Analysis of the Growth Parameters of Human Tumours: Clinical Implications

Abstract

1. Of all tumour growth parameters the potential doubling time (Tpot) is the most clinically relevant since: (a) it can be readily estimated in terms of the thymidine labelling index (TLI) or the porportion of S-phase cells (SPF), and (b) it correlates well with the clinical behaviour. 2. Ploidy can be expressed in terms of the DNA content of the G1/GO cell population (the DNA index, DI). All benign tumours are diploid and 80–100% of solid malignant tumours are aneuploid. Aneuploidy can predict the aggressive behaviour of premalignant lesions and correlates with the prognosis of malignant tumours. Aneuploid cell lines are generally more radiosensitive than the diploid ones and their disappearance durig radiotherapy can be a favourable sign. 3. Breast cancer illustrates well the independent predictive value of TLI, SPF and ploidy. Both node-negative and node-positive patients can be divided on the basis of the proliferative rate into favourable and unfavourable groups. The TLI is a useful predictor of early relapse of breast cancer and the course of the disease after a relapse. Thus,it can help in identifying patients in need of adjuvant therapy. Among node negative patients a high TLI is associated with a 50% risk of relapse and ILI may be used as a basis for selecting patients for adjuvant chemotherapy from the group of node negative patients. But patients with a low TLI and having ER−-tumours are at a high risk and are recommended for adjuvant therapy. 4. TLI. SPF and DI constitute useful prognostic parameters independent of the histopathological pattern and clinical stage in non-Hodgkin’s lymphomas. Indolent forms of nodular NHL not requiring immediate therapy may be identified on the basis of a low prol iferation rate. 5. All carcinomas in situ in the urinary bladder are aneuploid. But multiploid cases are at a higher risk of progression and have to be treated aggressively. After conservative treatment of superficial bladder tumours. aneuploidy detected in bladder washing is an early predictor of recurrence. In muscle-invading bladder cancer; a high TLI in the deep infiltrating margin is associated with a high risk of relapse and can constitute a basis for selecting patients for pre-operative irradiation. Downstaging after pre-operative irradiation is a favourable sign and can be predicted on the basis of the disappearance of aneuploid cell lines.