Variation of resection margins in oral cancer in dependence of tumor stage and subsite - a retrospective cohort study.

OBJECTIVES: Surgical resection is a key component of the treatment of head and neck cancer and the achievement of free surgical margins are essential for the patients' outcome in terms of survival. While there is a general recommendation for a free resection range of 5 mm, up to date, there is a lack of investigations on the quality of tumor resection in dependence of affected subsite and tumor stage. In the presented study, predictors for the achieved resection margins in surgically treated oral squamous cell carcinomas were analyzed. MATERIALS AND METHODS: A cohort of 567 patients was included in a retrospective analysis and resection status with exact margin ranges were analysed. Tumor stage, affected subsite and the results of the intraoperative frozen section analysis were assessed. Primary endpoint was the achieved resection margin in mm, secondary endpoints were overall and progression-free survival. RESULTS: The observed mean values of minimal resection margins differed significantly between the investigated subsites (p = 0.042),pathological tumor stages (p < 0.001) and in tumors which demonstrated perineural infiltration (Pn1, p = 0.002). Furthermore, there was a significant impact of the results of the intraoperative frozen section analysis on progression-free and overall survival (p < 0.001). CONCLUSIONS: Our data clearly indicate that resection status differs between tumors of different subsites and tumor stages. CLINICAL RELEVANCE: Clinical procedures should be adapted in order to achieve similar certainty in all resections, and, thus to improve patients' outcome.

Second primary squamous cell carcinoma of the oral cavity - a retrospective cohort study of therapeutic procedures and oncological outcome.

OBJECTIVES: In the presented study, the occurrence rates of second primary oral carcinomas and their prognostic relevance were analyzed. MATERIALS AND METHODS: All patients with surgically treated oral squamous cell carcinomas within the years 2010 and 2022 in our department were included in this retrospective cohort study. Two groups were designed including patients with second primary carcinomas and patients with local tumor recurrences. Occurrence rates, tumor stages and applied therapies were assessed. Primary outcome was overall survival in dependence of the index tumor. Secondary outcomes were overall survival in dependence of local recurrences or second primary tumors. RESULTS: An overall number of 908 patients was included in the analysis. 98 patients (10.8%) developed a second primary oral squamous cell carcinoma. Patients with second primary tumors presented significantly (p < 0.001) better overall survival in dependence of the index tumor compared to patients suffering from local recurrences. There was no significant difference in overall survival (p = 0.4) in dependence of the date of second primary tumor or local recurrence. Patients with second primary tumors were more likely to receive surgery-based therapy compared to patients with local recurrences who more frequently received definitive radiotherapy. CONCLUSION: Our data indicates different clinical courses in terms of therapy and survival of patients suffering from second primary tumors compared to patients with local tumor recurrences. This may be due to a more aggressive biology of local recurrences and earlier detection of second primaries due to oncological follow-up of the index tumor. CLINICAL RELEVANCE: The differentiation of local tumor recurrences and second primary tumors is of clinical relevance, as applicable therapies and resulting prognosis may differ significantly.

Dynamic Up-Regulation of PD-L1 in the Progression of Oral Squamous Cell Carcinoma.

The introduction of immune checkpoint inhibition for recurrent and metastatic head and neck cancer has brought a new treatment option for patients suffering from advanced oral cancers without a chance for curation using surgery or radiotherapy. The application of immune checkpoint inhibitors in most cases is based on the expression levels of PD-L1 in the tumor tissue. To date, there is a lack of data on the dynamic regulation of PD-L1 during disease progression. Therefore, this study aimed to evaluate the expression levels of PD-L1 in a large cohort of patients (n = 222) with oral squamous cell carcinoma including primary and recurrent tumors. Semiautomatic digital pathology scoring was used for the assessment of PD-L1 expression levels in primary and recurrent oral squamous cell carcinoma. Survival analysis was performed to evaluate the prognostic significance of the protein expression at different stages of the disease. We found a significant up-regulation of PD-L1 expression from primary disease to recurrent tumors (mean PD-L1 H-scores: primary tumors: 47.1 ± 31.4; recurrent tumors: 103.5 ± 62.8, p < 0.001). In several cases, a shift from low PD-L1 expression in primary tumors to high PD-L1 expression in recurrent tumors was identified. Multivariate Cox regression analysis did not reveal a significantly higher risk of death (p = 0.078) or recurrence (p = 0.926) in patients with higher PD-L1 expression. Our findings indicate that the exclusive analysis of primary tumor tissue prior to the application of checkpoint blockade may lead to the misjudgment of PD-L1 expression in recurrent tumors.

