Wednesday, December 24, 2014

Gestational Trophoblastic Tumours

1. Rules for Classification

The following classification for gestational trophoblastic tumours is based on that of FIGO adopted in 1992 and updated in 2001 (Gestational trophoblastic tumours. Ngan HYS, Odicino F, Maisonneuve P, Beller U, Benedet JL, Heintz APM, Pecorelli S, Sideri M, Creasman WT. J Epidemiol Biostatist 2001;6:175-184). The definitions of T and M categories correspond to the FIGO stages. Both systems are included for comparison. In contrast to other sites, an N (regional lymph node) classification does not apply to these tumours. A prognostic scoring index, which is based on factors other than the anatomic extent of the disease, is used to assign cases to high risk and low risk categories, and these categories are used in stage grouping.

The classification applies to choriocarcinoma (9100/3), invasive hydatidiform mole (9100/1), and placental site trophoblastic tumour (9104/1). Placental site tumours should be reported separately. Histological confirmation is not required if the human chorionic gonadotropin (hCG) level is abnormally elevated. History of prior chemotherapy for this disease should be noted.

The following are the procedures for assessing T and M categories:

T categories. Physical examination, imaging including urography and cystoscopy
M categories. Physical examination and imaging
Risk categories. Age, type of antecedent pregnancy, interval from index pregnancy, pretreatment hCG, diameter of largest tumour, site of metastasis, number of metastases, and antecedent treatment are integrated to provide a prognostic score that divides cases into low and high risk categories.

2.1. Primary Tumour

TM Categories FIGO Stages *
TX
Primary tumour cannot be assessed
T0
No evidence of primary tumour
T1 I Tumour confined to uterus
T2 II Tumour extends to other genital structures: vagina, ovary, broad ligament, fallopian tube by metastasis or direct extension
M1a III Metastasis to lung(s)
M1b IV Other distant metastasis
*Note: Stages I to IV are subdivided into A and B according to the prognostic score.

2.2. M - Distant Metastasis

MX. Metastasis cannot be assessed
M0. No distant metastasis
M1. Distant metastasis
  M1a. Metastasis to lung(s)
  M1b. Other distant metastasis
Note: Genital metastasis (vagina, ovary, broad ligament, fallopian tube) is classified T2. Any involvement of non-genital structures, whether by direct invasion or metastasis is described using the M classification.

3. pTM Pathological Classification

The pT and pM categories correspond to the T and M categories.

4. Prognostic Score

Prognostic Factor 0 1 2 4
Age <40 ≥40

Antecedent pregnancy H. mole Abortion Term pregnancy
Months from index pregnancy <4 4-<7 7-12 >12
Pretreatment serum hCG (IU/ml) <103 103-<104 104-<105 ≥105
Largest tumour size including uterus <3 cm 3-<5 cm ≥5 cm
Sites of metastasis Lung Spleen, kidney Gastrointes-tinal tract Liver, brain
Number of metastasis
1-4 5-8 >8
Previous failed chemotherapy

Single drug Two or more drugs

5. Stage Grouping

Stage T M Risk Category
I T1 M0 Unknown
IA T1 M0 Low
IB T1 M0 High
II T2 M0 Unknown
IIA T2 M0 Low
IIB T2 M0 High
III Any T M1a Unknown
IIIA Any T M1a Low
IIIB Any T M1a High
IV Any T M1b Unknown
IVA Any T M1b Low
IVB Any T M1b High

6. Summary

TM and risk Gestational Trophoblastic Tumours Stage
T1 Confined to uterus I
T2 Other genital structures II
M1a Metastasis to lung(s) III
M1b Other distant metastasis IV
Low risk Prognostic score 7 or less IA-IVA
High risk Prognostic score 8 or more IB-IVB