Cell kinetics of head and neck squamous cell carcinomas. Prognostic implications

Where Do We Look for Markers of Radiotherapy Fraction Size Sensitivity?

The response of human normal tissues to radiotherapy fraction size is often described in terms of cellular recovery, but the causal links between cellular and tissue responses to ionising radiation are not necessarily straightforward. This article reviews the evidence for a cellular basis to clinical fractionation sensitivity in normal tissues and discusses the significance of a long-established inverse association between fractionation sensitivity and proliferative indices. Molecular mechanisms of fractionation sensitivity involving DNA damage repair and cell cycle control are proposed that will probably require modification before being applicable to human cancer. The article concludes by discussing the kind of correlative research needed to test for and validate predictive biomarkers of tumour fractionation sensitivity.

The prognostic implications of the surgical margin in oral squamous cell carcinoma

The prime objective of tumour ablation in oral squamous cell carcinoma (OSCC) is the removal, with a 'margin' of normal tissue, of the whole tumour. Definition of what constitutes margin involvement varies. This study aims to examine the factors associated with close and involved surgical margins in the management of OSCC. A cohort of 200 consecutive patients with previously untreated OSCC provided the material for the study. Various clinical, operative and pathological parameters were related to the status of the surgical margin, as well as time to recurrence, and survival. Cox regression analysis of the survival was also undertaken. Of the 200 patients 107 (53.5%) had clear margins, 84 (42%) close and 9 (4.5%) involved. Poor correlation was found between the status of the surgical margin and clinical factors, but in contrast high correlation between histological indicators of aggressive disease and close or involved surgical margins. These results imply that close surgical margins in OSCC could be regarded as an indictor of aggressive disease.

Staging of the neck in patients with oral cavity squamous cell carcinomas: a prospective comparison of PET, ultrasound, CT and MRI

BACKGROUND

The choice of treatment in patients with oral malignancies depends on accurate pretreatment staging and particularly the detection of lymph node involvement. Therefore staging of the neck should be as accurate as possible.

PATIENTS

One hundred and six patients with histologically proven squamous cell carcinoma of the oral cavity.

STUDY DESIGN

In a prospective study, PET using fluoro-desoxy-glucose (18F-FDG), ultrasound, CT and MRI of head and neck were compared with the postoperative histologic tissue evaluation. Two thousand one hundred and ninety-six neck lymph nodes of 106 patients were investigated. In all patients the tumour was resected and a lymph node dissection was performed.

RESULTS

The diagnostic procedures showed the following results when compared with the histological findings: PET: sensitivity 70%, specificity 82%, accuracy 75%; Ultrasound: 84%, 68%, 76%; CT: 66%, 74%, 70%; MRI: 64%, 69% 66%. Thus PET showed the highest specificity while ultrasound had the highest sensitivity compared with the other staging procedures. A nonsignificant correlation was found between the size of a lymph node metastasis and the ability to detect it. In 10 patients, second primary tumours or distant metastases were detected by PET only.

CONCLUSION

Due to the high number of small lymph node metastases from oral cavity carcinoma, the non-invasive neck staging methods are limited to a maximum accuracy of 76%. Elective neck treatment should be mandatory for all patients with squamous cell carcinoma of the oral cavity.

Cell production rates in human tissues and tumours and their significance. Part II: clinical data

This paper reviews the available data for cell production rates of human tissues and tumours, measured in vivo using halogenated pyrimidine labelling and laser cytometry. The technique has now been widely evaluated, and we draw general inferences from the proliferative data over a broad range of tumour and tissue types. Estimates of the S-phase duration, the time taken for DNA synthesis in cycling cells, are consistent over a narrow range with a median value of around 10 hours, notwithstanding the constraints of the experimental and statistical technique, in normal tissues and tumours. This suggests that Ts values may be a species-specific constant. The more easily measured labelled S-phase fraction, or labelling index, shows much greater intra and intertumour variation within any one tumour class. It may thus be a surrogate for time dependent measurements to a first order approximation. The cell production rate, described by the potential doubling time (Tpot), is remarkably rapid in most tumours, a median value of the order of 5 days, and much faster than clinical volume doubling times for most lesions. The rapid cell production rates in normal tissues and tumours highlight the importance of cell loss in the growth and modelling of biological structures. Cell production rate measurements do not adequately describe the biological aggressiveness of tumours. They may be used to refine adjuvant strategies for radiotherapy and chemotherapy in experimental research. Dynamic halogenated pyrimidine labelling has provided unique and valuable insights into the living biology of human tissues and tumours.

