Single dose versus fractionated total body irradiation before bone marrow transplantation: radiobiological and clinical considerations

Internal Guidelines for Reducing Lymph Node Contour Variability in Total Marrow and Lymph Node Irradiation

BACKGROUND

The total marrow and lymph node irradiation (TMLI) target includes the bones, spleen, and lymph node chains, with the latter being the most challenging structures to contour. We evaluated the impact of introducing internal contour guidelines to reduce the inter- and intraobserver lymph node delineation variability in TMLI treatments.

METHODS

A total of 10 patients were randomly selected from our database of 104 TMLI patients so as to evaluate the guidelines' efficacy. The lymph node clinical target volume (CTV_LN) was recontoured according to the guidelines (CTV_LN_GL_RO1) and compared to the historical guidelines (CTV_LN_Old). Both topological (i.e., Dice similarity coefficient (DSC)) and dosimetric (i.e., V95 (the volume receiving 95% of the prescription dose) metrics were calculated for all paired contours.

RESULTS

The mean DSCs were 0.82 ± 0.09, 0.97 ± 0.01, and 0.98 ± 0.02, respectively, for CTV_LN_Old vs. CTV_LN_GL_RO1, and between the inter- and intraobserver contours following the guidelines. Correspondingly, the mean CTV_LN-V95 dose differences were 4.8 ± 4.7%, 0.03 ± 0.5%, and 0.1 ± 0.1%.

CONCLUSIONS

The guidelines reduced the CTV_LN contour variability. The high target coverage agreement revealed that historical CTV-to-planning-target-volume margins were safe, even if a relatively low DSC was observed.

The reduced number of nephrons with shortening renal tubules in mouse postnatal adverse environment

BACKGROUND

The intrauterine adverse environment during nephrogenesis reduces the nephron number, probably associates with impaired ureteric bud (UB) branching.

METHODS

The kidneys in C57/BL6 mice were irradiated with a single dose of 10 gray (10 Gy) as adverse environment on postnatal day 3 (irradiated PND3 kidneys) after UB branching ceased. The renal functions and pathological findings of irradiated PND3 kidneys were compared with those of non-irradiated control and 10 Gy irradiation on PND14 (irradiated PND14 kidney) from 1 to 18 months.

RESULTS

The number and density of glomeruli in irradiated PND3 kidneys were reduced by 1 month with renal dysfunction at 6 months. The morphologically incomplete glomeruli with insufficient capillaries were involuted by 1 month in the superficial cortex. Reduced tubular numbers and developmental disability with shortening renal tubules occurred in irradiated PND3 kidneys with impaired urine concentration at 6 months. Hypertrophy of glomeruli developed, and occasional sclerotic glomeruli appeared in the juxtamedullary cortex with hypertension and albuminuria at 12 to 18 months.

CONCLUSIONS

The reduced number of nephrons with shortening renal tubules occurred with impaired renal functions in a postnatal adverse environment after cessation of UB branching, and glomerular hypertrophy with occasional glomerulosclerosis developed accompanied with hypertension and albuminuria in the adulthood.

IMPACT

The reduced number of nephrons with shortening renal tubules occurred with impaired renal functions in a postnatal adverse environment after cessation of ureteric bud branching. The reduced number of glomeruli were associated with not only the impaired formation of glomeruli but also involution of morphologically small incomplete glomeruli after an adverse environment. The insufficiently developed nephrons were characterized by the shortening renal tubules with impaired urine concentration. In addition, glomerular hypertrophy and occasional glomerulosclerosis developed with hypertension and albuminuria in adulthood. The present study can help to understand the risk of alternations of premature nephrons in preterm neonates.

Preclinical validation and treatment of volumetric modulated arc therapy based total bone marrow irradiation in Halcyon™ ring gantry linear accelerator

AIM

This study aims​ to report preclinical validation, and the first clinical treatment of total bone marrow irradiation (TMI) and total bone marrow and lymph nodal irradiation (TMLI) using Volumetric modulated arc therapy in Halcyon-E ring gantry linear accelerator. Preclinical validation includes simulation, planning, patient-specific QA, and dry run.

MATERIAL AND METHOD

Four patients, two female and two male, with body weights of 116 kg, 52 kg, 64 kg, and 62 kg; with two with chronic myeloid leukemia, one each with acute lymphoblastic leukemia and acute myeloid leukemia (AML) were simulated and planned for TMI/TMLI. Patients were immobilized with a full-body vacuum bag. Head first supine (HFS) and Feet first supine (FFS) CT scans were acquired from head to knee and knee to toe. Planning target volume (PTV) was created with a uniform margin of 6 mm over the total bone marrow/bone marrow + lymph nodes. HFS and FFS PTVs were optimized independently using 6MV unflatten energy for 12 Gy in 6 fractions. Plans were merged to create the resultant dose distribution using a junction bias dose matching technique. The total number of isocenters was ≤ 10 per CT set, and two to four full arcs were used for each isocenter. A junction dose gradient technique was used for dose feathering between arcs between adjacent isocenters.

RESULT

Only one female patient diagnosed as AML received the TMLI treatment, while the other three patients dropped out due to clinical complications and comorbidities that developed in the time between simulation and treatment. The result presented has been averaged over all four patients. For PTV, 95% dose was normalised to 95% volume, PTV_V107% receiving 3.3 ± 3.1%. Total lung mean and V12Gy were 1048.6 ± 107.1 cGy and 19.5 ± 12.1%. Maximum lens doses were 489.5 ± 35.5 cGy (left: L) and 497 ± 69.2 cGy (right: R). The mean cardiac and bilateral kidney doses were 921.75 ± 89.2 cGy, 917.9 ± 63.2 cGy (L), and 805.9 ± 9.7 cGy (R). Average Monitor Unit was 7738.25 ± 1056.6. The median number of isocenters was 17(HFS+FFS), average MU/Dose (cGy) ratio per isocenter was 2.28 ± 0.3.

CONCLUSION

Halcyon-E ring gantry linear accelerator capable of planning and delivering TMI/TMLI.​​.

Analysis of Chronic Kidney Disease After Radiation Therapy for Gastric/Duodenal Mucosa-Associated Lymphoid Tissue Lymphoma

Purpose

This study aimed to evaluate the relationship between chronic kidney disease (CKD) after radiation therapy for gastric/duodenal mucosa-associated lymphoid tissue lymphoma and dose-volume histogram of the kidneys.

Methods and Materials

We retrospectively reviewed 40 patients who received 3-dimensional conformal radiation therapy. CKD was evaluated using the Common Terminology Criteria for Adverse Events version 5.0. The mean dose of bilateral kidneys/right kidney/left kidney (D_{mean of b-kidneys}) (D_{mean of r-kidney}) (D_{mean of l-kidney}), bilateral kidneys/right kidney/left kidney volume receiving ≥ x Gy (V_{x of b-kidneys}) (V_{x of r-kidney}) (V_{x of l-kidney}), and patients’ baseline clinical characteristics were analyzed.

Results

The median radiation therapy dose was 28 (range, 24-44.8) Gy in 14 fractions. The median follow-up period was 63.1 months, and the 5-year cumulative incidence of grade 2 CKD rate was 14.8%. Among several factors, V_{5 of b-kidneys} was most strongly associated with grade 2 or worse CKD, with an area under the curve of 0.81 in the receiver operating characteristic curve. The 5-year incidence rate in patients with V_{5 of b-kidneys} ≥ 58% was significantly higher than that in other patients (24.5% and 9.8%, respectively; P < .05).

Conclusions

In this study using 3-dimensional conformal radiation therapy, the rate of adverse events at 5 years was low, many patients showed toxicity after 5 years; thus, continuous follow-up is necessary to detect potential nephrotoxicity. Our data demonstrate that V_{5 of b-kidneys} was most strongly associated with the risk of CKD. With lower doses and more advanced techniques in recent years, the incidence of CKD may be further reduced.

Adverse Effects of Total Body Irradiation: A Two-Decade, Single Institution Analysis

Purpose

Several adverse effects have been reported in the literature associated with total body irradiation (TBI). Reports of the adverse effects of TBI have been primarily drawn from single-institution retrospective analyses. We report, to our knowledge, one of the largest cohorts of patients treated with TBI using multiple preparative chemotherapy and radiation regimens.

Methods and Materials

A retrospective chart review was performed for all 705 patients treated with TBI at our institution from 1995 to 2017. Based on availability of TBI records, 622 patients (88%) had sufficient evaluable documentation for analysis. Patients received 1 of 4 conditioning regimens: busulfan-fludarabine, 2 Gy (BUFLU); fludarabine-melphalan, 2 Gy (FLUMEL); cyclophosphamide, 12 Gy fractionated (CY); or etoposide, 12 Gy fractionated (VP16). Individual patients were evaluated for 13 specific recognized adverse effects based on the Common Terminology Criteria for Adverse Events, version 5.0.

Results

Mucositis (grade 3) was the most common serious adverse effect and occurred most frequently in the group receiving the VP16 12 Gy regimen (40% vs less than 14% in each of the other groups). Serious febrile neutropenia (grade 3-5) was less frequent (24%) among patients receiving CY than among those receiving the other conditioning regimens (more than 38% in each of the other groups). The incidence of serious lung infection was less common (5%) in patients receiving CY than in those receiving VP16 (18%). There was a higher frequency of grade 3-5 diarrhea among those receiving FLUMEL (5%) and VP16 (4%) than in the other groups (<3%) (P = .034). Otherwise, there were no detectable differences in serious toxicity by regimen for the 13 adverse effects reviewed. Only 2 secondary malignancies were reported, and both were in the BUFLU group. Cataract formation occurred in approximately 16% of patients overall, and the rates were similar across regimens. Median time to cataract formation was 1 to 4 years across regimens, with cataracts occurring earlier in the 2-Gy regimens. The overall rate of grade ≥3 pneumonitis was approximately 2% across the entire cohort.

