Analysis of a National Programme for Selective Internal Radiation Therapy for Colorectal Cancer Liver Metastases

AIMS

Patients with chemotherapy-refractory colorectal cancer liver metastases have limited therapeutic options. Selective internal radiation therapy (SIRT) delivers yttrium 90 microspheres as a minimally invasive procedure. This prospective, single-arm, observational, service-evaluation study was part of National Health Service England Commissioning through Evaluation.

METHODS

Patients eligible for treatment had histologically confirmed carcinoma with liver-only/liver-dominant metastases with clinical progression during or following oxaliplatin-based and irinotecan-based chemotherapy. All patients received SIRT plus standard of care. The primary outcome was overall survival; secondary outcomes included safety, progression-free survival (PFS) and liver-specific PFS (LPFS).

RESULTS

Between December 2013 and March 2017, 399 patients were treated in 10 centres with a median follow-up of 14.3 months (95% confidence interval 9.2-19.4). The median overall survival was 7.6 months (95% confidence interval 6.9-8.3). The median PFS and LPFS were 3.0 months (95% confidence interval 2.8-3.1) and 3.7 months (95% confidence interval 3.2-4.3), respectively. During the follow-up period, 143 patients experienced an adverse event and 8% of the events were grade 3.

CONCLUSION

Survival estimates from this pragmatic study show clinical outcomes attainable in the National Health Service comparable with previously published data. This study shows the value of a registry-based commissioning model to aid national commissioning decisions for highly specialist cancer treatments.

Radiotherapy treatment of non-melanoma skin cancer: a survey of current UK practice and commentary

OBJECTIVE

In the ongoing absence of available trial data, a national survey was carried out to provide details on radiotherapy treatment strategy for non-melanoma skin cancer (NMSC).

METHODS

A survey of clinical oncologists treating NMSC was performed. The respondents were asked for basic information on workload as well as a proposed treatment strategy for various clinical scenarios for patients of varying fitness.

RESULTS

A total of 43 completed and 20 partially completed surveys were received. There was a wide variation in the workload and additional disease sites that respondents had responsibility for. Kilovoltage radiotherapy was available to 81% of responders. The respondents' approach was affected by the fitness of patients, with longer fractionation regimes proposed for younger, fitter patients and shorter or non-standard fractionations more likely for the infirm elderly. Four daily fractionation regimes (18-20 Gy in 1 fraction, 35 Gy in 5 fractions, 45 Gy in 10 fractions and 55 Gy in 20 fractions) were most commonly suggested. There was a large degree of variation in non-standard fractions proposed with significant potential differences in radiobiological effect. Concern over the use of kilovoltage photons on skin over cartilage was apparent, as was a reluctance to use radiotherapy in areas of increased risk of poor wound healing.

CONCLUSION

The survey results largely showed practice to be in line with available published evidence. The variation seen in some areas, such as non-standard fractionation, would benefit from the publication of local outcomes to achieve a more consistent approach.

ADVANCES IN KNOWLEDGE

This study provides information on national practices and identifies variations, particularly within widespread use of non-standard fractionation.

The prognostic significance of the biomarker p16 in oropharyngeal squamous cell carcinoma

AIMS

There is an increasing incidence of human papillomavirus (HPV)-positive oropharyngeal squamous cell cancers (OPSCC) mostly associated with favourable outcomes. p16 immunohistochemistry is a surrogate marker for HPV positivity in OPSCC. The prognostic strength of p16 over traditional prognostic factors is not fully characterised. In this study, we evaluated the clinical and demographic differences between p16-positive and -negative OPSCC and characterised its prognostic strength versus traditional prognostic factors.

MATERIALS AND METHODS

Formalin-fixed, paraffin-embedded blocks and clinical information from 217 OPSCC patients, treated with radiotherapy (alone or in combination with other therapies) between 2000 and 2010 were collected retrospectively. Immunohistochemistry for p16 protein was carried out; cancer-specific survival (CSS), recurrence-free survival (RFS) and locoregional control (LRC) were calculated for both univariate and multivariate analyses.

RESULTS

Ninety-two per cent of the OPSCC originated from tonsil and tongue base sites, 61% were p16 positive. Patients with p16-positive OPSCC were younger (P < 0.0001), with lower alcohol (P = 0.0002) and tobacco (P = 0.0001) exposure. The tumours were less differentiated (P = 0.0069), had a lower T stage (P = 0.0027), higher nodal status (P = 0.014) and higher American Joint Committee on Cancer (AJCC) prognostic group (P = 0.0036). AJCC prognostic group was significant for RFS (P = 0.0096) and CSS (P = 0.018) in patients with p16-negative OPSCC, but not those with p16-positive tumours (P = 0.30 and 0.54). Other significant factors for CSS and RFS in univariate analysis were: pretreatment haemoglobin (P < 0.0001 and <0.0001), chemoradiotherapy (P = 0.005 and 0.03) and P16 status (P < 0.0001 and 0.0001). In multivariate analysis, p16 positivity was the strongest independent prognostic variable for both CSS, RFS and LRC (P < 0.0001, hazard ratio 4.15; 95% confidence interval 2.43-7.08), (P < 0.0001, hazard ratio 6.15; 95% confidence interval 3.57-10.61) and (P = 0.001, hazard ratio 3.74; confidence interval 1.76-7.95).

CONCLUSION

This study shows that p16 is the single most important prognostic variable in OPSCC, surpassing traditional prognostic factors for both CSS and RFS. Furthermore, disease stage has no prognostic significance in p16-positive patients, highlighting the need for routine p16 assessment in OPSCC.

Cisplatin plus capecitabine as first-line chemotherapy for recurrent or metastatic head and neck squamous cell cancer: experience outside of a trial setting

PURPOSE

Cisplatin/5-fluorouracil (5-FU) is an accepted palliative chemotherapy treatment for head and neck squamous cell carcinoma, improving quality of life but not overall survival. Capecitabine in place of 5-FU removes the morbidity of an infusional regime with potential benefit in patient well-being. This study looks at outcomes for cisplatin plus capecitabine (PX) outside of a trial setting.

METHODS

Consecutive patients receiving this treatment in a single centre were retrospectively analysed. Cisplatin (mean dose 75 mg/m²) was given on day 1 of a 3-week cycle and capecitabine (mean dose 808 mg/m² twice daily) on days 1-14, for up to 6 cycles.

