Molecular imaging in cancer treatment

Abstract

The success of cancer therapy can be difficult to predict, as its efficacy is often predicated upon characteristics of the cancer, treatment, and individual that are not fully understood or are difficult to ascertain. Monitoring the response of disease to treatment is therefore essential and has traditionally been characterized by changes in tumor volume. However, in many instances, this singular measure is insufficient for predicting treatment effects on patient survival. Molecular imaging allows repeated in vivo measurement of many critical molecular features of neoplasm, such as metabolism, proliferation, angiogenesis, hypoxia, and apoptosis, which can be employed for monitoring therapeutic response. In this review, we examine the current methods for evaluating response to treatment and provide an overview of emerging PET molecular imaging methods that will help guide future cancer therapies.

Fig. 1

Kinetic modeling through DCE is often used to measure K^trans, a metric measured in min⁻¹ that relates to tumor vessel permeability. Reprinted with permission from Nature [31]

Fig. 2

Several functions separate neoplastic cells from healthy cells. These differences can be targeted through various molecular imaging methods. Reprinted with permission from Elsevier [41]

Fig. 3

a ¹⁸F-FDG uptake is seen in the primary lesion and multiple lymph nodes. b 14 days after treatment with an EGFR inhibitor shows significant reduction in PET activity, corresponding with a 62% reduction in SUV at previous disease sites. Reprinted with permission from the Society of Nuclear Medicine [50]

Fig. 4

a Decreased FLT tumor uptake is seen a week after gefitinib treatment, followed by a CT scan which shows anatomic response after 6 weeks. Similar studies of a nonresponding patient (b) show no significant changes after a week after gefitinib. Reprinted with permission from the American Association for Cancer Research [83]

Fig. 5

A patient’s PET with a neuroendocrine tumor primary and multiple metastatic lesions in the liver, spleen, lymph nodes, and bone. Greater enhancement is seen with ¹⁸F-galacto-RGD PET (a) as compared with ¹⁸F-FDG PET (b). Reprinted with permission from the Journal of Nuclear Medicine [103]

Fig. 6

a, b A patient with bifrontal glioblastoma multi-forme, with MRI demonstrating a 20 cm³ mass with a necrotic core, and ¹⁸F-FMISO image in the same plane with a T/B_max ratio of 3.0. c, dA separate patient with left temporal glioblastoma multiforme tumor 7 cm³ in volume after total gross resection. ¹⁸F-FMISO had a T/B_max ratio of 1.7. Reprinted with permission from the American Association of Cancer Research [162]

Fig. 7

Non-Hodgkin’s lymphoma in a patient with enlarged lymph nodes of the left neck. Coregistered SPECT and CT images before (a, c) and SPECT 48 h after (b) low-dose radiotherapy showing a marked increase of labeled annexin V uptake in the tumor. Complete anatomic response is demonstrated in a CT performed 1 month later (d). Reprinted with permission from Wolters Kluwer Health [196]