Conclusions

Our nearly 20-year TBI experience showed relatively low rates of radiation-related toxicities. However, cataracts were common with a relatively short onset time.

Total Body Irradiation for Hematopoietic Stem Cell Transplantation: What Can We Agree on?

Total body irradiation (TBI), used as part of the conditioning regimen prior to allogeneic and autologous hematopoietic cell transplantation, is the delivery of a relatively homogeneous dose of radiation to the entire body. TBI has a dual role, being cytotoxic and immunosuppressive. This allows it to eliminate disease and create “space” in the marrow while also impairing the immune system from rejecting the foreign donor cells being transplanted. Advantages that TBI may have over chemotherapy alone are that it may achieve greater tumour cytotoxicity and better tissue penetration than chemotherapy as its delivery is independent of vascular supply and physiologic barriers such as renal and hepatic function. Therefore, the so-called “sanctuary” sites such as the central nervous system (CNS), testes, and orbits or other sites with limited blood supply are not off-limits to radiation. Nevertheless, TBI is hampered by challenging logistics of administration, coordination between hematology and radiation oncology departments, increased rates of acute treatment-related morbidity and mortality along with late toxicity to other tissues. Newer technologies and a better understanding of the biology and physics of TBI has allowed the field to develop novel delivery systems which may help to deliver radiation more safely while maintaining its efficacy. However, continued research and collaboration are needed to determine the best approaches for the use of TBI in the future.

Total marrow and total lymphoid irradiation in bone marrow transplantation for acute leukaemia

The use of total body irradiation as part of conditioning regimens for acute leukaemia is progressively declining because of concerns of late toxic effects and the introduction of radiation-free regimens. Total marrow irradiation and total marrow and lymphoid irradiation represent more targeted forms of radiotherapy compared with total body irradiation that have the potential to decrease toxicity and escalate the dose to the bone marrow for high-risk patients. We review the technological basis and the clinical development of total marrow irradiation and total marrow and lymphoid irradiation, highlighting both the possible advantages as well as the current roadblocks for widespread implementation among transplantation units. The exact role of total marrow irradiation or total marrow and lymphoid irradiation in new conditioning regimens seems dependent on its technological implementation, aiming to make the whole procedure less time consuming, more streamlined, and easier to integrate into the clinical workflow. We also foresee a role for computer-assisted planning, as a way to improve planning and delivery and to incorporate total marrow irradiation and total marrow and lymphoid irradiation in multi-centric phase 2-3 trials.

Dose-escalated volumetric modulated arc therapy for total marrow irradiation: A feasibility dosimetric study with 4DCT planning and simultaneous integrated boost

PURPOSE

To evaluate the planning feasibility of dose-escalated total marrow irradiation (TMI) with simultaneous integrated boost (SIB) to the active bone marrow (ABM) using volumetric modulated arc therapy (VMAT), and to assess the impact of using planning organs at risk (OAR) volumes (PRV) accounting for breathing motion in the optimization.

METHODS

Five patients underwent whole-body CT and thoraco-abdominal 4DCT. A planning target volume (PTV) including all bones and ABM was contoured on each whole-body CT. PRV of selected OAR (liver, heart, kidneys, lungs, spleen, stomach) were determined with 4DCT. Planning consisted of 9-10 full 6 MV photon VMAT arcs. Four plans were created for each patient with 12 Gy prescribed to the PTV, with or without an additional 4 Gy SIB to the ABM. Planning dose constraints were set on the OAR or on the PRV. Planning objective was a PTV D_mean < 110% of the prescribed dose, a PTV V_110% < 50%, and OAR D_mean ≤ 50-60%.

RESULTS

PTV D_mean < 110% was accomplished for most plans (n = 18/20), while all achieved V_110%<50%. SIB plans succeeded to optimally cover the boost volume (median ABM D_mean = 16.3 Gy) and resulted in similar OAR sparing compared to plans without SIB (median OAR D_mean = 40-54% of the ABM prescribed dose). No statistically significant differences between plans optimized with constraints on OAR or PRV were found.

CONCLUSIONS

Adding a 4 Gy SIB to the ABM for TMI is feasible with VMAT technique, and results in OAR sparing similar to plans without SIB. Setting dose constraints on PRV does not impair PTV dosimetric parameters.

A step and shoot intensity modulated technique for total body irradiation

Introduction

Total body irradiation (TBI) is a part of the conditioning regimen for bone marrow transplant.At the Royal Marsden (Sutton, UK) and Rigshospitalet (Copenhagen, Denmark), we introduced a step and shoot IMRT (SS IMRT) technique for TBI. This technique requires no equipment other than that used to deliver other external beam radiation. In this paper, we describe this technique and report on data from the two clinics.

Materials and methods

The patients were positioned supine, supported by vacuum bag(s). The entire body of the patients were CT scanned with 5 mm slices. Multiple multi-leaf collimator (MLC) defined fields were used.In-vivo dosimetry was performed at the Royal Marsden for 113 patients.Calculated doses for 18 adult and 4 paediatric patients from Rigshospitalet were extracted.

Results

The in-vivo data from the Royal Marsden showed that the mean TLD measured dose difference was -1.9% with a standard deviation of 4.5%.SS IMRT plans for 22 patients from Rigshospitalet resulted in mean doses to the brain, lungs and kidneys all within the range of 11.1-11.8 Gy, while the V(12 Gy) was below 5% for the brain, 2% for the lungs and 0% for the kidneys.

Discussion

SS IMRT is feasible for TBI and can deliver targeted doses to the organs at risk.

Early and late adverse renal effects after potentially nephrotoxic treatment for childhood cancer

BACKGROUND

Improvements in diagnostics and treatment for paediatric malignancies resulted in a major increase in survival. However, childhood cancer survivors (CCS) are at risk of developing adverse effects caused by multimodal treatment for their malignancy. Nephrotoxicity is a known side effect of several treatments, including cisplatin, carboplatin, ifosfamide, radiotherapy and nephrectomy, and can cause glomerular filtration rate (GFR) impairment, proteinuria, tubulopathy, and hypertension. Evidence about the long-term effects of these treatments on renal function remains inconclusive. It is important to know the risk of, and risk factors for, early and late adverse renal effects, so that ultimately treatment and screening protocols can be adjusted. This review is an update of a previously published Cochrane Review.

OBJECTIVES

To evaluate existing evidence on the effects of potentially nephrotoxic treatment modalities on the prevalence of renal dysfunction in survivors treated for childhood cancer with a median or mean survival of at least one year after cessation of treatment, where possible in comparison with the general population or CCS treated without potentially nephrotoxic treatment. In addition, to evaluate evidence on associated risk factors, such as follow-up duration, age at time of diagnosis and treatment combinations, as well as the effect of doses.

SEARCH METHODS

On 31 March 2017 we searched the following electronic databases: CENTRAL, MEDLINE and Embase. In addition, we screened reference lists of relevant studies and we searched the congress proceedings of the International Society of Pediatric Oncology (SIOP) and The American Society of Pediatric Hematology/Oncology (ASPHO) from 2010 to 2016/2017.

SELECTION CRITERIA

Except for case reports, case series and studies including fewer than 20 participants, we included studies with all study designs that reported on renal function (one year or longer after cessation of treatment), in CCS treated before the age of 21 years with cisplatin, carboplatin, ifosfamide, radiation involving the kidney region, a nephrectomy, or a combination of two or more of these treatments. When not all treatment modalities were described or the study group of interest was unclear, a study was not eligible for the evaluation of prevalence. We still included it for the assessment of risk factors if it had performed a multivariable analysis.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, 'Risk of bias' assessment and data extraction using standardised data collection forms. We performed analyses according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions.

MAIN RESULTS

Apart from the remaining 37 studies included from the original review, the search resulted in the inclusion of 24 new studies. In total, we included 61 studies; 46 for prevalence, six for both prevalence and risk factors, and nine not meeting the inclusion criteria, but assessing risk factors. The 52 studies evaluating the prevalence of renal dysfunction included 13,327 participants of interest, of whom at least 4499 underwent renal function testing. The prevalence of adverse renal effects ranged from 0% to 84%. This variation may be due to diversity of included malignancies, received treatments, reported outcome measures, follow-up duration and the methodological quality of available evidence.Seven out of 52 studies, including 244 participants, reported the prevalence of chronic kidney disease, which ranged from 2.4% to 32%.Of these 52 studies, 36 studied a decreased (estimated) GFR, including at least 432 CCS, and found it was present in 0% to 73.7% of participants. One eligible study reported an increased risk of glomerular dysfunction after concomitant treatment with aminoglycosides and vancomycin in CCS receiving total body irradiation (TBI). Four non-eligible studies assessing a total cohort of CCS, found nephrectomy and (high-dose (HD)) ifosfamide as risk factors for decreased GFR. The majority also reported cisplatin as a risk factor. In addition, two non-eligible studies showed an association of a longer follow-up period with glomerular dysfunction.Twenty-two out of 52 studies, including 851 participants, studied proteinuria, which was present in 3.5% to 84% of participants. Risk factors, analysed by three non-eligible studies, included HD cisplatin, (HD) ifosfamide, TBI, and a combination of nephrectomy and abdominal radiotherapy. However, studies were contradictory and incomparable.Eleven out of 52 studies assessed hypophosphataemia or tubular phosphate reabsorption (TPR), or both. Prevalence ranged between 0% and 36.8% for hypophosphataemia in 287 participants, and from 0% to 62.5% for impaired TPR in 246 participants. One non-eligible study investigated risk factors for hypophosphataemia, but could not find any association.Four out of 52 studies, including 128 CCS, assessed the prevalence of hypomagnesaemia, which ranged between 13.2% and 28.6%. Both non-eligible studies investigating risk factors identified cisplatin as a risk factor. Carboplatin, nephrectomy and follow-up time were other reported risk factors.The prevalence of hypertension ranged from 0% to 50% in 2464 participants (30/52 studies). Risk factors reported by one eligible study were older age at screening and abdominal radiotherapy. A non-eligible study also found long follow-up time as risk factor. Three non-eligible studies showed that a higher body mass index increased the risk of hypertension. Treatment-related risk factors were abdominal radiotherapy and TBI, but studies were inconsistent.Because of the profound heterogeneity of the studies, it was not possible to perform meta-analyses. Risk of bias was present in all studies.