Molecular markers as prognostic factors for local recurrence and radioresistance in head and neck squamous cell carcinoma

Squamous cell carcinoma of the head and neck affects more than 500,000 people worldwide each year. Local-regional recurrence of disease is a common and challenging oncological problem in patients affected by this disease. Identification of risk factors for local relapse after appropriate local therapy with surgery, radiation, or combination therapy remains an active area of clinical research. The recent development of novel molecular markers has resulted in numerous studies evaluating the prognostic significance and potential clinical utility of these markers in identifying patients at risk for local-regional relapse. This article reviews recent studies evaluating molecular markers, including p53, angiogenesis-related markers, cyclin D1, epidermal growth factor receptor, loss of heterozygosity, DNA ploidy, and cell kinetic markers. The potential clinical utility of these markers and future directions along this avenue of investigation are discussed.

The effect of heterogeneity in tumor cell kinetics on radiation dose-response. An exploratory investigation of a plateau effect

PURPOSE

To investigate the effect of heterogeneity in tumor cell kinetics on radiation dose-response curves for a population of patients.

MATERIALS AND METHODS

A series of exploratory calculations have been performed using an improved geometric-stochastic model of tumor cure.

RESULTS

Radiation therapy dose-response curves may plateau, or nearly so, at tumor control levels well below 100%, if a proportion of tumors would grow sufficiently fast to counterbalance the effect of fractionated radiotherapy. If the model assumptions of doubling time heterogeneity are correct, the difference between a short and protracted radiation regimen would be not only in the position and steepness of the radiation dose-response curve, but also in the level of the predicted plateau.

CONCLUSIONS

For a given rate of dose accumulation, the one-sided flattening in dose-response curves at high doses is predicted from the modeling, and determined by the proportion of most radioresistant and rapidly growing tumors. This shows that empirical models of tumor control probability which assume a symmetric sigmoid relationship from 0 to 100% have apparent limitations, seemingly not well acknowledged in the literature.

[Predictive tests of response to radiotherapy. Assessment and perspectives in 1997]

The potential tailoring of radiotherapy modalities to the biological characteristics of individual tumours and normal tissues appears to be an exciting way to improve the therapeutic, ratio in radiation therapy patients. Numerous assays have been proposed to provide the clinician with the biological information necessary to predict the outcome after irradiation and to guide the treatment prescription, but none of them has made its way to daily practice. Major difficulties are due to the technical burden of the procedures, the poor characterization of the assayed cells, and, moreover, the high complexity of tumour and normal tissues biology. The present paper reviews the present status of the assessment of tumour cells radiosensitivity, proliferation and oxygenation. Research remains extremely active in the field of biological predictors of response to irradiation. Future steps forwards are expected from progress in the available technologies, (re-)discovery of apoptosis and investigation of normal tissue tolerance.

Systematic heterogeneity and prognostic significance of cell proliferation in colorectal cancer

The prognosis of colorectal cancer has not significantly changed during the last 30 years. While evaluation of tumour cell proliferation may provide prognostic information, results obtained so far have been contradictory Heterogeneity in tumour cell proliferation may explain these contradictions. With in vivo injection of iododeoxyuridine (IdUrd), estimation of labelling index (LI), S-phase transit time (Ts) and potential doubling time (Tpot) may be performed from a single sample. A total of 109 colorectal cancers were studied after in vivo injection of IdUrd before surgical removal. From each cancer, four to eight samples were processed for both flow cytometrical (FCM) and immunohistochemical (IHC) visualization of IdUrd incorporation. LI/IHC was morphometrically quantified at both the luminal border and the invasive margin of these tumours. LI was significantly higher at the luminal border compared with the invasive margin, although they were correlated with each other. Using combined IHC and FCM methods, rapidly growing colorectal cancers (high LI and/or low Tpot) showed an increased survival (significant for LI at the invasive margin and for Tpot at both the invasive margin and the luminal border) in the entire unselected material and for radically removed Dukes' B tumours. FCM data alone did not discriminate for survival, with the exception of Ts in diploid and radically removed Dukes' B tumours.