RESULTS

Sixty-five patients (median age 58.6 years) received a median of 4 cycles of chemotherapy. The overall response rate was 30.7%, with a median overall survival of 7.3 months. Treatment was well tolerated with a 10.7% grade 3 and a 1.5% grade 4 neutropenia rate, with no other grade 4 toxicities. One patient died of neutropenic sepsis whilst on treatment. Twenty-seven percent of patients stopped treatment early due to chemotherapy-related side effects.

CONCLUSION

PX is well tolerated outside the trial setting with outcomes similar to historical published literature. Ease of administration and benefit to patient convenience make it an attractive alternative to standard palliative treatment.

Nasopharyngeal carcinoma: a retrospective review of demographics, treatment and patient outcome in a single centre

AIMS

Nasopharyngeal cancer (NPC) is relatively uncommon, especially in the Western world. We report our single institution experience of 20 years of data in 128 patients with NPC, including responses to different treatment modalities and outcomes by histological subtype.

MATERIALS AND METHODS

NPC patients presenting from 1992 to 2005 were located on the cancer registry database. Demographic data included age, gender, length of presenting symptoms and stage. World Health Organization classification (2005) was used for histological subtyping. The date of recurrence and survival outcomes were analysed using Kaplan-Meier curves.

RESULTS

Presentation data were analysed from 128 patients; the survival analysis included 123 patients. The median age at presentation was 57.7 years. Stage III and IV presentation rates were 34 and 38%, respectively. The most common presenting symptom was a palpable neck lump (55%) and the median duration of symptoms was 16 weeks. Forty-eight patients received radiotherapy alone and 75 received chemoradiotherapy. The median overall survival in chemoradiotherapy patients was 80.3 months versus 28.5 months with radiotherapy alone (P = 0.003). A significant difference was also seen with recurrence-free survival (RFS) (P = 0.017). Type 1 keratinising carcinoma had a significantly worse overall survival (P = 0.04) and a similar but non-statistically significant trend was seen for RFS (P = 0.051). The multivariate analysis for overall survival showed that histological subtype (hazard ratio 2.7, 95% confidence interval 1.3-5.5, P = 0.034), age (hazard ratio 2.3, 95% confidence interval 1.1-4.9, P = 0.018) and N stage (hazard ratio 3.7, 95% confidence interval 1.4-9.4, P = 0.024) were prognostic factors.

CONCLUSIONS

We present the first large-scale, single-centre retrospective review of NPC in a UK-based population. Demographic data were similar to that in other Western populations, with a significantly worse survival outcome in the keratinising group. Further prospective study of outcome in Western populations accounting for newer radiotherapy techniques such as intensity-modulated radiotherapy and dose escalation, particularly in the keratinising population who were more likely to present with an isolated local recurrence, is recommended.

Lack of prognostic effect of carbonic anhydrase-9, hypoxia inducible factor-1α and bcl-2 in 286 patients with early squamous cell carcinoma of the glottic larynx treated with radiotherapy

AIMS

To evaluate the prognostic significance of potential tumour markers of hypoxia and apoptosis in early squamous cell carcinoma of the glottic larynx managed with radiotherapy.

MATERIALS AND METHODS

In total, 382 patients with T1 and T2 squamous cell carcinoma of the glottic larynx (vocal cords) received radical radiotherapy (50-55 Gy, in 16 fractions in 98% of cases). Pre-treatment haemoglobin was available for 328 patients; biopsy samples were available for 286. Immunohistochemistry was carried out for carbonic anhydrase-9 (CA-9), hypoxia inducible factor-1α (HIF-1α) and Bcl-2.

RESULTS

At 5 years, locoregional control was achieved in 88.2%, cancer-specific survival in 95.0% and overall survival in 78.7%. Adverse prognostic factors for locoregional tumour recurrence were pre-treatment haemoglobin <13.0 g/dl (P = 0.035, Log rank test; sensitivity 0.28, specificity 0.84) and stage T2 rather than T1 (P = 0.002). The effect of haemoglobin level on locoregional control was not significant when stratified by the median of 14.2 g/dl (P = 0.43) or as a continuous variable (P = 0.59). High CA-9 (P = 0.11), HIF-1α (P = 0.67) and Bcl-2 (P = 0.77) expression had no prognostic significance.

CONCLUSIONS

High CA-9, HIF-1α and Bcl-2 do not add to the prognostic significance of tumour stage and lower haemoglobin in predicting failure of local control in early glottic larynx squamous cell carcinoma managed with radiotherapy. The effect of haemoglobin was not strong enough to be useful as a prognostic biomarker.

Phase II study of cisplatin and imatinib in advanced salivary adenoid cystic carcinoma

Patients with adenoid cystic carcinoma of the salivary glands show over-expression of KIT in a high proportion of cases. Options for systemic treatment are limited in locally advanced and metastatic disease. We explored the efficacy of imatinib and cisplatin combined in this group of patients. A Gehan's two-stage, phase II trial was conducted on 28 patients. Those with progressive, locally advanced, and metastatic disease with an over-expression of KIT were treated with single agent imatinib 800 mg daily for two months, followed by a combination of imatinib 400mg daily and cisplatin 80 mg/m(2) at four-weekly intervals for six cycles. This was followed by maintenance single agent imatinib 400mg daily until the disease progressed. Response was monitored using fluorodeoxyglucose positron emission tomography (FDG-PET) and morphological imaging using computed tomography, magnetic resonance, and chest radiographs (CT/MRI/CXR). Morphological imaging showed partial response in three of 28 patients, and five patients showed a response on FDG-PET. In addition, 19 patients had useful stabilisation of disease. The median time to progression and overall survival was 15 months (range 1-43) and 35 months (range 1-75), respectively. The combination of imatinib and cisplatin was reasonably well tolerated. This combination may provide stabilisation in locally advanced and metastatic adenoid cystic carcinoma of the salivary glands.

Developing a CTCAEs patient questionnaire for late toxicity after head and neck radiotherapy

PURPOSE

Patient-based reporting of symptoms is increasingly important in providing treatment toxicity information. However, observer-based scoring systems such as the CTCAEs which incorporate the LENT-SOMA scales are not adapted for patient-based reporting. We aim to (1) report the late toxicity in patients following head and neck radiotherapy using a LENT-SOMA patient-based questionnaire, (2) describe how the responses help to improve the questionnaire and (3) adapt the questionnaire for patient reporting using CTCAEs.

METHODS

A 31-item LENT-SOMA patient questionnaire was administered prospectively to 220 patients pre-treatment and at eight time periods post-radical head and neck radiotherapy over 3 years. Exploratory factor analysis was carried out and questionnaire reliability was evaluated using Cronbach's alpha coefficient.