AUTHORS' CONCLUSIONS

The prevalence of adverse renal effects after treatment with cisplatin, carboplatin, ifosfamide, radiation therapy involving the kidney region, nephrectomy, or any combination of these, ranged from 0% to 84% depending on the study population, received treatment combination, reported outcome measure, follow-up duration and methodological quality. With currently available evidence, it was not possible to draw solid conclusions regarding the prevalence of, and treatment-related risk factors for, specific adverse renal effects. Future studies should focus on adequate study designs and reporting, including large prospective cohort studies with adequate control groups when possible. In addition, these studies should deploy multivariable risk factor analyses to correct for possible confounding. Next to research concerning known nephrotoxic therapies, exploring nephrotoxicity after new therapeutic agents is advised for future studies. Until more evidence becomes available, CCS should preferably be enrolled into long-term follow-up programmes to monitor their renal function and blood pressure.

Total body irradiation in allogeneic bone marrow transplantation conditioning regimens: A review

Hematologic malignancies may require, at one point during their treatment, allogeneic bone marrow transplantation. Total body irradiation combined with chemotherapy or radiomimetic used in allogeneic bone marrow transplantation is known to be very toxic. Total body irradiation (TBI) induces immunosuppression to prevent the rejection of donor marrow. TBI is also used to eradicate malignant cells and is in sanctuary organs that are not reached by chemotherapy drugs. TBI has evolved since its introduction in the late fifties, but acute and late toxicities remain. Helical tomotherapy, which is widely used for some solid tumors, is a path for the improvement of outcomes and toxicities in TBI because of its sparing capacities. In this article, we first review the practical aspects of TBI with patient positioning, radiobiological considerations and total dose and fractionation prescriptions. Second, we review the use of intensity modulated radiation therapy in bone marrow transplantation with a focus on helical tomotherapy TBI, helical tomotherapy total marrow irradiation (TMI) and total marrow and lymphoid irradiation (TMLI) and their dosimetric and clinical outcomes. Finally, we review the perspective of dose escalation and the extension to older patients and patients with comorbidity who do not benefit from a standard bone marrow transplantation conditioning regimen.

The Total Body Irradiation Schedule Affects Acute Leukemia Relapse After Matched T Cell-Depleted Hematopoietic Stem Cell Transplantation

PURPOSE

We sought to determine whether the total body irradiation (TBI) schedule affected outcome in patients with acute leukemia in complete remission who received T cell-depleted allogeneic hematopoietic stem cell transplantation from HLA identical siblings.

METHODS AND MATERIALS

The study recruited 55 patients (median age, 48 years; age range, 20-66 years; 30 men and 25 women; 34 with acute myeloid leukemia and 21 with acute lymphoid leukemia). Hyperfractionated TBI (HTBI) (1.2 Gy thrice daily for 4 days [for a total dose of 14.4 Gy] from day -12 to day -9) was administered to 29 patients. Single-dose TBI (STBI) (8 Gy, at a median dose rate of 10.7 cGy/min on day -9) was given to 26 patients.

RESULTS

All patients achieved primary, sustained engraftment with full donor-type chimerism. At 10 years, the overall cumulative incidence of transplant-related mortality was 11% (SE, ±0.1%). It was 7% (SE, ±0.2%) after HTBI and 15% (SE, ±0.5%) after STBI (P=.3). The overall cumulative incidence of relapse was 33% (SE, ±0.5). It was 13% (SE, ±0.5%) after HTBI and 46% (SE, ±1%) after STBI (P=.02). The overall probability of disease-free survival (DFS) was 59% (SE, ±7%). It was 67% (SE, ±0.84%) after HTBI and 37% (SE, ±1.4%) after STBI (P=.01). Multivariate analyses showed the TBI schedule was the only risk factor that significantly affected relapse and DFS (P=.01 and P=.03, respectively).

CONCLUSIONS

In patients with acute leukemia, HTBI is more efficacious than STBI in eradicating minimal residual disease after HLA-matched T cell-depleted hematopoietic stem cell transplantation, thus affecting DFS.

Early and late renal adverse effects after potentially nephrotoxic treatment for childhood cancer

BACKGROUND

Great improvements in diagnostics and treatment for malignant disease in childhood have led to a major increase in survival. However, childhood cancer survivors (CCS) are at great risk for developing adverse effects caused by multimodal treatment for their malignancy. Nephrotoxicity is one of these known (acute) side effects of several treatments, including cisplatin, carboplatin, ifosfamide, radiotherapy and nephrectomy, and can cause glomerular filtration rate impairment, proteinuria, tubulopathy and hypertension. However, evidence about the long-term effects of these treatments on renal function remains inconclusive. To reduce the number of (long-term) nephrotoxic events in CCS, it is important to know the risk of, and risk factors for, early and late renal adverse effects, so that ultimately treatment and screening protocols can be adjusted.

OBJECTIVES

To evaluate existing evidence on the effects of potentially nephrotoxic treatment modalities on the prevalence of and associated risk factors for renal dysfunction in survivors treated for childhood cancer with a median or mean survival of at least one year after cessation of treatment, where possible in comparison with healthy controls or CCS treated without potentially nephrotoxic treatment.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2011), MEDLINE/PubMed (from 1945 to December 2011) and EMBASE/Ovid (from 1980 to December 2011).

SELECTION CRITERIA

With the exception of case reports, case series and studies including fewer than 20 participants, we included studies with all study designs that reported on renal function (one year or longer after cessation of treatment) in children and adults who were treated for a paediatric malignancy (aged 18 years or younger at diagnosis) with cisplatin, carboplatin, ifosfamide, radiation including the kidney region and/or a nephrectomy.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, risk of bias assessment and data extraction using standardised data collection forms. Analyses were performed according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions.

MAIN RESULTS

The search strategy identified 5504 studies, of which 5138 were excluded on the basis of title and/or abstract. The full-text screening of the remaining 366 articles resulted in the inclusion of 57 studies investigating the prevalence of and sometimes also risk factors for early and late renal adverse effects of treatment for childhood cancer. The 57 studies included at least 13,338 participants of interest for this study, of whom at least 6516 underwent renal function testing. The prevalence of renal adverse effects ranged from 0% to 84%. This variation may be due to diversity in included malignancies, prescribed treatments, reported outcome measurements and the methodological quality of available evidence.Chronic kidney disease/renal insufficiency (as defined by the authors of the original studies) was reported in 10 of 57 studies. The prevalence of chronic kidney disease ranged between 0.5% and 70.4% in the 10 studies and between 0.5% and 18.8% in the six studies that specifically investigated Wilms' tumour survivors treated with a unilateral nephrectomy.A decreased (estimated) glomerular filtration rate was present in 0% to 50% of all assessed survivors (32/57 studies). Total body irradiation; concomitant treatment with aminoglycosides, vancomycin, amphotericin B or cyclosporin A; older age at treatment and longer interval from therapy to follow-up were significant risk factors reported in multivariate analyses. Proteinuria was present in 0% to 84% of all survivors (17/57 studies). No study performed multivariate analysis to assess risk factors for proteinuria.Hypophosphataemia was assessed in seven studies. Reported prevalences ranged between 0% and 47.6%, but four of seven studies found a prevalence of 0%. No studies assessed risk factors for hypophosphataemia using multivariate analysis. The prevalence of impairment of tubular phosphate reabsorption was mostly higher (range 0% to 62.5%; 11/57 studies). Higher cumulative ifosfamide dose, concomitant cisplatin treatment, nephrectomy and longer follow-up duration were significant risk factors for impaired tubular phosphate reabsorption in multivariate analyses.Treatment with cisplatin and carboplatin was associated with a significantly lower serum magnesium level in multivariate analysis, and the prevalence of hypomagnesaemia ranged between 0% and 37.5% in the eight studies investigating serum magnesium.Hypertension was investigated in 24 of the 57 studies. Reported prevalences ranged from 0% to 18.2%. A higher body mass index was the only significant risk factor noted in more than one multivariate analysis. Other reported factors that significantly increased the risk of hypertension were use of total body irradiation, abdominal irradiation, acute kidney injury, unrelated or autologous stem cell donor type, growth hormone therapy and older age at screening. Previous infection with hepatitis C significantly decreased the risk of hypertension.Because of the profound heterogeneity of the studies, it was not possible to perform any meta-analysis.

AUTHORS' CONCLUSIONS

The prevalence of renal adverse events after treatment with cisplatin, carboplatin, ifosfamide, radiation therapy involving the kidney region and/or nephrectomy ranged from 0% to 84%. With currently available evidence, it was not possible to draw any conclusions with regard to prevalence of and risk factors for renal adverse effects. Future studies should focus on adequate study design and reporting and should deploy multivariate risk factor analysis to correct for possible confounding. Until more evidence becomes available, CCS should be enrolled into long-term follow-up programmes to monitor their renal function and blood pressure.

