FDG PET/CT of a Late-term Pregnant Woman With Breast Cancer

Estimated Fetal Radiation Dose From 18 F-FDG PET/CT During the Second and Third Trimesters of Pregnancy

PURPOSE

Data published in the literature concerning the doses received by fetuses exposed to a 18 F-FDG PET are reassuring but were obtained from small and heterogeneous cohorts, and very few data are available concerning the fetal dose received after exposure to both PET and CT. The present study aimed to estimate the fetal dose received following a PET/CT exposure using methods that include anthropomorphic phantoms of pregnant women applied on a large cohort.

PATIENTS AND METHODS

This retrospective multicenter study included 18 pregnant patients in the second and third trimesters. For PET exposure, the fetal volume and mean concentration of radioactivity in the fetus were measured by manually drawing regions of interest. Those data, combined with the time-integrated activities of the fetus and the mother's organs, were entered into the OLINDA/EXM software 2.0 to assess the fetal dose due to PET exposure. To estimate the fetal dose received due to CT exposure, 2 softwares were used: CT-Expo (based on geometric phantom models of nonpregnant patients) and VirtualDose (using pregnant patient phantoms).

RESULTS

The fetal dose exposure for PET/CT examination in the second trimester ranged from 5.7 to 15.8 mGy using CT-Expo (mean, 11.6 mGy) and from 5.1 to 11.6 mGy using VirtualDose (mean, 8.6 mGy). In the third trimester, it ranged from 7.9 to 16.6 mGy using CT-Expo (mean, 10.7 mGy) and from 6.1 to 10.7 mGy using VirtualDose (mean, 7.6 mGy).

CONCLUSIONS

The estimated fetal doses were in the same range of those previously published and are well below the threshold for deterministic effects. Pregnancy does not constitute an absolute contraindication for a clinically justified hybrid 18 F-FDG PET/CT.

Pregnancy and Gastric Cancer: A Narrative Review

Cases of digestive cancers diagnosed during pregnancy are rare. The increasing prevalence of pregnancy in women aged 30-39 years (and not exceptionally 40-49 years) could explain the frequent co-occurrence of cancers and pregnancy. The diagnosis of digestive cancers in pregnancy is difficult due to the overlap between neoplasm symptomatology and the clinical picture of pregnancy. A paraclinical evaluation may also be difficult depending on the trimester of the pregnancy. Diagnosis is also delayed by practitioners' hesitation to use invasive investigations (imaging, endoscopy, etc.) due to fetal safety concerns. Therefore, digestive cancers are often diagnosed during pregnancy in advanced stages, where complications such as occlusions, perforations, and cachexia have already arisen. In this review, we highlight the epidemiology, clinical aspects, paraclinical evaluation, and particularities of the diagnosis and treatment of gastric cancer during pregnancy.

Imaging modalities and optimized imaging protocols in pregnant patients with cancer

Medical imaging during pregnancy may be necessary to diagnose conditions that affect the outcome of the mother and fetus. Diagnosis and staging of cancer in pregnant women can be particularly challenging due to fear of inherent risk to the fetus, lack of standardized imaging protocols, and ethical challenges posed while choosing the best imaging option. Ultrasound and MRI, due to lack of ionizing radiation, are preferred over CT and nuclear imaging. The latter may be considered only if the benefits of imaging outweigh maternal and fetal risk without exceeding the cumulative established fetal radiation dose threshold. This article provides an overview of all currently available imaging options that can be used for imaging cancer during pregnancy to support the best possible maternal and fetal outcomes.

Use of Positron Emission Tomography for Pregnancy-Associated Cancer Assessment: A Review

Background. Positron emission tomography (PET) has proven clinical utility both in the initial and relapse staging phase, but this technique is controversial during pregnancy. The objective of this review is to provide a compendium of available information on the use of PET during pregnancy. Materials and methods. A systematic literature review was conducted from 1 January 2004 until 20 May 2021. A total of 4 small series and 9 case reports consisting of 25 cases were selected. Results. During the first trimester, the fetus is most sensitive to ionization damage, so lower doses are recommended (2.6E-02 mGy/MBq). Fetal-effective doses are higher in this period and the average fetal dose (4.06 ± 3.22 mGy) remains significantly below the threshold for deterministic effects. During the second and third trimesters, recommended doses are higher (1.4E-02 mGy/MBq at 6 months, and 6.9E-03 mGy/MBq at 9 months of gestation). 18F-FDG activity was distributed to the whole fetus with a prevalence of myocardial tissue in seven cases. The use of special precautions, such as PET-magnetic resonance (MR) and urinary bladder catheterization, reduces the amount of radioactive tracer. Breastfeeding interruption is not recommended. Conclusions. 18F-FDG PET is not contraindicated in pregnancy, but multidisciplinary discussion is necessary and strict precautions are recommended.