HLA-E and Its Soluble Form as Indicators of a Sex-Specific Immune Response in Patients with Oral Squamous Cell Carcinoma.

The human leukocyte antigene E (HLA-E) is associated with tumorigenesis in various cancers. Immunoncology along with sex-specific aspects in cancer therapy are now in scientific focus. Therefore, immunohistochemical HLA-E expression was retrospectively analysed in a cohort of oral squamous cell carcinomas (OSCC) after surgical therapy. Then, serum concentration of HLA-E (sHLA-E) was quantified in a prospective cohort by enzyme-linked immunosorbent assay. High HLA-E expression was associated with advanced UICC stage (Spearman's correlation: p = 0.002) and worse survival (Cox-regression: progression-free survival: hazard ratio (HR) 3.129, confidence range (CI) 1.443-6.787, p = 0.004; overall survival: HR 2.328, CI 1.071-5.060, p = 0.033). The sHLA-E concentration was significantly higher in the control group than in tumor group (Mann-Whitney U-test (MW-U): p = 0.021). Within the tumor group, women showed significantly higher sHLA-E levels than men (MW-U: p = 0.049). A closer look at the tumor group and the control group showed that gender-specific differences exist: while no differences in sHLA-E concentration were detectable between female subjects of tumor group and control group (MW-U: p = 0.916), male subjects of tumor group had a significantly lower sHLA-E concentration compared to those of control group (MW-U: p = 0.001). In summary, our results provide evidence for sex-specific differences in immune responses in OSCC. This fact should be considered regarding future immunotherapy regimens.

Clinical outcome and prognostic factors in recurrent oral squamous cell carcinoma after primary surgical treatment: a retrospective study.

OBJECTIVES: Survival for patients with recurrent oral squamous cell carcinoma is usually poor, and the most effective treatment has not yet been clearly defined. The present study evaluates the outcome in radiotherapy-naïve patients after recurrence of oral squamous cell carcinoma with respect to different treatment modalities including surgery, radiation, chemoradiation, and palliative treatment. PATIENTS AND METHODS: In this retrospective study, we included all patients with primary oral squamous cell carcinoma who received exclusively surgical therapy between 2010 and 2020 and who suffered from locoregional recurrence in their follow-up. Patients with previous adjuvant therapy were excluded from this protocol. Clinical and pathological parameters were collected and statistically evaluated. Survival analysis was performed according to Kaplan-Meier. The primary endpoints were overall and progression-free survival in dependance of treatment strategy for recurrent tumors. RESULTS: Out of a total of 538 patients with surgically treated primary oral squamous cell carcinoma, 76 patients met the inclusion criteria. The mean follow-up was 38 ± 32 months. Patients who received surgically based therapy had a significantly better outcome in terms of disease-free survival (DFS) and overall survival (OS) (DFS p < 0.001; OS p < 0.001). The presence of regional metastases and a short disease-free interval (DFI) between primary and recurrent cancer were significant predictors for adverse outcomes (DFI p < 0.001). CONCLUSION: We recommend primary surgical therapy for radiotherapy-naïve patients with recurrent oral squamous cell carcinoma, supplemented by risk-adapted adjuvant therapy. CLINICAL RELEVANCE: Surgical therapy continues to play a central role in the treatment of radiotherapy-naïve patients with recurrent oral squamous cell carcinoma.

S1-Guideline: Microscopically controlled surgery.

Microscopically controlled surgery (MCS) comprises various methods allowing histologically proven complete resection of malignant tumors while at the same time sparing the tumor-free tissue in the immediate vicinity as much as possible. All procedures subsumed under MCS have in common the marking of the excised tissue for topographical orientation, which provides an assignment of remaining tumor remnants. Indications for MCS are malignant skin tumors in problem localizations as well as aggressive subtypes of skin tumors. Established indications for MCS include basal cell carcinoma, cutaneous squamous cell carcinoma, Bowen's disease as well as Bowen's carcinoma, dermatofibrosarcoma protuberans, melanoma in chronically light-damaged skin as well as acral lentiginous melanoma and Merkel cell carcinoma. For other tumors such as extramammary Paget's disease and various cutaneous sarcomas, evidence exists that MCS has demonstrated benefits, such as local recurrence rates. In addition, MCS is indicated when it is foreseeable that a complex closure technique is required and complete resection of the tumor must be assured. Various methods of MCS have been described, including 3D histology, horizontal method and Mohs surgery. A close cooperation of qualified surgeons and (dermato)pathologists as well as laboratory staff is essential for the successful application of MCS.