In haematopoietic SCT for acute leukemia TBI impacts on relapse but not survival: results of a multicentre observational study

The aim of this study was to determine whether parameters related to TBI impacted upon OS and relapse in patients with acute leukemia in CR who underwent haematopoietic SCT (HSCT) in 11 Italian Radiation Oncology Centres. Data were analysed from 507 patients (313 males; 194 females; median age 15 years; 318 with ALL; 188 with AML; 1 case not recorded). Besides 128 autologous transplants, donors included 192 matched siblings, 74 mismatched family members and 113 unrelated individuals. Autologous and allogeneic transplants were analysed separately. Median follow-up was 40.1 months. TBI schedules and HSCT type were closely related. Uni- and multi-variate analyses showed no parameter was significant for OS or relapse in autologous transplantation. Multivariate analysis showed type of transplant and disease impacted significantly on OS in allogeneic transplantation. Disease, GVHD and TBI dose were risk factors for relapse. This analysis illustrates that Italian Transplant Centre use of TBI is in line with international practice. Most Centres adopted a hyperfractionated schedule that is used worldwide (12 Gy in six fractions over 3 days), which appears to have become standard. TBI doses impacted significantly upon relapse rates.

Feasibility study of a novel rotational and translational method for linac-based intensity modulated total marrow irradiation

Conventional TBI is primarily limited by the toxicity to organs at risk because of impossibility of sparing critical organs. The purpose of this study is to investigate the feasibility of a novel rotational and translational IMRT method (RTM) which able to conform the radiation dose to target organs and reduce critical organ dose for TMI using linac. To assess the feasibility, we investigated the planning and delivery of total marrow irradiation (TMI) using this method. The treatment plannig study showed that target coverage was achieved with 90% of the target volume receiving 100% of the prescription dose. Doses to critical structures indicated that a 1.28- to 2.35-fold reduction in median dose is achieved with total-marrow RTM compared with conventional TBI. Delivery of Rando phantom and TLD measurement demonstrated an accurate dose delivery (ranged from -6% to 7%) to the target and critical organs. Results from this study suggests that RTM can be accurately delivered and reduce irradiation to all critical organs with good target coverage.

Attempted depletion of passenger leukocytes by irradiation in pigs

Allograft/xenograft rejection is associated with “passenger leukocyte” migration from the organ into recipient lymph nodes. In Study 1, we attempted to deplete leukocytes from potential kidney “donor” pigs, using two regimens of total body irradiation. A dose of 700 cGy was administered, followed by either 800 cGy (“low-dose”) or 1,300 cGy (“high dose”) with the kidneys shielded. Neither regimen was entirely successful in depleting all leukocytes, although remaining T and 8 cell numbers were negligible. Study 2 was aimed at providing an indication of whether near-complete depletion of leukocytes had any major impact on kidney allograft survival. In non-immunosuppressed recipient pigs, survival of a kidney from a donor that received high-dose irradiation was compared with that of a kidney taken from a non-irradiated donor. Kidney graft survival was 9 and 7 days, respectively, suggesting that depletion had little impact on graft survival. The lack of effect may have been related to (i) inadequate depletion of passenger leukocytes, thus not preventing a direct T cell response, (ii) the presence of dead or dying leukocytes (antigens), thus not preventing an indirect T cell response, or (iii) constitutive expression of MHC class II and B7 molecules on the porcine vascular endothelium, activating recipient T cells.

Preclinical assessment of volumetric modulated arc therapy for total marrow irradiation

PURPOSE

A preclinical investigation was undertaken to explore a treatment technique for total marrow irradiation using RapidArc, a volumetric modulated arc technique.

MATERIALS AND METHODS

Computed tomography datasets of 5 patients were included. Plans with eight overlapping coaxial arcs were optimized for 6-MV photon beams. Dose prescription was 12 Gy in 2 Gy per fraction, normalized so that 100% isodose covered 85% of the planning target volume (PTV). The PTV consisted of the whole skeleton (including ribs and sternum), from the top of the skull to the medium distal third of the femurs. Planning objectives for organs at risk (OARs) were constrained to a median dose <6 to 7 Gy. OARs included brain, eyes, oral cavity, parotids, thyroid, lungs, heart, kidneys, liver, spleen, stomach, abdominal cavity, bladder, rectum, and genitals. Pretreatment quality assurance consisted of portal dosimetry comparisons, scoring the delivery to calculation agreement with the gamma agreement index.

RESULTS

The median total body volume in the study was 57 liters (range, 49-81 liters), for an average diameter of 47 cm (range, 46-53 cm) and a total length ranging from 95 to 112 cm. The median PTV volume was 6.8 liters (range, 5.8-10.8 liters). The mean dose to PTV was 109% (range, 107-112%). The global mean of median dose to all OARs was 4.9 Gy (range, 4.5-5.1 Gy over the 5 patients). The individual mean of median doses per organ ranged from 2.3 Gy (oral cavity) to 7.3 Gy (bowels cavity). Preclinical quality assurance resulted in a mean gamma agreement index of 94.3 ± 5.1%. The delivery time measured from quality assurance runs was 13 minutes.

CONCLUSION

Sparing of normal tissues with adequate coverage of skeletal bones was shown to be feasible with RapidArc. Pretreatment quality assurance measurements confirmed the technical agreement between expected and actually delivered dose distributions, suggesting the possibility of incorporating this technique in the treatment options for patients.

NCI first International Workshop on the biology, prevention, and treatment of relapse after allogeneic hematopoietic stem cell transplantation: report from the committee on the biological considerations of hematological relapse following allogeneic stem cell transplantation unrelated to graft-versus-tumor effects: state of the science

Hematopoietic malignant relapse still remains the major cause of death following allogeneic hematopoietic stem cell transplantation (HSCT). Although there has been a large focus on the immunologic mechanisms responsible for the graft-versus-tumor (GVT) effect or lack thereof, there has been little attention paid to investigating the biologic basis of hematologic malignant disease relapse following allogeneic HSCT. There are a large number of factors that are responsible for the biologic resistance of hematopoietic tumors following allogeneic HSCT. We have focused on 5 major areas including clonal evolution of cancer drug resistance, cancer radiation resistance, genomic basis of leukemia resistance, cancer epigenetics, and resistant leukemia stem cells. We recommend increased funding to pursue 3 broad areas that will significantly enhance our understanding of the biologic basis of malignant relapse after allogeneic HSCT, including: (1) genomic and epigenetic alterations, (2) cancer stem cell biology, and (3) clonal cancer drug and radiation resistance.

[Total body irradiation: present and future]

Total body irradiation (TBI) has an established role as preparative regimen for bone-marrow transplantation in the treatment of hematological malignancies. Many randomized trials demonstrated that the clinical outcomes obtained from the association of TBI and cyclophosphamide are equivalent, or, sometimes, better than those based on chemotherapeutic agents. Despite the therapeutic progress of the last years, and the consequent improvement in the overall survival, this preparative regimen remains always associated with a relatively high rate of acute and late toxicity. In this article, we review the actual indications of TBI in clinical practice, and analyze the technological progress in this domain. We focus on the hypothesis that a selective irradiation of the hematopoietic or lymphoid organs is actually possible with intensity-modulated radiotherapy. Technical limits and preliminary results in terms of acute and late toxicities of intensity-modulated TBI are analyzed. With these new technologies, treatment-related toxicity is not anymore a major limiting factor in the preparative regimens for bone-marrow transplantation, allowing for a larger spectrum of TBI indications, a possible extension to patients older than 50 years, or a dose escalation. Preliminary results warrant, however, further evaluation in clinical trials to better assess the impact of this new approach on disease control and the long-term toxicity.

HLA-identical haematopoietic stem cell transplantation for acute leukaemia in children: less relapse with higher biologically effective dose of TBI

To examine relapse, survival and transplant-related complications in relationship to disease- and pre-treatment-related characteristics, we evaluated 132 children, who consecutively received an allogeneic HLA-identical SCT for acute leukaemia in our centre: ALL in first remission (n=24), ALL in second remission (n=53) and AML in first remission (n=55). The source of the stem cells was bone marrow in all but three cases. Most patients (89%) were pre-treated with cyclophosphamide and an age-related dose of TBI. Initially, GVHD prophylaxis consisted of long-course MTX only (n=24), later short-course MTX and CsA (n=102) was given. All patients were nursed in strictly protective isolation and received total gut decontamination to suppress their potentially pathogenic enteric microflora. The 5-year probability of overall survival was 63, 53 and 74% for ALL1, ALL2 and AML1, respectively (median follow-up: 10.6 years). The overall transplant-related mortality was 6%. The incidence of acute GVHD was 17%; 6% was grades II-IV. A higher total biologically effective TBI dose (BED) resulted in a decreased relapse frequency (P=0.034) and increased overall survival. AML patients with acute GVHD got no relapse (P=0.02); this was not the case in ALL patients. Fractionated TBI regimens with higher BED should be evaluated in prospective studies.

Renal dysfunction after total body irradiation: dose-effect relationship

PURPOSE

Late complications related to total body irradiation (TBI) as part of the conditioning regimen for hematopoietic stem cell transplantation have been increasingly noted. We reviewed and compared the results of treatments with various TBI regimens and tried to derive a dose-effect relationship for the endpoint of late renal dysfunction. The aim was to find the tolerance dose for the kidney when TBI is performed.

METHODS AND MATERIALS

A literature search was performed using PubMed for articles reporting late renal dysfunction. For intercomparison, the various TBI regimens were normalized using the linear-quadratic model, and biologically effective doses (BEDs) were calculated.

