Adaptive RT in rectal cancer: superior to 3D-CRT? A simple question, a complex answer

PET imaging in adaptive radiotherapy of gastrointestinal tumors

INTRODUCTION

Radiotherapy is a cornerstone in the multimodality treatment of several gastrointestinal (GI) tumors. Positron-emission tomography (PET) has an established role in the diagnosis, response assessment and (re-)staging of these tumors. Nevertheless, the value of PET in adaptive radiotherapy remains unclear. This review focuses on the role of PET in adaptive radiotherapy, i.e. during the treatment course and in the delineation process.

EVIDENCE ACQUISITION

The MEDLINE database was searched for the terms ("Radiotherapy"[Mesh] AND "Positron-Emission Tomography"[Mesh] AND one of the site-specific keywords, yielding a total of 1710 articles. After abstract selection, 27 papers were identified for esophageal neoplasms, 1 for gastric neoplasms, 9 for pancreatic neoplasms, 6 for liver neoplasms, 1 for biliary tract neoplasms, none for colonic neoplasms, 15 for rectal neoplasms and 12 for anus neoplasms.

EVIDENCE SYNTHESIS

The use of PET for truly adaptive radiotherapy during treatment for GI tumors has barely been investigated, in contrast to the potential of the PET-defined metabolic tumor volume for optimization of the target volume. The optimized target definition seems useful for treatment individualization such as focal boosting strategies in esophageal, pancreatic and anorectal cancer. Nevertheless, for all GI tumors, further investigation is needed.

CONCLUSIONS

In general, too little data are available to conclude on the role of PET imaging during radiotherapy for ART strategies in GI cancer. On the other hand, based on the available evidence, the use of biological imaging for target volume adaptation seems promising and could pave the road towards individualized treatment strategies.

Effect of total mesorectal excision on the outcome of rectal cancer after standardized postoperative radiochemotherapy: do randomized studies translate into clinical routine?

PURPOSE

To compare local control, disease-free survival and overall survival after postoperative radiochemotherapy with or without total mesorectal excision (TME) in a retrospective analysis.

PATIENTS AND METHODS

Between 1993 and 2002, 103 patients with UICC stage II and III rectal cancer were treated by surgery and postoperative chemoradiation. Group B (n = 50; 1993-1998) were operated before TME era without using TME and group A (n = 53; 1998-2002) with TME; both groups received identical radiochemotherapy to a total dose of 50.4 Gy (median) and two courses of continuous 5-fluorouracil infusion.

RESULTS

Patients in group A (TME) showed a significant improvement in 5-year disease-free survival (71.1%; 46.8%) and freedom from distant metastases (76.3%; 46.9%) and a marked improvement of local control (85.2%; 62.5%). Acute and late toxicity were significantly less frequent in group A.

CONCLUSION

Radiochemotherapy cannot compensate an insufficient surgical procedure. These data confirm that TME is the standard. High outcome quality can be achieved in daily practice compared to results of randomized studies without patient selection.

Molecular targeted treatment and radiation therapy for rectal cancer

BACKGROUND

EGFR (epidermal growth factor receptor) and VEGF (vascular endothelial growth factor) inhibitors confer clinical benefit in metastatic colorectal cancer when combined with chemotherapy. An emerging strategy to improve outcomes in rectal cancer is to integrate biologically active, targeted agents as triple therapy into chemoradiation protocols.

MATERIAL AND METHODS

Cetuximab and bevacizumab have now been incorporated into phase I-II studies of preoperative chemoradiation therapy (CRT) for rectal cancer. The rationale of these combinations, early efficacy and toxicity data, and possible molecular predictors for tumor response are reviewed. Computerized bibliographic searches of Pubmed were supplemented with hand searches of reference lists and abstracts of ASCO and ASTRO meetings.

RESULTS

The combination of cetuximab and CRT can be safely applied without dose compromises of the respective treatment components. Disappointingly low rates of pathologic complete remission have been noted in several phase II studies. The K-ras mutation status and the gene copy number of EGFR may predict tumor response. The toxicity pattern (radiation-induced enteritis, perforations) and surgical complications (wound healing, fistula, bleeding) observed in at least some of the clinical studies with bevacizumab and CRT warrant further investigations.

CONCLUSION

Longer follow-up (and, finally, randomized trials) is needed to draw any firm conclusions with respect to local and distant failure rates, and toxicity associated with these novel treatment approaches.

Impact of (18)F-FDG-PET/CT on staging and irradiation of patients with locally advanced rectal cancer

PURPOSE

To investigate the impact of fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) on planning of neoadjuvant radiotherapy for locally advanced rectal cancer (LARC) patients.

PATIENTS AND METHODS

From January 2003 to December 2007, a total of 36 patients with LARC underwent a retroprospective PET/CT study for radiotherapy-planning purposes. Gross tumor volume (GTV), clinical target volume (CTV) and planning target volume (PTV) were defined in a retrospective analysis by a blinded reader. The hypothetical boost volume was defined primarily on CT alone, and afterwards on the fused PET/CT dataset. The CT- and PET/CT-based GTVs were quantitatively compared and percentage of overlap (OV%) was calculated and analyzed. The impact of PET/CT on radiation treatment planning and overall patient management was evaluated.

RESULTS

PET/CT-GTVs were smaller than CT-GTVs (p < 0.05). PET/CT imaging resulted in a change of overall management for three patients (8 %). In 16 of 35 patients (46 %), PET/CT resulted in a need for modification of the usual target volumes (CT-PTV) because of detection of a geographic miss.

CONCLUSION

FDG-PET/CT had significant impact on radiotherapy planning and overall treatment of patients with LARC.

Postoperative morbidity following chemoradiation for locally advanced low rectal cancer

BACKGROUND

Postoperative morbidity remains a significant clinical problem and may alter long-term outcome particularly after neoadjuvant chemoradiation in patients with locally advanced low rectal cancer. The aim of the present study was to identify a potential long-term effect of postoperative morbidity.

METHODS

Analysis of prospectively collected data of 90 consecutive patients who underwent neoadjuvant chemoradiation and curative mesorectal excision for locally advanced (cT3/4, Nx, M0/1) adenocarcinoma of the mid and lower third of the rectum during a 7-year period (1996-2002).

RESULTS

Major postoperative complications occurred in 17.8% and minor complications in 26.6% of patients. Hospital mortality and 30-day mortality was 0%. Infectious complications were seen in 34.5%. The leading causes of infectious complications were anastomotic leakage and perineal wound infection. Postoperative morbidity was statistically significantly associated with gender (P < 0.05), pre-therapeutic haemoglobin level (P < 0.05), ASA score (P < 0.05), hospitalisation (P < 0.001) and clinical long-time course (P < 0.01). Moreover, early postoperative morbidity was proven as an independent prognostic factor concerning disease-free (P < 0.05) and overall survival (P < 0.05).

CONCLUSION

Early postoperative morbidity in patients with preoperative chemoradiation due to locally advanced low rectal cancer is demonstrated as an independent prognosticator. Gender, pre-therapeutic haemoglobin level and ASA score indicate patients at risk for early postoperative complications and may therefore serve as predictive features.