Predicting the future: a critical appraisal of cancer prognosis studies

Telomerase and cancer: time to move from a promising target to a clinical reality

The past 25 years have seen unparalleled advances in our understanding of the molecular basis of cancer. As a result, novel molecular targets have been identified that provide great potential for the development of new cancer diagnostics and therapies. Four key features of cancer cells distinguish them from their normal counterparts: loss of cell-cycle regulation, loss of control over invasion and metastasis, failure of apoptotic mechanisms, and bypass of senescence. This review examines our understanding of the bypass of senescence and the process of immortalization during carcinogenesis. In addition, the realistic opportunities for telomerase in cancer diagnostics and the challenges faced in clinical trial design for telomerase therapeutics are discussed.

Scoring nuclear pleomorphism in breast cancer

AIMS

Nuclear grade has equal weight with mitotic index and acinus formation in grading breast cancer, but criteria for its assessment are less well defined. This study examines consistency of nuclear grading in breast cancer and whether improved nuclear grading criteria are required.

METHODS AND RESULTS

Photographic prints of haematoxylin-eosin sections of 100 unselected symptomatic breast cancers were circulated to histopathologists who assigned each carcinoma a nuclear pleomorphism score on a linear analogue scale 0-100 (0-33 equating to nuclear pleomorphism grade 1, 34-66 to grade 2, and 67-100 to grade 3). Seventeen histopathologists completed the exercise, including 11 breast specialists. While kappa scores for the implied nuclear grades indicated 'moderate' or 'good' agreement between individuals and the group as a whole, seven pathologists allocated analogue scores significantly lower than the median score allocated by the group to each case, while five allocated significantly higher scores. The range was from analogue scores 11.3 units lower on average than the median (assigning 27% of carcinomas nuclear grade 1, 60% grade 2, and 13% grade 3) to scores 7.5 units higher on average than the median (assigning only 2% carcinomas nuclear grade 1, 46% grade 2, and 52% grade 3). Five of six non-specialists allocated scores significantly lower than the group medians but only two of 11 specialists did so (P=0.018).

CONCLUSIONS

Systematic differences between pathologists in scoring nuclear pleomorphism in breast cancer potentially contribute to differences in allocating overall grade and confirm the need for improved nuclear grading criteria. Specialists tend to allocate higher pleomorphism scores than non-specialists.

Observer accuracy in estimating proportions in images: implications for the semiquantitative assessment of staining reactions and a proposal for a new system

BACKGROUND

The results of immunohistochemical staining are often assessed by semiquantitative scoring. However, these scoring systems are usually non-standardised and there has been little evaluation of the accuracy and reliability of this subjective assessment.

AIMS

To assess the accuracy of observer estimation of proportions of objects in an image.

METHODS

Images were generated that contained known proportions of pink squares in grids of 50 x 50 and 100 x 100 squares. Observers were shown each image for five seconds in random order and either estimated the proportion of pink squares or selected the image (from a pair of images) that contained the greater proportion of pink squares. The observers were four consultant histopathologists, seven trainee histopathologists, and six control non-histopathologists.

RESULTS

The raw estimations of proportions showed a close correlation with the real proportions, with correlation coefficients of 0.94 and 0.95 for consultant and trainee histopathologists on the 50 x 50 grids. However, the performance in the comparison task was much higher, with an almost perfect classification for grids of equal size even when the proportions only differed by 5%.

CONCLUSIONS

Histopathologists can estimate proportions of objects in an image with a reasonable degree of accuracy in this abstract test system. All observers, whether histopathologists or not, can discriminate between proportions that are only 5% different in equal sized image grids. This suggests that the generation and use of carefully calibrated reference images could greatly improve the accuracy and reliability of semiquantitative scoring of immunohistochemical or any other staining.