A six-gene expression signature related to angiolymphatic invasion is associated with poor survival in laryngeal squamous cell carcinoma.

PURPOSE: Angiolymphatic invasion serves as a histopathological risk factor for unfavorable survival in head and neck squamous cell carinoma. The aim of the study was to explore  the molecular mechanisms characterizing angiolymphatic invasion and therefore identify a gene expression signature related to angiolymphatic invasion. METHODS: Gene expression analysis of head and neck squamous cell carcinoma was carried out based on clinical and whole genome expression data provided by The Cancer Genome Atlas. Results were validated in an independent cohort of laryngeal squamous cell carcinoma and confirmed by immunohistochemistry staining. RESULTS: A gene expression signature consisting of six genes (SHH, SLC18A3, LCE3E, LCE2B, LCE3D and DSG-1) related to angiolymphatic invasion was identified. The gene expression profile identified a subset of patients with decreased overall survival (p = 0.02, log rank test), which was most prominent for patients with laryngeal squamous cell carcinoma (p = 0.004, log rank test). Furthermore, these patients showed a significant shorter progression-free survival (p = 0.002, log rank test). By use of this gene expression signature, patients at high risk of recurrence could be identified even if morphological changes were not yet recognizable. CONCLUSION: Angiolymphatic invasion is characterized by a distinct histopathological phenotype and specific gene expression signature. The newly identified signature might serve as a reliable predictor of outcome in laryngeal cancer and add additional benefit to histopathological evaluation.

Definitive radiotherapy vs. postoperative radiotherapy for lower gingival carcinomas of the mandible : A single-center report about outcome and toxicity.

PURPOSE: To assess radiotherapy (RT) outcomes in patients with gingival carcinoma and growth up to or involvement of the lower jaw bone. METHODS: This was a retrospective analysis of 51 patients with squamous cell carcinomas of the gingiva. Patients received definitive (group 1, 31.4%) or postoperative (group 2, 66.7%) RT between 2005 and 2017 at the Department of Radiation Oncology, University Hospital Heidelberg. The primary endpoint was overall survival (OS) in both treatment groups. Other endpoints were local-disease-free survival (LDFS), progression-free survival (PFS) and treatment-related toxicity (Common Terminology Criteria for Adverse Events, CTCAE, Version 4.03). RESULTS: Median age at first diagnosis was 63 years. All patients had a local advanced disease (American Joint Commission on Cancer [AJCC] stage III-IV). After a median follow-up of 22 months (range 3-145 months), 20 patients (39.2%) were still alive. At 5 years, OS rate was 36.6%. No significant differences in OS (p = 0.773), PFS (p = 0.350) and LDFS (p = 0.399) were observed between the two groups. Most common higher-grade acute RT-related complications (≥ grade 3) were dermatitis (78.2%), oral mucositis (61.7%), xerostomia (51.5%), and loss of taste (74.6%). Three cases (5.8%) of osteoradionecrosis (ORN) of the lower jaw were detected after 15-31 months. CONCLUSIONS: Definitive and postoperative RT have similar treatment outcomes for patients with lower gingiva carcinomas of the lower jaw. The most common acute complications (grade ≥3) were dermatitis, oral mucositis, xerostomia and loss of taste.

Free Vastus Intermedius Muscle Flap: A Successful Alternative for Complex Reconstruction of the Neurocranium in Preoperated Patients.

The reconstruction of large cranial and scalp defects is a surgical and esthetic challenge. Single autologous tissue transfer can be insufficient due to the defect size and the anatomic complexity of the recipient site. Alloplastic patient-specific preformed implants can be used to recover hard tissue defects of the neurocranium. Nevertheless, for long-term success adequate soft tissue support is required. In this brief clinical study, the authors describe calvarian reconstruction in a 33-year-old patient with wound healing disorder after an initial resection of ependymoma. The patient suffered from osteonecrosis and wound breakdown in the fronto-parietal region. An alloplastic polymethylmethacrylate implant for hard tissue support was manufactured based on 3-dimensional visualization of a computed tomography scan. After the resection of remaining pathologic bone from earlier surgical procedures, the alloplastic implant was inserted to achieve functional coverage of the brain. Due to anatomic variation of donor site vessels during anterolateral thigh flap preparation, the authors performed a vastus intermedius free flap as a new muscular flap for craniofacial reconstruction. The authors achieved excellent functional and esthetic results. The muscular vastus intermedius free flap in combination with a split skin graft proves to be a new alternative to the anterolateral thigh flap for soft tissue reconstruction of the neurocranium.