RESULTS

Eleven reports were found describing the frequency of renal dysfunction after TBI. The frequency of renal dysfunction as a function of the BED was obtained. For BED>16 Gy an increase in the frequency of dysfunction was observed.

CONCLUSIONS

The tolerance BED for kidney tissue undergoing TBI is about 16 Gy. This BED can be realized with highly fractionated TBI (e.g., 6x1.7 Gy or 9x1.2 Gy at dose rates>5 cGy/min). To prevent late renal dysfunction, the TBI regimens with BED values>16 Gy (almost all found in published reports) should be applied with appropriate shielding of the kidneys.

Feasibility study of helical tomotherapy for total body or total marrow irradiationa)

Total body radiation (TBI) has been used for many years as a preconditioning agent before bone marrow transplantation. Many side effects still plague its use. We investigated the planning and delivery of total body irradiation (TBI) and selective total marrow irradiation (TMI) and a reduced radiation dose to sensitive structures using image-guided helical tomotherapy. To assess the feasibility of using helical tomotherapy, (A) we studied variations in pitch, field width, and modulation factor on total body and total marrow helical tomotherapy treatments. We varied these parameters to provide a uniform dose along with a treatment times similar to conventional TBI (15-30 min). (B) We also investigated limited (head, chest, and pelvis) megavoltage CT (MVCT) scanning for the dimensional pretreatment setup verification rather than total body MVCT scanning to shorten the overall treatment time per treatment fraction. (C) We placed thermoluminescent detectors (TLDs) inside a Rando phantom to measure the dose at seven anatomical sites, including the lungs. A simulated TBI treatment showed homogeneous dose coverage (+/-10%) to the whole body. Doses to the sensitive organs were reduced by 35%-70% of the target dose. TLD measurements on Rando showed an accurate dose delivery (+/-7%) to the target and critical organs. In the TMI study, the dose was delivered conformally to the bone marrow only. The TBI and TMI treatment delivery time was reduced (by 50%) by increasing the field width from 2.5 to 5.0 cm in the inferior-superior direction. A limited MVCT reduced the target localization time 60% compared to whole body MVCT. MVCT image-guided helical tomotherapy offers a novel method to deliver a precise, homogeneous radiation dose to the whole body target while reducing the dose significantly to all critical organs. A judicious selection of pitch, modulation factor, and field size is required to produce a homogeneous dose distribution along with an acceptable treatment time. In addition, conformal radiation to the bone marrow appears feasible in an external radiation treatment using image-guided helical tomotherapy.

CT-based analysis of dose homogeneity in total body irradiation using lateral beam

A computed tomography (CT) based treatment planning system for total body irradiation (TBI) is presented and compared with the commonly practiced lateral treatment delivery. The TBI regimen has been proved to be an essential conditional regimen for patients undergoing bone marrow transplantation. The advantage of the TBI regimen with bone marrow transplantation (BMT) in hematological malignancies can be offset by toxicities arising from TBI in posttransplant complications. With the increasing survival rates, the evaluation of long‐term side effects and quality of life has become an important area of research interest. There have been several treatment techniques developed over the decades designed to achieve accurate dose delivery and dose homogeneity. This paper reports on the verification of the dose delivery for a basic lateral technique using thermoluminescent dosimeters (TLDs) placed in an anthropomorphic phantom and its correlation with CT‐based treatment planning. CT‐based treatment plans on several patients were used to evaluate the doses delivered to the whole body and critical organs. A large variation in doses delivered to the whole body was demonstrated, with some parts of the bone marrow failing to receive the prescribed dose and some critical organs, such as the lungs, receiving excessive doses. Placing the arms at the sides only partially compensates for the increased transmission of the lungs because the arms only shadow part of the lung. This study shows that CT‐based treatment planning for TBI provides precise and accurate dose calculations and allows for the correlation of clinical outcomes with the doses actually delivered to various organs.

PACS numbers: 87.53.Dq, 87.66.Xa, 87.66.Sq

Total body irradiation and pneumonitis risk: a review of outcomes

A review was undertaken of all patients treated at Royal Adelaide Hospital, South Australia with total body irradiation (TBI) for the purpose of assessing the incidence of interstitial pneumonitis (IP) and possible prognostic factors for its development. The aim was also to assess the impact of IP and other prognostic factors on long-term survival outcome following bone marrow transplantation. A total of 84 patients received TBI, with 12 Gy in six fractions delivered using two different instantaneous dose rates of 7.5 and 15 cGy min⁻¹. This series included 26 cases of acute lymphoblastic leukaemia, 26 of multiple myeloma and 15 of acute myelogenous leukaemia. On multivariate analysis, a higher dose rate was independently significant for an increased risk of IP.

Fractionated TBI correlates with less T cell mixed chimerism but increased risk of relapse compared to busulphan in patients with haematological malignancies after allogeneic stem cell transplantation

We prospectively evaluated mixed chimerism (MC) in the T cell and myeloid lineages and its correlation to busulphan, single-dose total body irradiation (TBI) and fractionated TBI (fTBI) conditioning in 180 patients with haematological malignancies after allogeneic stem cell transplantation (SCT). In all patients receiving busulphan, the area under curve (AUC) was calculated. The incidence of MC in the T cell lineage was significantly lower in patients receiving fTBI (22%) compared to those given TBI (53%, P=0.02) or busulphan (47%, P<0.01). The incidence of myeloid MC did not differ between the three groups. The overall probability of acute graft-versus-host disease grades II-IV was significantly higher in patients with complete T cell donor chimerism (49%) compared to patients with T cell MC (23%, P<0.001). The incidence of T cell and myeloid MC after SCT did not differ between low (55%), medium (42%) and high (43%) AUC levels of busulphan during conditioning. Patients receiving fTBI had a significantly higher probability of relapse compared to busulphan-treated patients (44 vs l6%, P=0.01). In multivariate analysis adjusted for diagnosis, busulphan-treated patients showed both a better survival (P=0.04) and less probability of relapse (0.03) compared to TBI-treated patients.

Lethal pulmonary complications significantly correlate with individually assessed mean lung dose in patients with hematologic malignancies treated with total body irradiation

PURPOSE

To assess the impact of lung dose on lethal pulmonary complications (LPCs) in a single-center group of patients with hematologic malignancies treated with total body irradiation (TBI) in the conditioning regimen for bone marrow transplantation (BMT).

METHODS

The mean lung dose of 101 TBI-conditioned patients was assessed by a thorough (1 SD around 2%) in vivo transit dosimetry technique. Fractionated TBI (10 Gy, 3.33 Gy/fraction, 1 fraction/d, 0.055 Gy/min) was delivered using a lateral-opposed beam technique with shielding of the lung by the arms. The median lung dose was 9.4 Gy (1 SD 0.8 Gy, range 7.8--11.4). The LPCs included idiopathic interstitial pneumonia (IIP) and non-idiopathic IP (non-IIP).

RESULTS

Nine LPCs were observed. LPCs were observed in 2 (3.8%) of 52 patients in the group with a lung dose < or = 9.4 Gy and in 7 (14.3%) of 49 patients in the >9.4 Gy group. The 6-month LPC risk was 3.8% and 19.2% (p = 0.05), respectively. A multivariate analysis adjusted by the following variables: type of malignancy (acute leukemia, chronic leukemia, lymphoma, myeloma), type of BMT (allogeneic, autologous), cytomegalovirus infection, graft vs. host disease, and previously administered drugs (bleomycin, cytarabine, cyclophosphamide, nitrosoureas), revealed a significant and independent association between lung dose and LPC risk (p = 0.02; relative risk = 6.7). Of the variables analyzed, BMT type (p = 0.04; relative risk = 6.6) had a risk predictive role.

CONCLUSION

The mean lung dose is an independent predictor of LPC risk in patients treated with the 3 x 3.33-Gy low-dose-rate TBI technique. Allogeneic BMT is associated with a higher risk of LPCs.

Total body irradiation using a modified standing technique: a single institution 7 year experience

We describe a simple standing technique for delivering total body irradiation (TBI) using large horizontal fields, made possible by the off-centre installation of a non-dedicated treatment unit in a pre-existing bunker. Patients are treated using anterior and posterior fields with customized lung compensators. This technique enables the dose to the lung to be accurately calculated and modified to avoid overdose and to minimize the risk of pneumonitis. From February 1991 to December 1997, 94 patients with a variety of haematological malignancies were given fractionated TBI using this technique prior to allogenic or autologous bone marrow transplantation. Patients received a total dose of 14.4 Gy given in eight fractions over 4 days, with at least 6 h between fractions. The prescribed dose to the lungs was reduced to 12 Gy in eight fractions. The technique was well tolerated, took less than 10 min to set up and did not disrupt the daily routine use of the machine. Doses to all measured points on the trunk and head were within +/-6% of the prescribed dose. Doses to the lungs were within +/-5% of the prescribed dose. There were no early respiratory deaths in the 37 autologous transplant patients. There were 10 (17%) respiratory deaths in the 57 allogeneic transplant patients, 3 of confirmed infectious aetiology.

