Introduction and outline 13 CHAPTER 1 Inorder tomaximize the ability toachieve clearmargins, neoadjuvant treatment options inLRRCare explored. In locally advanced primary rectal cancer, the role of preoperative chemoradiotherapy to downsize and downstage the tumour is already established. In most LRRC patients who are radiotherapy naive, full course of chemoradiotherapy will also be applied. In LRRC patients who have already received chemoradiotherapy for their primary tumour, the discussion is still ongoingwith regard to reirradiation.16 These local recurrences originate fromcancer cellswho have persisted after radiotherapy and may be considered more radiotherapy resistant. Previously irradiated healthy pelvic tissuewill impose dose limitations on reirradiation. The administration of reirradiation doses ranging from 30-40 Gy has proved to be feasible.17,18 However, these doses are considered too low to eradicate potentially radioresistant cancer cells. Some centres have opted not to use reirradiation to avoid the potential side effects of possibly even ineffective reirradiation, and go straight to surgery.19 Other centres seek to overcome the dose limitations combining limited external beam reirradiation with a relatively high intraoperative boost, while shielding sensitive tissues.20 The radiobiological equivalent of a single high boost is three times as high as a comparable fractionated dose. The combined external and intraoperative local dose at the area of risk can reach between 70-90 Gy. An intraoperative boost can be delivered with a dedicated electron beam accelerator or by means of high dose rate brachytherapy equipment. Evaluation of the tumour by MRI is pivotal for the surgical treatment planning in primary rectal cancer. It enables delineation of the tumour extension in relation to the mesorectal fascia,whichwill beremovedduringTMEsurgery. Incaseof closeor involved margins chemoradiotherapy will be used to downsize and downstage the tumour in order to be able to achieve clear resection margins. In LRRC interpretation of the MRI is hindered by postoperative changes, possible infectious complications or alterations in tissue after radiotherapy, all leading to more extensive fibrosis. Furthermore, the growth patternmay bemore spiculated rather than solid in this fibrotic tissue. A straight delineation of the mesorectal fascia like in primary cancer is absent and therefore the radiologist cannot simply state if the circumferential resectionmarginwill be involved. Radiologists and surgeons have to join forces in order to plan the extent of surgery required to achieve clear resection margins. In locally advanced primary rectal cancer a new concept of usage of chemotherapy has been developed in order to treat micrometastases more effectively. The classic treatment with chemoradiotherapy and surgery followed by chemotherapy was compared to chemoradiotherapy followed by chemotherapy and then proceeding to surgery. A much higher pathological complete response rate was found in the experimental arm of 36 percent versus 21 percent in the classic treatment arm,
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