Phosphorylation of AKT(Ser473) serves as an independent prognostic marker for radiosensitivity in advanced head and neck squamous cell carcinoma.

Head and neck squamous cell carcinoma (HNSCC) is frequently characterized by high resistance to radiotherapy, which critically depends on both altered signaling pathways within tumor cells and their dynamic interaction with the tumor microenvironment. This study evaluated the prognostic value of the phosphorylation status of AKT on Ser473 and Thr308 for the clinical outcome of patients with advanced HNSCC on radiotherapy. Furthermore, we investigated the impact of AKT(Ser473) phosphorylation [p-AKT(Ser473)] in the context of radioresistance using ex vivo tissue cultures that resemble the complex tissue architecture and paracrine interaction with the tumor microenvironment. In a cohort of 120 patients with advanced HNSCC, who were treated with primary or adjuvant radiotherapy, a significant association was found between relative p-AKT(Ser473) levels and overall survival (p = 0.006) as well as progression-free survival (p = 0.021), while no significant correlation was revealed for relative p-AKT(Thr308) levels. In ex vivo tissue cultures p-AKT(Ser473) levels were increased upon irradiation and treatment with the PI3K inhibitor LY294002 inhibited both basal and irradiation induced AKT(Ser473) phosphorylation. Strikingly, pretreatment with LY294002 sensitized tissue cultures derived from primary and recurrent tumors to radiotherapy as determined by impaired tumor cell proliferation and enhanced DNA damage. In conclusion, phosphorylation status of AKT(Ser473) in tumor specimens serves as a novel biomarker to identify patients with advanced HNSCC at high risk for treatment failure following radiotherapy, and our data from ex vivo tissue cultures support the assumption that pharmacological inhibition of AKT(Ser473) phosphorylation might circumvent radioresistance to improve efficiency and reduce toxicity of current treatment modalities.

Gait asymmetries after fibular free flap harvest: A cross-sectional observational study.

BACKGROUND: The ability to walk safely after head and neck reconstruction with fibular free flaps in tumor surgery is a high priority for patients. In addition, surgeons and patients require objective knowledge of the functional donor-site morbidity. However, the effects of fibular free flap surgery on gait asymmetries have only been studied for step length and stance duration. This study analyses whether patients who have undergone fibular free flap reconstruction have enduring gait asymmetries compared to age-matched controls. METHODS: Patients who underwent head and neck reconstruction with fibular free flaps between 2019 and 2023 were recruited, as well as age-matched controls. Participants walked on an instrumented treadmill at 3 km/h. The primary outcome measures were 22 gait asymmetry metrics. Secondary outcome measures were the associations of gait asymmetry with the length of the harvested fibula, and with the time after surgery. FINDINGS: Nine out of 13 recruited patients completed the full assessment without holding on to the handrail on the treadmill. In addition, nine age-matched controls were enrolled. Twenty out of the 22 gait asymmetry parameters of patients were similar to healthy controls, while push-off peak force (p = 0.008) and medial impulse differed (p = 0.003). Gait asymmetry did not correlate with the length of the fibula harvested. Seven gait asymmetry parameters had a strong correlation with the time after surgery. INTERPRETATION: On the long-term, fibular free flap reconstruction has only a limited effect on the asymmetry of force-related and temporal gait parameters while walking on a treadmill.

Expression analysis of SOX2 and SOX9 in patients with oral squamous cell carcinoma.

BACKGROUND: Lately SOX2 and SOX9, transcription factors associated with stemness-like phenotypes of cancer cells, have been linked to tumor growth, metastasis, and resistance to therapy. METHODS: This study aimed on evaluating the expression of SOX2 and SOX9 in a large cohort of patients with OSCC including primary and recurrent tumors and corresponding lymph node metastases. Semiautomatic digital pathology scoring was used to determine protein expression and survival analysis was performed to evaluate its prognostic significance. RESULTS: We found a significant downregulation of SOX9 from primary disease to lymph node metastases (p < 0.001). SOX9 expression and the subgroup SOX2lowSOX9high were significantly correlated with worse overall survival (p < 0.05). Additionally, SOX2lowSOX9high expression pattern was confirmed as independent prognosticator for overall survival. CONCLUSIONS: These results indicate the relevant role of SOX2 and SOX9 in patients with OSCC and show the clinical relevance for further investigation on the molecular mechanisms underlying SOX-related gene expression.

