Cancer and pregnancy

Cancer recurrence

With the possible exception of gestational trophoblastic disease, pregnancy does not affect the risk of recurrence of any type of cancer, although the diagnosis may be delayed because of the pregnancy. In particular, recurrence of melanoma (Grin Semin Cutan Med Surg 1998) and breast cancer (Velentgas Cancer 1999) appear to be unaffected by a subsequent pregnancy.

Gestational trophoblastic disease

The risk of recurrence after 1 year of remission is less than 1%, but late recurrences have been observed rarely. In case of malignant trophoblast disease, we advise patients to use a reliable form of hormonal contraception during the first 2 year after remission. In benign mola pregnancies, patients can become pregnant again 6 months after remission if HCG has normalised within 8 weeks after curettage, if it takes more than 8 weeks a period of 2 year after remission is advised. This strategy enables us to detect recurrences since pregnancy associated rise in HCG will mask trophoblastic disease.

Because of the 1-2% risk for a second mole in subsequent pregnancies, early ultrasound examination is recommended for all future pregnancies. There does not appear to be an increase in the risk of congenital malformations or other complications related to pregnancy. (Berkowitz J Reprod. Med.1998)

Breast cancer

The majority of studies have concluded that women who become pregnant after successful treatment for breast cancer do not worsen their prognosis with respect to their cancer (von Schoultz J Clin Oncol 1995, Mueller Cancer 2003, Kroman Lancet 1997, Velentgas Cancer 1999, Blakely Cancer 2004). Others are more cautious in the interpretation of the available data and conclude that the effects of subsequent pregnancy on breast cancer prognosis is unclear. Other data suggest that a subsequent pregnancy has a favourable impact on the outcome of early stage breast cancer (von Schoultz J Clin Oncol 1995, Mueller Cancer 2003, Kroman Lancet 1997, Gelber J Clin Oncol 2001, Rosenberg Int J Cancer 2004).

In the largest of these series, the risk ratio for death for women who gave birth within ten months of the diagnosis of breast cancer was 0.54, compared to women with breast cancer who did not have a subsequent pregnancy (Mueller Cancer 2003). Although these data could reflect selection bias (since women with worse prognosis might elect to delay or avoid pregnancy for medical and/or social reasons), they are also consistent with a possible antitumor effect of the pregnancy.

Gelber et al compared 94 women with early stage disease who became pregnant after breast cancer to 188 breast cancer survivors without subsequent pregnancies matched for nodal status, tumor size, age, and year of diagnosis (Gelber J Clin Oncol 2001). The risk ratio for death was significantly lower (0.44) for women who became pregnant subsequent to the diagnosis of breast cancer compared to women with breast cancer who did not have a subsequent pregnancy. Although these data could reflect selection bias, they are also consistent with a possible antitumor effect of the pregnancy. As the patients were matched for nodal status, tumor size, and early stage disease, a "healthy mother effect" whereby only patients feeling well with a good prognosis conceive and therefore show improved survival is unlikely to be the explanation for the findings.

Blakely et al reported on 383 premenopauzal patients followed after breast cancer therapy at the MD Anderson Cancer Center. 47 patients (13%) had at least one pregnancy after treatment for breast carcinoma, 32 succeeded full term, 10 had an abortion, 4 a miscarriage and 1 preterm delivery. The incidence of disease recurrence was 23% for women who experienced a pregnancy and 54% for women who did not, but the patients who experienced a pregnancy tended to have earlier-stage disease, fewer positive lymph nodes and younger age than those who did not. (Blakely Cancer 2004)

It is common for physicians to advise women to wait for two to three years before contemplating pregnancy. The primary reason for this recommendation is that most recurrences of breast cancer occur within the first two years after initial diagnosis and treatment (Donegan Obstet Gynecol 1977). There is no medical evidence to support termination when a spontaneous pregnancy occurs within two to three years after mastectomy (Harvey Surg Gynecol Obstet 1981, Clark Clin Oncol 1989). There are also some concerns with regard to cancer treatment. For example, the half-life of methotrexate is approximately 8 to 15 hours and it is retained for several weeks to months in the kidney and liver, respectively. Delaying conception at least 12 weeks after stopping methotrexate has been recommended (Donnenfeld Teratology 1994).
Furthermore, although few data exist, most clinicians advise against pregnancy for premenopausal women taking adjuvant hormonal therapy. Agents that ablate ovarian function will prevent pregnancy, but women taking tamoxifen should be advised to use some sort of barrier contraception, intra uterine contraceptive device or surgical sterilization (male or female).