RESULTS

At 3-years follow-up, grade 3/4 toxicity was recorded for xerostomia (44%), hoarseness (14.3%), altered taste (6.1%) and oropharyngeal pain (1.9%). Factor analysis indicated that questionnaire division according to anatomical sub-site was reasonable. Cronbach's alpha was 0.851 (95% CI: 0.820-0.883) indicating high reliability. Good compliance was obtained with all questions except for the 'weight loss' item. A satisfaction survey showed that the questionnaire was clear and concise. Teeth and mandible sections have been removed. Dietary change due to xerostomia has been incorporated in line with CTCAEs. LENT-SOMA scoring of analgesic needs and dysphagia not described in CTCAEs were found useful and have been retained.

CONCLUSIONS

The questionnaire has enabled reporting of late toxicity and the responses have enabled refinement of the questionnaire. It is reliable, feasible and has been validated for patient-based collection of CTCAEs late toxicity data.

Clinical and biological factors affecting response to radiotherapy in patients with head and neck cancer: a review

OBJECTIVE

The main aim of this article was to review the clinical and biological factors that have been shown to influence the response of the head and neck squamous cell carcinoma (HNSCC) to primary radiotherapy and briefly discuss how some of these factors could be exploited to improve outcome.

DESIGN

Medline based search covering 1982-2006 to identify the HNSCC literature where the effect of clinical and biological factors on locoregional control and overall survival were investigated.

RESULTS

Clinical factors are routinely used in management decisions. Nevertheless, identically staged tumours receiving the same treatment may have different outcomes. Biological factors such as hypoxia, proliferation and radio-sensitivity play an important role in radiation response. However, these are not currently used in practise because tests that are clinically reliable and feasible are not available.

CONCLUSION

High-quality translational research will allow us to develop biological tests that can be used in routine clinical practise to tailor individual treatment, with the ability to improve patient outcome further by modifying the underlying tumour biology.

Benign schwannoma in paranasal sinuses: a clinico-pathological study of five cases, emphasising diagnostic difficulties

OBJECTIVES

To highlight the difficulty in making a correct diagnosis of benign schwannoma in the paranasal region, to raise awareness of this rare condition, and to suggest the most appropriate treatment.

METHOD

Retrieval of cases retrospectively from archives of the histopathology department of a major UK cancer centre with central review of all cases.

RESULTS

Five cases were identified since 1990 and clinical and pathological features are summarised. Median follow up of patients was 8.1 years. Radiological appearances of local bone invasion and histological features of tumour unencapsulation and hypercellularity could give the mistaken impression of malignant disease and lead to unnecessary over-treatment.

CONCLUSION

Central pathological review and clinical awareness is required. Although local recurrence can occur, the prognosis is excellent. The treatment of choice is local excision. Radiotherapy can be considered, but in most cases it would incur unnecessary morbidity.

Should FDG-PET scanning be routinely used for patients with an unknown head and neck squamous primary?

Background: Between 1 and 2 per cent of head and neck squamous cell carcinoma patients will reveal no evidence of a primary malignancy. The management of this group poses many problems, including the morbidity associated with wide field irradiation as well as the difficulty in treatment when a primary does emerge. The aim of this study was to assess the use of fluoro-deoxy-glucose positron emission tomography (FDG-PET) imaging in patients presenting with an unknown head and neck primary and to consider its routine use in such patients.

Methods: We enrolled 25 patients into our study over a four year period. They all presented with a histologically proven, metastatic, squamous cell carcinoma of the neck for which no primary could be found despite full clinical, endoscopic and radiological evaluation with computed tomography (CT) and/or magnetic resonance imaging (MRI). Additionally, all the patients underwent imaging using FDG-PET. The images were interpreted by two radiologists experienced in PET imaging.

Results: A primary was identified in nine of the 25 patients (42 per cent); however, of these patients, six had false positive results and only three patients were true positives with supportive histology. In the remaining 16 patients, no abnormality was identified on CT, MRI or PET. Of these 16 patients, two eventually displayed a primary carcinoma, the other 14 patients remaining without evidence of any primary.

Conclusion: Despite the high number of positive PET scans, the actual true positive rate was 3/9 (33 per cent); conversely, the true negative rate was 14/16 (88 per cent). We conclude from this study that there is a role for FDG-PET in the patient with an unknown head and neck primary, particularly in the context of a negative PET scan.

Salivary gland adenoid cystic carcinoma: A review of chemotherapy and molecular therapies

Adenoid cystic carcinoma (ACC) accounts for about 1% of all head and neck malignancies. It has a tendency for a prolonged clinical course, with local recurrences and distant metastases sometimes occurring many years after presentation. Standard treatment for salivary gland ACC is surgery and post-operative radiotherapy. The aim of this review was to examine the reported efficacy of various chemotherapy regimens and molecular therapies on recurrent/metastatic salivary gland ACC. One hundred and fourteen publications were reviewed on chemotherapy as well as possible molecular targets of therapy, including KIT, epidermal growth factor receptor (EGFR), human epidermal growth receptor-2 (HER-2), oestrogen and progesterone receptors, proliferating cell nuclear antigen (PCNA), Ki-67 and the p53, bcl-2 and SOX-4 genes. Reported response rates to combination chemotherapy are low and response duration generally short lived. The response to molecular therapies is low also. More research into novel molecular targets is needed.

Hypoxia in head and neck cancer

A high level of hypoxia in solid tumours is an adverse prognostic factor for the poor outcome of cancer patients following treatment. This review describes the status of research into finding a practical method for measuring hypoxia and treating hypoxic tumours. The application of such methodology would enable the selection of head and neck cancer treatment based on an individual's tumour oxygenation status. This individualization would include the selection not only of surgery or radiotherapy, but also of novel hypoxia-modification strategies.

Case report: radical radiotherapy for early laryngeal cancer in a patient with human immunodeficiency virus: no evidence of increased toxicity

There are very few reported cases of laryngeal squamous cell carcinoma (SCC) in patients with a background of human immunodeficiency virus (HIV) infection. We report a case of a 42-year-old man who developed a T2 N0 left vocal cord well differentiated SCC with an 11 year history of HIV infection. He successfully completed a course of radical radiotherapy 66 Gy in 33 fractions over 47 days. During his treatment he experienced only a grade 1 Radiation Therapy Oncology Group (RTOG) acute toxicity reaction to the larynx and no weight loss. At 32 months follow up he remains disease free and has no significant late morbidity. Prior to his radiotherapy his CD4 count was 350 cells mm(-3); we discuss the view that the treatment chosen needs to be individually tailored with respect to the patient's immune status.