Impact of Salvage Surgery on Health-Related Quality of Life in Oral Squamous Cell Carcinoma: A Prospective Multi-Center Study.

BACKGROUND: Patients with recurrent oral squamous cell carcinoma (OSCC) have limited treatment options. Salvage surgery offers potential curative therapy. The need for extensive ablative surgery together with microvascular reconstruction implies invasive and painful treatment with questionable functional outcome. To address the impact of salvage surgery on the health-related quality of life (HRQoL) of patients suffering from recurrent OSCC, a multi-center prospective analysis was initiated. MATERIAL AND METHODS: Patients with recurrent OSCC from 2015 to 2022 at two German cancer centers were included. Interdisciplinary tumor board decisions determined surgery as the only curative treatment modality. HRQoL, was assessed via a EORTC questionnaire (European Organization for Research and Treatment of Cancer-EORTC: QLQ-C30 and QLQ-H&N35) in dependence of the recurrent tumor stage. Patients completed the questionnaires once before surgery (baseline) and then every 3 months during follow-up or up to the end of treatment. RESULTS: In total, 55 patients were included. The mean follow-up period was 26.7 ± 19.3 months. Global health status showed superior mean scores after 12 months (60.83 ± 22.58) compared to baseline (53.33 ± 26.41) in stage 1 and 2 recurrent tumors. In advanced recurrent tumors' mean scores for global health showed only minor positive differences after 12 months (55.13 ± 22.7) compared to baseline (53.2 ± 25.58). In terms of the mouth pain, mean scores were lower after salvage surgery in small recurrent tumors after 12 months (20.37 ± 17.73) compared to baseline (41.67 ± 33.07; Wilcoxon two-sample signed-rank test p = 0.028). In advanced recurrent tumors, a significant reduction in mean scores was detected 3 months after salvage surgery (29.7 ± 22.94) compared to baseline (47.76 ± 25.77; Wilcoxon two-sample signed-rank test p = 0.003). Up to 12 months, swallowing function was evaluated inferior compared to baseline independent of tumor stage (Mean score recurrent stage I/II: 12-months 48.15 ± 27.57, baseline 28.7 ± 22.87; stage III/IV: 12-months 49.36.42 ± 27.53; baseline 30.13 ± 26.25). CONCLUSION: Improved HRQoL could be obtained in advanced recurrent OSCC after salvage surgery despite reduced swallowing function. In small recurrent tumors, overall, HRQoL was superior to baseline. Salvage surgery positively affected pain burden. For advanced recurrent tumors, important pain relieve could be observed as soon as 3 months after surgery.

Surgical Treatment of Carcinomas of the Oral Minor Salivary Glands-Oncological Outcome in Dependence of Tumor Entity and Therapeutic Strategies.

The aim of this study was to analyze the clinical outcomes of three types of minor salivary gland carcinomas (adenoid-cystic carcinomas (ACC), adeno carcinomas not otherwise specified (AC-NOS), and mucoepidermoid carcinomas (MEC)) after primary surgical therapy. A retrospective cohort study was designed and patients with cancer of the minor oral salivary glands treated in our department in the years 2011 to 2022 were included. Clinicopathological data were evaluated to compare overall survival and progression-free survival between the entities. Eighty-one patients were included. The rates of cervical metastases were 38.9% for ACC, 25% for MEC, and 9.1% for AC-NOS. ACC exhibited significantly higher rates of local and systemic disease recurrence (p = 0.02), and the presence of neck node metastases was confirmed as an independent prognostic factor for progression-free survival (p = 0.014). Treatment success in terms of oncological outcome varied significantly between the different entities and implies different treatment regimens for each tumor entity.

Free-Flap Reconstruction in Early-Stage Squamous Cell Carcinoma of the Oral Cavity-A Prospective Monocentric Trial to Evaluate Oncological Outcome and Quality of Life.