Embryo/Fetus Doses from 18F-Fludeoxyglucose Radiopharmaceutical in Positron Emission Tomography/ Computed Tomography

Aim

The embryo/fetus may be accidentally exposed to ionizing radiation. The aim of this study is to calculate embryo/fetus doses in pregnant women who underwent F-18 fludeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scan.

Materials and Methods

Between June 2015 and June 2021, 15 pregnant women underwent F-18 FDG PET/CT applied to the Genetic Research Center (GETAM). The OLINDA/EXM package program was used for internal radiation dosimetry according to the Medical Internal Radiation Dose scheme. FetDose V4 computer software was used to compute the embryo/fetus absorbed dose from CT scan.

Results

The amount of the injected F-18 FDG activity to patients varied between 333 and 555 MBq. The mean embryo/fetal dose from F-18 FDG was 7.2 ± 2.8 mGy. In addition, the CT component dose to the embryo/fetus dose ranged from 8.5 to 16 mGy with a mean of 12.14 ± 2.05.

Conclusions

The embryo/fetus dose from F-18 FDG PET/CT was <15 mGy, however, questioning the women's childbearing prior to scintigraphy is the first-line strategy to avoid accidental radiation exposure and stochastic risks.

Fluorodeoxyglucose positron emission tomography-computed tomography in a pregnant woman with carcinoma breast

A 35-year-old female with a 15-week period of gestation was detected with locally advanced cancer of the left breast. She was suggested to undergo a medical termination of pregnancy (MTP) followed by invasive Oncological imaging - Contrast enhanced computed tomography (CECT) chest–abdomen–pelvis/fluorodeoxyglucose positron emission tomography-CT (FDG PET-CT) for staging the disease. However, to avoid the risk of iatrogenic novel coronavirus 2019 infection to the patient, on her request, the hospital admission was carried out after the oncological workup and thus PET-CT was conducted before the MTP. FDG PET-CT revealed FDG avid primary in the left breast along with extensive metastases to liver and skeletal lesions. The developing fetus also showed physiological FDG uptake. The patient has undergone an MTP and is presently under treatment for metastatic breast cancer. The case report illustrates the radiation safety guidelines on fetal radiation exposure, steps to decrease fetal radiation exposure, and illustration of fetal FDG uptake.

PET/CT Variants and Pitfalls in Gynecological Cancers

The role of hybrid imaging with 2-[18F] flourodeoxyglucose (FDG) positron emission tomography and computed tomography (PET/CT) is continuously evolving and now considered standard practice in evaluation of disease stage, treatment response, recurrent disease and follow-up for numerous primary malignancies. In gynecological malignancies FDG PET/CT plays an important role, not only in the assessment of disease in the pre-and post-therapy setting, but also in radiation therapy (RT) planning by defining the metabolically active gross tumor volume (GTV. The glucose analogue radiotracer, FDG, is by far the most utilized radiotracer in PET/CT and is typically seen with high uptake in malignant cells. The radiotracer FDG has a high sensitivity but low specificity for malignancy, as benign processes with an inflammatory response for example infection, are also FDG-avid. In the evaluation of the female pelvic region an awareness of potential confounding factors in the interpretation of FDG is essential as variations of FDG uptake occur in accordance with the menstrual cycle and the menopausal state. Incidental imaging findings in the female genital can pose differential diagnostic challenges as false-positive and false-negative findings in benign and malignant processes are not uncommon. Gynecological malignancies continue to pose major public health problems with cervical cancer as the fourth most common cancer in women ranking after breast cancer, colorectal cancer and lung cancer. Familiarity with frequently encountered benign and malignant variants and pitfalls in FDG PET/CT in the female pelvic region can aid the reader in differential diagnostic considerations.