Factors influencing the estimates of proliferative labelling indices in rectal cancer

PURPOSE

A detailed analysis was undertaken of some of the factors influencing the estimate of the labelling index (LI).

MATERIALS AND METHODS

Thirty-three human rectal carcinomas were studied for their proliferative activity as measured by the fraction of cells labelled with a single injection of IdUrd 1-8 h before surgical resection. Adjacent specimens were stained both for histological examination and for flow cytometry (FCM) assessment of labelled nuclei.

RESULTS

Two major differences were found. The superficial parts of each tumour almost always had significantly higher LI values than the deep part (34 versus 21%), yielding an average LI of 27%. The flow cytometry average value was much lower (17%). This was partly due to the influence of diploid tumours. There was a marked heterogeneity in the values, both within tumours, between tumours and between techniques. The average LI for the whole group differs by a factor of three, depending on the method of assessment.

CONCLUSIONS

All these values indicate a varying but rapid proliferative turnover of cells, surprisingly being more marked in the superficial region, i.e. the opposite from the proliferation pattern of the normal rectal mucosa. A biopsy, if taken from the superficial part of the tumour, would therefore be biased toward higher values. This has implications for biopsy sampling for cell kinetic analysis. Histological assessment avoids the contaminating effect of stromal cells, allows architectural arrangements to be detected and is presumably a more realistic representation of proliferative activity.

Predictive value of potential doubling time in head and neck cancer patients treated by conventional radiotherapy

PURPOSE

The goal of this study was to investigate the clinical utility of pretreatment measurements of tumor cell kinetics to predict the outcome of patients with squamous cell carcinoma of the head and neck receiving conventional radiotherapy.

METHODS AND MATERIALS

All patients received between 64 and 70 Gy as 2 Gy fractions, five fractions per week. Cell kinetics were assayed rapidly and quantitatively using flow cytometric evaluation of iododeoxyuridine (IdUrd) incorporation, in vivo, from a biopsy removed several hours after the administration of the DNA precursor to the patient prior to the start of treatment.

RESULTS

The measured proliferation parameters were not related to the clinicopathological features of the tumors, emphasizing the independent nature of these parameters. In univariate analysis, nodal involvement was the most important clinical feature of the tumors related to local control followed by Tpot, DNA aneuploidy, and attainment of complete regression at 6 weeks. Of these only Tpot and nodal status maintained significance in multivariate analysis, with respect to loco-regional control. In subgroup analysis, Tpot was able to stratify patients into high or low rate of loco-regional control in node negative patients, in aneuploid tumors and in patients who did achieve complete regression at 6 weeks. For cause specific survival, N-stage was the only parameter that significantly discriminated the prognosis in these patients.

CONCLUSIONS

The conclusion of this study is that Tpot provides clinically important information that can predict patients with a low probability of achieving long-term local control with conventional fractionation. Further improvements to the methodology to address the shortcomings of analyzing diploid tumors may increase the predictive power of the measurement.

Importance of overall treatment time for the outcome of radiotherapy of advanced head and neck carcinoma: dependency on tumor differentiation

PURPOSE

Accelerated repopulation of tumor cells during radiotherapy has been suggested as an important cause of treatment failure in squamous cell carcinoma of the head and neck. Due to tumor heterogeneity, not all tumors may benefit from accelerated radiotherapy at the expense of a lower total dose. This analysis evaluates the impact of histological differentiation on loco-regional control in relation to treatment duration.

PATIENTS AND METHODS

A total of 501 patients with advanced supraglottic and pharyngeal squamous cell carcinoma with known histopathological grading were treated with planned split-course (191 patients) or continuous radiotherapy (310 patients) in two consecutive randomized controlled trials. Irradiation was given 2 Gy per fraction, 5 fractions per week to a dose of 66-68 Gy in 9.5 or 6.5 weeks, respectively.