Carcinoma of the hard palate treated with radiotherapy: a retrospective review of 31 cases

There are few studies reporting the results of radical radiotherapy for carcinoma of the hard palate. We have examined our results of patients treated within a single institution, and assessed survival, local control and morbidity. A retrospective analysis was made on 31 patients with hard palate carcinoma treated with external beam radiotherapy at the Christie Hospital between 1990 and 1997. Twenty-six patients received radiotherapy alone and five were treated for post-operative positive surgical margins. The 5-year actuarial survival rate was 55%. The actuarial 5-year local control rate was 53%, rising up to 69% after salvage surgery. Survival was 48% for squamous cell carcinomas and 63% for salivary gland carcinomas, the difference was not significant. The only significant predictor of local control was T-stage, with 80% 5-year local control of T1-2 lesions and 24% control of T3-4 lesions. N-stage was the only significant factor predicting for survival. Radiation necrosis occurred in one patient. Radical radiotherapy for carcinoma of the hard palate is safe and well tolerated. It is an effective treatment for both squamous cell carcinoma and salivary gland carcinoma.

Randomized controlled trial to assess the effectiveness of a videotape about radiotherapy

In a randomized controlled trial, the additional provision of information on videotape was no more effective than written information alone in reducing pre-treatment worry about radiotherapy. Images of surviving cancer patients, however, may provide further reassurance to patients once therapy is completed.

Metastatic renal cell carcinoma to the nose and paranasal sinuses

BACKGROUND

Renal cell carcinoma represents 3% of all malignant tumors. Metastatic deposits of renal cell carcinoma to the head and neck region are infrequent. The objective of this work is to analyze the clinical presentation, radiologic features, surgical and radiotherapy treatment, and outcome of metastatic renal cell carcinoma to the nose and sinuses.

METHODS

Retrospective review of 6 patients diagnosed with renal cell carcinoma who had nasal metastasis develop and were seen at the Christie Hospital in Manchester over the past 8 years.

RESULTS

Six patients with renal cell carcinoma were seen with recurrent epistaxis, nasal obstruction, and unpleasant nasal crusting. Three patients had orbital involvement. Examination under general anaesthesia and biopsy was performed in all 6 cases. Histologic studies confirmed metastases of renal cell carcinoma in all 6 patients. All patients underwent local external beam radiotherapy. The most common dose used was 35 Gy in 8 daily fractions. All patients had symptomatic control of local nasal disease with a minimum follow-up of 2 years in 4 patients. Two patients died within 6 months of the radiotherapy treatment as a result of their primary tumor.

CONCLUSIONS

Metastatic renal cell carcinoma to the nose and paranasal sinuses is rare but has unpleasant symptoms. Local symptomatic control with radiotherapy is excellent.

331 cases of clinically node-negative supraglottic carcinoma of the larynx: a study of a modest size fixed field radiotherapy approach

PURPOSE

For node-negative supraglottic carcinoma of the larynx, radiotherapy with surgery in reserve commonly provides very good results in terms of both local control and survival, while preserving function. However uncertainty exists over the treatment of the node-negative neck. Elective whole neck radiotherapy, while effective, may be associated with significant morbidity. The purpose of this study was to examine our practice of treating a modest size, fixed field to a high biologically effective dose and compare it with the patterns of recurrence from other centers that use different dose/volume approaches.

METHODS AND MATERIALS

Over a 10-year period 331 patients with node-negative supraglottic carcinoma of the larynx were treated with radiotherapy at the Christie Hospital Manchester. Patients were treated with doses of 50-55 Gy in 16 fractions over 3 weeks. Data were collected retrospectively for local and regional control, survival, and morbidity.

RESULTS

Overall local control, after surgical salvage in 17 cases, was 79% (T1-92%, T2-81%, T3-67%, T4-73%). Overall regional lymph node control, after surgical salvage in 13 cases, was 84% (T1-91%, T2-88%, T3-81%, T4-72%). Five-year crude survival was 50%, but after correcting for intercurrent deaths was 70% (T1-83%, T2-78%, T3-53%, T4-61%). Serious morbidity requiring surgery was seen in 7 cases (2.1%) and was related to prescribed dose (50 Gy-0%, 52.5 Gy-1. 3%, 55 Gy-3.4%).

DISCUSSION

Our results confirm that treating a modest size, fixed field to a high biologically effective dose is highly effective. It enables preservation of the larynx in most cases, with acceptable regional control and no loss of survival compared to whole neck radiotherapy regimes.

Radiotherapy for carcinoma of the posterior pharyngeal wall

Posterior pharyngeal carcinoma has an extremely poor prognosis regardless of the method of treatment. The purpose of this study was to assess the local control and survival in patients with carcinoma of the posterior pharyngeal wall treated with definitive radiotherapy and to determine prognostic factors which may be relevant to the current UICC staging classification. Between January 1991 and December 1995, 22 patients with a mean age of 60 years (range 44-82) received definitive radiotherapy, using a homogeneous technique, for carcinoma of the posterior pharyngeal wall. The median follow-up was 42 months (range 25-66). The overall 3-year survival and local control for the whole group was 50% and 73% respectively. Patients with early stage (T1 and T2) disease had a significantly better overall 3-year survival rate of 77% compared to 11% for patients with advanced stage (T3 and T4) disease (p=0.0010). Similarly, patients with early stage disease had a significantly improved 3-year local control rate compared to patients with more advanced stage disease (92% and 44% respectively, p=0.0080). Patients with node positive disease had an inferior survival rate of 29% compared to 60% for those with node negative disease though the difference did not reach statistical significance. In addition only one patient with initial node negative disease had isolated nodal relapse. There was no significant late morbidity. For patients with early stage disease we have obtained local control and survival rates comparable to other groups with a once daily, short fractionation radiotherapy scheme but with reduced morbidity. In late stage disease altered fractionation schemes should be considered in order to achieve better local control and survival. Isolated nodal relapse was not a significant problem in this cohort of patients. Outcome correlates with primary tumour size and this is reflected in the current UICC staging classification.

Definitive radiotherapy for 114 cases of T3N0 glottic carcinoma: influence of dose-volume parameters on outcome

BACKGROUND AND PURPOSE

Assuming that the dose-response curve for T3N0M0 glottic carcinoma is steep and that the rate of occult lymph node metastases is low, it should be possible to employ high biological tumour doses to modest target volumes and thereby maximise laryngeal control without compromising final neck control. Within the constraints of a retrospective study we aim to examine this policy with respect to local control, incidence of nodal relapse and late complications.

