 2 and 26 weeks after completion of irradiation for assessment of injury. Mortality (i.e. the occurrence of lethal intestinal complications) and a semiquantitative histopathologic scoring system were used as endpoints to assess the degree of radiation injury. The most frequent intestinal complications were enterocutaneous fistula formation and intestinal obstruction. Logistic regression analysis ov complications data was used to estimate LD50 values and the alpha/beta ratio. There was good correlation between histopathologic scores and the incidence of lethal complications. The estimated LD50 values were 22.1 +/- 0.5 Gy, 37.0 +/- 4.4 Gy and 51.0 +/- 5.3 Gy for the single dose regimen and the fractionated regimens of 5.6 Gy and 4.2 Gy respectively. The estimated alpha/beta ratio was 10.7 +/- 2.4 Gy. The goodness of fit of the linear-quadratic isoeffect model to our data was satisfactory. Our results indicate that acute mucosal damage may be pathogenetically involved in the development of intestinal complications.