RESULTS

Overall, split-course and continuous treatment resulted in a 5-year loco-regional control of 30% and 41% (P = 0.007), respectively. However, the detrimental effects of split-course were only found in moderately and well-differentiated tumors, where the 5-year tumor controls were 38% and 21% after continuous and split-course treatment, respectively (P = 0.001). In contrast, in poorly differentiated tumors loco-regional control was obtained in 44% of the cases for continuous and 40% for split-course treatment (P = 0.63).

CONCLUSIONS

It is suggested that the ability to accelerate repopulation may be lost by dedifferentiation, and that prolongation of the overall treatment time only lead to reduced loco-regional control in well to moderately differentiated tumors.

Accelerated radiation therapy for locally advanced squamous cell carcinomas of the oral cavity and oropharynx selected according to tumor cell kinetics--a phase II multicenter study

PURPOSE

A Phase II multicenter trial testing an accelerated regimen of radiotherapy in locally advanced and inoperable cancers of the head and neck, in patients selected on the basis of 5-bromo-2-deoxyuridine/DNA flow cytometry-derived tumor potential doubling time (Tpot).

METHODS AND MATERIALS

From September 1992 to September 1993, 23 patients consecutively diagnosed to have locally advanced, inoperable carcinomas of the oral cavity and the oropharynx, with Tpot of < or = 5 days, received an accelerated radiotherapy regimen (AF) based on a modification of the concomitant boost technique: 2 Gy/fraction once a day, delivered 5 days a week up to 26 Gy, followed by 2 Gy/fraction twice a day, with a 6-h interval, one of the two fractions being delivered as a concomitant boost to reduced fields, up to 66 Gy total dose (off-cord reduction at 46 Gy), shortening the overall treatment time to 4.5 weeks. A contemporary control group of 46 patients with Tpot of >5 days or unknown was treated with conventional fractionation (CF): 2 Gy/fraction once a day, 5 days a week, up to 66 Gy in 6.5 weeks, with fields shrinkage after 46 Gy.

RESULTS

All patients completed the accelerated regimen according to protocol and in the prescribed overall treatment time. Immediate tolerance was fairly good: 65% of the patients in the AF group experienced Grade 3 mucositis vs. 45% in the CF group (p = n.s.). Symptoms related to mucosal reactions seemed to persist longer in AF than in CF patients. The crude proportion of mild (Grades 1 and 2) late effects on skin (p < 0.01) and salivary glands (p < 0.05) was higher in AF than in CF patients, although these reactions did not exceed the limits of tolerance. Three patients in the AF and 1 in the CF arm experienced a late Grade 4 bone complication. Actuarial estimates of severe (Grades 3 and 4) late complications showed a 2-year hazard of 33.3% in the AF arm and 49.7% in CF (p = NS). The actuarial 2-year local control rate of the AF patients was 49.4%, while actuarial 2-year overall survival for the same patients was 43.5%.

CONCLUSION

The results suggested that this accelerated regimen is worth testing in a controlled randomized trial to compare different accelerated schedules. Our findings also confirmed the 5-bromo-2-deoxyuridine/DNA flow cytometry technique as a suitable method of evaluating tumor cell kinetics in multicenter clinical studies, on condition that all measurements are carried out by one most experienced laboratory.

Cell proliferation in renal cell carcinoma--a comparative study of cell kinetic methods

Four different methods of assessing cell proliferation in renal cell carcinoma were compared in a total of 136 samples to analyze their degree of agreement and usefulness. The methods compared were flow cytometric S-phase (S-FCM) analysis, proliferating cell nuclear antigen expression detected by immunohistochemistry (PCNA-IHC), in vivo iododeoxyuridine incorporation analyzed with immunohistochemistry (IdUrd-IHC), and flow cytometry (IdUrd-FCM). The mean S-FCM fraction was 5.9%, compared with a mean PCNA-IHC labeling index of 4.7%. The mean labeling indices obtained by IdUrd-IHC and IdUrd-FCM were 1.2% and 1.7%, respectively. The four methods correlated well with each other. When the methods were compared according to Bland and Altman, good agreement was shown. A statistically significant difference in proliferation between diploid and aneuploid tumor samples was found with all methods (P < 0.001). The results showed that the four different methods provided comparable information on proliferative activity, although different cell cycle compartments were monitored.

