Tumor mitotic rate is a more powerful prognostic indicator than ulceration in patients with primary cutaneous melanoma: an analysis of 3661 patients from a single center.
BACKGROUND
The current study was performed to determine whether tumor mitotic rate (TMR) is a useful, independent prognostic factor in patients with localized cutaneous melanoma.


METHODS
From the Sydney Melanoma Unit database, 3661 patients with complete clinical information and details of primary tumor thickness, ulcerative state, and TMR were studied. TMR was expressed as mitoses per mm(2) in the dermal part of the tumor in which most mitoses were seen, as recommended in the 1982 revision of the 1972 Sydney classification of malignant melanoma. To determine which was the more prognostically useful method of grouping TMR, two separate methods (A and B) were used. Factors predicting melanoma-specific survival were analyzed using the Cox proportional hazards regression model.


RESULTS
Patients with a TMR of 0 mitoses/mm(2) had a significantly better survival than those with 1 mitosis/mm(2) (P < 0.0001) but no significant survival differences were recorded for the stepwise increases from 1-2, 2-3, 3-4, and 4-5/mm(2). Tumor thickness, ulceration, and TMR were closely correlated, whether TMR was grouped using Method A (0, 1-4, 5-10, and >/= 11 mitoses/mm(2)) or Method B (0-1, 2-4, and >/= 5 mitoses/mm(2)). However, Cox regression analysis indicated that the TMR was a highly significant independent prognostic factor, particularly when grouped according to Method A, in which it was second only to tumor thickness as the most powerful predictor of survival (P < 0.0001).


CONCLUSIONS
TMR is an important independent predictor of survival for melanoma patients. If confirmed by studies from other centers, it has the potential to further improve the accuracy of melanoma staging, as well as to define more rigidly the risk categories for patients entering clinical trials.
Azzola
Manuela F
MF
Sydney Melanoma Unit, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia.
Shaw
Helen M
HM
Thompson
John F
JF
Soong
Seng-Jaw
SJ
Scolyer
Richard A
RA
Watson
Geoffrey F
GF
Colman
Marjorie H
MH
Zhang
Yuting
Y
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008297:Male; D008545:Melanoma / Q000473:pathology*; D008875:Middle Aged; D008940:Mitotic Index; D011237:Predictive Value of Tests; D011379:Prognosis; D012044:Regression Analysis; D012878:Skin Neoplasms / Q000473:pathology*; D012883:Skin Ulcer / Q000209:etiology* / Q000473:pathology; D013534:Survival