MATERIALS AND METHODS

One hundred and fourteen patients with T3N0M0 glottic carcinoma who received a 3-week schedule of radical radiotherapy between 1986 and 1994 were analysed. The median age was 67 years (range, 34-85 years) and the median follow-up for living patients was 4.8 years (1.9-8.9 years). There were no strict selection criteria for those patients treated with radiotherapy.

RESULTS

The 5-year overall survival was 54%. The 5-year local control with radiotherapy and the ultimate loco-regional control following salvage laryngectomy were 68 and 80%, respectively. Nine patients (8%) suffered a regional nodal relapse but only three of these (3% overall) occurred in the absence of local failure. Four patients (3.5%) developed serious late complications requiring surgical intervention (three received 55 Gy and one 52.5 Gy).

CONCLUSIONS

It is possible to employ maximum tolerable doses to specific target volumes and thereby exploit the dose response demonstrated and minimise major late effects. The use of modest target volumes resulted in only 3% of patients requiring surgery that might have been avoided had prophylactic neck irradiation been employed.

The lack of correlation between proliferation (Ki-67, PCNA, LI, Tpot), p53 expression and radiosensitivity for head and neck cancers

A study was made of the relationship between measurements of radiosensitivity versus proliferation and p53 status in head and neck cancers. Inherent tumour radiosensitivity was assessed as surviving fraction at 2 Gy (SF2) using a clonogenic soft agar assay (n = 77). The results were compared to data on proliferation obtained by both flow cytometry (labelling index (LI), the potential doubling time (Tpot) n = 55) and immunohistochemistry (Ki-67 and PCNA; n = 68), together with immunohistochemical p53 expression (n = 68). There were no overall significant differences in the median values of the various parameters analysed for the different sites within the head and neck region, disease stages, grades of tumour differentiation or nodal states. A subgroup analysis showed that oropharyngeal (n = 22) versus oral cavity (n = 35) tumours were more radiosensitive (P = 0.056) and had a higher Ki-67 index (P = 0.001). Node-positive tumours had higher LI (P = 0.021) and a trend towards lower Tpot (P = 0.067) values than node-negative ones. No correlations were seen between SF2 and any of the parameters studied. The long-standing dogma of an increased radiosensitivity of rapidly proliferating cells in contrast to slowly proliferating cells was not confirmed. The study shows that parallel measurements of different biological markers can be obtained for a large number of patients with head and neck cancers. The independence of the various parameters studied suggests that there may be potential for their combined use as prognostic factors for the outcome of radiotherapy.

Clinico-pathological and treatment-related factors influencing survival in parotid cancer

One hundred and three patients with primary parotid cancer treated surgically at the Christie Hospital, Manchester (1952-1992), were analysed to assess the influence on survival of prognostic and treatment-related factors. Thirty-seven patients were treated by surgery alone (SG), 66 received post-operative radiation (SG+RT). Median follow-up was 12 years, minimum 5 years. The 10-year disease-specific survival rates for stage I, II and III/IV were 96%, 61% and 17% respectively (P < 0.0001). The various histological types segregated into three survival patterns: low-, intermediate-and high-grade with 10-year survival rates of 93%, 41% and 50% respectively (P < 0.0001). On multivariate analysis, the factors influencing risk of cancer death in order of importance were: tumour size > 4 cm (P < 0.001), presence of nodes (P = 0.001), histology of adenoid cystic carcinoma (P = 0.01), high-tumour grade (P = 0.02) and perineural involvement (P = 0.01). Neither the extent of surgery nor the operator influenced outcome. Overall, adjuvant RT significantly reduced locoregional recurrence (SG+RT 15% vs SG 43%; P = 0.002) but not survival, although on subanalysis, there was a trend to improved survival with large cancers and high-grade tumours. Long-term survival is determined primarily by tumour characteristics, namely clinical stage and grade. Post-operative RT contributes significantly to locoregional control and probably confers some survival advantage in high-risk patients.

The diagnostic value of positron emission tomography (PET) with radiolabelled fluorodeoxyglucose (18F-FDG) in head and neck cancer

Positron emission tomography (PET) scanning has recently been introduced into clinical practice but its usefulness in the management of head and neck cancer is not well defined. The aim of this prospective preliminary study was to examine the clinical value of fluorodeoxyglucose (FDG)--PET in patients with head and neck cancer treated by radiotherapy with surgery in reserve by (i) relating quantitative uptake of isotope to tumour type and histological grade and (ii) comparing the imaging findings of PET and magnetic resonance imaging (MRI) in post-radiotherapy assessment of tumour response. Twenty-one patients had pre-treatment PET and MRI scans and these were repeated four and eight months after treatment if there was no clinical relapse. Pre-treatment uptake of FDG using tumour to cerebellar ratio parameters was significantly related to the histological grade of squamous cancer (p = 0.04) but not to tumour type. Discordance of post-treatment PET/MRI findings in one case indicates a possible role for PET in the early detection of tumour recurrence. Other potential uses of PET scanning in the management of head and neck cancer are discussed.

Submandibular gland carcinoma; an audit of local control and survival following adjuvant radiotherapy

Carcinoma of the submandibular gland is a rare diagnosis, accounting for less than 2% of cases of salivary gland tumours. We have examined the treatment and outcome of a total of 30 patients treated with radiotherapy at the Christie Hospital, Manchester between 1980 and 1993. In most cases this followed radical surgery, though 12 patients were referred following either incomplete excision or biopsy only. Adenoid-cystic histology accounted for 19 cases (63%). Standard radiotherapy was delivered using a beam directed technique to treat the whole submandibular compartment. Doses prescribed were most commonly from 50 to 55 Gy in 16 fractions over three weeks. Cancer specific survival was 79% and 57% at 5 and 10 yr respectively, the continued fall at 10 yr reflected late recurrence seen in patients with adenoid-cystic histology. Local control was 85% and 73%, respectively. Nine of twelve patients with incomplete excision or biopsy only had local control with radiotherapy. Six patients developed lung metastases, all of whom had adenoid-cystic histology. Radiotherapy was well-tolerated acutely, and only one patient experienced osteoradionecrosis requiring surgical intervention. The incidence of adenoid-cystic carcinoma is higher in the submandibular than the parotid gland. This typically results in late recurrence, and a high incidence of lung metastases and this was confirmed in our study. However, overall survival was very similar to that of parotid carcinoma.