FDG PET/CT in a Pregnant Woman With Breast Cancer

This 37-year-old woman was diagnosed with breast cancer during pregnancy. After multidisciplinary meeting, she was referred to our department for an FDG PET/CT for staging, and chemotherapy with weekly infusion of paclitaxel was initiated before childbirth. We estimated the fetal dose from the PET/CT procedure, and our results show that, if deemed necessary, this examination can reasonably be performed during pregnancy. The patient gave birth vaginally at term to an apparently healthy girl.

Post Contusion Breast Hematoma Mimicking Malignancy on FDG PET/CT

A 32-year-old woman was treated for breast carcinoma. Posttreatment FDG PET/CT scan revealed complete response, but in the contralateral breast, unexpected incidental intense FDG uptake was seen with a differential diagnosis of both malignant and benign causes. Medical history revealed recent breast contusion. The lesion was further evaluated by mammogram and ultrasound, which were compatible with deep breast bruise. Histopathology showed no malignancy. Subsequent FDG PET/CT study showed breast uptake normalization. This case shows that postcontusion breast hematoma can cause a potential pitfall mimicking breast malignancy on FDG PET/CT.

18F-FDG Whole-body PET/MRI of a 30-Week Pregnant Woman With Breast Cancer Revealed Interesting Fetal Findings

A 35-year-old 30-week pregnant woman was referred to our institution for initial staging of a triple negative invasive ductal carcinoma of the left breast. To avoid fetal radiation exposure from CT, a whole-body F-FDG PET/MRI was performed. Simultaneous acquisition of PET, T1-, T2-, and diffusion-weighted sequences revealed left axillary node extension and no distant metastases. Fetal radiation dose was estimated at 1.9 mGy. Interestingly, low fetal brain uptake and high symmetrical myocardial metabolism in both ventricles were found. Delivery was induced at 37 weeks of amenorrhea, and the patient underwent 4 cycles of neoadjuvant chemotherapy.

Cancer in Pregnancy

This article reviews some of the more common types of cancer that may be encountered during pregnancy. It reviews the unique challenges with the diagnosis and treatment of breast, cervical, hematologic, and colon cancers in pregnant patients.

The use of PET/CT in pregnancy: A case report of malignant parathyroid carcinoma and a review of the literature

Positron emission tomography scanning is not commonly performed in pregnancy but can be done if required. Fetal doses of radiation can be minimized, and our case exemplifies the safe application of positron emission tomography/computed tomography in pregnancy. A 38-year-old woman in her first ongoing pregnancy presented at 28 weeks' gestation with symptomatic hypercalcemia. Given a history of parathyroid carcinoma, recurrence was suspected. Ultrasound and magnetic resonance imaging failed to locate the lesion. However, positron emission tomography/computed tomography identified a culprit supraclavicular lymph node. This was excised under local anesthesia resulting in normalization of parathyroid hormone and calcium levels. A term, healthy baby was delivered. The literature provides support that the use of positron emission tomography/computed tomography is acceptable when indicated, and there are modifications to protocols that can further limit risk.

Melanoma and pregnancy

Melanoma is the most common cancer in women during their reproductive years and kills more young Australians than any other single cancer. Care of women whose pregnancy is complicated by a diagnosis of malignancy is complex. The risk of delaying treatment to the mother, the short-term and long-term risks of premature delivery to the child, and the immediate risks to the foetus and long-term risks to the child of maternal treatment with surgery, radiotherapy or medical therapies must be considered.

Spectrum of the Breast Lesions With Increased 18F-FDG Uptake on PET/CT

Interpretation of ¹⁸F-FDG PET/CT studies in breast is challenging owing to nonspecific FDG uptake in various benign and malignant conditions. Benign conditions include breast changes in pregnancy and lactation, gynecomastia, mastitis, fat necrosis, fibroadenoma, intraductal papilloma, and atypical ductal hyperplasia. Among malignancies, invasive ductal carcinoma and invasive lobular carcinoma are common histological types of breast carcinoma. Rarely, other unusual histological types of breast carcinomas (eg, intraductal papillary carcinoma, invasive micropapillary carcinoma, medullary carcinoma, mucinous carcinoma, and metaplastic carcinoma), lymphoma, and metastasis can be the causes. Knowledge of a wide spectrum of hypermetabolic breast lesions on FDG PET/CT is essential in accurate reading of FDG PET/CT. The purpose of this atlas article is to demonstrate features of various breast lesions encountered at our institution, both benign and malignant, which can result in hypermetabolism on FDG PET/CT imaging.