Surgery is generally accepted as standard treatment in oral cancer, but the reconstructive procedures remain a matter of debate. The aim of this study was to evaluate oncological outcome and quality of life following surgical resection and free-flap reconstruction in patients with early oral squamous cell carcinoma. The presented trial was performed as a prospective, single-center observation study. Inclusion criteria were primary surgery in early-stage oral squamous cell carcinoma with free-flap reconstruction. Endpoints were overall and progression-free survival and quality of life up to 24 months after surgery. Twenty-six patients were included. Overall survival was 100% and progression-free survival was 92.3% in a maximum follow-up time of 21 months. Global quality of life showed no significant alteration after surgery. Patients reported a significant reduction in pain (p = 0.048) and a decreasing impairment of speech one year after surgery (p = 0.021). Free-flap reconstruction is a safe procedure that results in excellent oncological outcome and quality of life. Functional outcome is of high relevance in early-stage tumors of the head and neck and may mostly be affected by reconstructive procedures. Therefore, a prospective evaluation to explore success and the effects of surgical therapy is highly warranted.

IDO1 is highly expressed in macrophages of patients in advanced tumour stages of oral squamous cell carcinoma.

PURPOSE: Strategies for Indolamine-2,3-dioxygenase 1 (IDO1) inhibition in cancer immunotherapy once produced encouraging results, but failed in clinical trials. Recent evidence indicates that immune cells in the tumour microenvironment, especially macrophages, contribute to immune dysregulation and therefore might play a critical role in drug resistance. METHODS: In this study, we investigated the significance of IDO1 expressing immune cells in primary tumours and corresponding lymph node metastases (LNMs) in oral squamous cell carcinoma (OSCC) by immunohistochemistry. The link between IDO1 and macrophages was investigated by flow cytometry in tumour tissue, healthy adjacent tissue and peripheral blood mononuclear cells (PBMCs). IDO1 activity (measured as Kynurenine/Tryptophan ratio) was assessed by ELISAs. RESULTS: High IDO1 expression in tumour-infiltrating immune cells was significantly correlated with advanced stages [Spearman's rank correlation (SRC), p = 0.027] and reduced progression-free survival (multivariate Cox regression, p = 0.034). IDO1 was significantly higher expressed in PBMCs of patients in advanced stages than in healthy controls (ANOVA, p < 0.05) and IDO1+ macrophages were more abundant in intratumoural areas than peritumoural (t test, p < 0.001). IDO1 expression in PBMCs was significantly correlated with IDO1 activity in serum (SRC, p < 0.05). IDO1 activity was significantly higher in patients with LNMs (t test, p < 0.01). CONCLUSION: All in all, IDO1 expressing immune cells, especially macrophages, are more abundant in advanced stages of OSCC and are associated with reduced progression-free survival. Further investigations are needed to explore their role in local and systemic immune response. The IDO1 activity might be a suitable biomarker of metastasis in OSCC patients.

Mitomycin-C-treated peripheral blood mononuclear cells (PBMCs) prolong allograft survival in composite tissue allotransplantation.

BACKGROUND: Composite tissue allotransplantation (CTA) was introduced as a potential treatment for complex reconstructive procedures and has become a clinical reality. Hand and face transplantation, the most widely recognized forms of CTA, have intensified immunological research in this emerging field of transplantation. Mitomycin C (MMC) is an alkylating agent that suppresses allogeneic T-cell responses. MMC-treated dendritic cells/PBMCs have been shown to induce donor-specific tolerance in solid organ allograft transplantations. METHODS: Fully mismatched rats were used as hind limb donors [Lewis (RT1(1))] and recipients [Brown-Norway (RT1(n))]. Fifty-five allogeneic hind limb transplantations were accomplished in six groups. Group A (n = 10) received donor-derived MMC-treated PBMCs on transplantation day. Group B (n = 10) rats received no immunosuppression, group C (n = 10) received FK506 and prednisolon, group D consisted in isograft transplantation without immunosuppression, group E (n = 10) received non-treated PBMCs, and group F (n = 5) received PBS without any donor-derived cells. Rejection was assessed clinically and histologically. RESULTS: In group A, the survival times of the allografts were prolonged to an average of 8.0 d. Rejection was significantly delayed compared with the averages of the corresponding control groups B, E, and F (5.5, 5.9, and 5.8 d). No rejection was seen in control groups C and D. CONCLUSION: These results demonstrate that MMC-treated donor PBMCs significantly prolong allograft survival when administered systemically on the day of transplantation. However, the immunomodulatory effect is relatively modest with further research being required to clarify dose-effect relations, cell characteristics, and an optimized mechanism and timing for cell application.