Does salivary gland scintigraphy predict response to pilocarpine in patients with post-radiotherapy xerostomia?

This study was undertaken to determine whether standard salivary gland scintigraphy may be used for the objective assessment of salivary gland sialogogues, in particular oral pilocarpine, in the treatment of post-radiotherapy xerostomia. Nine patients, with xerostomia following radiotherapy to the head and neck region underwent salivary gland scintigraphy with technetium-99m pertechnetate (40 MBq) both before and following 1 month of oral pilocarpine (5 mg tds). For each scan, the percentage uptake in the first 14 min, the peak uptake, time to peak uptake and the percentage of activity excreted following lemon juice stimulation were calculated. The results were correlated with the subjective response as assessed by questionnaire and visual analogue scale. We found no correlation between subjective response and any of the four scan parameters analysed. We could not identify any parameter that predicted those patients who would respond to pilocarpine. In addition, only one parameter, the percentage of activity excreted following stimulation, correlated with previous dose of radiotherapy to the gland. In conclusion, in this study salivary gland scintigraphy did not appear to correlate with or predict response to oral pilocarpine. However, future studies might consider performing salivary gland scintigraphy prior to radiotherapy as well as at differing time points following the commencement of pilocarpine.

Intracranial juvenile nasopharyngeal angiofibroma

We report the case history of a 26-year-old man who was diagnosed with advanced juvenile nasopharyngeal angiofibroma with intracranial extension. The lesion was considered to be inoperable and the patient was treated with radical radiotherapy. Serial magnetic resonance imaging has shown continued tumour regression and he remains well after 3 years. The literature is reviewed and radiotherapy recommended as the modality of choice for these patients.

Radical radiotherapy for carcinoma of the oesophagus: an effective alternative to surgery

BACKGROUND AND PURPOSE

Despite advances in operative and postoperative care, long term survival rates following radical oesophagectomy are poor. Surgery remains the mainstay of radical treatment despite various series reporting similar results for treatment with radiotherapy, in particular in the upper third of the oesophagus. We have studied a cohort of patients treated with definitive radiotherapy to examine the influence on survival of changes in diagnostic scanning and radiotherapy computer planning as well as various patient and disease related prognostic factors.

PATIENTS AND METHODS

From 1985 to 1994, 101 patients with clinically localised carcinoma of the oesophagus were treated at the Christie Hospital with definitive radiotherapy. This included 11 patients with oesophageal adenocarcinoma. Diagnostic and planning techniques changed over the period studied, with increasing use of both diagnostic and radiotherapy planning CT scanning. Radiotherapy doses ranged from 45 to 52.5 Gy in 15 or 16 fractions over 3 weeks.

RESULTS

The 3- and 5-year survival figures were 27% and 21%, respectively, corrected for intercurrent deaths. Survival was better for adenocarcinoma than squamous cell carcinoma, though not statistically significantly. The only significant prognostic factor (P = 0.01) was the use of diagnostic CT scanning (42% versus 13% 5-year survival with or without diagnostic CT scanning, respectively) which was associated with an increase in field size. Radiotherapy was well tolerated with no acute mortality or significant morbidity. Late stenosis requiring oesophageal was seen in five of 20 patients surviving 3 years or more.

CONCLUSIONS

Survival following well planned radiotherapy is an effective alternative to surgery for both squamous cell and adenocarcinoma. Advances in staging and three-dimensional planning and the use of multimodality treatment may further improve survival.

The in vitro radiosensitivity of human head and neck cancers

A study was made of the intrinsic radiosensitivity of 140 biopsy and surgical specimens of malignant head and neck tumours of different histologies. Using a soft-agar clonogenic assay, the material was assessed for the ability to grow in culture (colony-forming efficiency; CFE) and inherent tumour radiosensitivity (surviving fraction at 2 Gy, SF2). The success rate for obtaining growth was 74% (104/140) with a mean CFE of 0.093% (median 0.031) and a range of 0.002-1.3%. SF2 was obtained for 88 of 140 specimens, representing a success rate of 63% with a mean SF2 of 0.48 (median 0.43) and a range of 0.10-1.00. There were no significant differences in radiosensitivity between different sites of the head and neck region. There were no significant relationships between SF2 and disease stage, nodal status, tumour grade, patient age, primary tumour growth pattern and CFE. The results were compared with those for other tumour types previously analysed with the same assay. The distribution of the SF2 values for the head and neck tumours was similar to that for 145 cervix carcinomas and there was no significant difference in mean radiosensitivity between the two tumour types. Also, there was no significant difference in radiosensitivity between head and neck tumours and either breast or colorectal cancers. However, a group of eight lymphomas was significantly more radiosensitive. These results confirm the feasibility of carrying out radiosensitivity measurements using a soft-agar clonogenic assay on head and neck tumours. In addition, the work has shown that radiosensitivity is independent of many clinical parameters and that the mean value is similar to that reported for cervix carcinomas.

An unusual case of carotid body tumour

Carotid body tumours are uncommon but fascinating lesions, which arise from paraganglionic tissue at the bifurcation of the common carotid artery. We report the case history of a 40-year-old female patient who presented initially with a malignant left-sided tumour, followed by a right-sided tumour 17 years later. Although there is no known family history, it is likely, because of the bilateral tumours and the young age at presentation, that the tumour was inherited in this patient. The literature on carotid body tumours is reviewed, with particular emphasis on malignant and multiple tumours and their treatment. We discuss the recently elucidated mechanism of inheritance and its implications for affected patients and their families.

Similar decreases in local tumor control are calculated for treatment protraction and for interruptions in the radiotherapy of carcinoma of the larynx in four centers

PURPOSE

Data on patients with cancer of the larynx are analyzed using statistical models to estimate the effect of gaps in the treatment time on the local control of the tumor.

METHODS AND MATERIALS

Patients from four centers, Edinburgh, Glasgow, Manchester, and Toronto, with carcinoma of the larynx and treated by radiotherapy were followed up and the disease-free period recorded. In all centers the end point was control of the primary tumor after irradiation alone. The local control rates at > or = 2 years, Pc, were analyzed by log linear models, and Cox proportional hazard models were used to model the disease-free period.

RESULTS

T stage, nodal involvement, and site of the tumor were important determinants of the disease-free interval, as was the radiation schedule used. Elongation of the treatment time by 1 day, or a gap of 1 day, was associated with a decrease in Pc of 0.68% per day for Pc = 0.80, with a 95% confidence interval of (0.28, 1.08)%. An increase of 5 days was associated with a 3.5% reduction in Pc from 0.80 to 0.77. At Pc = 0.60 an increase of 5 days was associated with an 7.9% decrease in Pc. The time factor in the Linear Quadratic model, gamma/alpha, was estimated as 0.89 Gy/day, 95% confidence interval (0.35, 1.43) Gy/day.

