It’s a good question and my caveat is that very little in the below is evidence, just opinion:
- we know that there is a dose-dependent relationship between chemotherapy and disease response. That is - a therapeutic window (hopefully) where it can kill tumour cells without killing the patient. In aggregate, doing chemo every 3 weeks rather than 2 weeks would result in a ~35% dose reduction over a period of a year. For some people, a 35% reduction would still elicit a clinical response; for others it may not be enough to control disease. It’s going to depend a lot on individual disease biology.
- cell repair is also relevant. Almost as soon as they start getting damaged, cancer cells begin attempting to repair themselves. So this means that even during treatment there is a balance between cell damage and cell repair, hopefully favouring the former. One argument toward a more metronomic (continuous) style of chemo is that you’re reducing the time available for cellular repair to take place (particularly time where the damage effects of treatment may have worn off), and thus reduce overall tumour burden (and perhaps hypothetically, cell resistance to treatment).
- one area that’s interesting is in the use of capecitabine rather than 5FU (ie CAPIRI/XELIRI). In this case the irinotecan is generally given even 3 weeks, to allow a 2 week oral program of capecitabine, and a recovery week. The pharmacodynamic profile of the resultant 5FU is clearly different - ie via IV it’s given as a higher-dose 48 hour infusion, whereas as capecitabine it’s a lower daily dose over an extended period. Research seems to suggest that the 3-week CAPIRI regime is non-inferior to the 2-week FOLFIRI.
If I restart chemo I will almost certainly be doing it as CAPIRI, as I’d prefer not to get a new port, want to avoid the 48 infusion and extra hospital visits, and less frequent exposure to irinotecan. So if you’re thinking about a 3 weekly cycle, perhaps doing the 5FU as Xeloda could give you some confidence that the protocol has more research behind it. If you’re after an aggressive approach, you might also consider adding a targeted therapy like Avastin to the treatment.
Last edited by Rock_Robster
on Wed Jul 20, 2022 7:48 pm, edited 1 time in total.
2018 RC, 12cm high
G2 EMVI LVI. 4 liver mets
pT3N1aM1a Stage IVa MSS NRAS G13R
CEA: Nov-18: 14 then <2. Jun-22: 5. Sep-22: 10
3/19 Liver resection
5/19 Pelvic IMRT
7/19 ULAR & ileo
8/19 Liver met
8/19 FOLFOX, FOLFOXIRI, FOLFIRI
12/19 Liver resection
NED 2 years
11/21 Liver met & node, 2 tiny lung things
3/22 Nodes & 3 liver mets. Lymphadenectomy
4/22 Liver SBRT
6/22 Liver clear.
10/22 Small liver spot. Some PALNs. Planning PALN SBRT.