Cell kinetic analysis of non-Hodgkin's lymphomas using in vivo iododeoxyuridine incorporation and flow cytometry

The aim of this study was to analyse dynamic cell proliferation parameters in non-Hodgkin's lymphomas. Sixty-one patients with newly diagnosed or with recurrent disease were given iododeoxyuridine (IdUrd) intravenously near 4 h prior to tumour biopsy. After staining with an IdUrd reactive antibody and propidium iodide, S-phase fraction (SPF), labelling index (LI), S-phase duration time (Ts) and potential tumour doubling time (Tpot) were determined by flow cytometry. Thirty-eight samples, 15 low grade (LGM) and 23 high grade (HGM) malignant lymphomas, were possible to evaluate. Twenty-three cases were excluded due to aneuploidy, insufficient amount of material or technical problems. Tpot values varied between 0.8-32.9 days (mean 7.0 days). HGM lymphomas had shorter mean Tpot times than LGM lymphomas (4.8 versus 10.4 days, p = 0.05). For Ts the range was 4.2-20.1 h (mean 9.1 h), and a difference between the two histological groups was demonstrated with a longer mean Ts for HGM compared with LGM cases (10.0 versus 7.8 h, p = 0.04). Tpot showed a negative correlation with SPF (P = 0.003), and Ts demonstrated a positive correlation to SPF (p = 0.02). The clinical significance of the dynamic cell proliferation parameters studied remains to be clarified, but the interrelationships between Ts/SPF and Ts/morphologic subtype might be factors of interest for future prognostic studies in malignant lymphomas.

p53 mutations, protein expression and cell proliferation in squamous cell carcinomas of the head and neck

Thirty-three patients with squamous cell carcinoma of the head and neck region were studied concerning p53 protein expression and mutations in exons 4-9 of the p53 gene using immunohistochemistry, polymerase chain reaction (PCR)-single strand conformation polymorphism analysis and DNA sequencing. Immunoreactivity was found in 64% and p53 gene mutations in 39% of the tumours. Thirty-three per cent of the immunopositive and 50% of the immunonegative tumours were mutated within exons 5-8. In one immunopositive tumour three variants of deletions were observed. Sequencing of the p53 mutated, immunonegative tumours revealed four cases with deletions, one case with a transversion resulting in a stop codon and one case with a splice site mutation which could result in omission of the following exon at splicing. All mutations in the immunonegative tumours resulted in a truncated p53 protein. No association between p53 gene status and expression of proliferating cell nuclear antigen (PCNA) or cell proliferation as judged by in vivo incorporation of the thymidine analogue iododeoxyuridine (IdUrd) was found.

p53 expression and cell proliferation in squamous cell carcinomas of the head and neck

BACKGROUND

In squamous cell carcinoma of the head and neck (SCCHN), overexpression of the p53 protein has been found in 34-80% of the tumors studied. No data are available regarding p53 expression versus tumor cell proliferation and prognosis for this tumor type.

METHODS

p53 protein levels were studied by immunohistochemical staining of 33 primary SCCHN using 3 antibodies (DO7, PAb 1801, and CM1) that react with different epitopes of the p53 protein. The cellular expression of p53 was compared with in vivo incorporation of the thymidine analog iododeoxyuridine (IdUrd) and expression of proliferating cell nuclear antigen (PCNA).

RESULTS

Twenty-one tumors (64%) had a positive nuclear staining for p53 with the monoclonal antibody DO7, which reacts with a denaturation-resistant epitope in wild-type and mutant p53. PAb 1801 and CM1 reacted with 19 and 20 tumors, respectively, all of which were DO7-positive. No correlation was found between incorporation of IdUrd and p53 expression or between PCNA and p53 expression. The data indicate that intracellular accumulation of the p53 protein was related to tumor stage and localization of the tumor. No indication of a clinical or prognostic significance of p53 expression in SCCHN was found.

CONCLUSIONS

No association between p53 deregulation and tumor cell proliferation was found.