CONCLUSIONS

Any gaps (public holidays are the majority) in the treatment schedule have the same deleterious effect on the disease free period as an increase in the prescribed treatment time. For a schedule, where dose and fraction number are specified, any gap in treatment is potentially damaging.

Modelling the optimal radiotherapy regime for the control of T2 laryngeal carcinoma using parameters derived from several datasets

PURPOSE

A number of previous studies have used direct maximum-likelihood methods to derive the values of radiobiological parameters of the linear-quadratic model for head and neck tumors from large clinical datasets. Time factors for accelerated repopulation were included, along with a lag period before the start of this repopulation. This study was performed to attempt to utilise these results from clinical datasets to compare treatment regimes in common clinical use in the UK, along with other schedules used historically in a number of clinical series in North America and elsewhere, and to determine if an optimal treatment regime could be derived based on these clinical data.

METHODS

The biologically-based linear-quadratic model, applied to local tumor control and late morbidity, has been used to derive theoretical optimum (maximising tumor control whilst not exceeding tolerance for late reactions) radiotherapy schedules based on daily fractions. The specific case of T2 laryngeal carcinoma was considered as this is treated primarily by radiotherapy in many centers. Parameter values for local control were taken from previous analyses of several large single-center and national datasets. A time factor and a lag period were included in the modelling. Values for the alpha/beta ratio for late morbidity were used in the range 1-4 Gy, which is compatible with the limited range of values reported in the literature for particular complications following radiotherapy for head and neck cancer. Early reactions and their consequential late morbidity were not modelled in this study, but assumed to be within tolerance.

RESULTS

For treatments using daily fractions there was a broad optimum treatment time of between 3-6 weeks. The theoretical optimum depended to some extent on the value of the alpha/beta ratio for late morbidity, but in many cases was at or just beyond the end of the purported lag period of 3-4 weeks, although small values of alpha/beta between 1-2 Gy favour longer treatment times. Similar results were obtained using a range of parameter values derived from four independent clinical datasets.

CONCLUSION

The mathematical modelling of this broad range of once-daily treatments for most of which differences in local control and late morbidity are essentially undetectable (< 5%) has shown how this clinically-recognised phenomenon is interpreted in terms of the combination of dose-response slopes, fractionation sensitivities and time factors for both tumor control and normal tissue morbidity. Although the conclusions are inevitably tempered by a number of caveats concerning confounding factors in different centers; for example, the use of different treatment volumes, the present analysis provides a framework with which to explore the potential value of modifications to conventional treatment schedules, such as the use of multiple fractions per day.

Late radiation change in the CNS: MR imaging following gadolinium enhancement

Magnetic resonance imaging is the best imaging technique for the detection of radiotherapy-induced changes in the central nervous system but there are few studies detailing the MRI appearances of radiation effects following enhancement with intravenous gadolinium. In this paper, gadolinium enhanced MR imaging findings were reviewed in seven patients with evidence of late radiation injury following radiotherapy for primary head and neck tumours. On T1-weighted enhanced sequences, abnormal focal areas were present in the anterior temporal lobes and antero-inferior aspects of the frontal lobes. These lesions were well defined and enhanced intensely following intravenous gadolinium. They were present in the white matter in five patients and involved both grey and white matter in two patients. Cystic components were present in larger lesions in three patients and mass effect was present around the enhancing lesions in four patients. All abnormalities occurred within the radiation treatment portals and corresponded to the distribution of increased signal intensity changes in the brain on T2-weighted images. Late radiation-induced injury should be considered in the differential diagnosis of any intensely enhancing lesion occurring within irradiated brain tissue.

Intracavitary radiotherapy boosting for nasopharynx cancer

Intracavitary radiotherapy is conceptually an attractive method of boosting dose to nasopharynx cancer whilst sparing sensitive normal tissues. A high dose rate (HDR) microselectron can be used to deliver a brachytherapy boost conveniently, safely, comfortably and effectively. Following external radiotherapy a single outpatient treatment has been given to patients using the remote afterloading system of sources placed in modified paediatric endotracheal tubes. This has been associated with good primary control and no evidence of serious morbidity in eight patients. The main limitation of this method is restriction of its utilization to small volume primary disease.

Extramedullary plasmacytoma of the head and neck region: clinicopathological correlation in 25 cases

Extramedullary plasmacytomas (EMP) of head and neck are rare tumours. Between 1972 and 1993, 25 cases of EMP of head and neck were seen at our institute. The clinical and pathological features and response to treatment are presented. At initial presentation, 23 (92%) patients presented with disease confined to a single extramedullary site only and two patients had in addition clinical involvement of cervical lymph nodes. All except these two patients received radiotherapy to the primary site only as initial treatment. Initial primary control of local disease was obtained in 16 of 24 (67%) patients treated with radical intent. With salvage treatment of further radiotherapy and/or chemotherapy, local disease control was achieved in 21 of 24 (88%) patients. One patient was treated with palliative intent. Conversion to multiple myeloma was seen in two patients (8%). Pathologically, the tumours were classified into low, intermediate and high grade, which correlated closely with outcome. This classification has been used for the first time in extramedullary plasmacytomas and is based on the multiple myeloma grading criteria devised by Bartl et al (1987). Fifteen of eighteen (83%) low-grade tumours and only one of six (17%) intermediate- and high-grade tumours were locally controlled after primary radiotherapy. This is statistically significant for local control (P= 0.0019) but not for overall survival (P= 0.12). The median survival and 5-year overall survival is 68 months and 58.9% respectively. We recommend consideration of adjuvant chemotherapy in patients with higher grade disease.

Olfactory neural tumours--the role of external beam radiotherapy

Olfactory neuroblastoma is an uncommon tumour arising in the nasal cavity or paranasal sinuses. We report the management of nine cases treated with external beam radiotherapy subsequent to surgery, either attempted definitive removal or biopsy only. Recent refinements in pathological evaluation of these tumours are discussed. Seven cases were deemed classical olfactory neuroblastoma whilst two were classified as neuroendocrine carcinoma. The clinical features, radiotherapy technique and variable natural history are presented. Seven of eight patients treated radically were controlled locally, with a minimum follow-up of two years. Three patients developed cervical lymph node disease and three patients died of systemic metastatic disease. Suggestions are made as to which patients should have en-bloc resection rather than definitive radiotherapy.