Idiopathic pneumonia syndrome after bone marrow transplantation: the role of pre-transplant radiation conditioning and local cytokine dysregulation in promoting lung inflammation and fibrosis

Pulmonary complications and graft-vs.-host disease (GVHD) remain severe threats to survival after bone marrow transplantation (BMT). Idiopathic pneumonia syndrome (IPS) accounts for nearly 50% of all the cases of interstitial pneumonitis after BMT. IPS is characterized by an early inflammatory phase followed by chronic inflammation and fibrosis of lung tissue; however, the immunopathogenesis of this disease is not yet clearly understood. This biphasic syndrome has been reported to be associated with pre-transplant radiation conditioning in some studies while others have suggested that GVHD or autoimmune phenomena may be responsible for its development. The early post-BMT phase is characterized by the presence of inflammatory cytokines whose net effect is to promote lymphocyte influx into lungs with minimal fibrosis, that leads to an acute form of graft-vs.-host reaction-mediated pulmonary tissue damage. Gradual changes over time in leucocyte influx and activation lead to dysregulated wound repair mechanisms resulting from the shift in the balance of cytokines that promote fibrosis. Using data from new animal models of IPS and information from studies of human IPS, we hypothesize that cytokine-modulated immunological mechanisms which occur during the acute and chronic phases after bone marrow transplantation lead to the development of the progressive, inflammatory, and fibrotic lung disease typical of idiopathic pneumonia syndrome.

Total body irradiation-based regimen in the conditioning of patients submitted to haploidentical stem cell transplantation

BACKGROUND AND PURPOSE

To evaluate the efficacy and toxicity of a highly immuno- and myelo-suppressive conditioning regimen followed by the infusion of large numbers of T-cell-depleted mismatched haematopoietic stem cells in 43 high-risk acute leukaemia patients.

RESULTS

A high rate of engraftment (95%) and no graft-versus-host disease (GvHD) were observed. The 4-year probability of event-free survival was 0.25+/-0.09 for acute myeloid leukaemia and 0.17+/-0.07 for acute lymphoid leukaemia patients.

CONCLUSIONS

This study shows that the main obstacles limiting the use of mismatched transplants, i.e. GvHD and rejection, were overcome.

Salvage extended-field irradiation in follicular non-Hodgkin's lymphoma after failure of chemotherapy

PURPOSE

To evaluate the efficacy of total abdominopelvic (TAI) and total body irradiation (TBI) in heavily pretreated follicular non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

From 1983 to 1998, 34 patients received TAI (n = 22) or TBI (n = 12). All had Stage III or IV, Class B, C, D NHL in the working formulation and failed after receiving 1-5 regimens of chemotherapy. TAI was given at 20 Gy over a 3-week period. TBI was delivered in two successive half-body irradiations of 15 Gy over a 2-week period with a 4-week interval between each.

RESULTS

Mean follow-up from TAI or TBI was 120 months (range, 6-180). Seventy-six percent of patients achieved complete response and 24% partial response. Median survival was 62 months, 5-year and 10-year overall survival was 59% and 41%, and disease-free survival was 56% and 30%, respectively. Grade III or IV toxicity was gastrointestinal in 38% of patients and hematologic in 30%. No toxic death or delayed complications were observed.

CONCLUSION

Extended-field irradiation is feasible and efficient after failure of chemotherapy in follicular NHL.

A dose escalation study of total body irradiation followed by high-dose etoposide and allogeneic blood stem cell transplantation for the treatment of advanced hematologic malignancies

Since approximately 30% of leukemia patients relapse after allogeneic BMT using total body irradiation (TBI)-based preparative regimens, treatment intensity may be suboptimal. The killing of leukemia cells is proportional to the radiation absorbed dose. We studied the feasibility and toxicity of escalating the doses of fractionated TBI above our previous prescription of 13.5 Gy. Sixteen evaluable patients with advanced hematologic malignancies were treated with twice daily TBI using a high-energy source (18-24 MV). The first patient cohort (n = 11) received a total dose of 14.4 Gy in nine fractions, and the second cohort (n = 5) received doses escalated to 15.3 Gy. All patients received high-dose etoposide (60 mg/kg) and allogeneic stem cell transplantation following the TBI. All patients had HLA-identical sibling donors. The median times for neutrophil and platelet engraftment were 13.5 and 12 days, respectively, and did not differ between the two cohorts. All but one patient developed treatment-related grade 3 or 4 mucositis. There were three cases of grade 4 pulmonary toxicity and three cases of grade 4 hepatic toxicity among the 14.4 Gy cohort, and one case each of grade 4 pulmonary and hepatic toxicities among the 15.3 Gy cohort. In most cases comorbid conditions contributed to these toxicities. Two patients had significant GVHD of the GI tract. Six relapses occurred, five (45%) in the 14.4 Gy cohort and one (20%) in the 15.3 Gy cohort. The 100-day treatment-related mortality rates were 9% and 20% for the 14.4 Gy and 15.3 Gy cohorts, respectively, and the median survivals were 226 and 201 days, respectively. We conclude that TBI dose escalation above the previously used 13.5 Gy dose is feasible using a high-energy source and high-dose etoposide. Acute and chronic toxicities were primarily related to GVHD, infection and relapse rather than to TBI.

Immediate toxicity during fractionated total body irradiation as conditioning for bone marrow transplantation

BACKGROUND

Total body irradiation followed by bone marrow transplantation is well established as a part of the conditioning regimen in high dose therapy. The immediate tolerance of fractionated total body irradiation (FTBI) was investigated prospectively.

METHODS

From January 1995 to December 1998 162 patients received a FTBI, 6x2 Gy on 3 consecutive days, lung dose 10 Gy, for allogeneic (n=112) or autologous (n=50) bone marrow transplantation. High dose chemotherapy (mostly Cyclophosphamide) was administered after the FTBI. A standardized supportive therapy was administered. The immediate toxicity of FTBI was evaluated prospectively prior to each radiation fraction using a defined questionnaire.

RESULTS

Main symptoms distressing the patient during irradiation period were gastrointestinal symptoms like nausea and emesis. The prevalence of nausea per fraction increased to 26.1% after the 4th fraction, with a significant higher prevalence in children younger than 10 years at 1st and 2nd fractions. 42.6 and 22. 8%, respectively, of all patients complained of nausea and episodes of emesis, during FTBI. Mild xerostomia and parotiditis were observed in 29.9 and 7.1% of all patients. Further gastrointestinal side effects during FTBI were loss of appetite in 16.0%, indisposition in 25.3%, mild oesophagitis in 3.7% and diarrhoea in 3. 7% of the patients. During FTBI 41.4% of the patients developed a temporary skin irritation (mild erythema). Pruritus was registered in 3.7% of the patients. Headache was observed in 14.8% and Fatigue syndrome in 49.2% of women and 28.3% of men (P<0.005).

CONCLUSION

FTBI is a well tolerated therapeutic regimen in high dose therapy. The 162 patients investigated revealed no severe immediate side effects.

Idiopathic pneumonia syndrome after allogeneic bone marrow transplantation in mice. Role of pretransplant radiation conditioning

Idiopathic pneumonia syndrome (IPS) is a significant clinical problem encountered among patients treated with bone marrow transplantation (BMT). IPS is identified as an inflammatory lung disease characterized by diffuse interstitial pneumonitis and alveolitis leading to interstitial fibrosis in the absence of an identifiable infectious agent. In an earlier study we characterized a murine model of IPS following allogeneic BMT that exhibits several features of human IPS. In this report we show that the lung represents a unique target of post-BMT disease in this model. The kinetics of developing lung disease were found to be markedly different from the kinetics of graft-versus-host disease in other tissues such as liver, colon, ear, skin, and tongue. Mice transplanted by our standard protocol with T-cell-depleted semiallogeneic donor bone marrow plus donor spleen cells in the absence of pretransplant radiation conditioning did not develop lung inflammation or fibrosis characteristic of IPS. Pretransplant radiation conditioning in the absence of BMT also failed to cause IPS, demonstrating an important role for radiation conditioning in the development of BMT-related IPS. The occurrence of lung disease post-BMT was found to be dependent on radiation conditioning in a dose-dependent manner. Finally, thoracic irradiation alone was demonstrated to be sufficient in causing IPS in mice transplanted with bone marrow plus spleen cells, albeit with reduced severity. Based on these findings, we conclude that pretransplant radiation conditioning plays an important role in the development of IPS following allogeneic BMT.

[Total body irradiation: techniques, dosimetry, and complications]

Total-body irradiation (TBI) has an established role in many preparative regimens used before bone marrow transplantation (BMT) in the treatment of hematological malignancies in children and adults. Better choice in TBI techniques and dosimetry have permitted better homogeneity of dose, and therefore a significant sparing of critical tissues. Advances in treatments over the past 20 years have greatly improved survival; therefore, the evaluation of early and late complications, with a sufficient follow-up, according to different conditioning regimens is important. In this article, we review and compare different TBI techniques and dosimetry, and their influence on the distribution and homogeneity of dose, and the possible relationship to the risk of complications. We also describe the acute and late effects of TBI in children and adults appearing in the first month post-BMT as veno-occlusive disease, interstitial pneumonitis, or after 3 months, i.e., endocrinal late effects and growth in children, cataracts, neurological and bone or other complications, secondary tumors and alteration in the quality of life. The responsibility of TBI in the increased rate of certain complications is difficult to assess from chemotherapy or allograft side effects (chronic graft vs. host disease) or from other associated medical treatments, such as long term steroid therapy.

[Biological basis of total body irradiation]

A comprehensive understanding of the radiobiological bases of total body irradiation (TBI) is made difficult by the large number of normal and malignant tissues that must be taken into account. In addition, tissue responses to irradiation are also sensitive to associated treatments, type of graft and a number of patient characteristics. Experimental studies have yielded a large body of data, the clinical relevance of which still requires definite validation through randomized trials. Fractionated TBI schemes are able to reduce late normal tissue toxicity, but the ultimate consequences of the fractional dose reduction do not appear to be equivocal. Thus, leukemia and lymphoma cells are probably more radiobiologically heterogeneous than previously thought, with several cell lines displaying relatively high radioresistance and repair capability patterns. The most primitive host-type hematopoietic stem cells are likely to be at least partly protected by TBI fractionation and may hamper late engraftment. Similarly, but with possibly conflicting consequences on the probability of engraftment, the persistence of a functional marrow stroma may also be fractionation-sensitive, while higher rejection rates have been reported after T-depletion grafts and fractionated TBI. In clinical practice (as for the performance of relevant clinical trials), the influence of these results are rather limited by the heavy logistic constraints created by a sophisticated and time-consuming procedure. Lastly, clinicians are now facing an increasing incidence of second cancers, at least partly induced by irradiation, which jeopardize the long-term prospects of otherwise cured patients.

