title: Planned and unplanned gaps in radiotherapy: the importance of gap position and gap duration.
abstract: Local tumour control in 971 patients with squamous carcinoma of the supraglottic larynx has been examined in relation to the occurrence of gaps in radiation therapy. The minimum follow-up time was 3 years. The reasons for a gap in radiotherapy fell into four categories: independent of the patient (national holidays, machine break-down, etc.), planned gaps (split-course therapy), severe normal-tissue reactions, and intercurrent disease. Only 11.7% of patients had no gap at all, 75.5% a single gap, and 2.1% had more than four gaps. The probability of tumour control increased with dose in all patient sub-groups; the average percentage increase for a 1% increase in dose was 4.3. The data were subjected to multivariate analysis, leading to the following conclusions. Patients in whom there was a single gap showed a remarkable trend of local control: if the gap began before day 19 after the start of therapy, the local tumour control was considerably below that in patients who did not suffer a gap in treatment. The local tumour control in patients whose gap began at day 20-29 was indistinguishable from that in patients who had no gap in treatment. A gap further towards the end of treatment was again associated with a severe drop in local control. This trend was independent of the recorded cause of the gap. The mechanism of this phenomenon is not clear. The effect of the timing of a treatment gap appears in this data set to have had a considerable impact on outcome and our observations should stimulate further study of this phenomenon in other clinical settings.
authors.affiliation: Centre of Oncology, Maria Sklodowska-Curie Memorial Institute, Gliwice, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Skladowski
authors.forename: M G
authors.initials: MG
authors.lastname: Law
authors.forename: B
authors.initials: B
authors.lastname: Maciejewski
authors.forename: G G
authors.initials: GG
authors.lastname: Steel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005931:Glottis; D006801:Humans; D007822:Laryngeal Neoplasms / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D013997:Time Factors