Radical external beam radiotherapy for 333 squamous carcinomas of the oral cavity--evaluation of late morbidity and a watch policy for the clinically negative neck

BACKGROUND AND PURPOSE

The aims of this study were to examine local control/morbidity for all cases and a 'watch policy' for the node-negative neck.

PATIENTS/METHODS

333 patients with squamous cell carcinoma of the oral cavity were treated with a short radical radiotherapy regime to the primary site and involved lymph node groups at the Christie Hospital, Manchester, between 1980 and 1987. Only 10 of 278 node-negative patients received elective neck node irradiation.

RESULTS

Actuarial cancer-free survival and local control rates at 5 years for the whole group were 55% and 61%, respectively. Control at the primary site was adversely related to increasing T-stage, node positivity and bone involvement at presentation. Osteonecrosis was seen in 14 (5.9%) of 237 cases without bone involvement at presentation. Taking all patients, late morbidity (non-healing soft tissue injury or bone necrosis) was seen in 45 patients (13.6%) at a median time of 21 months from treatment. The factors contributing to late morbidity were: (1) bone involvement at presentation, (2) synchronous MTX chemotherapy, (3) the contribution of scattered radiation from elective neck treatment, (4) increasing radiation dose, (5) increasing target volume for doses less than 55 Gy and (6) dental extractions. Eighty-four (31%) patients who were initially node-negative developed disease in the untreated neck during follow-up. Salvage neck dissections controlled neck disease in half of the node-only recurrences (21/42 cases).

CONCLUSION

These results have influenced our treatment policy, with lowering of the primary tumour dose in some cases and addition of elective neck irradiation for T2-T4 No patients.

A modelled comparison of the effects of using different ways to compensate for missed treatment days in radiotherapy

There is much evidence for the detrimental effect on tumour control of missed treatment days during radiotherapy, amounting for example to approximately a 1.6% absolute decrease in local control probability per day of treatment prolongation in the case of head and neck squamous cell cancer. Various methods to compensate for missed treatment days are compared quantitatively in this article, using the linear-quadratic formalism. The overall time and fraction size can be maintained by either treating on weekend days (the preferred way (Method 1a), although with unsocial hours and at extra cost) or using two fractions per day to "catch up' (Method 1b). The latter might incur a small loss of tolerance regarding late reactions, when intervals of 6-8 h are used rather than 24 h, and there may be logistical/scheduling difficulties with larger numbers of patients in some centres when using this method. A second type of strategy retains overall treatment time, and also one fraction per day, but the size of the dose per fraction is increased. For example, this may be done for the same number of "post-gap' days as gap days (Method 2). However, with this method, calculated isoeffect doses regarding late reactions indicate a probable decrease in tumour control rate (Method 2a). Otherwise, isoeffective doses regarding tumour control result in an increase in late reactions (Method 2b). In addition, this method is unsuitable for short regimens already using high doses per fraction. To reduce this problem, overall treatment time can also be retained by using fewer fractions, all of greater size in the case of planned gaps (statutory holidays), or larger remaining fractions after unplanned gaps (Method 2c). The problem also with this method is that equivalence for tumour control gives an increase in late reactions. The least satisfactory strategy (Method 3) is to accept the protraction caused by the missed treatment days, and give either the same prescribed number of (slightly larger) fractions or the planned treatment followed by one (or more) extra fraction to compensate for the gap. This would retain the expected local control rate, but there would be an increase in late reactions. An example of this, using average parameter values, is that a 3-day gap (necessitating four extra days to complete treatment with one fraction of 2.4 Gy) might maintain a 70% local control rate for glottic carcinoma, but severe reactions might rise from 1% to 4% and minor/moderate reactions from 37% to 50%. In this example, the inclusion of an extra weekend would increase the required extra dose and hence may further increase the morbidity rates. A final point is that the effect of treatment interruptions for an individual patient is expected to be greater than that for a group of patients because of interpatient heterogeneity tending to flatten dose-response curves. Calculations show that the above value of 1.6% loss of local control per day for a group of patients may reflect values for individual patients that range around a median value of as much as 5% per day, so stressing further the importance of gaps in treatment. It is concluded that, wherever possible, treatment days should not be missed. If they are missed, it is important to compensate for them, preferably by one of the first of the above methods (1a or 1b), in order to keep as close as possible to the original/standard prescription in terms of total dose, dose per fraction and overall time.

An analysis of radiotherapy in the management of 104 patients with parotid carcinoma

A retrospective analysis was made of 104 patients with parotid carcinoma treated with radical radiotherapy between 1977 and 1986. Eighty-seven patients received postoperative radiotherapy and 17 had radiotherapy alone. The 5- and 10-year survival figures, corrected for intercurrent deaths, were 60% and 49% respectively, with primary control rates of 68% and 58%. Local control was significantly better for patients initially presenting with T1/T2 disease, but local relapse still occurred in 23% of these patients. Of 13 patients with acinic cell tumours, four developed local recurrence and a further two had metastatic disease. These patterns of relapse suggest that patients with parotid carcinoma should receive postoperative radiotherapy irrespective of disease stage or histological type.

The influence of radiotherapy treatment time on the control of laryngeal cancer: a direct analysis of data from two British Institute of Radiology trials to calculate the lag period and the time factor

This study analyses node-negative laryngeal tumour control data from two clinical trials conducted by the British Institute of Radiology in order to determine the time factors and the presence or absence of a lag period before the time factor takes effect. A direct maximum likelihood approach is used to fit a double-logarithmic model including a repopulation term which commences after an initial lag period, Tk. The analysis yields a time factor of 0.8 Gy per day (95% confidence interval 0.5-1.1 Gy per day) as the extra dose required to counteract the reduction in tumour control probability (TCP) with extension of the treatment time. The latter reduction amounted to between 5 and 12% TCP per week, depending on the stage and time period. With this dataset, where few patients were treated for short times, no statistically significant lag phase can be demonstrated. However, the best estimate of Tk is 21 days (95% confidence interval 0-27 days), which is consistent with estimates from other studies on other datasets. If a lag phase exists, this study would indicate that the duration is less than 27 days. Other studies have used retrospective data and are subject to a number of potential biases. The present study, using data from multicentre prospective randomized clinical trials, is free from some of these sources of bias. The fact that very similar estimates of the radiobiological parameters are obtained lends credence to these other studies and suggests that the potential biases may be small in practice.