Total body irradiation correlates with chronic graft versus host disease and affects prognosis of patients with acute lymphoblastic leukemia receiving an HLA identical allogeneic bone marrow transplant

PURPOSE

To investigate whether different procedure variables involved in the delivery of fractionated total body irradiation (TBI) impact on prognosis of patients affected by acute lymphoblastic leukemia (ALL) receiving allogeneic bone marrow transplant (BMT).

METHODS AND MATERIALS

Ninety-three consecutive patients with ALL receiving a human leukocyte antigen (HLA) identical allogeneic BMT between 1 August 1983 and 30 September 1995 were conditioned with the same protocol consisting of cyclophosphamide and fractionated TBI. The planned total dose of TBI was 12 Gy (2 Gy, twice a day for 3 days). Along the 12-year period, variations in delivering TBI schedule occurred with regard to used radiation source, instantaneous dose rate, technical setting, and actual total dose received by the patient. We tested these different TBI variables as well as factors related to patient, state of disease, and transplant-induced disease to investigate their influence on transplant-related mortality, leukemia relapse, and survival.

RESULTS

At median follow-up of 7 years (range 3-15 years) the probabilities of leukemia-free survival (LFS) and overall survival (OS) for the 93 patients were 60% and 41%, respectively. At univariate analysis, chronic graft versus host disease (cGvHd) (p = 0.0005), age (p = 0.01), and state of disease (p = 0.03) were factors affecting LFS whereas chronic GvHd (p = 0.0005), acute GvHd (p = 0.03), age (p = 0.0001), and GvHd prophylaxis (p = 0.01) were factors affecting overall survival. The occurrence of chronic GvHd was correlated with actually delivered TBI dose (p = 0.04). Combined stratification of prognostic factors showed that patients who received the planned total dose of TBI (12 Gy) and were affected by chronic GvHd had higher probabilities of LFS (p = 0.01) and OS (p = n.s.) than patients receiving less than 12 Gy and/or without occurrence of chronic GvHd. Moreover, TBI dose had a significant impact on LFS in patients transplanted in first remission (p = 0.05). At multivariate analysis, TBI dose was an independent factor affecting overall survival (p = 0.05) as well as chronic GvHd (p = 0.001) and age (p = 0.04).

CONCLUSIONS

This retrospective analysis showed that different variables involved in TBI delivery may influence the occurrence of cGvHd and affect prognosis of patients with ALL receiving allogeneic BMT. The total dose of 12 Gy, administered in six fractions over 3 days, appears to be an effective and low toxic regimen for ALL patients transplanted in first remission.

Fractionated total body irradiation in allogeneic bone marrow transplantation in leukemia patients: analysis of prognostic factors and results in 136 patients

BACKGROUND AND PURPOSE

The results of a single-institution series of patients with chronic and acute leukemias are analyzed with regard to literature-reported predictor variables.

MATERIALS AND METHODS

Between 1985 and 1994, 136 patients, 82 patients with chronic myeloid leukemia (CML) and 54 with acute leukemia (AL), received a uniform preparatory regimen of fractionated total body irradiation (TBI; 12 Gy in 3 days) plus different chemotherapy regimens before bone marrow transplantation. Eighty-six patients were considered to be in early phase of disease (CML in chronic phase or AL in first complete remission) and 50 in advanced phase (all those beyond first remission or first chronic phase). Ninety-five patients received unmanipulated allogeneic BM, and 41 T-lymphocyte-depleted BM.

RESULTS

The 5-year overall survival (OS) and disease-free survival (DFS) of the whole series were 43% and 31%, and median survival was 43 and 10 months, respectively. A Cox proportional hazard model identified variables related to overall and disease-free survival. For OS, graft versus host disease (GVHD) was the first independent variable (P < 0.0001), followed by age (P < 0.001), T-depletion (P < 0.01), disease status (P < 0.05) and type of leukemia (P < 0.05). With regard to DFS, only T-depletion (P < 0.0001), disease status (P < 0.01) and GVHD (P < 0.01) resulted predictor factors. Early complications after BMT were reported in 59 patients, TBI-induced delayed toxicity in 9 patients, and 16 patients suffered late complications.

CONCLUSIONS

Our results confirm the curability of early phase leukemias with standard fractionated TBI-induced Allogeneic bone marrow transplantation (ABMT). With an homogeneous fractionated TBI schedule as employed in our series, T-cell depletion negatively affected the outcome.

Lethal pulmonary toxicity after autologous bone marrow transplantation/peripheral blood stem cell transplantation for hematological malignancies

BACKGROUND AND PURPOSE

Retrospective evaluation of the incidence of lethal pulmonary complications (LPC) with special emphasis on interstitial pneumonia (IP) in a large group of patients homogeneously treated with hyperfractionated total body irradiation (HTBI) before autologous bone marrow transplantation (ABMT) or peripheral blood stem cell transplantation (PBSCT) for hematological malignancy. The factors influencing IP are discussed.

MATERIALS AND METHODS

Of 260 patients (maximum follow-up 137 months) that were treated with ABMT or PBSCT for hematological neoplasms between 1982 and 1994, 209 patients received HTBI and could be evaluated with respect to lethal pulmonary complications and especially lethal interstitial pneumonia. For most patients (n = 155), the HTBI dose was 14.4 Gy (lung dose 9-9.5 Gy) given in 12 fractions over 4 days. Twenty-one patients received a total dose of > or =15 Gy with pulmonary doses of 9-10.5 Gy.

RESULTS

The actuarial overall 5-year survival for all 209 patients evaluated was 44 +/- 4%, enabling valid evaluation with respect to lethal pulmonary toxicity. The actuarial incidence of all LPC during the first year was calculated as being 8 +/- 2%. The actuarial incidence of lethal IP is certainly lower and was estimated to be between 3 and 5% for all patients. The overall treatment-related mortality was 12% in 188 patients that received a total dose of <15 Gy and 24% among the patients treated with a total dose of > or =15 Gy.

CONCLUSION

ABMT/PBSCT, like other transplant modalities without significant graft versus host disease (GvHD), has a low transplant-related mortality, a very small rate of overall LPC and a low incidence of lethal IP after HTBI. Doses up to 14.4 Gy with lung doses of 9-9.5 Gy can be administered safely. For total doses of > or =15 Gy with lung doses of 9-10.5 Gy, the risk of serious transplant-related complications cannot yet be finally assessed but such higher doses should be considered with caution because of the possibility of increasing toxicity in organs other than the lung.

Interstitial pneumonitis in acute leukemia patients submitted to T-depleted matched and mismatched bone marrow transplantation

PURPOSE

To identify factors that could contribute to interstitial pneumonitis (IP), which remains one of the major causes of morbidity and mortality after both matched and mismatched bone marrow transplantation (BMT).

METHODS AND PATIENTS

Ninety acute leukemia patients received an allogeneic T-depleted matched (n = 54) or mismatched (n = 36) BMT. They were preconditioned with total body irradiation (TBI), thiotepa, rabbit anti-thymocyte globulin, and cyclophosphamide. The TBI scheme was hyperfractionated in matched, and a single dose in mismatched patients. The dose to the lungs was reduced in both groups.

RESULTS

Five of the 54 matched patients developed IP. All cases were fatal. There were 16 cases of IP, 13 fatal, in the mismatched group. The probability of developing IP was 11.3 +/- 4.9% and 48.6 +/- 9.0%, respectively. The between-group difference was statistically significant (p < 0.0001). The type of transplant and the TBI scheme were the most important parameters for IP development in univariate analysis, whereas acute graft-versus-host disease, disease stage and sex were nonsignificant. Median follow-up was 342 days (range 17-2900).

CONCLUSIONS

The low incidence of IP in matched patients and the lack of idiopathic cases are evidence for the validity of the TBI schedule. In contrast, the incidence in mismatched patients remains too high; therefore, new strategies should be studied in an attempt to lower it.

[Total body irradiation: current indications]

The choice of dose and fractionation for total body irradiation is made difficult by the large number of considerations to be taken into account. The outcome of bone marrow transplantation after total body irradiation can be understood in terms of tumour cell killing, engraftment, and normal tissue damage, each of these endpoints being influenced by irradiation-, disease-, transplant-, and patient-related factors. Interpretation of clinical data is further hampered by the overwhelming influence of logistic constraints, the small numbers of randomised studies, and the concomitant variations in total dose and fraction size or dose rate. So far, three cautious conclusions can be drawn in order to tentatively adapt the total body irradiation schedule to clinically-relevant situations. Firstly, the organs at risk for normal tissue damage (lung, liver, lens, kidney) are protected by delivering small doses per fraction at low dose rate. This suggests that, when toxicity is at stake (e.g., in children), fractionated irradiation should be preferred, provided that interfraction intervals are long enough. Secondly, fractionated irradiation should be avoided in case of T-cell depleted transplant, given the high risk of graft rejection in this setting. An alternative would be to increase total (or fractional) dose of fractionated total body irradiation, but this approach is likely to induce more normal tissue toxicity. Thirdly, clinical data have shown higher relapse rates in chronic myeloid leukaemia after fractionated or low dose rate total body irradiation, suggesting that fractionated irradiation should not be recommended, unless total (or fractional) dose is increased. Total body irradiation-containing regimens, primarily cyclophosphamide/total body irradiation, are either equivalent to or better than the chemotherapy-only regimens, primarily busulfan/cyclophosphamide. Busulfan/cyclophosphamide certainly represents a reasonable alternative, especially in patients who may not be eligible for total body irradiation because of prior irradiation to critical organs.

The radiobiological basis of total body irradiation

Total body irradiation (TBI) is an all-pervasive systemic treatment modality which is well suited to the sterilization of small numbers of widely dispersed radiosensitive cells. This makes it attractive for the treatment of leukaemia or lymphoma in remission. It is unlikely that hypoxia or repopulation will be a problem in TBI treatment of leukaemia, and clonal resistance to radiation occurs less readily than to drugs. Leukaemic cells are often radiosensitive with poor repair capacities but considerable variation is seen in laboratory studies and leukaemias may be highly individual. It is possible that programmed cell death (apoptosis) contributes to leukaemic cell killing and variability of apoptosis may give rise to biological individuality. Molecular methodologies may now be used to monitor leukaemic cell populations and may enable semi-quantitative predictive assays of radiosensitivity. When the malignant cell population is not uniformly distributed throughout the body, as in lymphoma, non-uniform TBI is appropriate, e.g. by addition of local boosts or by the combination of TBI with radiolabelled antibody treatment. Major side-effects mostly relate to critical organs with late-responding characteristics (low alpha/beta ratio, high sensitivity to fraction size or dose rate). The radiobiological basis of developmental effects in children is not well understood. In future, improved selectivity of TBI may come from molecular biological strategies to sensitize malignant cells and to protect normal tissues.

MarCell software for modeling bone marrow radiation cell kinetics

Differential equations were used to model cellular injury, repair, and compensatory proliferation in the irradiated bone marrow. Recently, that model was implemented as MarCell, a user-friendly MS-DOS computer program that allows users from a variety of technical disciplines to evaluate complex radiation exposure. The software allows menu selections for different sources of ionizing radiation. Choices for cell lineages include progenitor, stroma, and malignant, and the available species include mouse, rat, dog, sheep, swine, burro, and man. An attractive feature is that any protracted irradiation can be compared with an equivalent prompt dose (EPD) in terms of cell kinetics for either the source used or for a reference such as 250 kVp x rays or 60Co. EPD is used to mean a dose rate for which no meaningful biological recovery occurs during the period of irradiation. For human as species, output from MarCell includes: risk of 30-day mortality; risk of whole-body cancer and leukemia based either on radiation-induced cytopenia or compensatory cell proliferation; cell survival and repopulation plots as functions of time or dose; and 4-week recovery following treatment.

[Splenic irradiation in myeloid hemopathies: evaluation and toxicity]

PURPOSE

Splenomegaly occurs frequently in patients with myelofibrosis (MF) or chronic myelogenous leukemia (CML), indicating significant splenic metaplasia. Symptomatic radiation therapy can be delivered, but the best irradiation scheme is still unknown. Results of splenic irradiation in patients with myelofibrosis or chronic leukemia were retrospectively analyzed.

PATIENTS AND METHODS

There were 24 patients: 15 presented with MF and 9 with CML. Median irradiation doses were 9.8 and 7.7 Gy, respectively. The hematologic toxicity was moderate (except for platelets in the acute phase of the disease).

RESULTS

No toxicity was observed. Various factors predictive of the response to radiation therapy are described. While high (around 14 Gy) radiation therapy dose appears necessary for MF and should be started before the increase in transfusion need, huge splenomegalies should be excluded in regard to CML. As for other cases, the optimal dose is still unclear, but should probably be high enough, ie, around 10 Gy.

CONCLUSION

To further study and better understand biological mechanisms underlying response to radiotherapy in patients with MF, prospective radio-chemotherapy phase II trials should be conducted in both CML and MF patients.

Intercellular adhesion molecule 1 knockout abrogates radiation induced pulmonary inflammation

Increased expression of intercellular adhesion molecule 1 (ICAM-1; CD54) is induced by exposure to ionizing radiation. The lung was used as a model to study the role of ICAM-1 in the pathogenesis of the radiation-induced inflammation-like response. ICAM-1 expression increased in the pulmonary microvascular endothelium and not in the endothelium of larger pulmonary vessels following treatment of mice with thoracic irradiation. To quantify radiation-induced ICAM-1 expression, we utilized fluorescence-activated cell sorting analysis of anti-ICAM-1 antibody labeling of pulmonary microvascular endothelial cells from human cadaver donors (HMVEC-L cells). Fluorochrome conjugates and UV microscopy were used to quantify the fluorescence intensity of ICAM in the irradiated lung. These studies showed a dose- and time-dependent increase in ICAM-1 expression in the pulmonary microvascular endothelium. Peak expression occurred at 24 h, while threshold dose was as low as 2 Gy. To determine whether ICAM-1 is required for inflammatory cell infiltration into the irradiated lung, the anti-ICAM-1 blocking antibody was administered by tail vein injection to mice following thoracic irradiation. Inflammatory cells were quantified by immunofluorescence for leukocyte common antigen (CD45). Mice treated with the anti-ICAM-1 blocking antibody showed attenuation of inflammatory cell infiltration into the lung in response to ionizing radiation exposure. To verify the requirement of ICAM-1 in the inflammation-like radiation response, we utilized the ICAM-1 knockout mouse. ICAM-1 was not expressed in the lungs of ICAM-1-deficient mice following treatment with thoracic irradiation. ICAM-1 knockout mice had no increase in the inflammatory cell infiltration into the lung in response to thoracic irradiation. These studies demonstrate a radiation dose-dependent increase in ICAM-1 expression in the pulmonary microvascular endothelium, and show that ICAM-1 is required for inflammatory cell infiltration into the irradiated lung.

Final height and hormonal function after bone marrow transplantation in children

AIM

To analyze final height and hormonal function in long-term survivors of bone marrow transplantation (BMT).

PATIENTS

Group 1 consisted of 16 patients (10 boys) with a hematologic malignancy, mostly leukemia, conditioned for BMT with total body irradiation (TBI), 7.5 to 12 Gy, and cyclophosphamide. Group 2 consisted of 14 patients (9 boys) with severe aplastic anemia, conditioned with chemotherapy only.

RESULTS

In group 1, patients achieved a reduced final height after BMT. The difference between the height standard deviation score (SDS) at BMT and the height SDS at final height was -1.96 (0.82) SDS in boys and -0.92 (0.71) SDS in girls (p = 0.0001, and p = 0.02 respectively). Final height was also lower than target height (boys, p = 0.01; girls, p = 0.03). Prepubertal growth in the first 3 years after BMT was normal but pubertal height gain was decreased. The patients in group 2 achieved normal height. Thyroid function and adrenal function were normal in all patients, and no growth hormone deficiency was detected. Serum follicle-stimulating hormone values after BMT were increased in all group 1 patients, with return to normal in two patients. Serum luteinizing hormone values were increased in all group 1 girls, with recovery in one girl. Normal serum luteinizing hormone values and spontaneous puberty were found in all group 1 boys. In group 2, disturbances in gonadotropins were seen only in three boys and two girls.

CONCLUSION

In patients treated in childhood with BMT after chemotherapy and TBI with 7.5 Gy or more, final height is compromised because of blunted growth in puberty. Patients who had not received TBI suffered no height loss. In the majority of patients, the combination of chemotherapy and TBI also resulted in irreversible disturbances of gonadal function.

Repair capacity of mouse lung after total body irradiation alone or combined with cyclophosphamide

PURPOSE

Cyclophosphamide (CTX) combined with fractionated total body irradiation (TBI) is frequently used in the conditioning of patients prior to bone marrow transplantation (BMT). This study was performed to investigate the effect of CTX on the repair capacity of lung tissue after TBI in a mouse model for BMT.

MATERIALS AND METHODS

TBI was given as a single fraction, 3 fractions in 3 days (Fx 3) or 9 fractions in 3 days (Fx 9) either alone or 24 h after a single dose of CTX. The single fraction TBI was given at either high dose rate (HDR) of 0.71 Gy/min or low dose rate (LDR) of 0.08 Gy/min. All mice were transplanted 4-6 h after the last TBI fraction. Lung damage was assessed using ventilation rate (VR) and lethality between 28 and 180 days. The repair capacity of lung tissue was estimated using the direct analysis method with the probability of reaching the end point described by a logistic formulation of the linear quadratic model.

RESULTS

The VR data confirmed the high repair capacity of lung tissue with an alpha/beta ratio of 4.4 Gy though with a wide 95% confidence interval (CI = 0.03-10.5). Giving CTX before fractionated TBI markedly reduced the doses needed to cause response in 50% of the animals. The sparing effect of using fractionated TBI was still evident in the combined CTX-TBI schedules. The estimated alpha/beta ratio was 1.6 Gy (CI = 0.01-4.7) which is within the range of values reported after thoracic radiation only. On the other hand, the sparing effect seen in going from single fraction HDR to LDR was completely abolished when CTX was given 24 h before TBI. The same pattern was repeated when lethality between 28-180 days was used. Yet, the use of lethality to estimate lung damage in a TBI model, markedly underestimated the repair capacity.

CONCLUSIONS

These results confirm the high repair capacity of lung tissue after TBI and emphasize the value of using a specific end point in testing lung damage after TBI. It also shows that there can be a negative effect of CTX on the repair capacity of lung damage which is more pronounced when CTX is followed (24 h later) by single fraction TBI at LDR than by a fractionated TBI course over a few days.